One of the most versatile and creative forms of gardening is container gardening. Planting a container garden is much like creating a floral arrangement. However, live plants can be enjoyed for a season or longer period of time. Almost any plant can be grown in a container when proper growing conditions are provided and can add a temporary splash of color and art wherever desired. Some other reasons for container gardening are:
- Your backyard or traditional gardening space is limited or unavailable.
- Your time for gardening is limited.
- Your mobility is limited to working in raised beds or containers.
- Your gardening site is unsuitable for growing the plants you want to grow because of poor drainage, soil conditions, or too much shade or sun.
- You have a desire to be a creative garden artist!
These are some of the advantages of container gardening. The biggest disadvantages to growing plants in containers are the maintenance requirements of watering and fertilizing. Some helpful techniques for container gardening, including choosing containers and soil mixtures, selecting plants, and planting, fertilizing, and watering your container garden, are discussed in these specific sections of this publication.
Choosing a Container
Generally, plants can be grown in anything that will hold soil and allow proper drainage. Some of the more traditionally used containers include terra cotta (clay) pots, plastic pots, hanging baskets, wire baskets lined with sphagnum moss or fibrous liners, concrete planters, planter boxes, whiskey barrels, 5-gallon buckets, tubs, and bushel baskets. Some of these containers are more durable than others are.
Don't limit yourself to the traditional when it comes to choosing a container. Be creative! Choosing a container that fits the look you are trying to create is half the fun of container gardening! Containers can be window boxes (wooden or plastic), wooden wine crates, tires, bags of potting soil, garbage bags filled with growing medium (called a sausage garden), or your favorite old boot!
Some self-watering containers have been manufactured to improve drainage and also have built-in reservoirs for watering plants.
Whatever container you choose, consider these tips:
Tips for Selecting Containers
- The container must have a hole for adequate drainage.
- The container must be large enough to hold the minimum amount of soil required for mature plants to grow in.
- The type of container used depends on the location and the plant selected: Avoid using black containers in full sun. Remember that terra cotta and other porous containers wick water away from plants. Consider whether the plant will do well in a windy site. Decide whether the container needs to be attractive (in a place of high visibility).
- Remember to coordinate container color with plant materials. Containers can be painted to create a different look or to create a cooler surface that will reflect heat.
- Consider whether you may want to move the container to a different location. If so, keep in mind the weight factor. Styrofoam peanuts can be used in the bottom of the container rather than filling it fully with soil mix. Also, the new Eurocast planters are lightweight and decorative.
It is important to select a growing medium that drains well but that will also help keep plants from drying out between waterings. Keeping containers moist yet well drained is the most important key to successful container gardening.
The best growing mixture is one that is soilless. Soilless media are free of any disease pathogens, insect pests, and weed seeds. They are also generally lightweight and porous, allowing for a well-drained yet moisture-retentive mix. Premixed growing media for container gardens are available from garden centers. However, be careful not to use peat or peatlite mixes alone. By themselves, these media tend to become compacted, too lightweight, and hard to wet.
You can create your own blend of soil mix by using peat moss, vermiculite or perlite, sterile potting soil or composted soil mix, and coarse builder's sand. In order to determine how much lime may be needed to bring the pH into the 6.0 to 6.8 range, send a sample of the mixture to a soil testing laboratory.
Some commercially prepared growing mixtures have an added wetting agent which is a great help when it comes to planting and watering. You may also consider adding water-absorbing polymers or "gel" that absorbs and retains up to 400 times its weight in water. Polymers are nontoxic and last for a number of years before breaking down in the environment.
Most soil mixtures become compacted and root-bound over time. It is best to replace containers with fresh soil mix at least once a year or every other season.
Most vegetables are grown in a particular season of the year and therefore make excellent container garden plants. Some vegetable varieties have a more compact growth habit, such as Fanfare cucumber and Husky Gold tomato. Look for All-American Selections Winners, many of which are excellent choices for container gardening.
The primary keys to successfully growing vegetables in containers are to put vegetables in the proper-size container and to keep them watered. Vegetables are about 99 percent water; therefore, if you are going to grow them, you must be able to keep the soil moist. Choose a container that is large enough so that plants don't dry out between waterings. For example, tomatoes must have a container with a minimum of 5 gallons of soil mixture. Smaller vegetables such as radishes and lettuce can be grown in 1/2 gallon or less of soil mix. Table 1 lists vegetables and varieties recommended for container gardens.
Plant a kitchen container garden that includes salad greens, herbs, garlic, and other easy-to-grow vegetables. Many of the salad greens can be thinned and harvested throughout the cool season, and leaves and herbs can be snipped as needed.
Container gardens can, but do not have to, be limited to one type of plant. Vegetables can be interplanted with herbs, bedding plants, vines, and some perennials. Some vegetables can be used as ornamentals with their contrasting colors, textures, and forms. Research has shown that interplanting and companion planting of plants interrupts disease and pest cycles. The limiting factor on interplanting is that all plants must have the same requirements for light (shade or sun) and drought tolerance. Work toward a balance of coordinating colors, textures, variety, height, and flow. The table below lists some examples of plants that can be combined in mixed container gardens based on their light requirements.
Before setting out plants in a container garden, first determine how the plants will fit or be arranged in the container. Always remove plants from the container they have been growing in before planting them in your garden. Cover the drainage hole in the container, using pieces of broken pottery or some mesh screen to prevent the soil mix from clogging the hole. Fill the container about three-fourths full with soil mix. Moisten the soil mixture thoroughly. Allow the mix to settle, and then add more soil mix to again fill the container to about three-fourths full.
Always start with healthy, disease-free, and pest-free seeds and plants. If direct-seeding a container garden, plant seeds at the proper planting depth and season according to the germination and planting recommendations. After the seeds germinate and the plants put out their first true leaves, thin the seedlings to the proper spacing by cutting off extra seedlings. This reduces root disturbance and allows seedlings to grow without competing with each other.
Some soilless mixes used for container gardening do not contain fertilizers. In this case, you will need to add trace elements that plants would otherwise obtain naturally from garden soil. Slow-release fertilizers that supply all the nutrients needed for a container garden are available. Another reason to use a slow-release fertilizer is that nitrogen is slowly released to plant roots, providing the necessary fertility throughout the growing season without burning plant roots. Fertilizers are salt and when overused can burn or kill plants. Fertilizer salts can build up over time in soil mixes and porous container materials such as terra cotta. Wash porous pots with a 10 percent bleach solution before planting to remove salt buildup.
If additional fertilization is needed, a water-soluble fertilizer (i.e., Miracle Grow, Peters, and others) can be used to supplement initial fertilization. Follow label directions on all fertilizers, and keep records of planting and fertilization dates.
The most critical and time-consuming part of maintaining container gardens is watering. This is particularly true as plants mature and roots leave very little soil in containers. As a general rule, plants grown in full sun require thorough watering two to three times a week. Mature plants may have to be watered once or twice a day during the hot days of summer.
Remember that porous containers such as terra cotta (clay) dry out more quickly and can wick water away from plants. Avoid growing plants that require full sun in black containers. Also remember that water-holding polymers or gels can be used to retain moisture as needed by plants. Another way to reduce watering time is to install a drip irrigation system with emitters on an automated timer.
Containers can also be placed on trays filled with gravel or marble pebbles covered in water to help keep them cool and to provide moisture without creating a drainage problem.
Other Tips for Successful Container Gardening
- Container-grown garden plants are more susceptible to freezing, thus requiring winter protection such as mulching, using a wind screen, putting the container in the ground, or moving the container inside to a protected area.
- Some vining plants require staking and trellising, such as tomatoes, cucumbers, beans, and ornamental climbers. Anchor these containers to prevent them from blowing over.
- Clean containers before planting in them, using a 10 percent bleach solution to kill any pests and to remove fertilizer salts.
- Season porous containers before planting in them by soaking them in water; then, do not allow them to dry out.
- Use styrofoam peanuts in the bottoms of containers to reduce the weight.
- Harden-off container plants by exposing them gradually to full sun and wind.
- Place containers on legs, bricks, coasters, or saucers to allow drainage and to protect the surface underneath.