Container Gardening
Gardening in Containers
Preparing Containers
Choosing A Potting Medium
Watering
Fertilizing
Repotting
Growing plants in containers allows you to have a garden even when the space for one is limited or nonexistent; install a planter box under a window or use flower pots to turn a small balcony or patio into a lush green haven. Even gardeners with plenty of space will appreciate containers, too, valuing the versatility they offer.
Blooming plants bring season color to garden beds, a porch, or the front steps and are easily replaced with new ones when their flowers fade. Additionally, containers give you the chance to experiment with new plant combinations and with kinds not suited to the native conditions. If your soil is alkaline, or claylike, but you are longing to raise aid loving plants or those that demand fast drainage, just fill their pots with the sort of soil they need. Plants too tender for your winters can be moved to sheltered areas when cold weather arrives.
Preparing Containers
Choose containers that have at least one drainage hole, so water won't accumulate around the roots. Submerge terra-cotta pots in clean water and let them soak thoroughly; if the pots are too dry, they can initially wick the moisture away from the roots and the planting medium. Use a mixture of 1 part Clorox type bleach to 9 parts hot water. Let them soak for about ten minutes. This will kill any organism or pathogens which may be present. Cover the drainage hole with a small piece of fine wire mesh to keep the soil from washing out.
Choosing A Potting Medium
A good potting soil allows roots to grow easily; it should be fast draining yet moisture retentive. Quick drainage means roots won't run the risk of suffocating in soggy soil, while good water retention saves you from having to water too often. Regular garden soil, even good loam, is too dense for container use. For best success, most gardeners turn to packaged potting mixes, which don't contain soil; they're soilless mixtures of organic materials (such as ground bark, sphagnum peat moss, and/or compost) plus mineral matter such as perlite, pumice, or sand. Limestone may be added to balance the acidity of peat moss; fertilizers and wetting agents (ie "Soil Polymers" ) may also be included. Before planting, flush the mix with water once or twice to eliminate excess salts.
A 2-cubic-foot bag of potting mix holds enough to transplant 8 to 10 plants from 1-gaUon nursery cans into individual 10- to 12-inch pots or to fill a 36- by 8- by 10-inch planter box. For large planting projects, though, you may want to make your own mix. For a basic no-soil mix, combine % cubic yard nitrogen-stabilized ground bark, coir dust, or sphagnum peat moss; 'A cubic yard washed 20-grit sand; 6 pounds 0-10-10 granular fertilizer; and 10 pounds dolomite or dolomite limestone. Mix all ingredients in a wheelbarrow.
Watering
Because they have only a limited area from which to draw moisture, container plants must be watered more often than those grown in the ground. In hot or windy weather, some (especially those in hanging baskets) may need watering several times a day; in cool weather, it may be sufficient to water weekly or even less often. Test with your finger: if the soil is dry beneath the surface, it's time to water.
Apply water over the entire soil surface until it flows from the pot's drainage holes. This moistens the entire soil mass and prevents any potentially harmful salts from accumulating in the mix. If the water drains out too fast—virtually the instant you pour it in—there's probably air space between the soil and the container walls. In this case, completely submerge the container in a tub of water for about half an hour; or, for large pots, set a hose on the soil surface near plant's base and let water trickle slowly into the mix.
A drip irrigation system (see page 723) can make watering container plants almost effortless. Kits designed for this purpose are widely available.
Fertilizing
Container plants need regular feeding, since the necessary frequent watering leaches nutrients from the potting mix. Apply a liquid fertilizer every 2 weeks during the growing season, following the directions on the label. Or mix a controlled-release type (see page 668) into the potting mix before planting.
Repotting
If roots are crowded and protruding from the drainage holes, the plant has outgrown its container and needs a roomier home. Because you want to keep the soil mass fairly well filled with roots, it's best to shift the plant to a slightly larger container rather than a much bigger one. If the pot is too large, the ratio of soil to roots will be too great for the roots to absorb all the moisture after watering—a situation that often leads to root rot. Select a new container that allows just an inch or two of fresh mix on all sides of the root mass. If the root ball is compacted (with tightly twined roots), make four shallow vertical cuts down its sides with a sharp knife to encourage the roots to move out into the new soil.
If you want to keep an older plant in the same large pot indefinitely you can root-prune the plant periodically Gently turn it out of its container and use a sharp knife to shave off an inch or two from all four sides and the bottom of the root ball. Place fresh potting mix in the bottom of the container, put in the plant, and add fresh mix around the sides.