Living in a container isn’t always a boon for garden plants. It can be a little like moving from a McMansion to a one-bedroom condo; some adjustments are necessary.
For example, many plants have wide-ranging root systems eager to forage for nutrients. In a pot, that kind of exploration is curtailed, so everything a plant needs must be either inside the pot or made available courtesy of the gardener.
Sometimes this is easy, like choosing an outdoor location that will offer a beneficial exposure. Other times, it can be challenging, like having to water a four-inch pot two or three times a day during sweltering summer weather. Let's identify some dos and don'ts that will get your container garden off to a good start.
The “container” aspect of container gardening is about more than decorative flare. Pots and other receptacles perform an important job. They offer support and stability, and a pot’s construction and materials can have an impact on plant health and longevity. You may have seen charming photos of plants growing out of old shoes or planted in upended tires, but not every object with a hollow in it is a suitable plant habitat.
Do choose a pot or other container with a drainage hole in the bottom.
Good drainage is a key component in maintaining container plants successfully. Without adequate drainage, plant roots sit in water, slowly disintegrating until the plant starves. You may have seen plant containers that do not have drainage holes. Called cache pots, these decorative containers are designed to house plants, but not directly. To maintain a plant in a cache pot, place it in a smaller container first. Then, add enough stones or other materials, such as gravel, to the bottom of the cache pot to allow for adequate drainage and place the smaller container on top of the stones. Cache pots are not suitable for plants maintained outdoors.
Do match the occupant to the pot.
Plant containers come in all shapes and sizes, but specific plants are better suited to one type of container over another. Here are a few examples: Taller plants need taller, sturdier pots or else they may become top heavy and cause the pot to fall over. Plants from bulbs typically require less soil depth and can be placed in shallower pots, while plants with long taproots need deep pots with plenty of soil. There are also specialty containers like strawberry planters or orchid pots that provide support, better air flow, or other enhanced features favored by specific plants.
Do consider the combined weight.
Once filled with grow media, plants, and water, containers can get heavy. If you plan to move a large plant around or want to position it on a potentially breakable or tippable surface, install it in a lightweight container. Prefer a composite or plastic one over stone, ceramic, or concrete.
Do choose the right pot size.
When repotting a seedling or immature plant, the general wisdom is to use a pot two inches in diameter larger than the pot the plant is currently occupying. Young plants may be repotted a few times over a season or two, and this allows for steady growth without waste. Do you need to repot a newly purchased plant right away? Unless you see roots dangling from the drainage hole, you probably don’t need to provide new lodging for a few months.
Don’t choose a container that’s unsafe for plants or people.
Select containers that will not decompose quickly or promote the growth of mold or mildew. If the pot will house an edible plant like a vegetable or herb, choose a food-grade container or one made of non-toxic, non-leaching material. The U.S. Department of Agriculture does not consider single-use plastics and pressure-treated woods safe for use with edible plants.
Do take porosity into account.
Some potting materials are more porous than others, which can be a good or bad thing depending on your objectives. A wooden or unglazed terra cotta container will allow water to evaporate more quickly. These materials can also leach moisture from the soil during dry conditions. If you plan on keeping succulents, your plants will probably be happy. If you plan on maintaining moisture-loving plants or want to keep watering chores to a minimum, consider a non-porous material like a glazed ceramic, plastic, composite, or metal.
Do consider using self-watering pots and containers.
If you have dozens of things to do every day and figure watering the petunias won’t ever top the list, using a cheat like a self-watering pot is a good idea. These containers have onboard reservoirs that release water into the soil as needed through a natural process called capillary action. They’re available in several sizes and configurations. Convenience pots cost a little more, but if you worry about unintended negligence, you’re likely to suffer fewer plant losses.
Bacteria, fungi, and insect incursions can quickly devastate container plants. Living in an environment where water may be available only sporadically and the temperature and humidity can change fast and often, stresses plants and can lead to lowered resistance to disease. Keeping things clean is added insurance against problems.
Don’t reuse pots without sterilizing them.
Clean loose material from containers and soak them in a bleach solution (one part bleach to nine parts water) for an hour or more. Drain and rinse. Dry, clean containers can be used immediately or stored.
Do remove mineral deposits.
If you don’t consider the mineral deposits on your pots a badge of honor, you can get rid of them with a little elbow grease and a 50/50 mixture of water and white vinegar. Brush deposits with an old toothbrush and rinse.
Do clean your gardening tools.
While you’re sterilizing pots, throw your hand tools into the mixture too. Tools should be cleaned at least once a year. And be sure to wash your garden gloves with soap and water. If they’re leather, you can lather up and clean them while wearing them. They’ll be more likely to hold their shape that way.
If you take a close look at the media used in most standard container gardens, you’ll notice it’s lightweight and porous. That’s no accident. Typical garden soil is inappropriate for container gardening because it’s too dense. It tends to compact and clump, making it difficult for plant roots to move around and inhibiting the flow of water through the pot.
Do use a specially formulated potting mix.
There are numerous quality potting mixes on the market. A few include additives like hydrogels, which are polymers that act as spherical reservoirs for water. Most potting mixes contain little or no soil, opting instead for a combination of ingredients that anchor plant roots and stems but still provide good drainage, adequate aeration, nutrients, and a balanced pH. Some constituents found in potting mixes include peat moss, sand, perlite, shredded bark, coconut coir, and vermiculite.
Don’t reuse potting soil.
It can be tempting to reuse potting mix, especially in pots that have housed annuals and are now free for new residents. Quality prepared mixes can be expensive. Dumping that nice, augmented media seems counterintuitive. However, plant pathogens can remain in potting mixes for months or longer. The safest way to protect container plants is to start with fresh media for every project.
Container plants have a big advantage over their garden bed brothers. They’re portable, which is convenient when conditions get too hot or too cold.
Do take materials and finishes into consideration.
Choose an insulated container if you plan to place a plant in an area where weather extremes may cause problems. When it’s hot and dry, water porous containers frequently. Prefer light-colored containers for warm or hot locations and dark containers for cool locations.
Do consider moving your containers around.
If your patio is sunny and warm in May but roasting by August, you can turn your plants into commuters by moving them from the patio to a dappled or shady location during high summer. This maximizes their visibility and saves you from having to water them as often.
Do consider parking container plants indoors in winter.
If you maintain tender perennials that won’t tolerate a hard freeze, instead of sacrificing them, consider bringing them inside during the winter months. If you can provide six hours of bright light, you can maintain many plant varieties indoors until spring. If your hardy perennials are in pots, put them in the ground—pots and all—for added winter protection.
Don’t abandon your pots during windy weather.
Secure and protect potted plants during windstorms and heavy rains.
Don’t forget fall container management.
An empty pot or gardening container is a sad sight, but don't ignore it until spring. Some container materials, like unglazed ceramics, are vulnerable to cracking when exposed to freezing weather. Clean, sterilize, and store unoccupied garden containers in a dry, protected location over the winter months.
Many plants thrive when “potted out”, but understanding how to establish and maintain a container garden will help you create a more consistent and nurturing environment for your plants over the long term.