Injured tomatoes

I planted some tomatoes early and on cold nights I covered them with clear plastic. One day I noticed that the leaves at the top of the plant had turned black. What happened? The rest of the plant looked okay.

It is very likely that it got cold enough to damage the plants only where the leaves touched the plastic. The plastic works by forming a film of water on its under surface. This film of water reflects the infrared (heat) energy being radiated from the soil so it is not lost to the atmosphere. Those leaves touching the plastic were less protected and were exposed to the temperatures experienced by the upper surface of the plastic, which probably fell below freeing. The lower parts of the plants were in the air kept warmer by the heat retained by the film of water.

The plant should not be severely injured by this. If the tip of the plant (the growing point) was injured, then new growth will need to develop from a bud lower on the plant. That will slow growth a little but should not result in permanent injury to the plant.

Try to use some material to keep the upper leaves from being in contact with the plastic, especially on cold nights.

Another possibility is that you removed the plastic a little too late one morning and the leaves were sunburned. However, it is more likely in that situation that the heat would accumulate under the plastic and the whole plant would be injured.

Removing ivy

I was wondering if you could tell me the best way to get rid of ivy. I'd like to re-do the landscaping in my back yard but am afraid that the ivy will grow back.

There are two types of ivy - deciduous ivy and evergreen ivy, and you didn't indicate which type you are describing. This will have some effect on your options.

If you prefer not to use chemicals (herbicides), you can dig the ivy to remove it. It doesn't matter which type of ivy in this case. It is a good idea to dig and screen the soil through a one-half or three-quarter-inch hardware cloth mesh to remove stems so that you do not get regrowth.

If you prefer to use the chemicals rather than the digging, you can use any of several of the broad-leaf herbicides that translocate through the plant. Be certain to choose which is labeled for the plant you are trying to remove. However, these may have residual soil activity and will require that you wait for a while before you can plant in the soil again. Glyphosate-based herbicide is also translocated and not specific to only broad-leafed plants. It does not have soil activity (it must be absorbed through the leaves to be effective), and you may plant again 10 days or so after treatment. If you choose to use herbicides, be sure to read and follow all directions. The waxy leaf surface of older leaves on some ivy may prevent absorption of the chemical, so plants with new tender growth are more likely to be affected. If the ivy you are trying to remove is Virginia Creeper or another deciduous ivy, you will need to wait until it has formed leaves.

Following use of the herbicide, it is a good idea to dig up much of what remains just to get it out of the way. Then water well and see if there is any regrowth. If there is regrowth, dig it or reapply the herbicide.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

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