Plant woody shrubs in the fall for best results in Houston
We have had several questions about spring planted shrubs that aren’t doing well in September. Although each situation may be different, there are a few reasons why this may be occurring. In one case, the homeowners had been applying root stimulator biweekly, along with an all-purpose foliage plant fertilizer, yet the plants still declined.
After the freeze in February, with subsequent landscape loss, new plantings occurred all over the area.
Here are some tips for new woody shrubs:
Fall is the ideal planting time, but that did us no good in the spring when the desire was high to replace, add color and soothe our souls. To understand the stress those plants may be experiencing now, let me start with the ideal situation: Most woody shrubs and trees would be planted in the fall, once it starts to cool down, with no added fertilizer. This temperature drop reduces transplant shock and reduces water loss through the leaves. Less energy is spent on foliage and top growth as the visible part of the plant may (or may not in our region) go into dormancy. This is the most important time to implement a watering schedule if there is no rainfall. A slow, deep watering once a week is best. At this time in the year, more energy is spent on root growth. Roots grow all fall and winter without much stress of environmental factors. Come spring, the top growth will be healthier and fuller. If you must fertilizer, then do so lightly.
However, this year, we had various cycles of heat, rain and dry conditions. Mother Nature did not provide an ideal situation for us. New plantings experience transplant shock to some degree. Typically, they have time to recover before being tested, but there was a lot thrown at them in their first few months. We had so much rain that it leached out nutrients and oversaturated the ground, which reduced oxygen to the
roots. This lack of oxygen (and nutrients) limits plant growth. Applying fertilizer during periods of high rain is not utilized and is instead washed away as nonpoint source pollution. On the other hand, during dry periods, overuse of fertilizers can burn the root system.
In addition, there is no research to support using root stimulators for woody shrubs, except in the case of propagation. The best recipe for healthy green growth is healthy root growth. Plant in the fall and water new plants slow and well, with little fertilizer.
Brandi Keller
Q: We had a large crape myrtle cut down and the stump ground out, but it keeps growing back. How do we prevent it from sending up new shoots and kill it once and for all?
A: Crape myrtles ( Lagerstroemia indica and hybrids) have a very dense and pervasive root system. As you have learned, even if one these trees is cut down and ground out, the roots still live on and send up new growth. If there is a lesson here for others to learn from your situation, it would be to cut the crape myrtle down, apply the herbicide to the fresh stump to prevent resprouting, then grind the stump after enough time has passed to give comfort that the roots are dead.
To address the current problem, remove some soil around the stump or large roots and put a fresh cut into the tissue. You do not have to go all the way through the root/stump. If it is not possible to get to the root, then the same treatment can be done on fresh sucker cuts. Brush dust and dirt away. Using a foam brush, apply an undiluted product with the active ingredient triclopyr (like Poison Ivy Killer, Brush B Gone, etc.) to the fresh cuts. Triclopyr is a systemic herbicide for woody and herbaceous broadleaved plants, so applying willynilly may have devastating effects on nearby plants. Be precise with the foam brush and concentrate inside the bark where the living tissue resides.
Then starts the waiting game. If new suckers emerge, treat as above until you no longer see new growth.
A few safety tips include: Do not spray (wind can carry it to other plants). Cut the stump or suckers as low to the ground as possible, and keep the cut even, to prevent runoff. The ideal temperature for use is between 50-80 degrees. Never use when the temperature is over 90 degrees, as this product can vaporize in heat and be absorbed by nearby plants. Always follow directions on the manufacturer’s label for each herbicide/insecticide you may use. More is never better.
Brandi Keller
Q: We have a severe outbreak of crape myrtle bark scale and have many crape myrtles on the property. What is the correct method to use to stop the spread?
A: Crape myrtle bark scale is a relatively new exotic scale pest of crape myrtle ( Lagerstroemia). It is the only scale insect to infest crape myrtles. Systemic insecticides have shown very good control of the pest. Apply them to the root zone as a soil injection or drench. The best control is achieved with applications of clothianidin, dinotefuran imidacloprid or thiamethoxam applied between May and July. For additional information, please refer to the “Crape Myrtle Bark Scale: A New Exotic Pest” fact sheet on the agrilife.org site.
Paul Winski
Q: My yard is infested with Virginia buttonweed. I have had issues for the past four years, and it just keeps getting worse. Is there anything I can do to treat for this? Are there any herbicides that are effective?
A: Virginia buttonweed, Diodia virginiana, is a difficult weed to manage in the lawn. It is a deep-rooted perennial plant with a spreading growth habit. If you have large patches of it, likely indicates the lawn is staying too wet from either overwatering or there is a compaction issue and the water is not draining. For chemical control on established weed populations, products with the active ingredient metsulfuron methyl or a product with iodosulfuron + thiencarbazone + dicamba is safe to use in the heat of the summer. Please read and follow all herbicide label directions. Paul Winski
Q: I had an infestation last year of twig girdlers on 1-inch caliper pecan trees that had been in the ground for four years and were, for the most part, surviving on their own. I picked up and disposed of all the branches that fell over. I am wondering if the pests will come back again and if I should still go ahead with spraying?
A: These insects seldom do any serious harm to trees and are mostly a nuisance. Spraying with a chemical insecticide is not recommended for controlling twig girdlers in a yard/ residential situation. Instead, collect and destroy clipped branches that have fallen. Paul Winski
Brandi Keller and Paul Winski are Texas A&M AgriLife Extension agents and garden experts.