More mulch is not better

Please settle an argument. You say to spread no more than 1-2 inches of mulch around a tree. Since mulch holds moisture in soil, isn't more mulch even better?

Seems logical — but more isn't always better in this case. Mulch does shade soil and slow evaporation by about 25 percent. When mulch gets too deep, however, tree roots will begin to grow into the mulch seeking moisture. This happens partly because in a light rain mulch gets moist, but the water never trickles down past the mulch. During dry periods, the vulnerable roots dry up and die. Furthermore, thick mulch reduces gas exchange between roots and atmosphere. Then, as deep mulch decomposes over the years, it in essence becomes new soil and raises the soil level so, again, roots grow up to reach oxygen as well as moisture.

Our spreader dumped a pile of fertilizer in one spot and the grass died there — that was 3 years ago. Still no grass — not even one weed! We can still see granules. Shouldn't fertilizer help the grass? And how can we grow grass there now?

You're seeing proof that synthetic fertilizer is manufactured as a salt. Your soil in that spot is so salty that no plants can grow (salt dessicates roots). That must have been quite a "dump" if normal dilution from precipitation hasn't diluted it by now. Scrap away any granules. At this point, either dig deep and turn over the soil or remove the top layer of soil and replace with fresh topsoil. Fall is the best time to reseed turf, and since weeds won't infest that spot meanwhile, you have the luxury of waiting until fall.

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to the website at

Plant of the week

Stokes' Aster

Stokesia laevis 'Klaus Jelitto'

Native to the Southeast, this easy-to-grow perennial makes a colorful addition to sunny borders, containers, and wildflower or cutting gardens. In summer floral arrangements, blooms persist about a week after cutting. "Klaus Jelitto" variety, named for the German seed man, bears large soft blue flowers 4 inch in diameter on erect stems from a rosette of glossy leathery leaves. Other cultivars are available in shades of white, pink, and yellow. Plants grow about 15 inches high and wide and bloom in midsummer. When flowers are deadheaded, they reward you with additional blooms. Best growth is in full sun in well-drained soil. Established plants are drought-tolerant. Flowers attract butterflies, and foliage remains evergreen into the winter. — Marian Hengemihle

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