Q My lawn looked pretty good this spring, but now there are lots of weeds popping up -- dandelions, something that looks like miniature clover with yellow flowers, and patches of a spreading plant with tiny leaves and white star-shaped flowers. What can I use to get rid of them?

A In addition to the dandelions, it sounds as though you have yellow woodsorrel (oxalis) and chickweed. They're all perennial weeds that survive our winters, bloom repeatedly and reproduce by dispersing seeds in the lawn. And they all can run rampant in a lawn that is thinning or growing poorly because of lack of moisture or nutrients.

There's nothing you can "use" in midsummer to get rid of them because weedkillers are likely to damage desirable lawn grasses right along with the weeds when applied in hot weather. All you can do now is dig out the dandelions before they develop big tap roots, and pull out the woodsorrel and chickweed. (They come out easily when the soil is moist after a steady rain or sprinkling.)

Once temperatures drop in September, you can spray the lawn with a broadleaf herbicide that's labeled for use on oxalis and chickweed. (Just about any broadleaf product will be effective on dandelions.) If necessary, you can spray again 10 to 14 days later. Using a pre-emergent herbicide in spring will help prevent more weed seeds from sprouting.

But improving the health of your lawn is an even better way to cut down on weeds. So fertilize the lawn at least once -- and preferably twice -- this fall and water it during dry periods to keep it growing vigorously.

Copycat crabapples Q I've planted two Whitney crabapples in my yard and I love the fruit they produce each fall. I'd like to save seeds from those crabapples and plant more trees. What's the best way to do this?

A I hate to discourage you, but neither apples nor crabapples come true from seed. The trees that would grow from the Whitney crab seeds wouldn't be identical to the original. And they most likely wouldn't be as good. That's because the seeds carry a genetic mix of Whitney and whatever tree produced the pollen that bees brought in. If you want more Whitneys, your best bet would be to buy some small trees at a nursery.

That said, if you want to experiment, go ahead and harvest the Whitney seeds this fall and store them in damp sand in a plastic bag in your refrigerator for the winter. In spring, plant them just below the soil surface in a sunny part of your garden.

Deb Brown is a garden writer and former extension horticulturist with the University of Minnesota. To ask her a gardening question, call 612-673-7793 and leave a message. She will answer questions in this column only.