Q: Why do some of my Christmas cactuses develop a woody stem that eventually rots and falls off? We don’t overwater them. A couple of them will develop the woody stems. I usually break them off, save the green parts and try to root them. Do you have any suggestions? — Mary Moore, email

A: Woody stems are an indication of an old plant and nothing can be done to prevent them. If they snap or break off, you should consider trimming some of the leaves when they come indoors in the fall to relieve weight. When you save the green leaves to root, break off only one or two segments at a time. Any more segments than this will lose moisture too rapidly and rarely root properly.

Q: A neighbor cut down a tree on the property line without consent. It was a mature 75-foot hardwood with a 6-foot trunk at the base. Can you recommend someone who can provide an appraisal of the value of the tree? — Gino Massafra, email

A: You won’t find a bigger group of tree huggers in one place than the regular meetings of the Georgia Arborist Association. They sponsor regular trainings in English and Spanish and hold an annual tree climbing contest. They are your best source for professional tree experts. When you hire someone, make sure they are certified by the International Society of Arborculture. Anyone who has ISA certification knows lots more than you and me about trees, including tree disease identification, limb weight determination and tree valuation. Most don’t practice the latter as a profession, but there are members of GAA who specialize. You can find a list of members and their specialties at georgiaarborist.org.

Q: We currently have pine straw as a ground cover. We are going to replace that with mulch. Do we need to remove the pine straw or can we place the mulch directly over the pine straw? — Jim Henry, Acworth

A: One of the greatest benefits of mulch is its contribution of organic matter to the soil beneath. The pine straw that you have now will eventually decompose, but I know it’s a slow process. There’s no reason to remove it. The mulch on top will press the pine straw closer to the earth where moisture and insects can more readily break it down. Eventually, your beautiful mulch on top will begin to break down as well. You’ll have to replenish it with fresh mulch. I think organic mulch is the best thing for trees and shrubs in the landscape. The constant addition of organic matter feeds microorganisms, makes the soil hold water and allows pore space to form. That’s why I’m not often in favor of using rocks, slate chips or marble chips for mulch.