MARIANNE BINETTI: Time to divide and conquer your summer bloomers

The end of September is a good time to dig in and move your plants.

  • Monday, September 28, 2009 7:10pm
  • Life

By Marianne Binetti

The end of September is a good time to dig in and move your plants. The cooler weather makes working outdoors more comfortable and fall is the season when trees and shrubs can be moved and added and many summer-blooming perennials – like daylilies, phlox and astilbe – can be divided and shared.

If you have summer-blooming perennials that are past their prime, don’t be shy about cutting them back to ground level and composting their tops. Then decide if they need to be dug up and divided. For perennials like daylilies, phlox, and grasses you can remove the more vigorous side shoots and toss out the dead, dry center of the plant. Replant the side growth into soil that has been improved with compost and you’ll see a whole new attitude next spring.

In the vegetable garden, continue to harvest crops, especially those that could be damaged by frost like tomatoes. You can get green tomatoes to ripen indoors by uprooting the entire tomato plant and hanging it upside down from the rafters of a garage or shed.

Tomatoes do not need sunlight to ripen. Check the blossom end of each green tomato and if you see a dark, green, star-shaped mark, the tomato is mature enough to ripen on its own.

The secret to keeping your tomatoes from rotting is to give them good air circulation once you bring them indoors. Do not allow them to touch one another. Arrange your green tomatoes on a tray or table and harvest them from indoors as they turn red, tossing out any that show brown spots before they pass on their bad habits to the others.

Q. I have some bearded iris that were once good bloomers but over the years I seem to get more foliage than I do flowers. When should I divide my iris and what type of fertilizer do they need? P.L., Longview

A. Fall is for planting and also for dividing perennials like iris. After three or four years most perennials will grow crowded and refuse to bloom as heavily. September is the month to dig them from the ground and break off the young side roots. Iris have knobby roots and you can cut or snap them apart, tossing out the old middle section.

Here’s the secret to happy, blooming iris. Plant them so the roots are just barely below the surface of the soil. Give them a sunny spot with good drainage. Don’t worry about fertilizing at this time but if you want to pamper the plants loosen the soil in the area and cut off all the foliage close to the ground. Removing the foliage of iris now will help prevent over-wintering disease and insects. In April you can fertilize the iris plants as soon as you see fresh sprouts emerging from the ground. Use any slow-release general purpose plant food and prepare to be amazed at the improvement.

Q. I heard you speak at a lecture and someone asked why their peonies were not blooming. All I remember about your answer was that it was your favorite question to be asked. Well, this year my peonies bloomed very little. What is the secret to growing peonies with more flowers? J.O., Enumclaw

A. I love to be asked about making peonies flower because it is such an easy answer. You’ll be humming “This bud’s for you” next spring if you just remove the mulch or soil on top of your peonies so the growth point or eye is just barely below ground level. Over time peonies become buried under soil and mulch and then refuse to bloom as they struggle under the heavy blanket. Late September is also the time of year to cut back your peony foliage to ground level. Removing the foliage now will help prevent peony leaf blight. September and October are also the best months to transplant peonies, but only if you have to. Unlike most perennials, peonies do best if they are allowed to grow undisturbed in the same location for decades.

Q. Help! There are giant mosquitoes flying around my lawn and I think they are crane flies. What do I spray or what can I do to save my lawn and plants? W.T., Tacoma

A. No worries, no spraying. You are seeing the adult version of the cranefly larvae and September is not the time to treat for cranefly. Birds will control the problem better than any spray you can use and cranefly larvae do not start feeding on your grass roots until early spring, when grasses in western Washington grow so fast that they outgrow any cranefly damage. If your lawn is looking weary this month, blame poor drainage, a lack of nutrients, drought or compaction. Remember that all lawns need fertilizer at least once in the fall. Seeing a festival of cranefly should remind you to feed your lawn with a slow-release fall and winter lawn food.

• • •

Marianne Binetti has a degree in horticulture from Washington State University and is the author of “Easy Answers for Great Gardens” and several other books. For book requests or answers to gardening questions, write to her at: P.O. Box 872, Enumclaw, 98022. Send a self-addressed, stamped envelope for a personal reply.

For more gardening information, she can be reached at her Web site,

Copyright for this column

owned by Marianne Binetti.

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