University of Maryland Extension: Garden Q&A
Q: I’m concerned about my garlic's early demise. Last month, their stalks withered and fell early. Those I pulled showed no sign of a bulb below ground. Today I pulled some early withering ones to find the stem beneath the ground frail and limp with tiny bulbs. I know that normally I should wait until the stalks produce a bulb, and then fade.
A: There are several possibilities, but the most common cause for the situation you describe is a fungal disease known as white rot. If you find a white growth on the leaves at the neck of the plant, and the growth is dotted with tiny black spots, the garlic has white rot.
On the other hand, if the neck tissue on the bulb becomes soft and brownish and shrivels, and if you find a gray to brown mold on the surface of the bulbs, the problem is botrytis rot.
The least likely problem is an infestation of nematodes. Symptoms would be stunted plants with leaves yellowing prematurely or not surviving until maturity.
If you suspect white rot, remove and destroy all affected plants, and plant your garlic elsewhere for the next 3 or 4 years. If you suspect botrytis, remove infected plants. Keep any harvested bulbs cool and dry in storage.
In any case, add 3-4 inches of compost this fall and rotate your garlic planting to a new location in the garden.
Q: I never want to pull a weed again. I plan to put down black plastic (or landscape fabric) and then put shredded bark mulch over that. All I’ll need to do it throw on some new mulch each year. Isn’t that a good permanent solution?
A: You’ll be creating a plastic mulch sandwich. As the bark mulch decomposes to an organic material, you’ll end up with a layer of good “soil” on top of the black plastic. Weeds will grow quite happily in it. Over the years, as you add more mulch, the organic layer will get deeper, and the black plastic will be buried deeper, rendering it useless. One option would be to remove the old mulch each year before you apply new mulch, though this robs your plants of all the good nutrients and benefits supplied by decomposed mulch. A better option is to simply use a 1-2 inch layer of mulch.