Q. The pyracantha that we have trained against the wall of our house never produces very many flowers or berries. It gets enough sun and isn’t droughted, so we can’t understand what could be wrong with it.
A. I suspect that you may be pruning your pyracantha a little too thoroughly. Pyracantha flowers on the previous year’s growth, so if you prune off the growing tips, you will have reduced flower and berry production. When you prune your pyracantha, be sure to retain enough of the previous year’s growth to ensure good flower production. A simple way to do this is by pruning during the winter when the berries are present, instead of in the following spring.
Q. I’ve noticed that the lawn service I hired uses a string-edger to trim around my trees. I’ve been told that a string edger can be harmful to trees. Is this true, and if so, why?
A. Under certain circumstances, trees can be damaged or even killed as a direct result of the use of a string edger. In most trees (dicots), the conductive tissues that transport water and nutrients between the roots and the top of a plant are located just beneath the bark. If this bark is not tough enough to withstand contact with the cutting string, the bark and underlying conductive tissues may be damaged. This damaged tissue becomes unable to function, and the tree’s health declines. If the damage occurs continuously around the trunk, the tree is said to be “girdled,” and this can be fatal.
In monocot trees such as palms, the conductive tissues are arranged in bundles throughout the trunk, so damage to the surface is not as debilitating. However, in both monocots and dicots, anytime damage is inflicted, the open wound becomes a possible site of infection from plant pathogens. Therefore, care should be exercised to avoid damaging a tree’s trunk, whether from a string edger, lawnmower or other implements.
You can lessen the possibility of trunk damage by removing any grass growing close to tree trunks. If removing the grass is not possible, there are heavy-duty plastic collars that can be wrapped around the trunks to protect them. By far, the best protection for your trees is for those working around them to exercise proper caution to prevent damage from occurring.
Ottillia “Toots” Bier has been a UC Cooperative Extension master gardener since 1980. Send comments and questions to firstname.lastname@example.org.