A beginner’s guide to container gardening

Photo by Aislinn Sarnacki

Finding space for your garden is one of the greatest challenges of urban homesteading. If you do not have space in your yard for a plot and your community garden has run out of raised beds, your growing season is not doomed. You can experiment with container gardening.

“In today’s world, there are a lot of people who are kind of portable in society,” Debi Harrington, container gardening chair of the National Garden Clubs. “[Container gardening] is one of the fastest growing segments of gardening these days.”

Growing crops and flowers in containers instead of in a traditional garden plot is easy to start, relatively inexpensive and space efficient. Container gardening also gives you more control over your growing conditions, giving you total control over your growing medium and the power to move your containers to sunnier, more favorable locations as the season progresses.

“In a container garden, you can more easily regulate the kind of soil you have and the amount of water it gets, and you can move them around so they can get sun,” said Kathryn Hopkins, extension professor at the University of Maine Cooperative Extension. “Containers give you more flexibility in gardening.”

Container gardens are also less prone to pests and diseases.

“They’re separated generally from the rest of their neighbors, so they don’t transmit diseases to each other as quickly as garden plants,” Hopkins said. “Plus because you’re out there watering them during the summer, you’re looking at them. At the first sign of trouble, you can do something. It’s easier to take care of containers than a one acre garden.”

What can I grow in containers?

Almost anything will grow in a container if it is given adequate room for its roots and leaves, but some plants will grow better than others.

“Some things just adapt better to container gardening,” Hopkins said.

Herbs and vegetables like salad greens, peppers, eggplant, tomatoes, beans, chard, beets, radishes, squash and cucumbers all grow especially well in containers. Bush, dwarf and determinant varieties of these crops will grow better in containers because of their size.

Corn, heavy vining vegetables like melons and tubers like potatoes and sweet potatoes are more challenging to grow in containers because they need more space.

“Growing corn in a container doesn’t really make sense,” Hopkins said. “You’d need a very large container.”

It can be done, though. Harrington said that she decided one year that she successfully grew corn in a galvanized steel water trough “about the size of a small kiddie pool, but deeper.”

Most flowers can be grown in containers as well, though Hopkins advised against perennials.

“I would not put perennial plants in containers unless you are going to take them out of the pot and overwinter them in the ground,” Hopkins said. “The root ball in the winter will be exposed to all the wind and cold if you leave it in the container and leave it outside. You could put it in the garage or root cellar and take them out in the spring.”

For her part, Harrington, who is based in New Mexico, said that it is possible to grow perennials in containers as long as you regularly tend to them with water and fertilizer. She said she has perennial salvia and echinacea that have been in the same container for 10 to 15 years.

Different plants will require different sized containers based on the depth or their roots and how they grow.

“You just want to consider how big your plant is going to be and how much root space does it need,” Hopkins said. “Then you can decide if your container is going to be big enough.”

Most local cooperative extension websites will have a list of the plants that grow best in containers in your area, as well as some recommendations for container sizes.

Can you grow more than one plant in the same container?

You will need to choose a larger container, but it is possible to grow several plants in the same container. Think about it this way: conceptually, raised beds are effectively large, stationary container gardens, and you can fill those with a wide variety of plants as long as they are properly spaced.

If you are growing a variety of plants in a single container, Harrington said to be cognizant of matching plants with similar light and water needs.

“You need to make sure that you have compatible plants within that container: same type of light during the day, same amount of water,” Harrington explained. “You don’t want to put succulents in the same container that’s got tomatoes, which need water every day. In a lot of container gardens you see at stores, that’s what they’ve done.”

Still, grouping compatible plants together also allows for some fun combinations.

“If I were a beginner and I wanted to try something fun, I would do a pizza garden,” Harrington said. “Tomatoes and basil and oregano and rosemary, put all in one container.”

What containers can I grow in?

The kinds of containers you can grow in are limited only by your budget, your imagination and a few health concerns.

There are many containers available for purchase at your local garden store. Harrington said to make sure the container you are purchasing for edible plants are lead-free. She said that plastic or terra cotta pots will likely be your best buy, but ceramic pots will last longer and be more resistant to frost.

It is also easy to upcycle materials for your container garden. Harrington, a self-professed “eclectic collector of things,” said she has made container gardens out of old wheelbarrows, baskets from the thrift store, vintage lunch boxes and even her late father’s old cowboy boots.

“One of my favorite containers for lettuce mixes is an old colander [with] a couple paper towels or coffee filters [on the bottom],” Harrington said.

There are some safety concerns with upcycling, though, especially for edible plants.

“If you’re growing food, you would want to use lumber that’s not pressure treated,” Hopkins said. “There’s not a lot of good scientific evidence on how much leeches out of old tires, but it might be worth your caution not to use old tires..”

Harrington and Hopkins both recommended choosing the container that best fits your needs, whether you are prioritizing price or weight.

“Every individual is different. It depends on each gardener and what their specific need is,” Hopkins said. “It could be the price is right, it could be the ease of carrying things around. If your mobility is kind of limited you probably don’t want to buy heavy rocks or cement blocks or something like that.”

Photo by Mahmudul Hasan Rifat on Pexels

How to set up a container garden

After you choose your container, ensure that it has proper drainage.

“They definitely have to have drainage,” Hopkins said. “Whatever pot you use should have good drainage holes in it. You can kill plants faster by drowning than drought. They’ll get root rot and go down really fast.”

If your container does not have them already, drill one large hole or a few smaller holes in the bottom. Be wary of store bought containers — do not assume they already have drainage holes prepared for you.

“A lot of the plastic containers do not have holes already drilled — they have hole spaces,” Harrigton said. “They say, ‘punch out here,’ or sometimes you’ll find one with a plug in the bottom.”

Harrington recommend adding materials like crushed soda cans, crushed water bottles or shards of broken plates or pots to the bottom of your containers, not only to help promote drainage but also to save on soil. (She does not recommend using pieces of wood or packaging peanuts because they get soggy at the bottom of the container.)

Some studies show, however, that adding these extra materials does not actually help with drainage.

“Putting soda cans or rocks or empty milk jugs seems like a good idea, but actually what the research has shown is it actually doesn’t drain better,” Hopkins said. “You create layers and sometimes the water doesn’t drain through these things that we like to put in the bottom of our containers. Just fill it up with potting mix.”

Harrington and Hopkins agree that rocks should not be put at the bottom of containers because they generally do not help with drainage, they are heavy and make containers difficult to transport and they can cover drainage holes.

“By the time you put a layer or rocks across the bottom and put your soil and plants in and water it, it’s pretty heavy,” Harrington said. “One of the disadvantages to putting rocks is you need to make sure a large rock or a rock exactly the size of your hole so it doesn’t block it. Plus, who wants to go buy rocks if you don’t already have them?”

Regardless, lining the bottom of your container with a coffee filter will help keep the soil in its place.

Once you have your drainage set up, fill the container with potting soil.

“It’s usually better to use not garden soil. That’s very heavy and compact,” Hopkins said. “What you would want to use is soilless mix, which won’t have insects and disease in it. It’s lighter, and mixing that with a good quality compost will give you the best growth in your plants.”

Harrington and Hopkins both said that you can use the same soil year to year as long as you add compost.

“If you cram your container full of plants, may use up all nutrients,” Hopkins said. “Dump out and mix fresh compost with it and put it back in the pot.”

Then, transplant your seedlings into your container.

“Once you have everything in there, water it really well,” Harrington said. “Let it drain for a couple hours and then go back and water it one more time. That usually settles it in really well.”

Add a layer of mulch to help it to look more attractive and retain water.

“If you were trying to keep the soil moist because it’s in full sun, mulching will help retain some of the moisture in the pot,” Hopkins said. “If you have a problem with [lack of] light, you could put a few white rocks as a mulch to reflect what little light you get back up into the plant canopy. [If you’re] trying to keep it well watered, mulch can help with that.”

Place your container in a warm, sunny spot with adequate western and southern sun exposure.

“Most vegetables and herbs are going to need six or more hours of sun each day, so you do need to keep that in mind,” Harrington said. “As far as floral and flowers, you’re going to want to plant your ones that want sun together and [flowers that want] shade in a separate [container].”

Consistent and adequate watering is essential for container gardens because they dry out more quickly than garden plots.

“Container gardens dry out faster,” Hopkins said. “They are above ground, so the whole root ball is exposed to sunlight and they tend to dry out. They need careful monitoring.”

“You have to water one or two times a day depending on where you live,” Harrington added. “You can also put it on a drip system. If you’re a person that doesn’t like checking on things often, container gardening is probably not for you.”

You also may want to fertilize your container garden occasionally to keep the plants fed and happy.

“The rule of thumb for fertilizing container gardens is weekly and weakly,” Harrington said. “Dilute your fertilizer down to half of what you would normally use and do it every week.”

Whether you are a beginner or a seasoned expert looking to get creative with your yard space, container gardening is a fun way to grow all sorts of plants.

“There’s so many container options and there are so many good plants that you can put in containers,” Hopkins said. “Everybody should have success.”

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