I tried composting my lawn clippings and leaves in two compost tumblers with zero success. The mixture doesn't even get warm. Sources say to mix X part green (nitrogen) with X part brown (carbon) ingredients, and voila. Are they talking volume, weight or what? I turn the compost once a week and keep it moist, but still no bio breakdown. I need a composting class!

For hot (fast) composting, the green-brown ratio is determined by weight. This doesn't need to be exact. All compost needs moisture, oxygen (hence the turning of ingredients) and warmth. You won't get much action in the cold of winter, especially in a shady, northern site. Cool, or passive, composting involves the regular addition of materials and no turning, while hot composting involves putting all of the material in at once and turning regularly. If you keep adding new materials to your tumbler, you will never achieve finished compost. Hot compost can be finished in about eight weeks, but it requires green/high-nitrogen ingredients that are mainly available in the spring and summer.

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The Japanese andromedas on the east side of our house are in much more sun this past year due to removal of a tree. Now leaves are yellowish and miserable-looking. What should we do?

Yellowing can have several causes. Send the Home and Garden Information Center a photo so we can best determine them. Andromedas do not like a lot of sun — as broad-leaved evergreens, they are susceptible to winter sunburn. Also, lace bugs quickly move onto unhappy andromedas. Their sucking mouthparts pierce the leaf surface and suck out cell contents, causing leaves to fade and yellow. Look to see if leaf undersides are dirty from excrement and bugs. Yellow chlorotic leaves can also be caused by high pH — check the soil pH. If the andromedas are planted near a foundation — which is highly alkaline — that could also be part of the problem. You may have to move these unhappy andromedas to a shadier, less stressful site.

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland's Gardening Experts” to send questions and photos.