A: You have a very common problem. People who plant comfrey often regret it. It came from Europe as a medicinal herb. It still is used for that purpose, but it has escaped.
It is a perennial, so you probably need a two- or three-pronged attack to get rid of it. The most important thing, of course, is to stop it from making seeds. It makes a lot of seeds and although it's easy to propagate, it spreads mostly by seeds. As with any weed, the fastest way to get rid of it is not to keep pulling it, but just to keep cutting it off every time you see a bloom stalk.
If you have individual plants mixed in your garden beds, you again have a couple of options. If you own a weed burner, use it on them as soon as they come up, then keep an eye out for them throughout the summer and burn them again as new leaves appear. If you have no weed burner, cut the whole plant to the ground, not just the flowering stems. It will resprout, but it will take a while and the leaves will be smaller. Cut it again. After three or four times the roots won't have enough reserves to put up new leaves. (If you really like the feeling of digging out a weed and saying, "There! I've got you!" that works equally well.
Since you already have a serious problem, expect that it will probably take at least two growing seasons to get rid of the comfrey. You'll kill all the existing plants the first year, but you have a stock of seed in the ground so you'll see seedlings for at least one or two more years. At least they will be small and you can deal with them quickly and avoid repeat applications.
Many times, after trying these methods, people decide they're not working. However, it's not that the plants are surviving your efforts, you're just seeing new ones. You have a seed bank that must be disposed of.
Q: My lucky bamboo is perfectly happy, but the leaf tips are turning brown this winter. What can I do to avoid that?
A: This is probably tip burn caused by low humidity. When the air is dry, the roots just can't get enough water to all the leaf surfaces to keep them healthy. It is a common problem with houseplants in this dry climate and most common with plants that have narrow leaves with a sharp point.
Your "bamboo" is really a dracaena and is related to the spider plant. With these plants you also can get brown tips from chlorine and some other salts, so if you have chlorinated water, try leaving it in the filled watering can for a day before applying it to your plant. You could even try giving the plant bottled water. Be careful with fertilizer; too much makes the problem worse. You can certainly cut off the brown tips, but leave a hairline edge of brown on the plant. Otherwise the plant will seal the open wound by making more brown cells on the edge of the cut. Springtime will probably seasonally cure the problem.
A year ago we talked about giving your plants an aspirin as a treatment to increase the plants' natural defenses against diseases. We now can offer updated information on the subject.
Plants activate the equivalent of an immune system when they are attacked by pests or diseases. The term for how they do this is systemic acquired resistance, or SAR. The first product on the market intended to stimulate SAR is called Messenger. The active ingredient in Messenger is harpin, a substance isolated from the fire blight bacterium.
When it is sprayed on plants it seems to trigger their natural defenses. It is nontoxic, so it sailed through the U.S. Environmental Protection Agency tests. It can be used on food plants up to the day of harvest. During testing, the EPA found it was effective against some viruses and previously untreatable fungal diseases and nematodes. It also seemed to stimulate plants to grow more quickly. One of the big advantages of this type of pesticide is that it does not attack the pests, so they can't develop immunity to it.
Aspirin stimulates systemic acquired resistance in the same way Messenger does. There are now a couple of anecdotal reports from last year's growing season suggesting that with tomato plants, green beans, eggplants and basil it was definitely helpful. One set of experiments was done with aspirin and the harpin protein and both produced the same results. The plants continued to show symptoms of fungal disease, but they were definitely more vigorous and produced almost twice as much in the way of fruit or vegetables.
One big difference is cost. Harpin is expensive. Aspirin you apply at a rate of 1 to 10,000, which means 1 1/2 aspirin per two gallons of water, sprayed on the plants every three weeks. That's where we are with a year's experimentation. We will see what next year brings and report again then.
Master gardeners Molly Hackett and Georgianna Taylor, whose motto is "Never trust a gardener with clean fingernails," welcome your questions. Send them to: 191 Eastside Highway, Hamilton, MT 59840; call 961-4614; or e-mail tenrecs@aol.com.
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