Taking control of cedar elm seedlings in your landscape
Q: Is it possible to sterilize cedar elm trees so we won’t have all the seedlings come spring? We put down corn gluten meal in September to stop the germination, but millions have come up in the spring.
A:
There is no process or product that will do what you are wanting. I have cedar elms on our property, too, and the way that I cope with the myriad seedlings is to apply an inch of compost or finely ground pine bark mulch across all my beds in the fall. If seedlings emerge in the spring, I use a well-sharpened garden hoe to scrape the mulch lightly. It’s more just to turn it over, not actually to chop at it. I do so when the seedlings are less than 1 inch tall. It’s a very easy process, and the seedlings are still rooted totally within the loose mulch. Their tiny roots can’t withstand the shock of being disturbed. They dry out and die. Those that sprout up in my lawn are easily addressed with a broadleaf weed killer applied with a pump sprayer (not a hose-end sprayer, which would apply far more of the active ingredient). Cedar elms are outstanding landscape trees. This is a small inconvenience in return for the benefits they bring to our landscapes. Give it a try. I think you’ll agree.
By the way: I’m not a fan of corn gluten meal for preemergent control of any weed. It’s supposed to help control grassy weeds like crabgrass, but its effective life is very short and its efficacy is low. Other products are much better.
Q: When it gets hot, our oakleaf hydrangea loses all its leaves and dies back to the ground. Then it regrows. It gets shade most of the day but some hot afternoon sun. What can we do to help it?
A: Oakleaf hydrangeas need full shade and constant moisture, they also need highly organic planting soil. It sounds to me like the best thing you could do to help it would be to move it to a more suitable location.
Q: During the past two weeks, our very mature live oak has been dropping leaves. The first time was during the first cold front and then one other time since. Is this related to the stresses of the past two winters and summers, or is there something else we should be concerned about?
A:
All our plants have been through 30 really rough months. You hit it right on the head in your reference to the past two extreme winters and the terrible summers and their associated droughts. Trees across Texas are currently facing leaf drop and even limb death (even loss of entire trees) like we haven’t seen since 2011 and even further back). I think your trouble is all about the extremely high temperatures, low humidity and limited rainfall of the past several months. But live oaks have been around for millennia, and my guess is that they’re going to come through this just fine.
Q: Do you have any idea what might be going on with this tree (I believe a cedar elm)?
A:
I assume you’re talking about the darkened line in the bark? If I try very hard, I can convince myself that the line extends up and down in that same plane, and that would make me suspect some type of decay might be going on within the wood of the trunk. I can’t tell enough from this distance and without looking at the other side of the trunk. I would suggest that you retain an Isa-certified arborist to inspect the tree and advise you on what needs to be done to protect it (or to protect you and your property should it be in a weakened condition). The International Society of Arboriculture’s website will help you locate a certified arborist near you.
Q: Due to a tree dying and the intense summer we’ve just encountered, the liriope across the front of my house is basically brown, with some green left in it. Should I trim it back?
A:
Anything that is browned can be trimmed off, but I’d suggest not cutting back flush with the soil line. Leave an inch or two of the old leaf stubble as protection for the new sprouts as they emerge this fall and early winter and early next spring. I hope the roots weren’t killed by the drought. If they were, that would preclude their being able to send out new shoots. You could apply an all-nitrogen lawn fertilizer, even this late, to the bed, followed by a thorough watering. That might speed the regrowth a bit. Make sure the fertilizer does not contain a weed killer product.
Q: What has ruined my lawn? I applied insecticide the first week of July and never saw any signs of chinch bugs. Except for a few spots, the lawn had adequate water. I improved the sprinkler system in September by adding 10 new heads. I applied fertilizer and preemergent according to your guidelines, always followed by thorough watering. Might I have watered too much?
A:
To quote you verbatim, you “…applied insecticide the first week of July and never saw any signs of chinch bugs.” If you did things in that order, that would explain why you didn’t see the chinch bugs — you would already have killed them. They very probably had already done their damage, since their season begins when it first turns really hot and dry. You will always see them in the sunniest parts of the yard (nearest concrete or painted fences and walls). Look how true that is in your photos. As much as it hurts to tell you, I fear you’re going to have big parts of your yard to replace late next April or May. For the record, this does not look like take all root rot or gray leaf spot, and no, there is no way you could have overwatered St. Augustine in this record hot, dry year.