In many ways, planting and maintaining a container garden is the easiest form of gardening. All you need is a container, potting soil, plants that play well together in the growing environment, slow-release fertilizer, and water. Here are five key elements to successful container gardening.
Drainage Is Critical
Adequate drainage might be the single biggest factor in determining if container-grown plants live or die. In a garden bed, excess water percolates down to deeper layers of soil and runs off into surrounding areas. However, if a container or the potting soil doesn't drain well, plants can drown or rot.
All containers must have adequate drainage holes for excess water to drain. Containers intended for indoor use are typically sold with a matching saucer. If you purchase a container that does not have drainage holes or has inadequate drainage holes, you have to make or enlarge them yourself.
- For plastic or metal containers, use a hammer and pointy tools, such as an awl, screwdriver, or large nail to make drainage holes in the bottom of the container. You could also use a drill to bore a few good-sized holes. On some plastic containers, you might see pre-stamped drainage holes and all you have to do is apply pressure to poke them through.
- For ceramic and terra cotta containers, use a drill with a masonry bit (remember to wear safety goggles).
Generally speaking, the more drainage a container has, the better. Many more plants are killed by drowning or rot than are killed by under-watering.
Prevent soil from being washed out of drainage holes. Before you fill a container with potting soil, place a permeable material at the bottom of the container to cover drainage holes. Use material that won't disintegrate but allows water to pass through such as a piece of vinyl window screen or landscape fabric. Covering drainage holes might also prevent insects from crawling up into the container.
Never add a layer of gravel, stones, or rocks, or broken shards of pottery to the bottom of a container; those materials don't improve or enhance drainage and might even impede it.
Elevate containers off the ground. Don't place a container directly in contact with any surface that might block water flow out of drainage holes. You can use any number of ways to elevate containers, but pot feet are the easiest and most effective. You can purchase pot feet from online garden supply vendors or local garden centers and nurseries. Typically three or four pot feet will do the job, depending on container size. If a container is large and heavy, you can also use a planter caddy on wheels which can serve double duty—elevating a container off the ground and enabling you to easily move the container if you need to.
Removing Plants From Their Nursery Containers
Carefully removing plants from their nursery containers is important to the survival of any plant. Novice gardeners often remove nursery plants by tugging plants out by their stems, which can very well injure the plant before you even begin to plant them into your container garden. Here are a few best practices for removing plants from nursery containers:
- Before removing any plant from its container, make sure the plant is adequately hydrated. For plants in half-gallon or larger nursery containers, you might have to submerge the entire nursery container into a bucket of water if they are extremely dry.
- For plastic cell packs (four or six cells), hold the plant close to the soil line with the thumb and finger of one hand, and then use the other hand to squeeze the plant out of the cell by gently pinching the cell.
- For plants in individual nursery pots (4 inches and larger), you might be able to push the plant up from the bottom of its pot. If the plant is root-bound, you might need to cut off the roots that are protruding from the bottom of the pot. Then, use a knife to score around the inside edge of the pot to loosen the plant and gently remove it.
- For larger, more mature plants, remove them from their containers by turning the pot upside down while supporting the base of the plant at the soil line with one hand and tapping on the bottom of the container with your other hand. This should loosen the root ball and cause the plant to slide out.
If a plant is root-bound when you remove it from its container, use one or more the following methods to untangle the root ball:
- If the plant is only slightly root bound, use your fingers to gently tease the roots apart.
- If roots are encircling the bottom of the container, unfurl them; if they are extremely long, prune them to a manageable size. This will enable the roots to grow freely in the soil, rather than in a circular pattern that can strangle the plant.
- If a container is packed solid with roots, don't be afraid to use a knife to cut off an inch or two of the bottom of the root ball and then score the sides to allow roots more freedom to grow.
Fertilize Before Planting
Container plants can fall victim to a lack of nutrition because frequent watering causes nutrients to leach from containers. The easiest way to remedy this is to mix a slow-release fertilizer into the potting soil before planting. Many types of slow-release and time-release fertilizers are available on the market, but a standard granular all-purpose organic fertilizer is a good option.
When planting a container, or anywhere else for that matter, also consider the following important steps
- Eliminate air pockets. Break up dirt clumps to eliminate air pockets around roots and tamp down soil lightly as you're filling a container with potting soil. A plant's roots must be in close contact with the soil in order to be properly hydrated. A thorough watering immediately after planting helps settle the soil. After that first watering, use extra potting soil. to fill in any areas that have settled.
- Plant at the right depth. Situate the plant in the container at the same depth that it was planted in its nursery pot, don't plant it any deeper than that. (The rare exception to this rule is when you are planting tomato plants; they are able to generate roots from nodules along their main stem, and the deeper you plant them, the stronger and deeper the root system will be.)
Water and Feed Correctly
Watering a container garden is more art than science. Although plants vary in their water requirements, container plants dry out much faster than those planted in the ground—especially if they receive a full day of hot sun, are planted in containers that quickly heat up, or if the containers are seated on a hard, hot surface, such as concrete or asphalt.
Most plants prefer moist, but not wet, soil. You might find that you need to water a container once daily, and sometimes twice in hot weather. To test soil moisture, stick your finger into the soil at least up to the second knuckle. If your fingertip feels dry, it's time to water.
Water slowly and deeply and don't stop until water is draining from the drainage hole. Make sure soil is being thoroughly moistened from top to bottom rather than just running down the inside edge of the container.
After planting, feed container gardens with a diluted liquid fertilizer every two weeks during the growing season. Container gardens need to be fed more frequently than plants grown in a garden bed because access to food is limited by the amount of soil in the container and by nutrients leaching from the soil at every watering.
Plants Grown in Containers. North Carolina State University Extension
Peerless, Veronica. How Not to Kill Your Houseplant: Survival Tips for the Horticulturally Challenged. Dorling Kindersley Limited, 2017
Richardson, Fern. Small-Space Container Gardens: Transform Your Balcony, Porch, or Patio with Fruits, Flowers, Foliage, and Herbs. Timber Press, 2012