How to grow vegetables in containers

Growing food in containers is fun. If you live in a small space with no ground at all, you can have access to fresh vegetables, herbs and fruit, all planted out in containers. If you have a garden full of vege beds, you can still find value in a lemon tree in a planter on your patio or a pot of mint by the back door tap (mint loves being kept moist)!

Summer vegetables are usually smaller plants and are therefore more suited to containers than winter vegetables.  They produce more prolifically, compared to, for example, one winter broccoli plant that produces one head and takes 3 months to mature.

container gardening

Before you start, do bear in mind that anything grown in a container is at your mercy entirely. Food grown in the ground benefits from rain and the ecology of the soil of a garden bed.  Growing in containers means you need to invest in good quality potting mix and good quality organic fertilisers and check your plants every day to make sure they have enough water.  Containers dry out more easily than a garden bed.  Checking containers every day also means you’ll catch pests or diseases that might affect your plants in good time.

Let’s start with fruit.  The fruit trees that grow the best in containers are citrus.  Every 3-5 years you’ll need to do a root prune in order to keep them strong and productive. Strawberries will do well too.

You’ll need a bag or tub or pot that is ideally around 75L for a citrus tree.

For vegetables, containers need to be a reasonable size too.  Most vegetables will only grow in something no less than 40cm deep.  The exception is lettuces and other similar leafy greens like rocket, mesclun and Asian greens like mizuna and pak choi.  They can grow in a 20-30cm deep pot as long as they’re well fed.  That’s because they mature quickly.

Spinach and silverbeet grow bigger roots and need 40-60cm depth in the container.  They’re bigger plants and are in the ground longer.

Fruiting vegetables like tomatoes, eggplants and capsicums need more depth too, as they’re in the ground a long time too and need a lot of food (fertilisers).

Cucumbers are a good container plant, as the vine can trail over a balcony.

Potatoes do well in a grow bag and carrots and beetroot can be grown in grow bags too, as long as they’re about a 45L capacity bag.

Vegetables that are not good choices for containers are large plants like zucchini because they take up too much space.

Growing herbs in containers is worth its weight in gold.  They cost so much to buy and so often you don’t use all you buy.  Dry-loving herbs like rosemary, sage, thyme and oregano do particularly well in containers, as they require very little nutrition and are shallow-rooted. 

Herbs like parsley do best in the ground or a deep container (40-60cm deep) as they have a long tap root.  Mint does well in a container as it has a spreading habit and the container doesn’t allow that.  Keep mint and coriander well-watered (once a day in summer).  Coriander likes to be picked and will go to seed if it’s not.

Drainage is important for container gardening.  Grow bags drain through their fabric.  If you’re using a flexi bucket or a large re-purposed plastic container, drill holes about 2cm up from the base if it has a flat base.  If it has ridges on the bottom, you can drill the holes in the bottom, as it will sit up off the ground.  If you’re lining a wooden container with polythene, make sure you slash slits in the bottom.

Containers will mark a deck or concrete eventually, so you may like to sit your containers on a piece of plastic or polythene.

Site your containers in the maximum amount of sun.  They’ll need at least 8 hours of sun a day. A north or north-west aspect is best.  If you don’t have a sunny spot, put casters on the bottom of your containers and move them during the day to chase the sun.  But truly, sun is key and you don’t want to invest something that you know might fail due to not having enough sun.  Keep containers out of the prevailing wind or create a wind shield, as wind can be damaging.

You must use potting mix in a container.  It is blended with the right combination of pumice and coconut fibre to aid drainage.  The better the quality, the better the plants will do.

Leafy greens benefit from a nitrogen fertiliser like sheep pellets, fruiting plants benefit from a potassium fertiliser like liquid comfrey, and everything benefits from a well-balanced fertiliser applied at the time of planting.

Now, the containers we’ve been discussing here are all the large permanent variety.  If we refer to the waste hierarchy, re-using is higher up (ie more desirable) than recycling.  Given we have so many plastic containers in our lives, food gardening is one area where we can usefully deploy disused plastic containers. ecostore have teamed up with the Little Garden promotion at New World for a competition to upcycle used ecostore containers into planters for your Little Garden seedlings. You’ll germinate your seeds in the peat pots provided according to those instructions.  Then for the period when you grow them on (which is once they have their second set of leaves), consider using a cut-down Ecostore container for the middle stage, before you plant them out in your garden or a larger container.  Make sure you cut the neck of the container off (if it has one, as you’ll have to knock the plant out eventually and you don’t want to disturb the roots).

For instructions on how to prick out seedlings, see here.

Here we’ve got tomato plants growing on in handwash containers.  When the plants get to about 20cm tall, and ideally around Labour Weekend when it’s warm enough, we’ll plant these guys out in the garden.

But, as mentioned earlier, lettuces will grow in small containers, so in these two 5L containers (used for re-filling), we’re growing lettuces through to maturity. 

In all of them we’ve drilled holes on 2 sides 2cm above the bottom for drainage. This is because they have flat bottoms and so the excess water can drain freely out the sides.

For more information on the competition, see here.

Happy container gardening this summer!

Organic Edible Garden’s vision is to make organic edible gardening achievable for everyone. Visit their website for Getting Started videos, and regular blog posts to find out what to do in your edible garden.