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Growing Food in Containers

While some types of vegetables are simply better suited to growing with their roots in the ground, the determined gardener can grow almost any kind of food plant in containers. It is the nature of all plants that some require more root space than others. Lettuce, for instance, has a relatively small root system that grows shallowly, near the surface of the soil. By comparison, some squash plants have roots that will have an eventual diameter of thirty feet if they’re allowed to grow unrestricted. Clearly, squash plants are not well suited to container growing.

Other kinds of plants don’t have enormous root systems, but they get too tall to manage in all but the largest container. Corn and quinoa grown for seeds are both good examples. And some plants need space for their roots to develop – beets, garlic, onions, parsnips, radishes, and turnips all need depth combined with lateral growth in order to develop fully.
 
Containers for growing food need three essentials:
  1. They need to hold the soil in place. You can use thick plastic or burlap bags, tires, terracotta pots, or anything that will provide a stable receptacle for soil.
  2. They need drainage. Plants don’t want to sit in water, so it needs some place to go. Drain holes at the bottom of the container are critical.
  3. They need to be at least 10cm (4”) deep. Deeper than this is even better – in fact the more room you can offer the plants, the larger their root systems will grow, so they’ll be able to take up more nutrients.
 
It’s important to remember that the soil in containers is going to be warmer than the soil in the ground. While this benefits heat-loving plants like peppers, eggplants, tomatoes, and melons, it also means that evaporation of water out of the soil will become an issue in hot weather. On a sunny balcony in mid-summer, you might have to water twice a day to keep plants healthy. While the soil needs drainage, it also never wants to be completely dry, so this can be a challenge for container growers.
 
Sunlight is another matter to think about before you get started. All plants need at least some direct sunlight in order to thrive, but fruiting plants like peppers and tomatoes require a minimum of 6-8 hours of direct sunshine every day. At least with containers, you can move plants around to make the most of the sunshine.
 
Soil for growing veggies in containers needs to be very fertile. Many store-bought potting soils will suffice, but you should mix some balanced organic fertilizer into the soil at planting time, and provide a liquid fish or kelp based fertilizer at regular intervals throughout the season – every three weeks should suffice. In her outstanding book, Backyard Bounty, Linda Gilkeson recommends this mix for homemade container blends:
“Mix equal parts peat moss/coir, good garden soil, compost and sand. Using perlite or vermiculite instead of the sand will make the mix lighter in weight.” Gilkeson also provides a lightweight recipe in her book for growers on rooftop gardens.
 
One final piece of advice is to avoid over crowding your containers. If you’re sowing mesclun seeds, use only a scant pinch of seeds. Over crowded plants will not have access to the light and nutrients they need for steady growth, so they’ll end up leggy or stunted. Whenever you’re growing the plant on to full maturity (like with fruiting plants or for full sized leafy heads), grow one plant per pot. For these plants, 5 gallons is a standard minimum pot size – otherwise look for containers that are as wide as they are deep. These will probably be so heavy that they cannot be moved once they are planted.
 
Some of the best vegetable varieties for containers:

Amaranth – for baby leaves.
Arugula
Bush Beans – choose the most compact varieties like Golden Child, and use large containers.
Broccoli Raab – Raab grows on smaller plants than heading types.
Carrots – you want deep, wide containers, and small varieties like Mignon or Little Fingers. Others can be grown and harvested as baby carrots.
Corn Salad
Cress
Cucumbers
Edible Flowers
Eggplants
Endive & Radicchio – choose large, deep containers.
Herbs – all but the bigget herbs (Fennel & Lovage) are recommended, but small plants (basil, chervil, chives, cilantro, dill, mint, oregano, parsley, rosemary, sage, stevia & thyme) are just made for container growing.
Lettuce
Mesclun mixes – so easy, and they don’t even need full sun!
Microgreens – you can grow pretty much any edible plant in containers if you harvest them just after the first pair of leaves open. Pull them out of the soil, rinse, and you have an instant salad.
Mustards
Melons – they’ll benefit from the extra heat of containers, but they need 5 gallons or more, plus plenty of water.
Onions – well, scallions anyway. Shallots and small cipollini onions might work as well.
Orach – for baby leaves.
Pac Choi & Choi Sum
Peas – choose only the most compact varieties like Little Marvel.
Peppers
Potatoes – large containers or grow bags are needed, and ample water.
Purslane
Quinoa – for baby leaves.
Radishes
Spinach
Swiss Chard – great baby leaf production, but suited to large containers as well.
Tomatilloes & Ground Cherries
Tomatoes

 
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Comments
I used to have a huge, wonderful garden and greenhouse in the country but now live in a smal townhous- a ten minute walk from downtown Victoria. So, I'm learning how to garden in containers. Flowers are gratifying but I need to be able grow and eat my own vegetables. Thank you for your informative article, it was very helpful, indeed. I don't get full sun at the front (I think it faces west- in Victoria its difficult to know without a compass!) but I'm going to give some pots a try this year. My questions: Do you think that a zucchini such as Soleil would work in a pot? How big? Would there be any difference in light requirement between gold and green? Thank you, Sincerely, Della Mae Johnston.
Posted by: Della Mae  
Replying to the woman in Victoria about growing zucchini in containers. I did it one year on an east facing balcony that had about 6 hours of sunlight. It worked okay - but it takes a LOT of room and as zucchini can be bought very cheaply, it didn't seem to be a good use of limited space. I grew pretty near everything on that balcony in containers. Best things were snow peas, pole beans, small cabbage and cauliflower, beets, cucumbers, tomatoes, green onions and chard. Good luck - it's a bit of a challenge but there are a lot of books out there and as long as you track what you've grown in what container, rotating crops is a piece of cake because you just move the containers around!
Posted by: Jan