University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article

Dr. Leonard Perry, Extension Professor
University of Vermont

According to the survey of the National Gardening Association, over one quarter of households are involved in some form of vegetable gardening and, of these, almost half are growing at least some vegetables in containers.  If you already grow vegetables in containers, try some new varieties or crops.  If you don’t use containers yet, check out all the opportunities this easy type of gardening can provide.   
Many garden vegetables can be grown in containers, tubs, or boxes, right on your porch, deck, or patio.  They’re easy to maintain, so are a good choice if you’re new to gardening or pressed for time.  They’re a great way to get children interested in gardening.  Being up off the ground, they’re a good fit for older gardeners that aren’t as agile as they once were.  For whatever age, you'll find that harvesting some tomatoes, cucumbers, and salad greens for your table becomes much more convenient than in ground beds away from the house.
As in the garden, most vegetables “prefer” a sunny site (a minimum 6 to 8 hours direct sun a day—the more the better).  A nice aspect to containers is that even if you don’t have a large garden space for such, you may have a smaller sunny area for a few containers. Or you can group containers in various sites, depending on the available light. 
If you only get 3 to 4 hours of sun a day, some crops that tolerate this level include arugula, chard (for its leaves), many herbs, kale, lettuce, mustard greens, scallions and spinach.  Requiring even less—at least 2 hours of sun a day—are mesculun and Asian greens.  These also take “dappled shade”, or no direct sun but rather bright light filtered by trees.  If you have, on the other hand, a bit more direct sun (4 to 5 hours a day), you should be able to grow all these plus peas, beans, and many root vegetables.
One aspect to containers that’s different from ground beds is that the soil volume is of course limited, so especially when plants grow large and their roots fill the pots, they’ll need more watering than if in the field.  That’s not so bad as it gives you an excuse every two or three days to check on your plants for water (perhaps daily during hot weather), and at the same time look for pests, watch their growth, and see if any are ready to harvest.  Fertilize when watering, according to label directions on the product of your choice.  Use a fertilizer for vegetables, as those with too high nitrogen will cause great leaf growth, but few if any fruits.
When potting, using an organic well-drained soil mix with lots of peat moss or compost will help reduce watering, as these hold onto lots of water.  I often use one part compost to two parts of one of these soilless mixes, or equal parts bagged potting soil and compost. You also can incorporate a water-absorbing product to hold onto even more water. Don’t use garden soil as it is too heavy, holds too much water in pots usually, and may introduce soil diseases. Make sure pots have drainage holes in the bottom. 
Many vegetables and herbs are ornamental as well as useful.  Examples that come to mind are the brightly colored stems of some Swiss chard varieties like ‘Bright Lights’, variously colors in peppers— both sweet and hot, and some of the newer tomatoes with different colored fruits such as gold, black, white, or green and white zebra-stripes.  The ornamental cabbage and kale are often used for fall container plantings, and last well through many heavy frosts up until heavy snow covers them.  Many kale have frilled or deeply cut, attractive leaves, in purples or green and white combinations.
Vegetables that grow rampantly and large, or that must be grown in great numbers to obtain satisfactory yields, generally should not be selected for container growth. Many catalogs offer newer varieties bred to be dwarf, or smaller bush types.  Look for these, or those in your garden stores labeled as good for containers. If you get large containers, consider casters for the bottom if they’ll need frequent moving.  Lettuces and other greens, radish, and herbs are good for smaller or shallow containers, even windowboxes.
Traditional pumpkin and squash vines and cucumbers usually are not recommended for container growth because they take up so much space.  If you have a large raised bed, or large container such as a whiskey barrel half or one that holds 15 gallons or more of soil, you might consider one of the newer varieties with bush habits. Look for bush beans too, rather than the traditional vining or spreading types (unless you have a high raised bed, or container they can hang down the sides).
Other plants that may need large containers include cabbages and corn.  Corn in particular can get quite large, and tip over smaller containers or dry out too often.  It also needs several square feet at least of plants, or several rows in a rectangular bed, in order to get good cross pollination and so good ear development.
I like to grow potatoes in thick, black fabric gro-bags (15 gallon).  Fill them one-third full when planting the tubers in May, then fill more as the potatoes sprout and grow.  You can then harvest in mid to late summer.  Growing in such bags is a great way to try several different varieties that you won’t find in stores, and they’ll grow with a half day of sun.
Even if you don't have a very large container, vining crops such as cucumbers and squash can be grown.  Simply train up a trellis, around a window, or allow to cascade down a raised deck.  You may even train such vines over an arch, the fruit hanging down so you can watch them develop and easily pick them when ripe. If you’re growing squash with large fruit, these will need additional support later in the summer such as from a cheesecloth sling.
A common container vegetable, and one of the most attractive, is of course the tomato.  Special dwarf “bush” varieties have been bred under a foot high, with small to medium-sized fruits.  Larger tomato varieties that grow to a set height (determinate) are suitable for large containers.  Those that keep growing taller (indeterminate) will need taller and more elaborate staking if grown in containers.  A range of fruit types are available, from the large beefstake types, suitable for slicing, to the small grape, cherry, and pear shapes.
There are many leafy greens and lettuces you can combine in containers.  Consider those with lacy or frilled leaves for fine texture, or those with colored leaves such as the red leaf lettuces.  A key to lettuces is to make “successive sowings” every 3 weeks or so.  This way, once you finish harvest of the first crop, you’ll have another reaching harvest size. Growing in pots or windowboxes is a good way to keep your lettuces away from rabbits.  If not full sun, but a choice of locations, morning sun for lettuces is better than hot afternoon sun.
Then of course you could plant just an herb container to have near the kitchen door.  Tall herbs such as dill and fennel, with their attractive flowers and tall lacy foliage, might be underplanted with lower ones such as chives and parsley. Thyme may be used to hang over the sides of a pot.  Chives tend to spread and seed around, so pots are great for them.  Or you can plant a whole container just of various basils (they like sun) to use in Italian sauces and pestos.
Mint is great for pots, as these contain the aggressive growth and roots of this easy herb.  In fact, they are so aggressive, roots will grow out of the pot holes and into the ground if touching it.  Keep them raised, and repot each spring to keep them healthy.  Keep a pot or two near the door so you can easily harvest for cooking or use in beverages. Look for different mints, including spearmint, peppermint, apple mint, or even chocolate mint.

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