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Ask the Gardener: Tips to help your irises thrive (Hint: Sun!)

Ask the Expert Gardening
A bearded iris at Tranquil Lake Nursery in Rehoboth photographed in 2001.
A bearded iris at Tranquil Lake Nursery in Rehoboth photographed in 2001. Globe/file

What to do this week Enjoy the June garden in all its glory. Harvest vegetables and flowers in the cool of the morning or early evening when they are most hydrated. If you harvest leaf lettuce by picking the outside leaves as needed, the center leaves will continue to grow. Finish up planting annuals, perennials, and vegetables. Sow sweet corn, summer squash, carrots, and bush beans. Erect scaffolding like tomato cages for plants that need support before it is too late. Remove suckers from tomato plants. Pull weeds before they go to seed. Plant native trees and shrubs to support our declining bird population. Parent birds are frantically scouring your yard now for caterpillars to feed their nestlings, so don’t use insect sprays. Keep cats indoors this month while fledgling birds are learning to fly. Cut off spent flowers and foliage to keep the garden neat, discourage disease, and encourage rebloom. Buy an inexpensive rain gauge so you know whether your garden has gotten its weekly inch of rain. The early morning is the best time to water, so the leaves can dry in the sun. When it gets hot, reduce you mowing frequency and let your grass grow to 3 inches to shade the soil and conserve moisture.

Q. I have a new home with gorgeous irises growing in the shadow of a large tree. Any advice on the best way to move and replant these beauties? Or should I leave well enough alone?

M.D., Warwick, R.I.

A. There are many kinds of irises, but nearly all of them need full sun to bloom well. Flamboyant bearded irises like to bake in the summer in a hot, dry spot. As with many perennials, iris can be safely moved soon after blooming, so this is a good time to do it. First dig a bag of compost into the soil of the new (sunnier) planting bed to enrich it and loosen the texture. Most irises actually like having their roots dug up, pulled apart, and replanted in fresh soil every five years to prevent overcrowding. Pry out the shallow roots with a garden fork. Cut or pull large roots into smaller pieces, each with at least two fans of leaves. Discard roots and leaves that are mushy, diseased, or contain the white grubs called iris borers. Place the pieces 2 feet apart horizontally, barely covering the tops of the roots with soil and making sure the side-sprouting little root hairs are facing downward. Do not mulch them. Iris bloom sparsely the year after dividing, and then better each year after that until they get overcrowded again. There is a saying about newly planted perennials: “The first year they sleep. The second year they creep. The third year they leap.’’

Q. I have azaleas that have not bloomed this year and last. It looks like something is eating the buds and the leaves, just leaving the stems. What is eating my azaleas?

G. E., Wakefield

A. Look for caterpillars. One candidate is the red-headed azalea caterpillar. Pick them off by hand and drown them in soapy water. Sometimes I wear disposable, powder-free nitrile medical gloves, which I order in boxes of 100 online. They are more flexible than regular gardening gloves.

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