GARDENER'S MAILBAG: What is causing the dried, dead patches on my oak?
Dear Neil: I had my live oaks pruned two years ago. They did not use pruning paint on them, and ever since, dried or dead patches have appeared on them. I have purple wandering Jew around them, and I’m wondering if it could have a poisoning effect on them. I’m also wondering if it could be oak wilt, although a couple of people have said it was not. What would cause that? I’m attaching a photo.
Unfortunately, no photo came attached to your email. If you’re talking about individual branches that turned brown and dried, I would suspect squirrel damage. That’s somewhat common on live oaks (also pecans). If that’s the case, the trees will be fine in the long run. As for remedies, you can’t harm the squirrels legally. Perhaps you could catch them with a humane trap and release them in a park somewhere a distance away, but I’m going way out on a limb to explain that since I haven’t even seen the symptoms. I do note, however, that the damage apparently pre-dates the February 2021 freeze that caused so much dieback on live oaks across Texas.
Dear Neil: I am being covered up with dollarweed in my St. Augustine and also in my shrub beds. I’ve used a product labeled specifically to control dollarweed, but without success. What will kill it?
First, dollarweed has leaves the size of the palm or your hand borne on stems 2-4 inches above the ground. That’s to distinguish it from the commonly mis-identified dichondra. The latter has kidney-shaped leaves the size of your thumbnail, and it trails along the ground barely 1 inch above the soil surface. Both can be controlled with a broadleafed weedkiller spray containing 2,4-D, but each presents special challenges. Dollarweed leaves are ultimately glossy, so it’s hard to get the spray to adhere to the leaf surfaces. Include one drop of liquid dishwashing detergent per gallon of spray to help break the surface tension and coat the leaves. Near the shrubs, however, you’ll have to apply it with a foam rubber paintbrush to avoid damage to the shrubs since they’re broadleafed plants in their own right. And the dichondra is so low-growing that it hides beneath St. Augustine. Its leaves also form small funnels that direct the spray off the leaves and onto the soil. Once again, you must coat the leaf surfaces carefully. And, with both plants, you will probably have to treat two or three times a few weeks apart.
Dear Neil: What can I do to stop the leaves from falling off my hybrid poplar?
Not a thing. It’s a deciduous tree, just like their common relatives, our native cottonwoods. Aspens are another plant out of this group. They’re the source of the brilliant gold colors in fall in the Rocky Mountains. Your tree is behaving exactly as it was programmed to do.
Dear Neil: I have a large Nellie R. Stevens holly that I’d really like to train into a tree form. Can that be done? If so, how do I start?
Absolutely, it can be done! In fact, they make very lovely small trees to 15 to 18 feet tall. If you want a straight trunk you must start with a young tree from the outset and prune it to a vertical trunk as it grows. But if you have a plant that has gotten too massive at its base and you want to try it as a tree, you might opt for a multi-trunk specimen. Start by removing the lowest branch with lopping shears or a pruning saw. Make the cuts flush with the trunk. Pull the cut branch out, then step back and see what impact you’ve made on the looks of the plant. If you’re satisfied, move up to the next lowest branch, and remove it. Step back and look. Repeat several times, looking carefully at the tree after each cut. When you get 35 to 40 percent of the way up the trunks, stop and observe the tree for a few weeks. You may very well want to remove a few more branches, but it’s best to consider each limb and perhaps have someone hold them out of the way before you make the last cuts. You can never put them back.
Dear Neil: I was given a box of really nice tulip bulbs a couple of days ago. I know they need to be planted around Christmas, but I also know they also need to be in the refrigerator for 6 or 7 weeks to give them an artificial winter. Obviously, that hasn’t been done. Is it a waste of time to plant them? The friend who gave them to me will be aware if they don’t come up and bloom next spring.
Give them a try. Plant them in a massed bed 3-4 inches apart and twice as deep as the bulbs are tall. The problem with not having them “pre-chilled” is that they often will bloom on very short stems. Hopefully we’ll have enough cold weather to fool them into thinking they’re in Holland. But, also hopefully, it won’t be as cold as last February! Good luck with them.
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