Weather & Hardiness
From America’s Expert Source for Heirloom Flower Bulbs
Here’s a wealth of information about WEATHER PROBLEMS & HARDINESS ZONES from our email Gazette and past catalogs, starting with the most recently published. For other topics, please see our main Newsletter Archives page.
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If you’re enjoying a cool rainy summer, lucky for you! Unfortunately much of the country is once again suffering through high heat and low rainfall. (When even the weeds are wilting, as in the photo here from my neighbor’s yard, you know it’s bad!)
It’s a topic we’ve addressed frequently in recent years, so rather than write a whole new article about it, here are some links to our Weather and Hardiness archives that we hope you’ll find useful (and maybe even a little bit “cooling”).
“Hot, Dry Summer: Is it Bad for Bulbs or Good?” (Aug. 2016),
“Hot Summer = Dahlia Hell” (Aug. 2012),
“Got Drought? Bulbs Are Built for It” (Aug. 2011),
“High Heat Stresses Your Bulbs, Too” (Aug. 2010). (July 2018)
Warmer than usual winters can cause all sorts of problems for plants, including bearded iris. In a recent post at the AIS blog, World of Irises, Bonnie Nichols of zone-8a Dallas explains:
“In December [last year] when the Christmas Day temperature was 82 degrees . . . , we knew the iris bloom season was in jeopardy. And, it didn’t get better when on January 31 the high was 79 degrees.
“When I saw various bearded irises blooming in December and January, I asked friends if they thought it was rebloom or what would have been our spring bloom. We all had no idea. In April, we knew [it] was the ‘spring’ bloom because we . . . had no additional bloom. Maybe 20% of tall bearded irises bloomed. . . .
“We saw more than normal increases on some of the plants because they did not use their energy to bloom. On other plants we noticed something that we had not had much experience with – ‘lightbulb’ rhizomes. Lightbulbs are rhizomes with no increases and the roots wither away. . . . The rhizome increases in size and twists slightly as if it is pushed out of the ground. [If it blooms] the stalk comes up in the middle of the fan and dies back quickly. The rhizome eventually dries up and dies also. . . .”
Commenting on Bonnie’s post, Phil Williams offered an alternative explanation: “Strong root growth is what produces good spring bloom here. Makes me wonder if the prolonged heat [in summer and fall] might have created a false dormancy . . . , and the plants did not root deeply.”
Either way, warmer temperatures are the culprit. Is that global warming? Bonnie says she’s not sure but “I’m beginning to believe it is.” (Dec. 2017)
But wouldn’t it be great if ALL glads were that hardy? A recent article in the NAGC journal Glad World makes me think that might just be possible.
In his always excellent “Talk Radio” column, Cliff Hartline says that glad grower Bert Blanton “is noted for NOT digging his glads yearly,” even though he lives in zone-6b Missouri. Bert used to protect his glads in winter with a thick mulch of straw, but he says it “always blew around and I was constantly replacing it.”
So three years ago he tried landscape cloth instead, and it worked so well that he’s been using it ever since.
“I plant my rows six feet apart,” he says, “and cover my aisles and rows with landscape cloth, putting the seams right over the rows.” He pegs it down with wire landscape-cloth pins (also called sod staples), and then rolls it back in the spring.
The only problem? After three years of no digging, “I now have jillions of flowers,” Bert says. “I have about 20 spikes to a foot, and the rows have expanded themselves to 15 inches wide. I am getting so many spikes, it is more than I can sell at the Farmers Market or give away. My spikes are larger than anyone else’s, so I sell them for $2.00 each.”
We’re going to experiment with Bert’s technique this winter, even though our gardens are half a zone colder than his. If you try it, too, please let us know how it works for you and we’ll share our results here. (Oct. 2016)
It’s been a hot, dry summer in much of the US. In fact, it’s been so bad in Maine that we had to drop a whole page of rare glads from our catalog because our grower there is worried he won’t have any corms to share with us!
But how will it affect your bulbs? First some good news:
Bulbs are one of Nature’s clever survival strategies. They’re essentially underground bunkers where the plant can stay cool and store moisture. And once the weather improves, bulbs often bounce back better than most plants.
Some bulbs even prefer dry summers. Tulips and hyacinths, for example, evolved in parts of the world with little to no summer rainfall. That means yours may bloom better next spring than they usually do – at least if you’re in the eastern half of the country where normal summers are rainier.
And some bulbs like it hot. As long as you’ve kept them well watered, your tuberoses, rain lilies, crinums, and cannas are probably thriving this summer, and we hope you’re enjoying them!
On the other hand, dahlias often struggle or fail in hot summers. That’s because they’re native to the highlands of Mexico where days can be hot but nights are much cooler. When nights in your garden stay warm, growth will slow or stop and they may even die. If you water them too much when growth has stalled, they may rot underground.
Don’t despair, though! If you can just keep your dahlias limping along until temperatures cool, they’ll kick back into gear and bloom gloriously until frost. And for dahlias that can handle warm nights better, look for “heat-tolerant” in our descriptions – although even these have their limits.
Glads in hot summers can be attacked by tiny, almost invisible sucking insects called thrips. Thrips proliferate when it’s hot and can leave glad leaves and blossoms mottled, or even prevent buds from opening. For tips on control, see oldhousegardens.com/Thrips.
Glads may also develop kinked stems in hot weather, as they sag a bit during the day and then grow upright at night when evaporation slows. To minimize the kinks, keep your glads well-watered and avoid damaging their shallow, wide-spreading roots.
High heat also affects flower colors. Deep-colored lilies such as ‘African Queen’ may be paler, bicolor dahlias such as ‘Deuil du Roi Albert‘ may bloom temporarily as solids, and the rosy tones of ‘Kaiser Wilhelm‘ and others won’t develop fully until the weather cools.
This fall is expected to be warmer and drier than usual, too. Since most spring-blooming bulbs start growing new roots in late summer or early fall, keep their soil reasonably moist then, and be sure to keep the bulbs you plant this fall especially well-watered.
And try not to worry. Bulbs have been dealing with challenging weather for millennia. And there’s always next year – which, as every gardener knows, is one of the great things about gardening. (Aug. 2016)
Like most gardeners, I’m a big fan of rain. But until I read a short article in the Ann Arbor News recently, I had no idea that lightning itself is also good for my garden.
“Lightning is nature’s greatest fertilizer,” writes meteorologist Mark Torregrossa. “The air around us is 78% nitrogen. Nitrogen is the main nutrient in most fertilizers. But the nitrogen in the air is not usable by plants, until lightning strikes through it. Once the air is heated by lightning, two [atoms] of nitrogen are split apart. The single [atom] of nitrogen then joins with oxygen or hydrogen and is rained into the soil. Now it’s usable by plants. A lightning storm applies more nitrogen on lawns and crops than we could ever afford to buy.”
With Google’s help, I learned that lightning can briefly heat the air it passes through to 50,000 degrees F, almost ten times hotter than the surface of the sun. That enormous energy breaks up the nitrogen (N2), freeing the atoms to recombine into nitrate (NO3), ammonia (NH3), and ammonium (NH4). The latter two are also produced by nitrogen-fixing bacteria in the roots of the enormous Fabacaea or legume family, but some scientists believe that lightning is responsible for as much as 50% of the nitrogen available to plants.
Although this may never convince Toby our rat terrier that lightning is a good thing, the next time a boom of thunder makes me jump I’m going to be happy for my garden. (May 2016)
“My bulbs are already coming up! What should I do?” We’ve been hearing that from a lot of customers recently.
The good news is that most plants are tougher than you might think, and they’ve been evolving to cope with erratic weather for millennia.
Most fall-planted bulbs, for example, require a certain number of hours below 40 degrees or so in order to produce enough gibberellic acid to allow the leaves and flower stems to lengthen normally — which means most foliage won’t emerge very far above ground this early. And most bulb foliage and even flowers can take freezing in stride. When temperatures drop below 15 degrees or so, any foliage that’s above ground may be killed, but whatever is still underground will be unharmed and continue growing normally in the spring.
On the other hand, there’s not much you can do to protect your plants from the weather.
You could scatter a layer of loose straw, hay, or evergreen branches over any foliage that has emerged. This will help protect it from the drying effects of winter sun and wind, and prevent the ground from repeatedly freezing and thawing which can damage roots.
You can find other helpful information in the Weather and Hardiness section of our Newsletter Archives, or check out “How Will This Mild Weather Affect Our Plants” at Larry Hodgson’s Laidback Gardener blog.
Other than that, we suggest you just relax, accept that Nature is a lot more powerful than we are, have faith in the resiliency of plants – and maybe make a New Year’s resolution to do something more this year to be good to the Earth. (Jan. 2016)
Although winter is rarely a gardener’s favorite season, in A Gentle Plea for Chaos Mirabel Osler encourages us to embrace its enforced stillness:
“When the ice of winter holds the house in its rigid grip, when curtains are drawn early against the vast frozen waste of landscape, almost like a hibernating hedgehog I relish the security of being withdrawn from all that summer ferment that is long since past. Then is the time for reappraisal: to spread out, limp and receptive, and let garden thoughts rise to the surface. They emerge from some deep source of stillness which the very fact of winter has released.” (Jan. 2015)
Congratulations to our friends in California who, faced with what’s been called the drought of a lifetime, have cut their water use by 28% in the first three months of state-mandated reductions.
In September, my wife and I saw the drought first-hand while visiting our son and daughter-in-law in San Francisco. Plants drooped, dead leaves littered the sidewalks, and lawns in the city’s parks sported signs proclaiming “Brown is the New Green.”
It’s no wonder our orders from California are down 25% this fall! But bulbs, ironically, are built for drought. Many have evolved in areas where summers are so dry that to survive they have to hide out underground. Tulips, hyacinths, alliums, Byzantine glads, freesia, and oxblood lilies, among others, actually do better with dry summers — although they need some water in fall through winter to develop roots and more in spring to grow leaves and bloom.
In August the Pacific Horticulture Society newsletter offered some excellent tips for xeric gardening, by editor (and OHG customer) Lorene Edwards Forkner:
“Recently I read some great, if somewhat blithe, advice from garden writer Amy Stewart on tending a low/no water garden:
“1. Plant drought tolerant plants.
“2. Wait and see what dies.
“3. Plant more of what didn’t die.
“You can read the entire piece at The No-Water California Garden.
Lorene also recommended “Adventures in Growing” about an American woman “creating a fertile landscape in Saudi Arabia and winning the hearts and minds of its caretakers,” this advice from “the great minds at Flora Grubb Gardens,” and Jeff Moore on the “Generosity of Succulents.”
“Then hit those fall sales,” she concluded, “for a dose of colorful, graphic, and resilient plants that take dry weather in stride” — including our fall-planted bulbs! (Oct. 2015)
Thanks to all of you who responded to our query about growing pink surprise lilies, Lycoris squamigera, outside of the narrow range we’d been recommending for them. You gave us lots of great feedback, and here’s the short version of what we learned.
ZONES — Many readers told us they’ve had long-term success with surprise lilies in zones 5b and 8a, and for the past couple of years we’ve been getting our bulbs from a third-generation bulb farm in 8a, so we’ve now expanded our zone recommendations to include zones 5b-8a(8bWC).
SOIL — Although well-drained soils are usually recommended for surprise lilies, several readers say theirs grow just fine in clay soil. Clay is dense, though, which makes it harder for bulbs to multiply, and it holds water longer which can cause bulbs to rot.
WATER — Many readers say they never water their surprise lilies, and that may be a good thing. Like most bulbs, they do best when they’re relatively dry during their summer dormancy. Since many of us water our gardens then, this could be one reason they’re often found surviving in lawns and “neglected” areas that get less watering — though of course they do need water when they’re not dormant, from fall through the end of spring.
SUN/SHADE — Full sun seems to suit them best, especially the further north they’re planted. But many of our readers said they do well in partial shade, too, especially if it’s from deciduous trees which leaf out later.
PLANTING DEPTH — Some authorities say to plant them with the neck just under the soil surface, but our expert North Carolina grower recommends planting them so they’re covered with 2-4 inches of soil. Since the bulbs we ship are 3-4 inches tall, that means planting them with the base 5-8 inches deep.
LONG WAIT FOR BLOOM — If you dig them from a neighbor’s yard you probably won’t have this problem, but if you plant dry, dormant bulbs you’ll have to be patient. Although most will put up leaves their first spring, sometimes nothing emerges until the spring after that, and they virtually never bloom until their second or even third year.
Thanks again to everyone who helped us “crowd-source” this article! For the longer version, including quotes from customers growing them everywhere from zone-3 Saskatchewan to zone-9 Florida, see our More About Surprise Lilies page. (late Sept. 2014)
It’s been a grueling winter this year, with record drought in California and extreme cold and snow throughout much of the rest of the country. (According to the National Weather Service’s new “Accumulated Winter Season Severity Index,” here in the Detroit area it’s been the worst since 1950.) Of course heirloom plants have been taking extreme weather in stride for decades if not centuries, but — leaving aside drought for a future article — let’s take a look at some of the factors that determine how much the cold and snow will affect your plants.
How COLD It Got — Of course the colder it gets, the more damage it causes to a wider variety of plants. That’s why average minimum low temperatures are the basis for the USDA hardiness zones. But there’s more to it than that.
How SUDDENLY the Cold Arrived — As winter approaches, plants go through a series of bio-chemical changes that prepare them to survive the cold. However, if the cold comes on suddenly, instead after a long period of slowly dropping temperatures, plants that would normally take it in stride can be killed outright.
How LONG the Cold Lasted — One night of extreme cold may only injure a plant, especially in warmer parts of the country, but if temperatures stay that low for two or three days the damage may be so great that the plant will never recover. In colder areas, the longer the weather stays cold, the deeper the ground will freeze — and the colder it will get down there — which can result in the death of plants that, with a more normal mix of up and down temperatures, would usually survive.
How BARE the Soil Was — Like a down comforter, snow traps air which makes it a great insulator. In fact, according to our friend Dan who runs a local cemetery, the one to three feet of snow that we’ve had on the ground here pretty much all winter has insulated the soil so well that it’s virtually frost-free — which makes grave-digging easy — except near roads, paths, and other areas where his crew has cleared the snow. Snow also protects bare soil from the cycle of freezing and thawing that occurs when sunny days are followed by much colder nights, and which can break roots and heave new plants out of the ground. Of course wet, heavy snow can wreak havoc on the branches of trees and shrubs, but most of the time, where winters are cold, snow is a good thing.
How WELL-ESTABLISHED Your Plants Are — Plants that are recently-planted are always more vulnerable to the cold, mainly because they’ve had less time to establish an extensive root system to anchor and hydrate them. That includes woody plants and perennials you planted anytime last year, and especially bulbs and other plants that you planted last fall.
How HARDY Your Plants Are — If you enjoy stretching your hardiness zone and experimenting with plants that are only marginally hardy in your area, you can expect more losses than if you’re a more conservative gardener. The way we figure it, though, a plant that brings us years of pleasure is worth the investment, even if an extreme winter every now and then kills it and we have to replant it. It may also be comforting to remember that all of our tulips, lilies, crocus, and many of our fall-planted diverse bulbs, if well-established, are recommended for zone 5 with its ten-year-average lows of minus 20 F, and many will be fine in zone 4 or even zone 3 with lows to 40 below — and with good snow cover to insulate them they’ll take even lower temperatures in stride.
Severe winters have their SILVER LININGS, too. Deep cold kills insect pests, heavy snow replenishes soil moisture, and — although most of your plants will be just fine this spring — the few that don’t make it will give you more room to plant new ones. (March 2014)
“Why didn’t my buds open?” That’s a question we heard a lot more than usual this spring. When buds form but fail to develop into flowers it’s called “blasting.” This usually happens because the plant didn’t get what it needed, and first-year plants with immature root systems are most at risk.
Too Little Water — Spring-blooming bulbs such as daffodils and tulips need plenty of water (a) in the fall to grow roots and (b) in the spring to grow leaves and buds that open successfully. If there’s a stretch of dry weather in the fall, initial root growth will be hampered and the bulb may never catch up. The same thing canhappen when there’s a stretch of dry weather in spring. Either way, once the rush of spring growth begins above ground, a bulb without plenty of roots may manage to develop foliage and buds, but if it can’t draw up enough water fast enough, those buds will blast.
New Bulbs and Late Planting — Inadequate root development is more often a problem for newly planted bulbs, and even more so for bulbs that are planted late in the fall.
High Temperatures— When spring heats up or temperatures spike, even bulbs with good root systems can struggle to supply their buds with enough water to make up for what’s being lost through transpiration. When they can’t, the buds blast. Late-blooming varieties are most at risk, as well as bulbs planted in hot spots.
Too Little Sun — Sun-loving plants such as marigolds and peonies won’t bloom well in the shade, and the same is true of sun-loving bulbs. If they can’t photosynthesize enough to fully develop their buds, they’ll blast.
Storage Problems— Dormant bulbs should be stored at temperatures above freezing but cooler than 72 degrees or so, and protected from ethylene gas which is contained in automobile exhaust fumes and produced by ripening fruit.
Doubles, Etc. — To develop their many extra petals, double flowers require more moisture and sunlight, which means they blast more easily. Pheasant’s-eye narcissus do, too — and especially double pheasant’s-eyes — because their roots develop slowly and they bloom late when spring is at its warmest.
Solutions — In most cases — and especially for newly planted bulbs — the most important thing you can do is keep your bulbs well watered from early fall, when they start growing new roots, until a couple of weeks before the ground freezes solid (or all winter if it doesn’t), and then again in the spring while they’re busy producing leaves and flowers. If you do that, and Mother Nature is kind, you can expect to have very few blasted buds and lots of beautiful spring flowers. (June 2013)
The blistering weather that ravaged Texas and Oklahoma last summer was just the tip of the (melting) iceberg, it seems, as this year more than half of the country is suffering from record-breaking heat and drought. Farmers, of course, have the most on the line and our hearts go out to them, but it hasn’t been much fun for gardeners this summer either.
Our dahlias have been especially hard hit — and we bet yours have, too. Some in our trial garden never emerged, others sprouted but died no matter how much we watered, and the rest are less than half the size they usually are by now (a couple are barely a foot tall!) and none of them have many blooms. The problem is that dahlias are native to the high-altitude plateaus of Mexico where days are hot but nights are dramatically cooler. When nights stay warm, it’s as if they can’t breathe well and they almost seem to go into suspended animation, growing very slowly or not at all. Some varieties handle warm summer nights better than others, such as those we recommend at our “Dahlias for Hot Nights” page, but even they have their limits.
The good news is (a) you’re not depending on dahlias to feed your family through the winter, (b) as fall approaches and temperatures start to cool, the ones that are still alive should kick back into gear and bloom until killing frost, and (c) there’s always next year — which, as every gardener knows, is one of the great things about gardening. (August 2012)
“Call it spring’s fever,” wrote Seth Borenstein in a recent Associated Press article that confirmed what many gardeners already suspected. “Federal records show the US just finished its hottest spring on record. March, April, and May in the lower 48 states beat the warmest spring temperature record by a full 2 degrees. The three months averaged 57.1 degrees, more than 5 degrees above average. That’s the most above normal for any US season on record. . . . The National Oceanic and Atmospheric Administration also reported that it was the second warmest May since records began in 1895. May averaged 64.3 degrees, just behind 1934.”
And it wasn’t only spring. “The first five months of 2012 were the hottest start to a year in US weather record history. The 12-month period starting last June is also the hottest on record.” Whew!
It’s hard to predict all of the ways that this extreme weather will affect plants. Our good friend Art Tucker of the University of Delaware, for example, wrote us in surprise: “This spring was one of the driest and hottest on record for Delaware. About 50% of my established peonies refused to emerge and those that have emerged have prolific botrytis, which I have only occasionally noticed here and there in the past. Why botrytis now, after the driest spring on record? I thought botrytis was fostered by moist weather???”
Tulips have also been impacted, especially in zone-7 gardens in the East and Southeast where temperatures last winter were more like those of zone 8. Tulips and many other spring-blooming bulbs need a certain number of hours below about 48 degrees F to develop the gibberellic acid that allows their bloom-stems to lengthen and emerge from the soil — which is why gardeners in zone 8 typically pre-chill tulips for 8-12 weeks before planting. Without that, tulips will bloom on very short stems or even attempt to open their flowers underground.
Gardeners should expect to see long-term effects, too. In many areas, for example, the warm, dry spring pushed bulbs into dormancy earlier than usual, giving the plants less time to photosynthesize and bulk up — which could mean diminished bloom next spring. So stay tuned, and keep your green thumbs crossed. (June 2012)
Warmer, colder, wetter, drier — weird weather seems to have been the norm this winter. Of course heirloom plants have been taking weird weather in stride for decades if not centuries, but here’s how it may affect your plants this spring.
WARMER? Mild winters allow the eggs of iris borers and spores of fungal diseases to over-winter more successfully, so it’s especially important to remove all of last year’s peony foliage and clean up around your iris before temperatures warm any further. If you mulched your peonies with straw or leaves last fall, loosen the mulch now and make sure it’s not starting to mold.
NO SNOW? Like a down comforter, snow traps air which makes it a great insulator. If your winter was short on snow, your bulbs and newly planted perennials such as peonies may have gotten a lot colder than usual, which could result in dead or weakened plants this spring.
Snow also protects the soil from the freeze-thaw cycle that occurs when sunny days are followed by much colder nights. Freezing and thawing can break bulb roots and heave newly planted perennials out of the ground. Check now and re-set any plant that’s been heaved, putting a brick or rock on either side to anchor it. In colder zones you might even want to add a light straw mulch now to protect your plants through the last weeks of winter when the freeze-thaw cycle is often at its worst.
When snow melts, it recharges soil moisture which is especially important to the mad rush of spring growth. If snowfall was skimpy in your area, water your bulbs and perennials as soon as they emerge this spring instead of waiting till later on.
MORE RAIN? If your winter — or fall — was wetter than usual, that may lead to better bloom on your daffodils this spring, but it could be hard on other bulbs. The freeze-thaw cycle is most damaging in water-logged soils, and some bulbs such as crocosmia always do best in very well-drained winter soils. Soggy soils are never good for iris or peonies, so if water puddles around yours this spring, drain it away to avoid rot.
DROUGHT? Bulbs are built to conserve moisture during dry periods and often bounce back after a drought better than most plants, although it may take a while for them to recover completely. Some bulbs like tulips and hyacinths actually bloom better after a dry summer, but even they will suffer without good moisture through fall and winter.
No matter how weird your winter was, paying attention to how your plants respond will make you a better gardener. And try not to worry. Most of the time, most plants will be just fine — and on the bright side, dead plants give you more room for new ones! (March 2012)
Big news! The new hardiness zones map that the USDA has been working on for over a decade has finally been released. It’s based on newer and much more extensive data as well as sophisticated mapping algorithms. Although the USDA claims that the new zones aren’t much different than the old ones, we think you’ll find that they’re similar to the zones on the Arbor Day map which we’ve been using for years. In other words, a lot of people are going to find that their gardens are a half-zone warmer than they used to be — and that means they can grow a lot of plants they never thought they could.
To check out your new zone, simply enter your zip code (and the site’s case-sensitive security code) at http://planthardiness.ars.usda.gov/PHZMWeb/. Then for a list of all the exciting bulbs you can grow in your new zone, use our easy, awesome Heirloom Bulb Search. (Feb. 2012)
Though it was cooler than usual in Oregon and Washington, much of the country suffered through punishing heat this past summer. In fact, according to USA Today, 2011 was the country’s “hottest summer in 75 years and the second-hottest summer on record” — topped only by the Dust Bowl year of 1934. Texas and Oklahoma were hardest hit. Their averages of 86.8 and 86.5 degrees — based on the entire 24-hour cycle, not just daily highs — were the hottest ever recorded for any state.
Texas also suffered through its driest summer on record, and drought continues to be a problem in a third of the contiguous states. Parts of the East, on the other hand, were inundated with rain, and California had its wettest summer ever. Read the entire article here. (Sept. 2011)
Our condolences to you if you’re one of the millions of gardeners suffering through the drought that’s afflicted huge swaths of the country this summer. (And our hearts go out to the farmers who are already facing billions of dollars in losses.) It may be small consolation, but bulbs are one of Nature’s clever ways for hanging on to a back-up supply of moisture, safe underground, and surviving when there’s no rain for days and days on end. They have their limits, of course, but when the drought finally breaks, you’ll probably find that your bulbs recover better than most plants. Here’s hoping that’s soon. (Aug. 2011)
Most bulbs are easy to grow, and of course we guarantee everything we sell 100%. But sometimes even the best bulbs don’t bloom well. If that ever happens in your garden, it might be because:
1. Leaves removed too early. (To multiply and recharge for future bloom, bulbs need to photosynthesize. The more the better, so leave foliage alone until it yellows.)
2. Planted too late. (Bulbs need to establish good roots before the ground freezes. Bulbs stored too long, especially small ones, may dry out so much they struggle or fail.)
3. Fall was too dry. (Good root growth in the fall is essential for good bloom in the spring, and roots can’t grow well in dry soil.)
4. Too much shade. (Most bulbs need plenty of sun, more the further north you garden. As nearby trees and other plants grow, once sunny areas may become too shady for bulbs.)
5. Soil too wet. (In heavy, clay, or water-logged soils, many bulbs struggle or rot. Plant in sandy to average soils, improve heavy soils with organic matter, or plant in raised beds. Even average soils can be too damp for some bulbs during their summer dormancy. This is especially true for tulips in the rainier eastern half of the country and in gardens that are regularly watered.)
6. Over-crowded. (As bulbs multiply they can become so congested that they’re starved for moisture and nutrients. Gently dig and divide.)
7. Too small. (You’ll never have this problem with our bulbs, but under-sized bulbs are widely sold. In difficult conditions, even the best bulbs can dwindle until they’re too small to bloom.)
8. Wrong climate. (Both winters and summers can be too cold or too warm, too wet or too dry, depending on the type of bulb. Tulips, for example, need a certain number of winter hours below a certain temperature or they won’t bloom, and they rebloom best where summers are dry.)
9. Under-fed or over-fed. (Bulbs can starve in nutrient-poor soils, but over-rich soils cause problems, too. Too much nitrogen, for example, spurs leaf growth at the expense of flowering. Let a soil test guide you.)
10. Animals, insects, or diseases. (Burrowing rodents and daffodil flies can eat bulbs, leaving little trace, while other pests attack their flowers and foliage. Learn more here.)
Whew! The good news is that most bulbs are tough and adaptable. And once you understand what they need, it’s even easier to keep them blooming gloriously year after year. (April 2011)
Our customers are continuing to report success in over-wintering their glads outside. Daniel Ostenberg, for example, emailed us this past August:
“I live near Naples, Idaho, 35 miles south of Canada. It’s zone 5. I forgot an ‘Atom’ glad two winters ago while digging the rest of them and it came up the next spring. We did have good snow cover that winter and it wasn’t cold long before it snowed. I do have a neighbor nearby who mulches her glads every fall with six inches of straw and never digs them and she says they do fine. [Idaho’s relatively dry weather and well-drained, alkaline soils probably play a role in this success, too.]
“Also I saved some little bulblets from my ‘Atom’ last fall and planted them this spring in a container and four out of five of them are blooming. I didn’t think they would bloom the first year.
“One of the best gardeners I know told me that glads love calcium nitrate but she couldn’t find any. I’m an ex-apple farmer from the East Washington apple country, and I always get calcium nitrate from the ag-supply companies in apple country. I use it on my glads and get it for her for the 1000 glads that she grows. Orchardists use a lot of calcium nitrate. Trees love it.
“I’m going to leave one each of a few other kinds of glads in the ground this fall and mulch them heavily with straw and see what happens. I’ll let you know next summer how it turns out.” (Dec. 2010)
Although most experts say gladiolus won’t survive winters north of zone 8, our customers kept telling us that theirs were returning like perennials in zones 7, 6, and even 5. So we asked our readers, “Have your regular glads survived zone-6 or colder winters? And what do you think made that possible?” Many replied (thanks!), and now you can read what they said along with our conclusions at oldhousegardens.com/HardyGlads.
Although warmer, shorter winters are probably the biggest reason why so many glads are surviving in colder zones, other important factors seem to include reliable snow cover, winter mulch, deep planting, good drainage, micro-climates, plenty of sun, and the time-tested vigor of heirlooms. To add your two-cents to the discussion, email firstname.lastname@example.org. And if you’d like to experiment with glads as perennials in your own garden, we suggest starting with the tough little one our readers recommended most: ‘Atom’. (August 2010)
High heat has plagued much of the country this summer. Some bulbs like it, but others suffer. Dahlias, for example, have struggled or failed in many gardens where they usually thrive. That’s because they come originally from the mountain plateaus of Mexico where days are hot but nights are dramatically cooler. When nights are too warm, dahlias just can’t grow well. Some varieties are more sensitive than others and can even die. The good news is that if you can keep them going till temperatures cool (which has to happen sometime, right?), they’ll kick back into gear and bloom gloriously till frost.
Glads may develop kinked stems in unusually hot weather as they sag a bit during the day, unable to fully replenish the water evaporating from them, and then grow upright at night when evaporation slows. This is most often a problem with glads like ‘Atom’ that have thin, wiry stems. To help, keep your glads well-watered and protect their shallow, wide-spreading roots from disturbance. Tiny sucking insects called thrips proliferate when it’s hot, too, and can leave glad leaves and blossoms mottled, or even prevent buds from opening. For tips on control, see oldhousegardens.com/Thrips.asp
Heat affects flower color, too. Deep-colored lilies such as ‘African Queen’ may be paler in high heat, bicolor dahlias such as ‘Deuil du Roi Albert‘ may bloom temporarily as solids, and the rosy tones of ‘Kaiser Wilhelm‘ and others won’t develop fully until the weather cools.
Of course some bulbs love the heat. In many gardens this summer, cannas, tuberoses, and rain lilies have been especially happy — and we hope you’ve been enjoying them. (August 2010)
It’s official. According to the National Oceanic and Atmospheric Administration, this past June was the hottest ever recorded. TIME magazine reports that "The combined global land and ocean temperature was 1.22 degrees F above the 20th century average." Temperatures in March, April, and May were also the hottest ever recorded, and "2010 is well on its way to becoming the warmest year worldwide since 1880, the earliest date for which global data is available." (July 2010)
A brief note in the current April issue of Garden Gate magazine tells of a new development that could have North Dakota gardeners growing cannas year-round:
“Scientists at Miami University and the University of Alabama have developed a spray called Freeze-Pruf which improves a plant’s cold tolerance by 2.2 to 9.4 degrees F, depending on the species. This solution works kind of like antifreeze by lowering the level at which a plant’s tissue is damaged by cold. . . . [It also] prevents ice crystals from forming in a way that damages plant cells. It’s been used successfully on palms, house plants, bananas, citrus plants, and a variety of flowers, . . . [and] it’s safe for vegetables, too. Spray Freeze-Pruf once in the fall, right before a freeze, to extend your tomato [or dahlia!] season. Or improve your temperature zone by about 200 miles for your favorite banana. . . . Developers expect to have Freeze-Pruf available for purchase within the year.” (Apr. 2009)
Last winter when we wrote that hardy bulbs are rarely bothered by mid-winter thaws, our good customer Bonnie Dean of Minnesota offered a different perspective:
“I live in Minneapolis. Occasionally we get a week of spring-like weather in February, once as high as 76 degrees. The bulbs are fooled — up they come! By the time the shoots are about 3 inches high, the usual teens to twenties temperatures come back and stay for weeks. In those situations, the plants do die. Or they end up blighted and stunted, taking years to recover, if at all.
“But I found a way to circumvent this. Each year when I pack away the Christmas decorations, I make sure a few strings of the small lights are kept accessible. Then, when a prolonged mid-winter thaw is followed by even more hard, hard cold, I get out the lights. I plug them into the outside outlet and string them along the ground, around and between but not touching the emerging daffodils and tulips. (I am careful to remove dead leaves on the ground so there is nothing flammable near the lights.)
“Then, using old pizza boxes or whatever cardboard I have on hand, I make long low ‘tents’ over the plants and lights. Over that, to keep out the wind and keep in the warmth, I put old blankets, worn out bathroom rugs, frayed towels, whatever — even old painting tarps. I keep the lights plugged in until the temperature approaches 32 degrees more consistently, as long as it takes.
“The little bit of warmth from the bulbs keeps the soil just warm enough to keep the tender shoots alive. So, instead of shriveling in the hard winter, the shoots hold their own and even grow a bit. As a result, I have the most showy, prolific and early daffodils in the neighborhood. Some years, I have had the ONLY daffodils in the neighborhood!
“Please share this idea with your readers. Here in Minnesota, even hardy bulbs can lose their zip when the weather fluctuates as much as it does these days.” (Dec. 2008)
Our usual high in mid-January is 30 degrees, but tomorrow it’s supposed to reach 50 here and some of our bulbs think it’s already spring. Are we concerned? Not at all, and if your bulb foliage emerges earlier than you think it should, you generally don’t need to worry either. Bulbs have been around for eons and they’re built for unpredictable weather. Even when it snows on tulips and other hardy bulbs in bloom, they’re rarely damaged, and emerging foliage is even tougher. So relax and have faith in Mother Nature. (Jan. 2006)
The first killing frost does NOT mean you have to rush and get your bulbs planted. Soil cools down much more slowly than the air, and it’s usually weeks after the first killing frost before it’s ideal for planting most bulbs. Here on the border of zones 5 and 6, for example, we routinely plant until Thanksgiving, though we often have a killing frost in early October. So relax. You’ve got plenty of time. (Sept. 2005)
The thermometer hit a record high of 85 here this past Sunday, 25 degrees above normal, and we bet you’ve had some sizzling days this spring, too.
High heat affects bulbs in many ways. It rushes them into bloom, which is fun, but it rushes them right out of bloom, too. Hyacinths that might last a week or two in cooler temperatures topple in a couple of days. It may also keep bulbs from reaching their normal height, especially first-year bulbs with under-developed root systems. The rims of daffodil cups or tulip petals may wither to a crisp, and normally jewel-like colors may fade.
If the heat persists too long, bulbs may think summer is coming and head into dormancy before they’ve fully recharged themselves. This is one reason the Dutch excel at bulb-growing. Spring there stays cool a long time, giving bulbs plenty of time to bulk up for the future.
Though you can’t air-condition your garden, you can help your bulbs by keeping them well-watered when it gets too warm. And try not to worry. Bulbs have been dealing with erratic spring weather for millennia. (April 2004)
Our condolences to our friends in the Northeast as they struggle with record cold! Yes, you can expect some losses, especially among newly-planted bulbs. The colder the weather is, the longer it lasts, and the barer the ground is, the deeper the soil will freeze. We’ve had bulbs survive 20 degrees below zero here for one night with a foot of snow blanketing them that years later were killed by temps that never got below zero but that simply lasted for an unusually long time.
Though heart-breaking, winter losses open up new opportunities for the gardener. And hopefully you’ll lose less than you might expect. All of our tulips, lilies, crocus, and many of our diverse treasures, if well-established, are recommended for zone 5 with its ten-year-average lows of minus 20 F, and many will be fine in zone 4 — or even zone 3 at 40 below! Remember plants have been facing brutal, unpredictable weather for eons, and no matter what, spring WILL be beautiful. (Jan. 2004)
Joss Moroney of Boston writes: “I use the brick wall of my house that faces south to plant the really tender stuff. The east wall works well, too. I wintered over ‘Bishop of Llandaff’ last winter by mistake, and I always winter over my glads. Planting things deeply helps, and I also mulch carefully. I get bags of leaves from my neighbors in the fall. At the solstice I get Christmas tree branches from a nearby vendor and fling those over the leaves to hold them in place. Then I pray for snow!”
Kathy Hill of Dallas seconds that advice: “We’re in zone 8a but I have successfully grown several zone-9 plants. I plant them close to the house where they get heat from the bricks plus protection from the wind. But the major thing I do to stretch my zone is mulch, mulch, mulch. I add three inches or more of cedar mulch in the fall before it gets cold, and I believe that does more to stretch my zone than anything.”
Bev Youngs of zone-4 Sault Ste. Marie, MI, praises a different mulch: “Our first winters here were pretty “normal” — about 100 inches of snow. The last two years have been pretty mild. This year, in fact, I’ve been shoveling snow onto bare spots in the garden because the snow cover is what protects those plants I have that are on the zone edges — crocosmia, for example, and even zone-6 ‘St. Brigid’ anemones. I’ve learned to pay close attention to cultural instructions, too. Healthy plants survive the cold better.” (Feb 2003)
If you haven’t seen rain in way too long, one bit of good news is that bulbs are built for drought and most of yours should be fine. Some, like tulips and hyacinths, may even perform better than ever next spring, since they prefer dry summers — as in their ancestral homelands.
Even tulips and hyacinths, though, need good moisture while in growth — from fall till six weeks after bloom — so be sure they get that or their performance will suffer. Newly-planted bulbs are especially vulnerable.
Cannas and elephant ears like LOTS of water. In our trial gardens here we build a ring of soil around each plant and fill it with water every day or two, or we set pots of them in saucers kept full of water. Regular fertilizing helps these heavy feeders, too. (Sept. 2002)