There are a few simple things you have to understand to ensure success when you’re growing vegetables in containers.
Vegetables are 90% (or more) water
If you allow your containers to dry out, you’re going to reduce or eliminate your vegetable harvest.
A perfect example is the tomato. We want to grow it everywhere and containers answer that need for balcony growers as well as those with no soil. But the minute the plant gets too dry, calcium stops moving up the plant to the fruit and your fruit will develop blossom end rot (a black rotting on the bottom). It’s not a disease, it’s poor watering and you only have to let the plant dry out once or twice when it doesn’t want to and your entire crop is ruined.
So we need to really watch the watering and get it right.
The easiest way to do this is to have huge containers.
Forget tiny pots; anything smaller than a 12-inch flower pot isn’t going to make it.
To give you an idea of this, I used to grow tomatoes commercially in green plastic garbage bags on the floor of my greenhouse. It took 6 full shovels of soil to give enough support to the plant and I had to water every day and most often twice a day to keep those plants properly watered. They would dry out with 6 shovels of soil in a day. So if you can water every day or twice a day in the heat of the summer, you can grow in 6 shovels of soil.
But if you want to skip a day (or a weekend) then you had better increase the amount of soil you’re using. And that means larger pots.
You need to feed your plants.
When you water, the fertilizer that is in the soil is washed out the bottom of the pot or driven down away from the roots. If you want your plants to grow, you have to feed them.
Commercially, we fed all plants every time we watered so there would always be food there for them to eat. Bottom line.
If you’re not feeding every time or every second time you water, then your plants aren’t getting enough food. A rule of thumb would be to feed at half-strength plant food every second time you water.
You need to keep the pots cool.
I never use black plastic pots because the sun beats down on them and heats up the soil. When the soil gets too hot, the plant stops growing (and dies if it gets way too hot).
You see, we know that leaves start shutting down when the air temperatures reach 28C (83F)
What isn’t common knowledge is that when soil temperatures get into the 30C (86F) to 40C (104F) range, plant performance is going to suffer. It is fairly easy to have soil temperatures above the 30C mark on a hot summer’s day with a black plastic pot.
I use clay pots for this reason.
They take more water than plastic pots but are much cooler (don’t absorb as much sunlight and evaporate/cool through water sweating out of the pot).
You want to use the right kind of soil in your container.
Fill the pot from top to bottom with an soilless peat-moss based soil.
Do not use real soil or any potting soil that contains real soil.
The reason for top to bottom is that putting shards or other material on the bottom of the pot to “increase drainage” is an old wives’ tale.
The second is that real soil compacts during the summer, turning into concrete and eliminating air spaces the tiny feeder roots need to feed the plant.
In answer to the question, “What vegetable can I grow in a container?”
I propose the answer, ‘Anything you want.” There is no reason you can’t have your entire garden in containers on a back deck (away from deer – although they will wander up there if hungry) or on the cottage dock or even right beside the tiny backyard patio in the midst of downtown. You can do it!
Treat all vegetables and herbs the same in a container as in the ground.
There is no difference between growing in a container and growing in a small garden. The plant doesn’t know the difference if you provide it with everything it needs so you get to grow what you want!
- Water properly – soak so the water runs out the bottom every time you water.
- Use peat-based artificial soils from top to bottom in the pot.
- Feed properly – every time or every second time with half-strength fertilizer.
- Give the plant enough soil in containers that don’t absorb heat and look good.
- Grow what you want to eat.