Container vegetable gardening is addictively fun. I grow a lot of things in various containers on our patio, even though I have a big vegetable garden about 20 feet away.
Vegetable container gardening has become especially popular now that fewer people have big backyards, but also because it's a productive, low-maintenance, easy-on-the-back, and cost-effective way to grow fresh produce, no matter how big or small your space.
Many vegetables can be grown in containers, provided the containers are big enough. I don't use anything smaller than a 15" pot because I don't want the roots to be cramped, and because smaller pots dry out too fast.
My favorites for container vegetable gardening are:
Tomatoes and herbs are the most popular veggies to grow in containers. Everyone loves them, and even in summer they are expensive from the store. Plus, no matter how much you're willing to spend, you just can't match the taste of homegrown, fresh-from-the-garden.
Commercial tomatoes have been bred for shelf life and durability in shipping, not flavor, so even if you only have a small patio or balcony, it is well worth it to grow your own in containers.
Container vegetable gardening is very different though from growing vegetables in the ground. There are three major differences:
You must use a high quality commercial or homemade potting mix rather than garden soil in order to provide both aeration and drainage. Garden soil will compact down into a dense, heavy mass that will be a challenge for plant roots to penetrate. The mix should have plenty of perlite or vermiculite in it (up to 25%), and the rest should be a diverse blend of composted organic materials such as peat, manure, mushroom compost or homemade compost.
NOTE: Some brands of potting mix have fertilizer and moisture control pellets pre-mixed in, which help with the two problems described below. I’ve been using Miracle-Gro Moisture Control™ the last couple of years with good results.
The other thing that can be challenging in container vegetable gardening is keeping them from drying out. Because you have to provide aeration and good drainage, they also tend to dry out much more quickly than in-ground gardens, and so you will need to water almost daily in the hot part of the summer. There are a couple of things you can do to cut down on how frequently you have to water (nice if you like to be able to get away on the weekends!):
Hydrogel retains water in little jelly-like blobs, which prevent water from evaporating too quickly but which at the same time keep plants from becoming waterlogged. You must mix hydrogel up in water and let it sit for 10 or 15 minutes before mixing it with the potting soil, or else when it swells it can actually push some of the soil up out of the pot. It used to be that this was a specialty item only available at good nurseries, but now Miracle-Gro makes one called "Water Storing Crystals", available at Home Depot.
While all gardens need some form of fertilizer, container gardens especially do because you have bypassed the complex natural ecosystem that exists in healthy soil and that provides for plant nutrition. There are many good brands of commercial fertilizer out there, but for container vegetable gardening, it is hard to beat either Osmocote, or “Miracle-Gro Shake and Feed Tomato, Fruit and Vegetable™”. The reasons I like it are 1) it is time release and will feed the plants all summer, and 2) it is formulated to not give too much nitrogen to tomatoes.
Too much nitrogen will cause a lot of green growth, but inhibit fruit setting. I spoke with Miracle-Gro and they told me that this product is not approved for use in containers, but I have used it at half the recommended application rate with good results.
I flush my pots with water at the end of the season, which helps flush out concentrated mineral salts from fertilizer residues. I pull out the plants and roots, and store the potting soil in big covered trash cans over the winter. In the spring I recharge it with about 1 part homemade compost to 3 parts old mix.
If you wish to grow your container vegetables strictly organically, you will absolutely need to start composting as well, because good quality homemade compost is essential to an organic garden. There are a variety of ways to compost on a small scale in an apartment or condo, including having a small compost bin or tumbler on your balcony.
Worm composting totally rocks and actually works great even indoors in a corner of your kitchen. It may sound gross, but it actually works really well, doesn't smell, connects you to the whole cycle of the natural world, and I think it's really fun.
Another way is to use a contained, anaerobic system called a bokashi system. These work in a different way than other composting systems, but they work great! You can buy one or make one, but you have to buy the Bokashi starter mix.
Upside Down Planters
It's really fun to grow things upside down! (For people, at least, I'm not sure how the tomatoes and peppers feel about it!) The Topsy Turvy™ planter, the Revolution Planter™ (from Gardener’s Supply Company), or even a modified hanging basket or bucket, will grow carefree tomatoes hanging from south-facing eaves or another sunny support. Be sure to check out the upside down tomatoes article for complete instructions and tips on how to grow upside down tomatoes successfully.
One day I just woke up to how much time it was actually taking me every day to water all the various vegetable and flower containers I had on my patio. Here in Colorado in the summer it's more like the desert southwest than the mountains - so hot and dry that sometimes I had to water my pots twice a day to keep my plants from turning into crispy critters.
Then I discovered self-watering containers, which I only have to water twice a week. They work wonderfully, so do check out the article devoted to them. They require different care than ordinary containers (and not just regarding watering).