A Greener View by Jeff Rugg

Q: I have a question about my basil plant, which I have been growing indoors. The leaves still look very healthy, but the stems are turning black (starting at the soil and traveling up approximately 1 inch). Is it still OK to harvest the leaves?

A: As plants mature, they often have stems that change color and develop other characteristics, such as corky ridges. Plants that we don't normally think of as shrubs may still develop woody stems, especially at the base to help support the plant.

There are diseases that also cause stems to turn black, and some of them start in the roots and move upward. Root rotting and stem diseases become visible as they damage the above-ground tissue. The stem tissue will typically shrivel and look like a raisin as it turns color. Overwatering is often the cause, because the roots drown in the waterlogged soil. Decay organisms start consuming the dead roots and move to the live roots and stem.

If it is a disease, the normal-colored leaves, far from the base, are still fine and can be harvested. If the disease is slow moving, it won't be in upper reaches of the branches, so you can take a few cuttings off the upper branches and root them in water. The disease organism may be spread throughout the plant and the cuttings will rot, too. In that case, it is time to start over with new seeds, fresh pots and new soil.

Each place on the branch with leaves is called a node. New branches and roots can grow from nodes, but most plants won't grow from the branch section between the nodes. Prune the cutting just above a node. If the plant is not dying, the node will send out new branches.

On the cutting, prune the section of stem below a node and take off any leaves at any nodes that will be in the water.

Place the cutting in plain water that you can change every few days — set it a little farther from the window than it was before. You can also use damp sand, perlite or vermiculite as the rooting medium. A rooting hormone powder can be sprinkled on the cutting to help promote root growth. Covering each cutting's container with a greenhouse of plastic wrap can help keep the humidity high. In a month or two, the roots should be a few inches long and you can plant the cutting into soil.

Q: I brought a mandevilla vine indoors for the winter and it has lost all of its leaves. Should I just throw it out or will it come back?

A: Mandevilla vines are beautiful tropical vines that need bright light, warmth and high humidity. Indoors, they often don't get any of those requirements met, so they go dormant first. And without watering, they die.

A sunny, warm and humid environment is good for overwintering many tropical plants, including geraniums. If you have a sun room or other windows where there is light and some warmth without direct dry heat from a furnace, then many tropical plants can survive the winter just fine. Keep the soil slightly damp, don't fertilize, watch out for insects and pick up fallen leaves. If the plant isn't happy with those conditions, it might go dormant.

If a plant drops its leaves, you will probably be better off trying to keep it in a dormant stage over the winter. Clean up all the leaves and trim the stems and branches down to about a foot above the pot. Put it in a cool and dark location where you can occasionally add some water to keep the soil slightly damp. A temperature in the mid-50s is good. If it is warmer, it will try to grow and will die without enough light. If it is kept in the 40s, it will also die.

In the spring, repot with fresh soil and set them outside after the last frost date.

E-mail questions to Jeff Rugg, University of Illinois Extension at jrugg@illinois.edu. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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