'Top killing' is best bet when dealing with wild morning glory

Question: I have a morning glory vine that has invaded my garden in the soil. I have tried to treat it with a special liquid that should kill it but it still grows and grows, and the sprouts wind around all my plants. Is there any way to get rid of it?

Answer: Field bindweed (Convolvulus arvensis), also known as wild morning glory, is a challenging weed to eradicate. According to recent studies at the University of California at Davis, the best control method involves repeatedly "top killing" the plants -- physically removing new growth by pulling it or by "flaming" it (a very fun method of weeding involving a hand-held propane torch). The trick is to remove the new growth as soon as you see it, eventually starving the roots of a carbohydrate source and killing them. This process takes time, but it is the most effective way to rid your garden of bindweed.

The same study also notes that repeated applications of a clove oil and/or acetic acid based organic herbicide (brand names BurnOut, MatramII or Xpress) provide another means of "top killing" and are quite effective when used consistently.

Other research recommends covering the area with a black plastic or weed fabric mulch for three to four years; and, for vegetable gardeners, the National Sustainable Agricultural Information Service suggests planting a year-round cover crop of annual rye grass for a full season (rye has the ability to suppress the growth of other plants).

Whatever you do, don't till the area. The roots can be as much as 10 feet deep and tilling will just chop them into smaller pieces, each of which will grow into a new plant.

Q: I have a large Christmas cactus (2 feet in diameter and 1 1/2 feet high) that looks like a bush and is in need of a trim, but I have no idea where to begin or if it can survive a trim. Please let me know if you have any ideas.

A: Pruning Christmas cactus isn't necessary; although since yours has grown so large, it might be needed simply for size control. Remove only a few inches of the outermost growth immediately after the plant blooms (the pieces you remove will easily root and form new plants if desired). Pruning all the way back to the woodier growth might affect the health of the plant and might even kill it. Less is better.