Growing plants in containers can offer many benefits and there might be circumstances in which it's the only way to achieve success. For instance, if the garden soil is poor or doesn't drain well, containers allow you to create the ideal soil conditions plants require.
Containers offer the flexibility to move them around to take full advantage of sunlight. If your yard is deeply shaded, sun-loving plants might still be an option because you can move a container into the sun. Container gardening also offers some design options not found in other forms of gardening—particularly window boxes and hanging baskets.
Growing plants in containers is not quite the same as in-ground gardening, however, so here are a few special techniques to help you do it successfully.
When to Plant a Container Garden
Container gardens are generally planted about the same time as in-ground gardens—after the danger of frost has passed in spring or before the last hard frost in the fall. You might be able to plant a bit earlier because container soil warms up faster than garden soil in the spring. Thus, a container garden can extend the growing season. However, be ready to cover the containers or move them indoors if an overnight cold spell threatens in the early spring or late in the fall.
Equipment / Tools
- Garden trowel
- Container with adequate drainage holes
- Window screen or landscape fabric
- Plants with similar growing requirements
- Potting mix
- Time-released or granular fertilizer
How to Prepare for the Container Garden
Assess the Sunlight
It's possible to grow a gorgeous container garden even if your yard receives very little direct sunlight. You can also grow spectacular containers if your yard is bathed in sunlight all day long.
The first step is to accurately assess how much sunlight is available to choose the right plants for your container garden. It is quite common for gardeners to grossly overestimate the amount of sun an area receives per day so it's important to be accurate in your estimations.
To calculate how much sun an area receives, go outdoors several times a day to observe the area where you plan to locate your containers. It helps to take timestamped photos of the area several times per day to record how many hours of direct sun or shade the area receives.
Measure sunlight at the time of year when you will be planting your container garden because the sun angle makes a difference. The sun angle during the winter months is not the same as it is in the summer months; also remember that nearby deciduous trees are not leafed out in winter. The total daily hours of full sun, dappled sun, or shade an area receives determines the plants that will grow well under those conditions.
Choose a Container
Almost anything can be turned into a planting container provided it has adequate drainage holes. However, remember that the larger the container is, the more soil it will hold. And the more soil, the more water is retained and available to your plants.
Small containers 10 inches or less in diameter dry out very quickly in hot and dry spells, and though some plants don't mind dry conditions, most plants become stressed when they dry out. Stressed plants are more susceptible to pests and diseases. In other words, there are advantages to using the biggest containers possible.
When purchasing a container, make sure it has adequate drainage holes; if not, you must create drainage holes. A large container should have at least 1 drainage hole of 1 inch in diameter—and preferably several holes. If the container doesn't have enough drainage, you can usually drill, punch, or use a pointy tool to pierce some extra holes.
Self-watering pots are great because they contain a water reservoir system to provide a constant source of moisture to the roots without any intervention from you other than to keep the reservoir filled with water.
Buy (or Make) Potting Mix
While the growing medium used for container gardens is often called potting soil, it actually contains no soil at all—at least not the same kind of soil found in garden beds. More properly called potting mix, this sterile growing medium contains a mixture of organic and inorganic materials such as peat moss, perlite, compost, sand, and other ingredients. What is notably missing are the living organisms (including pathogens and insects) and other minerals generally found in garden soil.
Do not buy topsoil or garden soil for your container gardens, and don't dig soil from your garden beds. Most gardeners buy commercial potting mix by the bag, but it is also possible to make your own potting mix by blending peat moss, perlite or vermiculite, and well-decomposed compost together in an even ratio. (There are many homemade recipes for potting mix that you can find online.)
Commercial potting mixes sometimes include time-released fertilizer already blended in. It is fine to choose either fertilizer-enhanced or plain potting mix, but this might reduce your regular feeding schedule, which is usually every two weeks.
Choose Plants Wisely
Once you've determined how much sunlight an area receives, selected a container, and purchased or made a potting soil mix, now the fun begins—choosing your plants.
If your container design calls for various kinds of plants, make sure that all of the plants you purchase have the same requirements for sunlight, the type of soil, and moisture. In other words, purchase plants that play well together.
Do your research to learn about container design philosophies and concepts, A general rule of (green) thumb is for a container to have one "thriller" plant that is just as tall as the container surrounded by mid-sized filler plants (plants with a full, mounded growing habit). To complete a balanced look, include low-growing or vining plants that spill over the sides of the container to soften its edges. This design concept is called "thriller, filler, and spiller".
Also, don't be afraid to design a container with only one fabulous plant or several plants of one variety. Many great container gardens use just a single plant variety.
How to Plant the Container Garden
Cover the Drainage Holes
Cover the container drainage holes with a small piece of permeable window screening or landscape fabric to keep soil inside the container and keep out insects. The material you choose must allow water to drain freely from the container.
Fill the Container With Potting Mix
Fill the container with potting mix to within 1 to 2 inches of the top of the container. Mix in fertilizer, carefully following directions for exact measurements (this is particularly important if you are using conventional fertilizer, which can burn the roots of your plants if you over-use it). An organic all-purpose, granular fertilizer is usually a good choice. Make sure to mix well.
Remove the Plants From Nursery Pots
Carefully take your plants out of their nursery pots. To do this without harming the plants, turn the pot upside down and push the plant out through the drainage holes in the bottom of the pot. If it's stuck, run a knife around the pot, between the soil and the plastic. If you find that a plant is root-bound, make sure to gently tease apart the root system after you extract the plant from the pot. Arrange the plants in the container, keeping in mind the direction from which the container will be viewed (from the front, rear, or from all sides).
Place the Plants in the Container
Dig a hole for each plant just deep enough so that the plant will be at the same depth it was growing in its nursery pot. Don't cover the plant crown (where the stem meets the roots) with soil. Read plant labels to make sure you leave enough room for plants to reach their mature size. Your container might initially look sparse, but it will fill out.
Fill in around your plants with potting soil. Make sure to achieve good contact between roots and the soil and press down around each plant to remove air pockets.
Water the Plants
Water gently and generously until the water flows out the bottom of the container. After the first watering, you might need to add more potting soil to account for settling.
Tips for Maintaining Your Container Garden
Maintaining a container garden is mostly a matter of watering correctly and providing adequate food at the right time and with the right amount of water and fertilizer.
As a rule, potting mix should be kept damp but not wet. To determine soil moisture, stick your finger down to the second knuckle into the soil. If the soil still feels moist, don't apply water.
Watering is particularly tricky because your container will dry out faster on sunny days, and wind can suck moisture out of a pot. On cloudy or damp days the container might not dry out as quickly. That said, it's easy to be fooled by a gentle rain, which often leaves a container garden relatively dry.
Depending on the climate in your area and how high temperatures reach, you might have to water them more than once per day in the heat of summer, especially if containers are 10 inches or less in diameter.
Regular feeding won't be required if you have added fertilizer to the potting mix when you planted the container. If you did not add time-released or granular fertilizer to the potting mix, follow the feeding schedule recommended for containers, usually once every two weeks with a diluted solution of water-soluble fertilizer.
Be aware that nutrients leach from containers every time they are watered. Thus, container-grown plants require more frequent feeding than plants do when grown in a garden bed.