Garden Doctor on tomatoes, trumpet vines and shrubs

Q: My tomatoes keep flowering, but the blooms drop off before I get tomatoes. What's wrong? And how can I fix it? -- Orlando, Florida

A: Tomatoes can be touchy about forming fruits. There are a couple of common reasons why the blooms might fall off before setting fruit. The most common is drought stress. If the tomato plants don't get enough moisture, they'll abort their fruits at a very early stage.

It's also quite possible your plants are too hot. Many tomatoes are shy to set fruits if the daytime temperatures are over 92 degrees F. or if the nighttime temperatures stay over 82 degrees F. (There are a few heat-tolerant tomatoes, such as Solar Set, that have come from the University of Florida that do set fruit in higher temperatures.)

If the environmental conditions are good, then lack of pollination may be a factor. Avoid using insecticides around your plants while they're in bloom.

Q: My tomatoes split open before they ripen all the way. What's going on? -- Versailles, Missouri

A: Split tomatoes are a common problem and occur for a couple of different reasons. The first is that the plants are getting inconsistently watered or getting too much water; it makes the skins weak so that as the fruit expands, the skin breaks open.

The other common reason is that plants are getting fed more than they need. The fertilizer encourages the fruits to grow faster than they should, and as a result, the skins are weak and break open easily. This is more common in some varieties (especially older ones) than others, so you might try a few different tomato varieties and see which are least susceptible for your growing conditions.

Q: I have a huge lantana bush that's really beautiful. Can you tell me when I can prune it back and if I can start new plants from the cuttings? -- Birmingham, Alabama

A: Most lantana cuttings root most easily when taken from midsummer to late autumn. Make your cuttings 3 to 6 inches long and insert them into moist sand, perlite, or vermiculite. Keep them moist (but not saturated) and out of direct sun. They should root in about three weeks.

Q: My trumpet vine is gorgeous. What I would like to know is what are those pea pod-like growths after the flowers bloom? Can I plant them and get more plants? -- Adel, Iowa

A: The pods you're seeing on your trumpet vine are seed pods. Like a pea or bean, you can wait until they're fully brown and dry, split them open, and collect the seed. To plant them, soak the seeds in water overnight or gently file away a small corner of the hard seed coat with a nail file. Then plant them outdoors in a protected spot. Keep the soil moist while the seeds sprout.

Note: To increase trumpet vines, dig up any suckers that grow up around the roots or take cuttings.

Q: Can you recommend any ever-green shrubs that will get at least 8 feet tall but no more than 6 feet wide? And what about trees? Can you suggest any for my area that will mature with no more than a 10- to 15-foot spread? -- Killbuck, Ohio

A: For shrubs, there are a number of junipers and hollies that are tall but relatively skinny. For example, Sky Pencil holly gets about 8 feet tall and only 2 feet wide. The juniper Sky Rocket grows about 15 feet tall and 3 feet wide.

There are also columnar trees that have a tall, narrow habit. Columnar yew grows 12 feet tall and 4 feet wide; Capital pear grows 30 feet tall and 12 feet wide; and columnar white pine grows 30 feet tall and 6 feet wide.

Questions for the garden expert?

Justin W. Hancock is a gardening editor at Better Homes and Gardens magazine. Visit http://bhg.com/app/qa/plant/ to see the most commonly received questions or to e-mail your own inquiry to our team of gardening experts.

Photograph: Meredith Print Center