By Joel M. Lerner
Saturday, July 22, 2006; F09

Your thought-provoking questions are enjoyable to read and to answer.

Q: I am perplexed by an invasion of poison ivy covering my hillside and several mature azaleas. If I spray the azaleas with Roundup, I'm afraid it will kill them. -- Linda Florence

A: If the poison ivy is young enough, put on heavy, leather gloves and pull it out by the roots. If it can't be pulled, maybe it can be dug. Even if you are allergic to it, as long as you don't touch the surface of gloves or tools that came into contact with the allergen in poison ivy oil -- urushiol -- it won't cause a rash. Keep gloves used to pull poison ivy separate for a couple weeks, or use them for other work, and the oils will wear off.

Where poison ivy is growing through a shrub or up a tree, or is impossible to pull or dig, first cut the stems as close to the base as possible. The top growth will die, but don't grab it with bare hands. Stems contain urushiol until they are fully decayed. When at least six to nine new, mature leaflets grow from the base of the vine, spray foliage with a non-selective, systemic herbicide such as Roundup or other glyphosate-based herbicide. It will kill the plant, including the roots. This method might require a second application, but by cutting the poison back, you use a fraction of toxic material to control it and save the azaleas, too. Follow all labeled instructions.

We were in Northern California and saw lovely, large-flowering bushes with red, pink and white blossoms. The foliage had slender green leaves. We would like to know the plant name, whether they would be suitable for Southern Maryland and where they can be obtained. -- Frances Rutt

In California, you can cultivate almost any plant, so it's difficult to answer with complete surety. From your description, I would venture a guess that you are asking about oleander ( Nerium oleander ), which has slender leaves and colorful flowers. These natives from Alabama, Mississippi and Georgia are widely planted in California, and flowers are red, pink or white, depending on the variety. You can get oleander at some garden centers, mostly for summer flower.

They are not planted in this region because they begin to have freeze damage below about 15 degrees Fahrenheit. If you buy one, plant it in ground in a protected, warm, sunny location within four to six feet of a house wall and see how it does. A hardier variety than most is named "Snow Frost," if you can find it. All parts of the plant are poisonous. People have been known to cut sticks of this shrub and use it for toasting marshmallows or roasting hot dogs with very toxic effects.

We have a vegetable garden with five raised garden beds. We primarily plant tomatoes, cucumbers and squash. The squirrels eat our tomatoes. We would have to fence the entire area and cover the top to keep the critters out. Any suggestions? -- Katharine E. Alter

As a last resort, because your tomato yield is declining or you are losing fruits and seeds to birds, you could get netting and lay it across the top edges of a barrier fencing that encloses the entire vegetable garden. Covering fencing with a lid to protect against squirrel damage is an extreme fix. Squirrels are much more interested in seeds than vegetables. I do recommend fencing a vegetable garden against rabbits, voles and other ground pests. In fact, a six- to eight-foot-tall fence will also keep deer out of the vegetable garden. Make sure the mesh is fine enough (one inch square or smaller) to keep small animals out. Bury the bottom of the fence six to 12 inches below the surface to discourage burrowing critters. Some fences are more aesthetically pleasing than others. Choose one that you like the looks of, though its most important function is as a barrier against animals.

You might also investigate products that are animal repellents and possibly avoid a fence. Check out http://www.critter-repellent.com/ .

Have you heard of taking funnels and straws and pouring white vinegar down the hollow shafts of bamboo, after clipping off the green shoots? It wipes out that stalk and future generations. What is your opinion on using white vinegar in the garden for weed eradication? -- Barbara Bryant

I will try your method of pouring white vinegar down the clipped, green, hollow stem of bamboo. The Environmental Protection Agency approved vinegar as a non-selective organic herbicide a couple of years ago. Vinegar is completely water-soluble and, therefore, has no residual effect. It has been a helpful, safe tool to control weeds, such as Canada thistle, plantain and other broadleaf weeds.

You must be careful with any solution over 11 percent vinegar because it can burn you. Higher concentrations than the 5 percent white distilled vinegar found on grocery store shelves will give better weed control. They can be found at food manufacturers such as Fleischmann's Vinegar Co. Call 1-800-443-1067 or visit http://www.fleischmannsvinegar.com/ . Also look for BurnOut II Weed & Grass Killer, a solution of vinegar and citrus, that can be found at health food stores and garden centers.

You must use vinegar as carefully as other non-selective herbicides. It can kill any plant it contacts. Find more information about vinegar as an organic herbicide by surfing the U.S. Department of Agriculture's research site at http://www.ars.usda.gov/ and searching for "vinegar herbicide."

Please help us all by providing information on nontoxic ways to keep our gardens growing beautifully. -- Karen Berry

I appreciate your concern about the use of toxic chemicals to control problems in the landscape, and I always consider the least toxic methods of controlling pest problems. If there are no natural products available, I will choose a material that the academic, scientific community considers to have the least negative effect on the environment. As more natural methods are discovered and approved for use, the safer our environment will be. To that end, readers might peruse some of the Web sites listed below that specialize in information and environmentally friendly materials to control pests in the landscape:

· http://www.centralsan.org/education/ipm/resources.html

· http://www.gardensalive.com/

· http://www.montereylawngarden.com/

· http://www.saferbrand.com/lawncare/lawncareproducts.htm

I have a Japanese maple that seems to be dying off bit by bit each year. It is 15 to 20 feet tall. At the base of the trunk, there is some extensive decay and stripping of the bark just above the soil. Leaves are sparse, and the branches have a black coating on them. Do you have any sense as to what may be happening? Is there any treatment for it? -- Devon Brown

My first speculation, if the tree is planted in lawn, is physical mower damage, especially considering the extensive stripping of bark that you describe at mower height.

If Japanese maples are planted in hard clay and are subject to periods of drought, they will be stressed. They do not like afternoon sun and are sensitive to heat. These conditions make them susceptible to a variety of insect and disease problems, and they will decline because of their tender nature. Plant in an eastern exposure with protection from western sun, and keep a bed around them as a buffer from lawn mower damage.

If your Japanese maple is ornamental enough to try saving, help it along by watering whenever the soil begins to dry. With every other watering, supplement with a water-soluble fertilizer for acid-loving plants, such as Miracid. Also, water in a mixture of growth stimulants, such as Roots, Superthrive, Bio-Plex or a seaweed-and-fish meal-based product. If you lose this tree, try again. Install the new one in a well-drained site. Dig the hole four times as wide as and no deeper than the root ball. Fill with one part compost, two parts native soil and keep moist.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site,http://www.gardenlerner.com.