We say this every fall because it’s just so easy, important, and we have new subscribers since last fall (hurray!): For more flowers and healthier plants, give your peonies and iris a simple fall clean-up.
PEONIES – Although relatively care-free, peonies can be afflicted by powdery mildew (pictured here) and other fungal diseases.
To prevent spores from overwintering, cut stems as close to the ground as possible, carefully bagging everything as you go. It’s best to do this earlier rather than later, before the leaves get dry and crumbly – or even as early as August if the foliage has been hard hit.
Disinfect your tools with rubbing alcohol or bleach between plants to avoid spreading disease. Dispose of all clippings in the trash. Do not compost!
If you’ve tried this and still have problems, you may also want to try a fungicidal spray. Mancozeb is one good choice. Drench the ground around the base of the peonies after your fall clean-up, and then spray in spring as soon as sprouts emerge and again every 7-10 days until bloom-time.
IRIS – Fall is also the best time to control iris borers which are a common pest in gardens east of the Rockies.
Borers hatch in spring from eggs laid in the fall on iris leaves and anything similar that’s nearby. To destroy them, simply (a) wait until a hard frost kills the adult moths and then (b) cut back all leaves to a couple of inches and (c) remove, bag, and throw the clippings in the trash along with any nearby debris or mulch. Do not compost!
Fungal diseases such as leaf spot may also afflict iris, and fungicides such as mancozeb can help control them, too. Spray after fall clean-up and once again in early spring.
Healthier plants look better and bloom more – so get out there and give yours a boost!