No yard? Grow vegetables (and more) in containers
By Steve Reiners, Professor and Chair, Horticulture Section, School of Integrative Plant Science, Cornell University, Cornell AgriTech. This is part of a series of columns that he wrote about vegetable gardening during the pandemic.
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April 23, 2021
What’s an aspiring vegetable gardener do if you have no good place to put a garden. Maybe you only have a small patio or deck. Perhaps the place where you could put a garden is waterlogged. Perhaps you’re surrounded by concrete and blacktop. If this is the case, you can still grow your own vegetables -- in containers.
Most vegetables will grow just fine in containers. The key is sunlight. Fruiting vegetables like tomatoes, cucumbers and squash require at least 6 to 8 hours of direct sun. Root crops like carrots, beets and radishes need at least 4 to 6 hours. Leafy crops like lettuce, spinach and many herbs can get by with just 2 to 4 hours. But if the only place you can put your containers is in full shade, you really can’t grow vegetables. Think about growing flowers like impatiens and coleus that thrive in shadier conditions.
As far as the containers go, just about anything will work. They need to have holes in the bottom so excess water can drain away. And generally, the bigger the container, the better.
With no drainage, the soil gets soggy and anerobic. Roots will die, plant diseases will thrive and eventually the plants will die. Drainage holes ensure that does not happen. Yes, you will need to water often, maybe daily in the middle of summer. But good drainage is critical for success.
Obviously, larger containers hold more soil, increasing your initial investment. But more soil provides more room for the roots and a greater reservoir for water and nutrients. And you may not have to water as often.
Aesthetics may factor into your container choice . A 5-gallon bucket works great but may not look nice. A wine barrel looks sharp but can be pricey. As long as they can hold soil, containers can be made from almost any material -- plastic, wood, clay, and fibers. Large plastic storage containers are cheap and hold a lot of soil. Plus, you can often use the lid as a tray to catch excess water. I have even seen people use reusable grocery bags.
What should you use for the soil? Don’t just shovel in your garden soil. Chances are it will not drain well and it may harbor plant diseases. You can purchase bagged soil mixes formulated just for container growing at garden centers. The nice thing about prepared mixes is that lime is usually added to optimize pH along with some fertilizer to feed the plants. (Organic options are available.)
Fill the containers up to within an inch or two from the top. This will allow you to water more easily as it creates a reservoir and water won’t flow over the top of the container. It’s best to start with fresh soil each season. You can add the old soil to your compost pile or directly to your garden.
As far as fertilizer goes, most veggies will benefit from a light feeding throughout the season. Compared to garden grown plants, the root system is limited and contained. So, the roots can’t forage far and wide for water and nutrients. Plus, some of the nutrients will be leached away through the drainage holes. I recommend using a half strength solution of a soluble fertilizer every two weeks. If the label calls for 1 tablespoon in one gallon, use 1 tablespoon in two gallons.
Adequate watering is essential. When the plants get big, the soil can dry out quickly in the summer heat and plants can wilt suddenly. Try to protect the plants from wind as this will reduce their water demand. Plan on watering once a day, and always water until it flows out the bottom. You can collect that leachate and use it to water and feed your garden plants.
In the garden, we might mulch around the plants to conserve soil moisture. You could try this in a container, but I doubt if it will have much impact. Ninety percent of the water loss is coming through transpiration through the plant, which the mulch can’t prevent. Only about 10% is evaporating directly from the soil.
You can buy items that will provide water if you are away. But there are some do-it-yourself tricks you can try to help with watering. Take an old wine bottle, fill with water, turn it over and insert in the soil. The water will slowly flow out. And you can use any kind of bottle -- water or wine, plastic or glass. If you are going to be away for more than a day in the summer, best bribe a friend with a tomato or two to stop by and water for you.