Here are this week’s gardening questions and answers, provided by Parker County Master Gardeners. To submit a question, send it to firstname.lastname@example.org. For more information about Parker County Master Gardeners, or to become a member, call 817-598-6096 or visit www.pcmg-texas.org.
Why are my pecan trees dropping very small green pecans?
Normally premature pecan drop is due to one of three things. The first is due to the pecan nut case bearer. Those that drop from this insect will normally have a little frass (insect debris) where the insect enters the nut. The second is from poor pollination. The pecan grows for a short period of time and then the auxins (plant growth substances) needed to continue growth are no longer in sufficient amounts to maintain the pecan. The third cause can be from drought.
Special thanks to Dr. Jerral Johnson, Professor Emeritus, Dept. Plant Pathology and Microbiology, Texas A&M University
When should I apply pre-emergent?
To control winter annual weeds put down pre-emergent herbicides. Timing is everything. A layer of the control element needs to be in place as the seeds germinate so that the seedlings can be killed. For our area, Sept. 15th is a good target date. Be sure to read the product instructions and water in if recommended. Warning, if you have desirable seeds in your landscape, the herbicide will kill them just as quickly as the weeds you want to eliminate.
What is the best time to divide iris for replanting or sharing?
Divide iris in late August and then water sparingly until the weather cools. When there is too much water and it is hot, irises are susceptible to rot. Once your rhizomes are clean, look for small to medium holes. These are telltale signs of borer damage. If your bearded iris leaves have dark streaks in them, you probably have iris borers, so look closely.