Ask Garden Girl.

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Author: Ciesinski, Therese

FOR THE PROBLEMS THAT BUG YOU

Q Are there any hardy avocado plants that I can plant outdoors in my USDA Plant Hardiness Zone 8 garden?

A There is a reason that San Diego County, California (known as "Avocado Country" to industry insiders), produced nearly 150 million pounds of avocados in 2003. It's almost always warm there--in fact, the average temperature consistently hovers near 70°F.

Unfortunately, "Avocados will not survive in northeast Texas or anyplace else in Texas, except right along the coast," says Gary Bender, Ph.D., subtropical horticulture expert at the University of California--Davis San Diego County Cooperative Extension. Jacksonville's tendency toward extreme heat in the summer and occasional frost in the winter, including freezing rain and even snow, makes your corner of the world inhospitable to avocado trees.

Avocados are subtropical trees native to southern Mexico, and they grow best in semihumid climates with moderate temperatures (60° to 80°F). Even the most coldhardy varieties ('Mexicola' or 'Topa Topa') freeze at about 25°F, Dr. Bender says.

You can, however, grow avocados in containers and move them inside during cold weather, but there are no dwarf varieties available, so the trees tend to get too big within about three years.

Before I broke the bad news, I wanted to make really sure that avocados would not survive in Zone 8. So I called up Jacksonville's local extension horticulture agent, Joseph Daniel. "I'm afraid that we're a little too far north for avocados," says Daniel. "We can have fun germinating the seed and growing the plant for a while, but that's about as far as we can take it." So it seems the only avocados you'll be picking will be from the supermarket. But if you still want to grow your own indoor baby avocado tree, the California Avocado Commission has helpful instructions online at www.avocado.org.

Q I have a five-year-old wisteria vine that grows by leaps and bounds and has tons of foliage, but it puts out barely any blooms. What's going on?

A Patience comes in handy when growing wisteria. "The biggest frustration that gardeners face when growing wisteria is that plants have a longer-than-average juvenile period and sometimes fail to bloom as expected," says Jane C. Martin, horticulture agent for the Ohio State University Extension.

The plant's environment and how you care for it also affect blooming. Many gardeners suffer from a desire to fertilize indiscriminately, usually to the detriment of the plant. Juvenile plants, such as yours, should be fertilized only once a year. Use an organic fertilizer with a balanced NPK ratio. Too much fertilizer encourages vigorous vegetative growth at the expense of blooming. Established wisteria needs little fertilizer or additional water. After the plant fills in its trellis, water it only during drought and fertilize if the foliage yellows and new growth is poor.

Wisteria must be properly pruned to promote blooming. Chinese wisteria (Wisteria sinensis) and Japanese wisteria (W. floribunda) are the most commonly planted species, and they produce flower buds on old wood. Don't prone heavily in winter and early spring, because you'll be pruning off flower buds and encouraging new (nonblooming) vegetative growth. You can improve flowering by pruning heavily after bloom time, in late spring or early summer. This practice reduces new vegetative growth and promotes flower production. Since wisteria has very specific pruning needs, I suggest that you get a copy of Cass Turnbull's Guide to Pruning (Sasquatch Books, 2004), which acknowledges the challenges of caring for wisteria and clearly explains how to maintain it properly. (Turnbull is the founder of Plant Amnesty, an organization dedicated to rescuing plants from bad pruning.)

Also, wisteria will grow in partial shade, but it needs at least six to eight hours of full sun to bloom best. You can encourage flowering by pruning heavily in the summer and then root-pruning in late fall: Starting about 4 feet from the think, cut 18 inches down into the soil with a spade, circling the mink. This process tends to "shock" plants back into flowering.

Plants grown from seed can take 10 to 15 years or longer to bloom, Martin says. If you know your plant was grown from seed, you may want to take it out and start over. Before purchasing a replacement, check with your nursery about how their wisteria were propagated, and be sure to buy one propagated by grafting or cutting. This will greatly shorten the time to flowering.

Q I live in an apartment with no yard, but I'd like to start an organic vegetable garden. How should I approach this?

A As a fellow apartment dweller, I understand the urge (okay, the need) to have a vegetable garden. Luckily for us, vegetables have only three basic requirements: light, soil, and water. And they don't have to be planted in the ground--they grow great in containers.

You have to start by finding a spot for your pots that gets six to eight hours of sunlight a day and has access to water. I grow my veggies on the roof and in window boxes, but patios, doorways, sidewalks, and even roof eaves (for hanging baskets) can house a few containers. Most landlords are happy that tenants actually want to improve the property, but it's a good idea to get your container garden okayed before you start planting.

In general, shallow-rooted plants, such as lettuce, spinach, radishes, and most herbs, need only 6 to 8 inches of soil depth to grow well, while deeper-rooted plants, such as tomatoes and squash, need 12 inches of soil. Terra-cotta pots, wooden boxes, and even 5-gallon buckets make great containers. Just make sure your containers have drainage holes, are not translucent or opaque (sunlight will fry plants' roots), and are big enough to support the plants growing in them. Fill your containers with a well-draining potting mix (topsoil will compact in containers) that has some compost or an organic granulated fertilizer mixed in.

Almost all vegetables grow well in containers, but choosing the right variety helps. 'Window Box Roma' tomato, for instance, stays a size that's manageable for pots, and 'Tumbler' tomato vines spill nicely out of hanging baskets. Beans, peas, and even squash can be grown up trellises set into a larger container. Try the compact 'Sunburst' yellow scalloped squash and 'Spacemiser' zucchini. 'Miniature White' cucumbers have small vines and unusual white fruit. Carrots such as the heirloom 'Oxheart' and the miniature 'Kinko' grow to only 4 to 6 inches long. There are a ton of resources on container gardening, but the two that I turn to most are The Bountiful Container, by Rose Marie Nichols McGee and Maggie Stuckey (Workman, 2002); and Lasagna Gardening for Small Spaces, by Patricia Lanza (Rodale, 2002). Both of these books have great information on soil, plant varieties, and plant combinations.

If you want to actually sink your hands (and your plants) into the earth, try community gardening. You share a plot of land, as well as advice and friendship, with other urban gardeners. You happen to live in a city with a large and vibrant community garden culture, so there is most likely one in your neighborhood. For more information on community gardens, check out the American Community Garden Association (www.community garden.org, 877-275-2242) or your local Philadelphia community garden organization, Philadelphia Green (www.phillygreen.org, 215-988-8800).

Q I'm considering using creosote-soaked railroad ties to terrace my vegetable garden. Are they safe to use? And is there a low-cost alternative?

A There are two main types of creosote: wood creosotes, which are derived from the creosote bush (Larrea) or beechwood (Fagus); and coal-tar creosotes, which are produced in the distillation process of coal tar. The creosote you are concerned with is the latter--a thick, sticky black substance used to preserve wood, including railroad ties, utility poles, and marine pilings.

Creosote is composed of a mixture of chemicals, about 300 of which have been identified, but there could be up to 10,000 more present in the mixture. Some components of this chemical cocktail dissolve in water or seep from treated wood. They can contaminate soil and move into groundwater, and persist for many years.

Of perhaps greater concern than contaminating your garden is the health risk that creosote presents to you. The International Agency for Research on Cancer and the Environmental Protection Agency have both found creosote to be a probable carcinogen. Low-level, long-term exposure can also cause reddened, blistered, or peeling skin, increased sensitivity to light, and eye damage. Preparing and handling the ties during installation and simply gardening around them could expose you to potential health risks. You could be allowing creosote to enter your body by getting it on your skin, ingesting contaminated food or soil, drinking contaminated water, or breathing contaminated air.

In short, don't use the railroad ties. It's not worth the risk to you or your garden. So what's your best and cheapest alternative? Cinder blocks, or the more attractive concrete retaining wall blocks. These blocks are inexpensive, durable, and widely available. Manufacturers have branched out from the traditional (and institutional) gray color and now offer blocks in a variety of colors and textures, including faux rock. So your garden will look and feel good.

Q Last summer, most of my tomatoes, especially 'Brandywine', were filled with a green, woody substance that made them inedible. On the outside, they were perfect. Can you tell me what happened?

A What a nasty surprise on the inside of your tomatoes! Weather conditions, over- or underfertilization, or an insect pest could all be your culprit. Chances are the plants were under stress of some kind. In high-stress situations, such as extremely high or low temperatures, defoliation, drought, or underfertilization, tissues can become hard and white. Occasionally green tissue also forms, says J. W. Scott, Ph.D., professor of horticulture at the University of Florida. An outside possibility is blotchy ripening, a disorder thought to be caused by a potassium deficiency. But this disorder is usually characterized by external and internal areas of the fruit that never ripen.

A southern ripening disorder that somewhat matches your description is the result of sweet potato whitefly (Bemisia tabaci) or silverleaf whitefly (B. argentifolii), Dr. Scott says. The whiteflies introduce a toxin into the fruit that causes irregular ripening. Parts of the skin do not ripen and remain yellow to white, while the inside of the fruit has severe white tissue formation. Sometimes the exterior discoloration disappears but there can still be a lot of white tissue inside, Dr. Scott explains.

Protect this summer's crop by covering all your bases. Use sticky traps to capture whiteflies, fertilize regularly to maintain soil potassium levels, and keep your fingers crossed for good weather.

Send your questions to Willi Evans, Garden Girl, 33 East Minor St., Emmaus, PA 18098, or og@rodale.com.

PHOTO (COLOR): Wisteria, a.k.a. "hysteriua."

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Edited by Therese Ciesinski