Question: Someone told me to cut off branches that are too low, but I don't know how to do it properly. What am I looking for?
Answer: When trees are pruned, they produce their own version of scar tissue that closes wounds and creates a barrier against wood rot and wood-boring insects. If the branch is pruned too close to the trunk, it will be difficult to form this protective layer, and a branch root that is too long increases the risk of infection by trunk cancer-causing fungi. Since there is little we can do to intervene after a bad cut (do not apply wound sealant or any other type of “paint” or resin), it is important to place the cut in the right place.
The base of the branch joins the trunk in an area called the branch collar. Cabbage is stem tissue, not branch tissue. When pruning stems, the stem tissue should not be damaged as this is an important distinction. The top of the branch-trunk junction is called the branch-bark ridge and can be viewed as a small ridge of bark raised up by a small ridge on each side of the branch base. Together, these specialized areas form a raised ring around the base of the branch and contain tissue that attaches to the tip of the wound.
When pruning, remove enough branches so that the callous tissue in the collar area covers the small branches of the exposed wood, but do not remove the trunk wood itself, but rather cut it flush with the trunk. The Proper Pruning section on our Tree Pruning page describes where trees need to be pruned. For more information , see the USDA Forest Service brochure “How to Prune Trees . ” There is a great video at Iowa State University Extension that shows pruning techniques for a young tree as an example of what to look for , as the same principles apply to older trees and larger branches. (The video on her YouTube channel is called “Pruning Principles – Good Pruning.”)
If, after about a year, you see a ring of callus tissue forming on either side of the cut, this indicates that the cut was done correctly. Depending on the size of the branch removed, it may take several years for the wound to fully heal, which is normal. If you are unsure or have no control over where to prune large, heavy, or long branches, always hire a certified arborist or Maryland licensed professional to do the pruning.
Q: How can I tell if my orchid is growing a stem or another stem?
Answer: Although the shape and size of the stems and flower stalks depend on the type of orchid, there is a fairly easy way to tell them apart. Phalaenopsis, the most common orchid, the “ moth orchid ,” has spikes that grow like roots from the leaf axils (where the leaves connect to the stem). Others, like the “dancing lady” Oncidium , form roots on the underside of the leaves, called pseudobulbs, with spines that appear upward in the middle of the leaves.
Orchid roots are covered with a layer of absorbent cells called velamen, which helps protect the roots from damage by retaining moisture and nutrients in the external environment where most orchids live (e.g. tree bark). In living roots, the velamen is either white (may darken over time in the soil mix) or silver. The root tip is light green or even pink when actively growing. In contrast, the spine is uniformly green along its entire length and the tip is generally sharper in shape than the taper of the main tip. The direction of growth is less clear; Generally, the roots grow downwards or outwards and upwards, but this can vary depending on the way the plant is growing, the direction of the light source, and the type of orchid.
The short days of winter are a common blooming time for many orchids (there's a reason trade shows and sales happen this time of year). So if you just see a small bulb of a Phalaenopsis stem and wonder if it's a plant ? Look at the shape of a thorn or root: if it looks like a mitten and has one or more slits at the end, it is a thorn. If it is smooth and evenly tapered, it is a root. As the spine lengthens, it develops at least one node (joint) on the trunk, similar to the band around an earthworm's body. When the flowers on a spike fade, one or more of these nodes may produce a second flower before the spike dies.
The University of Maryland Home and Garden Information Center offers free gardening and pest information at Extension.umd.edu/hgic. Click Submit Extension to submit questions and images.
