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Q: We have a large tree-form lilac that needs to be trimmed back quite significantly. I can鈥檛 trim very far before I cut off a lot of leaves. What鈥檚 the best way to do this? Should I be concerned that I鈥檒l over-trim and damage the plant? 鈥� Ross L.

A: Lilacs growing on a single trunk are termed 鈥済rowing on a standard.鈥� Most are formed by grafting the shrubby Dwarf Korean Lilac onto the trunk of a related lilac, such as Japanese Tree Lilac, to produce a lollypop-shaped miniature tree. The graft is usually 3 or 4 feet above ground level.

Although they begin as miniature tree-form lilacs, they can become quite large, as you鈥檝e found, with the top part of the 鈥渓ollypop鈥� becoming 6 feet or more in diameter. Several of us have consulted in the past as to how best to prune them, once they鈥檝e become larger than desired in their location.

In our experience, they can be pruned quite dramatically from a 6-foot diameter crown down to 3 feet, and they come back beautifully.

Depending on the size of the location in which they were planted, they can usually be pruned back to once again fit the spot.

Pruning is never a 100% guarantee that a plant will thrive afterward, but I鈥檝e rarely killed anything by pruning, no matter how drastically, if the tree or shrub was healthy before.

There鈥檚 always a small chance that something can go wrong, but the advantages of pruning far outweigh the risks in most cases.

To further encourage pruning, if these tree-form lilacs aren鈥檛 trimmed, they can become overly woody and begin declining. Sucker shoots growing from the base are also common, and need to be pruned away while tiny.

Please keep us posted. Lilacs can be pruned now after blossoming. I can already picture your tree-form lilac with a neater, less expansive canopy.

Q: The cucumber plants we purchased from a garden center quickly went downhill. We鈥檝e since replaced them. What might have caused the cucumber problems? 鈥� Loretta J.

A: Cucumber and its relatives like squash, muskmelon, watermelon and pumpkin love warmth and stable temperatures. Our spring weather has been anything but stable, and many cucumbers and members of the Cucurbit family have been affected.

The hot, windy days we had in May, followed directly by chilly days and nights, could easily have caused cucumber plants to wither and suffer.

When such plants begin a downward spiral, it鈥檚 often difficult to pull them out of it, so replacement, as you鈥檝e done, is often the best option.

Q: How do we get rid of mushrooms in the lawn? There鈥檚 been a small patch for several years, and now there are eight. 鈥� Carol N.

A: Mushrooms popping up in the lawn can be annoying but don鈥檛 usually harm the turf. The visible mushroom is the spore-producing structure of these fungi that grow on organic material, which can be the thatch layer, old tree roots, or other underground material.

Most of the mushroom fungal structure is below ground, and once the decayed material is decomposed completely, the mushroom fungus usually disappears. Such fungi are part of nature, necessary for decomposing wood, stumps, roots and similar organic materials.

Mushrooms pop up during certain times and under certain moisture conditions, especially when rainfall or irrigation is plentiful.

There are no chemical products that successfully remove mushrooms from lawns. Rake off and dispose of the visible mushrooms, as they can spread spores.

Aerating the lawn with a core aerator and increasing the airflow into the turf can speed the decomposition of the organic material on which the fungi are growing, speeding their disappearance.

Bleach, vinegar or other home remedies suggested online can be harmful to lawn grass. Fungicides are generally preventive, so once mushrooms are established, such chemicals are ineffective.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at donald.kinzler@ndsu.edu . Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.