Growing in Containers in Oklahoma
I'm starting this thread for Melissa, who asked questions in another thread about using containers to give herself more space for vegetables. I hope the rest of you who grow in containers will comment as well.
Growing in containers can work out really well as long as you match your ultimate plant size to your container size, use a quality soil-less container mix that drains well, and pay careful attention to fertility and watering issues.
You can grow anything in a container successfully--veggies, flowers, herbs, ornamental grasses, dwarf fruit trees, etc. as long as the container you choose is large enough for the mature size of the plant you place into it. If the container is too small, the plant may survive but it will not reach its full capability.
CONTAINERS: Anything that will hold an adequate amount of soil and yet allow drainage of excess water can be used as a container. Here's a list of some of the containers people use to grow plants: clay or ceramic pottery, plastic pots, plastic or metal buckets, molasses feed tubs, kiddie wading pools, galvanized metal stock tanks and feed buckets, window boxes, wooden boxes, old (leaky) watering cans, Rubbermaid and similar storage totes, burlap bags, feed bags, bags of potting soil (poke drainage holes in the bottom, and cut an X" in the top of the bag and plant right into it), purchased self-watering containers like Earth Boxes, homemade self-watering containers, and grow bags. The possibibilies are endless.
Any container you use needs to have adequate drainage holes, and lots of them. We drill nickle-sized to quarter-sized holes in the bottom of containers, like feed tubs, that we turn into containers for plants. You can line the inside of the container with landscape fabric cut to fit the bottom to help keep soil from washing out the bottom of the container if you want.
Self-watering containers are wonderful for many crops because they keep the moisture level high so that the plants don't dry out or suffer from a lack of moisture. Because you put fertilizer (chemical or organic, your choice) in the container's fertilizer strip, good plant nutrition is assured. I'm not sold on the idea of SWCs for tomatoes, though, because tomatoes are one of the few crops that suffer a distinct loss of flavor if grown in soil that is too wet. Tomatoes give better flavor if kept on the dry side as the fruit ripens.
If you want to learn more about self-watering containers, google and read about the commercial product called "Earth Boxes". If you want to make your own self-watering containers, go to the GW container forum and search there to see how various people have made them, or go to the GW Forum and search there for Raybo's homemade Earthtainers.
CONTAINER MIX: The ideal container mix will not contain any dirt or soil from your yard or garden. Instead, it will be a soil-less mix. You can buy any high-quality potting soil mix for containers or you can make your own. Do NOT buy the cheapest 'potting soil' you can find (unless you're going to add lots of compost or peat moss to it) because a lot of cheap potting soils have a heavy clay content and drain poorly--which is why they are so cheap.
The ideal potting soil will be light and fluffy because it has lots and lots of air holes that allow roots, water and nutrients to move around freely within the container. A good soil-less mix will have a good percentage of organic matter like compost (homemade or purchased) or sphagnum peat moss, or coir (coco peat, often sold compressed), and usually contains vermiculite or perlite and usually a little lime added to give your plants the calcium they need. I also add very finely shredded pine bark, often referred to as pine bark fines.
I normally add some blood meal to the mix in each pot as a source of nitrogem, some bone meal for good root growth, and an organic fertilizer like Tomato-Tone (for tomatoes, peppers, eggplants and other similar veggies) or Plant-Tone. You also can add composted manure, greensand (for potassium and micronutrients), soft rock phosphate (for phosphorus and microutrients), and other ingredients depending on what is necessary for whatever plant is going into that container.
There's an old thread where we discuss soil-less potting mixes in great detail. I'll try to find it and link it at the end of this thread.
CONTAINER SIZE: If your containers are large enough, you can grow anything you want in them. Try to match the container size to the ultimate size of the veggie you are growing. A standard indeterminate tomato plant will not grow well in a 5-gallon bucket for example, but a dwarf tomato or a determinate will do OK, although they'll do even better in a 7- or 10-gallon container. A standard indeterminate tomato plant will need at least a 20-gallon container in order to grow and produce well, and you can use molasses feed tubs, whiskey half-barrels, or something similar in size.
If you are curious about what size container is needed for each specific veggie variety, visit containerseeds.com and read their recommendations which are included with each veggie. In our climate, I wouldn't go any smaller that the container sizes suggested on that website and, because of the heat, it wouldn't hurt to go a little larger.
If you want to grow really large plants, like bush pumpkins (Cheyene is a bush pumpkin variety) or some of the more compact winter squash (Bush Delicata is a good one) or mini-melons, like Bush Sugar Baby or Yellow Doll, go with nothing smaller than 20 or 25 gallons. A child's wading pole with lots of drainage holes in the bottom can work well for these, or metal/rubber stock watering tanks or very large storage totes with drainage holes drilled in them. Large indeterminate tomatoes need large containers too. Corn can be grown in very large containers with several plants per container, but you'll need a block of containers covering at least a 4' x 4' area or a 6' x 6' area to esure adequate pollination of the ears to get good tip fill. If I were trying to grow corn in a container, I'd use Jade Blue or Early Sunglow because they are naturally small plants. Summer squash of all types, including zucchini, need very large containers.
In medium-sized containers (5-10 gallons) you can grow most peppers, eggplants, determinate and dwarf tomato varieties, broccoli (can put one plant in a 5-gallon container or two in a ten-gallon if you use smallish plants like 'Small Miracle'), bush beans or peas (number of plants per container would vary depending on container size), carrots, onions (a dozen or more per container depending on container size), cabbage (if using dwarf varieties, you can plant several in a medium to large sized container), cauliflower (one per medium container or 2 to 4 in a really large container), cucumbers (one plant per container unless you have a really large container, and then maybe two), lettuce (can grow in any container from small to large), radishes can be grown in almost any size container like onions...the size of the container dictates how many you can plant in each container), strawberries (strawberry pots are made just for them) or swiss chard (1 or more plants per container depending on how often you harvest the outer leaves).
Sweet potatoes can be grown in containers....maybe 2 plants per large-sized containers or 1 plant per medium-sized container.
Potatoes can be grown in containers, but they need large, deep containers---at least a foot deep and 5 to 7 gallons for one plant. Smartpots, a mesh-like pot originally developed for growing trees in a nursery setting, are great for potatoes. Because potatoes form their tubers (that's the potato part you eat) along an underground stem, you need to plant them deep, deep, deep and add soil as that main stem grows up, up, up. When growing them in the ground, you plant them 8" deep and 'hill up' the soil as they grow, and that's the practice you want to emulate when raising them in containers.
SMALL CONTAINERS: I would consider anything less than 5 gallons to be a small container for growing veggies or herbs in our climate. You can normally put almost any herb in a small pot, as well as short, round carrots like Tom Thumb or Parmex, garlic, bunching onions, onions (but not too many in one container), VERY dwarf tomatoes like Canary Yellow, Red Robin, Orange Pixie, Tumbling Tom, Red or Yellow Tumbler, or Tiny Tim. You can grow some of the smaller bell pepper plants like Blushing Beauty in smallish containers, but pick plants that only get about 18" tall.
PLANT SUPPORTS: Plants like cucumbers or peas (even dwarf ones) do best if you provide them with a trellis or stake to climb, and trellises or cages are better than stakes. Even so-called bush cucumbers more or less vine and sprawl, so it is better to let them grow upward where you can easily find and harvest the cukes, than to let them hang over the edges of the pots (which gives cukes a hiding place).
With every veggie and herb variety, there is at least one dwarf or semi-dwarf form that will grow better in pots than similar veggies that are more used to growing to a larger mature size.
WATERING: Most people who fail with containers will fail because of watering issues: too much water, too little water, too little fertilizer (because water washes fertilizer out of the pots constantly), or poor drainage in pots which keep plant roots too wet. Understand that in hotter weather....and here in Oklahoma that generally means all of July and August and sometimes portions of June and September as well.....plants in containers will need water daily, and sometimes twice a day.
You cannot go away on vacation for a week, or even a long weekend, without arranging for someone to check your plants every single morning and every single evening and to water them as needed once or twice a day. You might be able to skip that step if you have a drip irrigation system set up on a timer, but it still would be best to have someone check the plants twice a day because, if your timer fails or dripline clogs, your plants will die while you are away on vacation.
FERTILIZATION: I put as heavy of a compost/manure/organic matter content in my pots as I reasonably can. I add organic fertilizers and will feed the plants with a water-based organic fertilizer (compost or manure tea, fish emulsion, liquid seaweed, etc.) as needed. You also can use a pelleted, slow-release chemical fertilizer if you use chemical products. You have to be careful about overfeeding with nitrogen, which gives you lush leafy growth but fewer of non-leafy veggies. The issue with container is that every time you water, nutrients wash out of the soil so you have to constantly add nutrients to counteract the leaching.
CONTAINER PLACEMENT AND MULCHING: Choose your container location carefully. I normally put down a couple of thick layers of carboard on top of the ground to keep weeds and grass away from my containers, and then line up the containers in a row on that cardboard. Then, I layer 4-6" of mulch, usually straw of hay, on top of the cardboard and all around the pots.
I also normally stop my soil about 3-4" below the top of the container so I can add a lot of mulch to the surface of the soil after the plants are up and growing. The mulch will reduce soil splash, which will reduce disease, and will keep the soil cooler and more moist.
Position your containers where they will get enough light, where you can access them easily to water them and to harvest, and where they are sheltered from strong winds.
I normally put tomato cages in my large containers, and then stake those cages to 2 to 4 large stakes hammered into the ground. This keeps the heavy winds from blowing over the containers most of the time. If you get 50 mph or higher winds, though, even a staked plant may be blown over. I use zip ties, purchased in bulk at Lowe's every spring (if you are a gardener, zip ties are a great stocking stuff for Santa to leave in your Christmas stocking!) to attach the cages to the stakes.
WATERING: You need to water consistently. Self-watering containers will do this for you but you still have to remember to check and refill the water reservoirs. Plants need to grow in soil that is consistently moist, but you should avoid putting the through a flood/drought cycle by watering very, very heavily one day and then letting them dry out and wilt before you water them again. Consistenc is the key to successful watering.
One advantage to containers is that you can move them around to suit you. If they seem like they are not getting enough light, move them to a less shady location. If the July or August heat are brutal, move them to a shadier location.
I put container tomato plants in medium-sized containers on the concrete patio in full sun in February because they need all the sun and heat they can get at that time of year. (They go into the garage on cold days or nights.) However, I move those plants to a cooler location in late May or early June because they don't need the extra heat from the slab once hot weather arrives.
PESTS: If you are in a rural to semi-rural area where rabbits and deer, among other critters, nibble or even devour your plants, they likely will bother the container plants as much as they bother the in-ground plants, so site your containers in a location where the plants are protected from the animals, whether by fencing or deer netting or whatever. Deer won't bother plants that I have lined up along the dog yard fence, but rabbits will bother those plants at night when the dogs are sleeping inside the house or garage.
I cage almost every container I have to keep the rabbits and deer from having easy access to the plants.
Got more questions about growing in plants? Ask away.
There are smaller bush or dwarf varieties of almost everything you could want to grow in containers, so ask if you need a variety name.
P.S. Since the GW search function is not working well, I haven't been able to find the old thread on potting soil mix. I'm going to go ahead and 'submit' this thread before I lose it, and then I'll keep looking for that old thread and will come back and link it after I find it.