Q. I know you don't like pear trees, but I hope you'll answer this question. I planted a callery pear two years ago that is now 11 feet high. The lowest branch is only 3 1/2 feet from the ground. If I just wait, will those lower branches be higher or should I prune them so that I don't have low branches on a mature tree? Yes, yes, I know I should have planted a crabapple.
A. Did I give the impression that I don't like Bradford pears? They are wonderful trees in Southern California, where lack of moisture keeps their growth in check and where ice storms and the occasional hurricane are not a factor.
All trees grow from the tips of their branches and also lay down a new ring of wood every year. A pear trunk will not grow to carry the branch to a higher position. You should remove the lowest branches as the tree grows to allow for maintenance of the area under the branches. The process of removing these lower branches is called heading. A tree can be given a high heading or can be maintained with a low heading as needs dictate. Most landscape trees are given a heading of five to 10 feet to permit easier maintenance of the area under the tree.
If the tree is young, it may have not yet grown enough for heading to be completed at one time. If this is the case, just reduce branches that you know you won't be keeping in the long term by about half. Don't worry too much about the aesthetics or health of these pruning cuts since the branches will be gone in a few years anyway. This can and should also be done with co-dominant branches at the top of the tree that compete with the main vertical branch of the tree, known to arborists as its leader. You want to maintain a single dominant leader, particularly on Bradford pears, since this will create the strongest possible branch structure. Co-dominant branches have a narrow and weak crotch angle that will split in a future wind or ice storm.
Q. I have a shady back yard and the soil is acidic: lots of pine, oak and holly. What would be a good ground cover that doesn't get taller than four inches, is a perennial and can take some foot traffic?
A. Moss is the best answer for these conditions. There are no ground covers that tolerate shade, competition from trees and foot traffic. If you don't want to rely on the moss alone, simply create broad mossy walkways and use a variety of small ground covers to complete the picture. Sweet box, Sarcococca hookeriana var. humilis, is a bit taller than you desire, reaching to about a foot in height, but is worth planting for its fragrant March flowers alone.
Dwarf mondo grass is a nice contrast to moss, and if you are patient, it will slowly spread to create what will appear to be a neatly mowed coarse-leafed turf. Epimediums add another leaf texture, and they do very well in dry shade. None of these take much foot traffic, so stick to moss for the paths.
Q. Can coffee grounds be recycled in the yard?
A. Yes, they can. Coffee is acidic, so I wouldn't use the grounds on plants that crave lime, such as peony and clematis. They also have a tendency to float away, so I'd recommend mixing them with mulch or compost.
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