|Differences in trees can be because of their genetics and how they were propagated in the nursery, differences in soil in very small areas and management.|
Q. We had 3 African sumac trees planted in our backyard 1½ years ago. We treated them the same during this time but the tree the farthest away has large dark green, healthy leaves and the other 2 trees have lighter color leaves and they are curled.
A. African sumac is propagated from seed so there is a lot of variation among trees. They also come in male and female trees so let’s remember that as well.
|Seeing seed pods in African sumac is a good indicator the tree is female.|
Lighter leaf color can mean the trees are not getting enough nitrogen fertilizer, they are watered too frequently, or the soil does not drain water quickly enough. Because these trees were not planted by you, it’s not known if the soil where these trees are growing drains water similarly or not.
Let’s tackle the fertilizer issue first. Apply a high nitrogen fertilizer in the basin of the trees just before an irrigation. Let the irrigation water transport this high nitrogen fertilizer to tree roots. If nitrogen fertilizer is the culprit, you should see a change in the leaf color before one week.
|Moisture sensors like this inexpensive type used for houseplants can tell you the approximate time to water. Push the probe into loose soil in several places to get a rough idea when the soil is wet or dry.|
Inexpensive soil moisture meters, such as they use for house plants, can give you a rough approximation if the soil is wet or dry and when to irrigate again. Water these trees only when the soil is beginning to dry, never while the soil is still wet. If trees are watered too soon and the soil is still wet, leaves can discolor and become yellow rather than dark green. But the differences in leaf density between the trees indicate a difference in the amount of water they are receiving.