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Finish cutting back perennials in early April for garden success

Finish cutting back perennials and cleaning up garden debris early in April. Try to avoid working in beds where the soil is wet.

It is best to cut back perennials before they start growing to minimize damage to the new growth. Be careful not to cut or break any new green stems or foliage. They can easily be damaged by vigorous raking. Watch out for any bulbs that have started growing. A leaf blower will work well to clear debris out of beds.

It can be hard to see new growth on ornamental grasses, so be sure to cut them back before consistently warm weather sets in later in the month. If the weather has already warmed up and the grasses are growing, cut the old growth back a few inches above the ground, keeping clear of the new shoots.

I generally let be any tree leaves that fell in my beds during the fall, as I prefer a more natural look and like to save time instead of doing a detailed cleanup.

During most springs, early April is the time to begin uncovering hybrid roses. Delay this task a little if very cold weather in the low 20s is predicted in the coming days.

A bamboo stake works well for gently raking the mulch around a plant. Leave a small amount of mulch at the base for protection, in case of a late hard freeze. A large part of the canes will likely have been killed by winter cold; prune them back to live wood, which in some years may leave only 1 to 2 inches of stem.

It is time to begin spraying crabapples that are susceptible to apple scab. Typically, this fungus disease affects only older varieties. Most newer varieties of crabapple have been selected for resistance to scab.

If you know that your tree's leaves become covered with black spots and fall off in late summer, you need to start a fungicide treatment program. Begin spraying after the buds open, and treat once every seven to 10 days until the leaves are fully open. Generally, three treatments suffice.

The actual date to start these treatments can vary from year to year, as it depends on the weather and the tree's stage of growth. Consult the Plant Information Service of the Chicago Botanic Garden by calling (847) 835-0972 or visiting chicagobotanic.org for recommended fungicides and timing.

The other alternative is to replace the tree with a newer, disease-resistant variety. The Plant Information Service also can advise you on selecting a new tree.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.

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