Q: I understand that the temperature...

Q: I understand that the temperature maintained in a compost pile or pit during decomposition is important. Is that true?

--G.C., Pasadena A: Many people believe that monitoring the temperature of the material in the interior of a compost pile is the proper way to determine whether it needs attention. When temperatures exceed 180 degrees Fahrenheit, the material should be chopped or aerated to increase its oxygen content and thereby slow down decomposition. When temperatures are close to the temperature of the surrounding air, no composting is occurring. The secret to producing a good compost is not so much a matter of temperature as it is of the texture of the material in the pile. The most useful material is that which is of uniform size so that it can be spread evenly over the garden or used as a soil amendment. A good compost also will release nutrients evenly and quickly so that it has a fertilizing effect. Compost is ready when it crumbles freely in your hand.

Q: Should palm trees ever be pruned?

--N.A., West Los Angeles A: You don’t need to prune established palms for their own well-being, but you do have to take off dead or damaged fronds to minimize disease or fire damage. Take care to avoid cutting into live growth; unsightly scars will be the result.

Q: Last fall I applied what I believe was called a pre - emergent weed killer around a neglected, weedy area I wanted to beautify. The weeds kept growing. Why?

--A.C., Gardena A: Most selective, preemergent herbicides aren’t effective against established weeds. Unwanted vegetation must be hoed out or otherwise removed mechanically before you apply pre-emergent materials, which work against newly sprouting weed seeds. Most such herbicides form a thin barrier on the surface of the soil. Remember that some moisture--such as rain or sprinkling--must follow the application to activate the herbicide’s week-killing properties.

Q: I know that winter oil spraying for disease control should be avoided if leaves are on the tree. The ‘Gordon’ apple never loses all of its leaves here. I still need the protection of a dormant treatment. What can you suggest?

--R.G., Whittier A: The ‘Gordon’ apple is one of the best for mild-winter areas like ours, and it retains some leaves through the winter. Nevertheless, you may apply dormant sprays, but avoid spraying nearby non-target evergreen plants.