Don't Put the Fertilizer Away Just Yet

It's time again to answer some of your gardening questions.

Q: Is it still necessary to fertilize flowers and other plants at this time of year? -- William

A: Annuals can be fertilized with a water-soluble nutrient every other watering until the first frost. Lawn can be fertilized with slow-release lawn food once in September and once in October. Shrubs and trees can receive a general-purpose fertilizer until the end of September. And remember, all fertilizer requires watering to work.

I planted five small crape myrtles last summer. They are about three feet tall and had blooms on them when I bought them. This summer, they have not bloomed at all. I have not cut them back. Why haven't they bloomed this year? -- Jenny

We had a cool, dry spring that was not conducive to bud formation on crape myrtles, but they should have been budding and flowering by August. If there is still no sign of flowers and they are healthy, move them to where they will receive at least seven hours of sunshine a day.

Please recommend a book on lawn and garden plant identification and cultural requirements in this region. -- Tom

Since there are more than 100,000 named herbaceous plants, 5,000 or more native to the United States, a single volume would not be practical. Here are several titles we use in our office: "Herbaceous Perennial Plants" (Stipes Publishing, 1997); "Armitage's Manual of Annuals, Biennials and Half-Hardy Perennials" (Timber Press, 2001); and "Armitage's Native Plants for North American Gardens" (Timber Press, 2006), all by Allan M. Armitage. These texts have images and contain information about plants. Use "Better Lawns Step by Step," by Joe Provey and Kris Robinson (Creative Homeowner, 1999) for weed identification and grounds maintenance. You can also contact your county's cooperative extension service.

How can I do my own aerating? I have a 3/4 -acre area to do. -- L. Jackson

A core aerator is an easy tool for one person to use, but it takes two people to load and unload the machine. It can fit into a station wagon with the handle sticking out, though a small pickup truck is best. The machine is self-propelled; it's easier to use than a lawn mower and starts the same way, moving or stopping with a lever on the top of the handle. If you can walk a mile or two, you can aerate your lawn. Because it can move at a brisk pace, you might want to break it into quarter-acre parcels and take breaks. You will remove a lot of plugs in a half- to full-day rental. Wear sturdy shoes and long pants. The soil should be slightly moist, not soggy.

Along my driveway, I have 80 feet of daylilies. The deer eat the buds and flowers in one night every season. Are there any deer-repellent plants I can plant with the daylilies to keep the deer away from that area?

-- Dinesh

Deer are smart animals. They will remember that you have an accessible "salad bar." But they dislike plants with fragrant foliage. Try installing some of the following around the daylilies: lavender, catmint, rosemary, artemesia, oregano or lemon balm. Another option is deer repellent made of animal products, such as egg-based mixes, predators' urine or other byproducts. If used according to labeled instructions, they are effective. They must be applied at regular intervals throughout the growing season. Another alternative is to separate the deer from the plants by installing netting or deer fencing on tall stakes around the daylilies.

We have many plants that reproduce by sending underground runners from the base of the plant (oakleaf hydrangea, nandina, fothergilla and clethra). I have tried to control the spread of these plants by pulling and digging the offending runners. They are becoming more difficult to control. Is there a spray I can use to kill the new plants without harming the parents? How can I make maintenance more manageable?

-- Beth

There is nothing safe to spray to control your plants' growth. Cutting back and thinning might be needed every few years, especially if they are too close to structures or losing their "designed" intent. These plants are best when sited where they can form colonies. In a cultivated environment, they require management.

Oakleaf hydrangea ( H. quercifolia) flowers on buds formed last year. It can be retained as a tall mass for flowering value. Next year's bud lies below last year's flower. To keep it flowering and inbounds, about a quarter of the oldest stems can be cut to the ground every two to four years. You will sacrifice a year of flowers to reduce the height. Do not prune until you enjoy the maroon-orange fall foliage. To renew shrub, head back one-quarter by cutting stems to a leaf node the end of February before spring growth begins.

Nandina also colonizes, and the tallest stems can be cut to the ground to thin them before growth begins in spring, creating a natural versus sheared looking shrub.

Fothergilla ( F. gardenii) produces few suckers from the roots. Prune the main shrub after flowering removing suckers growing from roots or base of main trunk.

Clethra ( C. alnifolia) flowers on the current year's growth. Prune in early spring before growth begins. Suckers can be pruned to control the spread of this shrub. It should not be sheared but allowed to grow in its natural form, with little pruning.

If you have massive numbers of suckers growing from the plants' roots, or stolons -- underground stems -- get a heavy steel nursery spade with a high-quality, sharp, square edge. Use it to slice out roots with suckers when you see them.

I have a dwarf fig tree that is rich in foliage year after year but rarely produces edible figs. It is next to the house for protection in winter with limited southern exposure. I have tried fertilizers, maintained good watering practices and have seen no diseases. Any suggestions? -- Arnold

Figs need seven to eight hours of sun to flower well. Track the hours of direct light, and you might find that it needs a sunnier location. Flowering is almost always directly proportionate to the amount of sunlight the plant receives. They are self-pollinating, and the more flowers, the better chance fruit will form. The Smyrna fig is the only one I'm aware of that must have a fig wasp enter the immature fig to pollinate the flower.

Figs also like shaded roots. Mulch with straw, four inches thick, or shredded pine bark at two inches to help shade roots. Do not pile against tree bark. They prefer clay-like, moist well-drained soil.

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.