It's time to let all your plants go to pot

Just as today's families are on the move, so, too, are today's gardens. Flowers, herbs, trees, and even vegetables can be planted in moveable containers.

Gardeners have pushed the limits with container gardening. No longer presenting just a colorful array of annuals, creative containers may hold perennials as well as herbs.

Tropicals, such as bougainvillea, hibiscus, gingers, Datura, Brugmansia, and dwarf banana trees are now as popular in Northern as in Southern gardens, when grown in containers.

Give traditional entry urns - crammed with red geraniums and vining vinca - added kick with trailing purple verbena and sweet potato vine varieties such as Blackie, which has deep purple stems, and chartreuse-foliaged Sulphur.

Effective layering is as important as flower choice. A pot can be jammed full, but still look slight if height and balance are not considered.

Plants that produce flower spikes can be added to almost any style pot, or look for the taller varieties of most annuals to give a container planting a boost.

Ornamental grasses, such as red pennisetum, can also be used effectively.

Let plants trail over rim

Likewise, all but the most formal arrangements benefit from some overhang. Ivy geraniums naturally trail, as do cascading petunias and purple heart vine (Setcreasea pallida 'Purple Heart'). The Wave petunia series has proven exceptional for pots. Trailing verbena adds bubbles of intense purple and bright rose.

Nasturtiums tumbling over containers edges are hard to beat for beauty, but can be finicky if the weather gets too warm. Scaevola from Australia drapes its purple fan flowers gently, even in the hot summer sun, with little attention from the gardener.

Just how much care a pot needs depends largely on soil preparation before planting. The potting mixes on the market are better than soil dug from the garden because they are lightweight and sterile. Experiment with brands and quantities until you have a mix that feels right to you.

Despite what you may have heard in the past, it's not recommended to put plant shards or gravel in the bottom of a container; scientific experiments have shown that they do more harm than good to the plants. Roots grow down into the rocks, and the absence of soil may harm the plant. To keep soil from washing away, cover the pot's hole with a small piece of screen.

By the middle of summer, most containers may need to be watered daily - and on the very hottest days, even twice. That's the bane of containers gardeners.

Water-holding polymers, which absorb up to 20 times their weight in water and slowly release it, are available at garden centers and may be worth buying to lengthen periods between waterings. But it's important to read and follow the label when using them; you'll end up with a mess if you use too much or don't mix the product correctly.

In spite of the increased need for water, all containers must have excellent drainage. Plants drown as easily as they die from drying out. If you have a large, impressive container without drainage holes in the bottom, consider using it for moisture-loving plants, such as cannas, ferns, or rushes, which tolerate "wet feet" (extra water around their roots).

Or simply fill the pot with water and "plant" a water lily or dwarf lotus, rather than forcing garden plants to adapt to it.

Slow-release fertilizer makes sense in the crowded conditions of container gardens. These pellets should be added just before placing the plants in the potting mix and can extend fertilization for three to nine months, depending on the type. Formulations are available for both foliage plants and flowering plants.

However, because constant watering washes nutrients out of the container, it's a good idea to also use water-soluble fertilizer from midsummer on. Container plants need the extra boost to keep blooming in such tight quarters and under stress. Use it every other week at half the rate recommended on the label.

Once you have the potting mix and watering routine down, don't stop with just entry pots. Use a variety of containers grouped together as a focal point on a deck. A small tree or flower standard placed in the right spot can produce just enough shade for an afternoon break on the patio.

Check nurseries and garden centers for containers made of new lightweight materials. These are ideal for balconies, where weight may be a problem. They also make moving pots from one area to another - or non-hardy plants indoors for winter - much easier.

Even some hardy species may need to be moved to a protected area when cold weather arrives to protect the roots from freezing. In those cases, move the plant to a cool room or garage kept above freezing. There it should be allowed to go dormant by watering minimally.

In the spring, increase watering and watch for signs of awakening: bud break or other growth. Allow the plant to readjust slowly to a regular spring schedule, and when the weather permits, move it back outdoors, hardening it off by protecting it from the sun and wind for a week or more before placing it where it will spend the summer.

Herbs and veggies

Create a portable kitchen garden outside the back door with pots of herbs, lettuces, tomatoes, and peppers.

Even smaller varieties of eggplant, cucumbers, squash, and melons are available for container gardening. Look for bush or dwarf varieties with names that indicate that they stay small, needing less room to grow.

Don't hesitate to add a few colorful annual flowers to these edible container gardens. Nicotiana and marigolds are traditional in vegetable gardens and do nicely in containers,too.

Vegetables will grow best with full sun, but herbs do fine with filtered sun.

Herbs take to pots very well, and are much less demanding of soil type and fertilization than most annual flowers or vegetables.

Fresh herbs like parsley, basil, and cilantro have no equal, so keep a pot or two of them handy. Plant purple-leaved and ruffle-leaved basils in the same pot with cinnamon and lemon-scented ones for both beauty and bouquet.

Allow one of the decorative-leaved sages (some are yellow and green; others purple and white) to overflow a container that holds a bush tomato.

Some herbs are lovely enough on their own to be planted in hanging baskets and other containers. Certainly parsley is as attractive a "filler" as asparagus fern. Thyme can overflow a pot with as much grace and fragrance as alyssum. Using chives instead of an annual flower gives the added benefit of a lovely purple flower early in the season while other plants are still establishing themselves.

Even if you never use a sprig of rosemary in cooking, there is something exotic about growing it just close enough that you can brush by it for a whiff of its intoxicating, pungent scent. It does best grown in a terra-cotta pot with a well-drained - even sandy - soil, and can be brought inside to a sunny windowsill during the winter.

With the upsurge in container gardening, urns are not just for entries anymore, vegetables don't always grow in in-ground gardens, and trees don't anchor landscapes. And with a container garden, if you're not happy with it, just move it someplace else.

(c) Copyright 2001. The Christian Science Monitor