Container Gardening

Spring containersA container garden can be as simple as a window box overflowing with annuals, as playful as a tub filled with tomatoes, or as romantic as an antique urn laced with roses and baby's breath. Choose a style to make your own!

Versatile and Beautiful

On decks and rooftops, container plantings bring life, color, and softness to hard edges. Close to doorways, they welcome visitors with texture and fragrance. By the back porch, they encourage soft touches and occasional pinches as herbs and vegetables are checked for perfect picking.

Containers satisfy the need to design complete gardens — but in small spaces, where mistakes are forgiven and quickly corrected. They provide uniquely controlled environments for plants with special needs. Garden borders can be revitalized in an instant by moving a flowering container into an empty spot left by the waxing and waning of showy perennials.

A Four-season container

Rotate seasonal plants into containers to reflect the best of the garden and to extend the growing season. Begin your flowering display the second week of April by planting cool-season annuals or vegetables, along with previously started early bulbs. As summer's heat picks up, harvest and replace these plants with warm-season annuals, herbs, vegetables, and vines. As fall approaches, switch out again and substitute asters, chrysanthemums, grasses, and decorative items like gourds or small pumpkins. The final, fourth-season change consists of cut boughs and brightly colored branches rather than live plants. Fragrant firs, soft weeping pines, lacy arborvitae, and evergreen boughs in every color and texture combine beautifully with cut stems full of bright berries and seed pods.

TYPES OF CONTAINERS

Choose your container to suit your site, the design of your home, and the types of plants you want to grow. Every pot must have drainage holes. An inch or two of crushed gravel, styrofoam pellets, or broken shards of terra cotta will provide additional drainage in large pots.

  • Rooftop gardens require extra heavy, large pots to avoid being blown over in high winds, especially if any woody plants are part of the design. These containers are often anchored further with cables attached to the rooftop surface. Large-scale gardens will require engineering advice to determine acceptable weight load of rooftops.
  • Limestone pots are beautiful and highly resistant to frost cracks, but are also very heavy and expensive and should be used only as permanent containers.
  • Terra cotta is a popular, medium-priced material, available in all sizes and therefore a good choice for groupings. Its porous clay evaporates water faster than plastic — good for the plants but extra maintenance for the gardener.
  • Cement composite containers such as hypertufa English troughs are wide but shallow, intended for alpine plants, miniature conifers, sedums, and other small collections. These minigardens can be placed directly into the larger garden or elevated on a tabletop, a step, or a garden wall.
  • Plastic is lightweight, nonporous, inexpensive, and suitable for hanging baskets or for plants that are then slipped into a larger, more decorative container. Plastic trays are ideal as windowbox liners.
  • Molded plastic pots are lightweight, modestly priced products that simulate terra cotta, limestone, metal and other natural materials at a fraction of the cost.
  • Natural wood is beautiful, but it will rot unless lined with plastic or metal. Treated lumber products will last longer but are not recommended for growing edible plants.

SOIL, WATER, FERTILIZER

Soilless potting mix is the best choice for containers because it is lightweight, drains quickly, and permits rapid root growth. Most soilless mixes are composed of peat moss, vermiculite, and perlite, sometimes with a little sand and fertilizer. Since containers dry out quickly, especially in hot and windy weather, plants require frequent watering, which tends to flush out soil nutrients. Regular applications of fertilizer are therefore recommended. Water the plants first before fertilizing with a very dilute, quarter-strength balanced product several times a month. Plants that flower constantly right up to frost have the greatest need for fertilizer.

CHOOSING PLANTS

Group plants with similar needs together. Put sun lovers in one pot and shade-tolerant plants in another. Separate drought-tolerant plants from ones that need moisture. Use the same design techniques for pot gardens that apply to garden beds. Combine spiky plants with cascading ones; feathery ones with solid, succulent ones; and mounding plants with upright ones. Experiment with contrasting textures and even extreme color combinations. Container gardens provide opportunities to be adventurous and grow plants not normally found in large gardens.

WINTER CARE

Consider most container plants as annuals, since it is too difficult to overwinter them in their containers without greenhouse conditions. At the end of the growing season, discard or compost them. Some plants can be saved:

  • In early September, before frost, take leaf or stem cuttings from prized geraniums or unusual foliage plants and pot them up to grow indoors over winter.
  • At the same time, prune back and repot herbs in small pots filled with fresh soilless mix; bring them indoors to a south-facing window or under artificial lights. Rosemary, curry plant, lavender and other herbs requiring exceptional drainage can be grown in a cactus mix over winter.
  • Miniature evergreens, low-growing perennials, or ground covers can often survive in troughs if they are heavily mulched.

Save the potting mix for one year, combining it with equal parts fresh mix. Wash and sterilize containers and store them in a basement or garage. Empty and clean all permanent containers and half-fill them with straw to prevent cracking due to ice expansion. Make notes of what worked, what didn't, and which new plants will be candidates for next year's container collection.