Cold and snowy weather delayed work in the garden this year, but it is time to finish cutting back perennials and cleaning up garden debris. It is best to cut back perennials before they start growing to avoid damaging the new growth. It is especially important to cut back ornamental grasses early, because it can be hard to see their new growth in the dense clump of last year's stalks. If the weather warms up and the grasses are growing, cut the old stalks off at a few inches above the ground to avoid the new shoots.
The freeze-thaw cycle in spring can push perennials out of the ground, especially if they were planted last fall or summer and did not have time to grow an anchoring root system and if they were not mulched over the winter. Gently press back any plants that have heaved out of the ground back into the soil. There still is a chance of frost heaving in early April.
When you are cleaning up the garden, be careful of any bulbs that may have started growing. I prefer to stay out of the garden when soil conditions are wet to avoid compacting the soil with my weight.
Begin uncovering hybrid roses in early April by carefully removing mulch from around the base. A bamboo stake works well as a tool for this task. Leave a small amount of mulch for protection in case of a late hard freeze. Prune these roses back to live growth. In some years that may mean leaving only 1 to 2 inches of stem.
It is time to begin spraying crabapple trees that are susceptible to apple scab. If your tree's leaves become covered with black spots and fall off in late summer, it suffers from apple scab, a fungal disease. The tree is in need of a protective spray program or should be replaced with a new disease resistant cultivar. Typically apple scab affects older varieties.
If you choose to keep the tree and spray it with a fungicide, begin spraying after the buds open and treat once every seven to 10 days until the leaves are fully open. Generally three treatments suffice. For recommended fungicides and timing for applications, call the Plant Information Service at the Chicago Botanic Garden in Glencoe at 847-835-0972.
Protect emerging tulips from deer and rabbit damage by spraying them with a repellent or covering them with netting. Repellents will need to be reapplied after rain. Netting will need to be adjusted as bulbs grow and may need to be weighted down to keep it from blowing away.
Animals do not typically eat daffodils, Siberian squill and ornamental onions (alliums).
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.