Once again, the key is drainage. Since the roots of container-grown plants are confined and can't go searching for what they need, you need to provide them with the best possible conditions. It's best to use purchased soil mixes for containers, rather than garden soil. Garden soil often drains poorly, and can harbor disease organisms. There are many commercial mixes; if you prefer to create your own, you can start by mixing potting soil, seed-starting mix, and compost in equal proportions, then adjust the proportions and add other materials to suit individual plants.
Following are some general guidelines for choosing containers for various types of plants.
Annual flowers. Many annual flowers have compact root systems and grow well in relatively small containers, provided you give them adequate water and fertilizer. Since you'll be discarding them at the end of the growing season, you don't need to worry about their long-term health. Any container smaller than 8 inches in diameter will dry out quickly, but as long as you are prepared to be diligent in your daily care, you can go even smaller. You've probably seen annual flowers planted in all sorts of odd containers, from discarded tires to old boots!
Vegetables. As a general rule, for optimum production vegetables require somewhat larger containers than annual flowers. Minimum container sizes vary depending on the vegetable. Tomatoes, for example, grow well in 5-gallon buckets, though some compact varieties have been bred to thrive in smaller containers. Peppers and eggplant will thrive in 2-gallon containers. (Two-gallon nursery pots measure about 8 inches in diameter and 10 inches tall). If you plan to grow root crops, choose a container that can accomodate the mature size of the root. Beets, for example, will grow in a container as shallow as 8 inches, but to grow full size carrots you'll want to choose a pot that's at least 12 inches deep.
Perennials, shrubs, & trees. Because these plants will remain in their container for more than one growing season and they'll need to withstand winter conditions, be generous when considering the size of the container. Keep in mind the mature size of the plant--that small daylily or hosta in the 4-inch nursery pot will grow quite large. In regions with mild to moderate winters, many perennials will thrive in containers with minimal winter protection. Regions with long, cold winters pose challenges, however. Even plants hardy in your zone can suffer root damage if the soil in the container freezes solid, and alternating freeze/thaw cycles can cause heaving. In cold climates, choose generously-sized containers, and be prepared to provide winter protection.
Saucers. Waterproof saucers protect the surface underneath the plant. Note that unglazed clay saucers are porous, so surfaces underneath can be damaged by the moisture the saucers absorb. Consider using glazed clay or plastic saucers instead.
Dollies. If you'll be needing to move large planters, you may want to set them on dollies or casters before planting. Be sure they have locking wheels to prevent them from rolling away!
Self-watering containers. These contain a reservoir for a supply of water, plus a mechanism, usually some type of wick, for providing the plant with a sustained supply.
Hanging baskets. Nurseries often sell plants in simple white plastic pots with wires and a hook for hanging. You can also create your own baskets with lightweight containers. Remember that a planter full of moist soil can be surprisingly heavy; be sure hardware is suitably sturdy.
Wire and moss baskets. Plants can be set through spaces in the moss, creating a nice, full look. Since these baskets aren't waterproof, use them outdoors in a place where draining water won't cause any harm.
Found objects. Consider wheelbarrows, wagons, crates, and buckets. Be as creative as you like! Just be sure the containers have adequate drainage.
Why would you choose to grow plants in containers, instead of planting them right in the garden? Let's look at some of the benefits of container gardening.
Many plants adapt well to growing in containers, and some actually do better in containers than they do planted right in the garden. For example, in climates with cool summers, heat-loving plants like eggplants and peppers thrive in containers because the container and soil are warmed by the sun.
While many annuals, perennials, shrubs, and even small trees will grow in containers, it's important to match the plant with the proper container. You'll also need to consider the challenges of your climate, and how much time you can devote to caring for your plantings.
Almost anything can serve as a container! You may have seen plantings in barrels, buckets, bathtubs--even old shoes! Your primary consideration in choosing a container is drainage: the planter must have drainage holes in the bottom to allow excess water to drain away.
Containers are available in a variety of materials. Let's look at the characteristics of a few of the most common.
The most common clay pots are the familiar reddish-orange terra-cotta containers. These come in a variety of shapes and sizes, from inexpensive, unadorned flower pots to large, ornate urns and planters.
Pots come in a range of colors, sizes, shapes, and designs. Glazing reduces porosity, so soil retains water longer. Glazed saucers protect surfaces from moisture.
Includes half whiskey barrels, window boxes, and other purchased containers, plus homemade boxes and raised beds.
|Acquires character with age; surface weathers, grows moss, etc.||
Common types included galvanized metal, copper, and lead.
|Acquires character with age||
Includes inexpensive nursery pots and hanging baskets, as well as more ornate containers. Often crafted to resemble natural materials.
With a little ingenuity, you can overcome some containers' shortcomings. For example, you may like the look of unglazed clay, but find that your plants dry out too quickly because of the high porosity. Here are two solutions:
Article published on June 23, 2008.