Greenhouse alone won’t shield tree from the cold
Q: I have a 3-year-old Meyer lemon tree that I have protected for the winter with a 8-by-6-by-8-foot collapsible greenhouse. It has two large “windows” on the sides and two large zipper doors at each end that I leave open in the daytime, then zip close if temperatures are going to drop to 45 degrees.
If it’s going to drop to 32 degrees or below, will I need to provide a heat source? The tree and greenhouse are in full sun, and it gets very warm very quickly in the morning when the sun hits it.
A: It sounds like you have made very good provision for your tree. It may eventually outgrow that space, so you may end up having to trim it a bit to fit. Or you might be able to raise the greenhouse with some kind of base.
Yes, you will need a type of heat source. A small electric heater might work, but be careful that it doesn’t make contact with the plastic cover or structure and that it doesn’t blow directly onto the plant’s foliage. Light bulbs alone won’t work. Even the old incandescent bulbs don’t put out that much heat. (Remember, LED lights don’t put out any heat.)
I assume the plant is too heavy to hoist onto a plant dolly and roll into the garage for the coldest of nights. Is it possible to position the greenhouse adjacent to a window or door of a heated garage? You could rig up some kind of attachment that would be weatherproof. That would allow you to open the door or window just enough to let warm air into the greenhouse.
Without seeing your layout, it’s difficult to give you more specific suggestions.
Q: A reader said they put down “weed barrier.” Back in Minnesota, we put down heavy-duty plastic sheeting and covered it with rock. The weeds stayed away. Thoughts?
A: If you’re talking about black polyethylene plastic film, that’s not a good plan. Granted, it will stop weed growth, but it also traps water during periods of wet weather. There is no passage of air (oxygen) through it, so the soil simply cannot dry out. If you’ve ever walked on a Texas clay soil under those circumstances, you know how spongy it can become. The weed barrier products have been designed to allow air and water movement in and out of the soil.
Q: I have moved into a house with a wonderful bed of asparagus. Unfortunately, it is overrun by equally “wonderful” Bermuda grass. Is there a product I can use to eliminate the Bermuda without killing the asparagus? I’m willing to take a year off harvesting if necessary.
A: There is no way to kill
Bermuda at this time of year short of digging it out by hand (and foot). Once it all starts growing, however, you could use a glyphosate-only herbicide to kill the active Bermuda. That would be late April and May. By then your asparagus harvest would have run its course. (You should cease cutting spears six or seven weeks into their production.)
Your secret will be to use a 2-gallon pump sprayer so you can direct the herbicide precisely onto the Bermuda. Keep it off the asparagus stems. I use a large piece of cardboard as a screen. I hold it in my left hand while I spray with my right hand. (I’m right-handed.)
The glyphosate weedkiller is inactive in the soil so it will not harm the roots. That’s why I specified “glyphosate-only.”
The manufacturer has also packaged products that combine glyphosates with other active ingredients that do soak into the soil and enter plants through their roots. Those are the products you want to avoid.
Q: We have an abundance of red oak seedlings growing in tandem with Ashe junipers. Can they successfully be separated and the oaks then brought into our landscape?
A: That’s going to be really tough, if not impossible, especially if all the oaks look like the example in your photo. You would destroy the oaks’ root systems.
You would be far better off if you could hunt for small saplings 12 to 18 inches tall. You’d be able to capture all their roots and hold the soil intact around them by digging them with a sharpshooter spade. Do so now while the trees are dormant. Water immediately after you replant them.
Q: We have three large Turk’s cap plants. When should they be cut back, and by how much?
A: As with most perennials, you want to prune Turk’s cap only once its foliage has been killed by the first freeze. Depending on where you are, this has been an unusually late winter for that to happen, but it’s close at hand for many of us. Once temperatures fall below 30 degrees, you can expect the top growth to be killed to the ground. But it will come roaring back in midspring, so leave the stems 1 to 2 inches above grade so you’ll remember where the clumps are.
Q: We have an older home where a prior owner used trailing myrtle (Vinca major) as the ground cover in several shady beds. I’m resigned to the trouble it has with leaf rollers in summer, but I love the way it looks in the spring, especially with its purpleblue flowers.
Can I dig and transplant what appear to be clumps of it now as it begins its new growth?
A: Yes. Choose fairly small clumps (tennis ball-size) and replant them as soon as you can. Trim their top growth back by half (assuming they are already growing vigorously). Plant them into well-prepared garden soil and space them 10 to 12 inches apart checkerboard style. Water immediately.
As for the vinca leaf rollers, you might try applying Imidacloprid systemic insecticide granules in late May or early June before the damage starts to show up. One treatment per summer might be enough to stop their disfiguring damage. You’ll still probably want to trim the old vines back considerably come late August to take advantage of the fresh, new growth that the plant puts out in the fall.