Growing Vegetables In Pots & Containers

four french bean plants in a large pot
four french bean plants in a large pot

Introduction

Pot growing is an excellent way of starting to grow vegetables, and it is surprising just how much can be grown in a small space. Many people who have an allotment choose to grow salad vegetables at home and use their allotment to grow crops that require more space.

If space is short, vegetables can be grown indoors in a conservatory, on a balcony, around the edges of a patio, dotted around a garden, or in a greenhouse or polytunnel. With careful planning, a sizeable quantity of vegetables can be grown in a small space, taking full advantage of vegetables that grow vertically.

Fresh vegetables can be harvested from mid-year until well into the autumn, and enjoyed for even longer when properly stored. Being close to home, the plants are easy to care for, and can be picked when needed for cooking.

Step By Step Video

YouTube Video

polytunnel growing vegetables in containers

There is a wide choice of vegetables to choose from including garlic, shallots, peas, beans, tomatoes, cucumbers, and chillies. This article provides ideas for vegetables to grow with a recommended pot size.

Nevertheless, growing vegetables in pots is not as straightforward as it may seem. Whilst it is possible to grow pretty much any vegetable in a big enough container, this is not the focus of this article. Big containers in many ways are similar to raised beds, and if this is your interest, you may like to see this article on allotment no-big beds, or shop here for a variety of raised beds.

It is rather more tricky to grow vegetables in the pots that are commonly found in garden centres for use on patios and other small spaces. The smallest pots I like to use are about 7 inches high (20 cm). The largest I use are about 15 inches high (38 cm). Any larger than this size becomes difficult to manage for one person alone, due to the weight of the pot when filled with soil, and its awkward size to lift.

The challenge with growing vegetables in patio sized movable pots is that not all plants suit this method. Some plants develop large root systems, sending their roots deep looking for water. Keeping up with their demand to keep the soil moist requires consistent watering.

There are plants that do not like their roots getting warm. In hot sunny weather, the high surface area of pots combined with relatively little soil, means that the soil can become too warm for some crops.

Finally, there is also the question of physical size. Some plants are big, growing tall with long stems and large leaves, and these may require support. In strong winds, a big plant in a small pot has a good chance of being blown over.

The next sections provide example growing techniques to help overcome these challenges, as well as tips on how to protect crops from being eaten by common garden insects and animals.

Vegetables For Small Pots

drawing of small size containers

Some vegetables grow well in shallow depth containers because they do not send their roots deep into the soil. Many salads crops (and herbs) can be grown this way, and examples include:

  • Carrots (round varieties)
  • Chillies (dwarf varieties)
  • Garlic
  • Lambs lettuce
  • Lettuce
  • Onions (& Spring Onions)
  • Radish
  • Rocket

lettuce growing in trough

The advantage of shallow containers is that they require less soil. Also, shallow containers come in a range of styles, including long troughs which are particularly suited to salad crops. These tend to more stable than small round containers (that are susceptible to being blown over by the wind).

Even though these plants can grow well in small containers, it is important that the soil is kept moist at all times. If not, the plants will not grow to full size, may have tough chewy leaves, or run to seed (flower). On hot sunny days, this may mean watering in the morning and evening. Some pots and troughs contain a water reservoir at the bottom, and this can be a big advantage for a forgetful (or busy) gardener.

Vegetables For Medium Sized Pots

drawing of medium sized containers

Medium sized pots really open up the range of vegetables that can be grown, not just in the type of vegetable, but also in the range of varieties of any one crop. Examples include:

  • Aubergine
  • Beetroot
  • Broad beans
  • Chard
  • Sweet peppers
  • Cucumber
  • French beans
  • Courgette
  • Peas
  • Runner Beans
  • Spinach
  • Tomatillos
  • Tomatoes

From this list, my preferred vegetables are tomatoes, chard, and French or runner beans. A few tomato plants can provide a harvest from July to September. Chard is packed full of nutrients, easier to grow than spinach, and can be harvested a few leaves at a time over many months. Beans are unusual for a vegetable with their protein content, can be picked over many weeks, and freeze well too.

tomatoes growing in pots

All the listed crops enjoy the greater root depth of medium sized pots (and will enjoy bigger pots even more). A consistent and regular watering regime will often make the difference between success and failure. The plants will be much healthier if the soil in which they grow is kept consistently moist.

Unlike growing in open soil where too much watering may lead the soil to become waterlogged (and bad for the plants), plant pots will allow surplus water to drain off (if properly prepared - see the section below). This creates a different problem, potentially washing away important nutrients contained in the soil. To mitigate this, a weekly feed using a tomato type plant food will help the plants remain strong and healthy.

Vegetables For Large Pots

drawing of large size containers

There are a few vegetables that are only best attempted to grow when using large pots. This is because they either grow deep below ground, or they are particularly large plants. Examples include:

  • Carrots (long varieties)
  • Globe artichokes
  • Jerusalem artichokes
  • Potatoes
  • Squash and pumpkin
  • Sweet potatoes

carrots growing in a large container

Keeping the soil moist in big pots and containers is important, but this task is much easier with the relatively greater amount of soil. From the above list, my favourite option would be a spreading squash (or marrow), with the runners from the plant tumbling and spreading across a patio to provide a bumper harvest of fruit.

There are a few disadvantages with choosing to use big pots:

  • The pots are relatively expensive to buy
  • They require a large amount of soil to fill up
  • They are heavy and awkward to move around

In addition, harvesting potatoes and sweet potatoes from deep in the soil can be hard and messy work, requiring excavating the soil from the pot to reach the crop below the plant. There are specialist containers for potatoes that allow the side of pot to be removed to overcome this problem.

Difficult Vegetables To Grow In Pots

There are a few vegetables I would not recommend for growing in pots.

Asparagus
A plant that thrives below ground, sending up delicious tasting spears in the spring. Asparagus takes two to three years to become established, and once established, a gardener needs to allow a few spears to grow to maturity each year to allow the plant to recover energy. Full grown asparagus shoots are about two metres in height.

Broccoli, Cabbage, Cauliflower, Brussels Sprouts
All members of the brassica family, these are large plants with big leaves that occupy a lot of space for a relatively small harvest. The plants are particularly sensitive to dry and hot conditions, which may cause them to bolt or not form heads.

Sweetcorn
Growing to almost two metres in height, sweetcorn is a wonderful sight in the summer swaying in a gentle summer breeze. In a pot, they are susceptible to being blown over. Sweetcorn benefits from being grown in a close block of other plants, with the wind helping the plants to pollinate each other.

How To Prepare Pots

My preferred way of preparing pots is described below. The purpose is to ensure that the pots drain well, to prevent the soil becoming waterlogged when watering. It is much easier to prepare well, than notice a problem and try to correct it once the plants have become established

Step 1 - Drill Drainage Holes

Some plastic pots come with the holes already drilled, but many mark the points to drill with indented circles. Please note this step may not be required for pots that contain a water reservoir, as these containers are likely to have a way for draining surplus water.

pot with drilled drainage holes

Step 2 - Cover The Base With A Layer Of Stones

The purpose of the stones is to prevent the holes at the bottom of the pot becoming blocked with soil.

pot base covered with stones

Step 3 - Half Fill The Pot With Compost, And Water

For medium and large pots, the purpose of this step is twofold:

Ensure that the water drains out from the bottom of the pot
Ensure that the soil at the bottom of the pot is wet through
Before I water, I like to rub the soil in the pot between my gloves to loosen it and break apart any clumps.

Step 4 - Complete Filling The Pot With Compost, And Water

I like to drench the soil at this stage to ensure that all the soil in the pot is thoroughly wet through. It is much better to do this before sowing any seed, as the seed can be washed away with heavy watering.

Unless the weather is hot, there is no need to water again until after the seeds have germinated.

Step 5 - Sow Seed Or Transplant Plant(s)

The planting depth of seed is no different to growing in pots than if growing in beds (follow the instructions on the seed packet). After sowing, I sprinkle a layer of fresh compost on top to cover the planting holes or drills.

If transplanting plants, I create a hole big enough for the plant, and then firm up the soil around each plant after planting. A final shower of water can help the roots bed in.

Growing Media For Pots

The growing media used to fill pots can make a big difference to the results achieved. This section introduces the different types available. Supplementing the soil you have with different types of media, often in the ratio of 1:1 (or fifty percent soil and fifty percent other media) is a common way of making good use of what you have whilst giving your plants a nutrient boost.

Soil (from a garden or allotment)

Garden or allotment soil varies greatly depending on where you live. Clay based soil will naturally hold water and be sticky to touch, whilst sand based soil will drain very well and have a gritty texture. Both will be improved by additional compost, which will help dense clay based soils become more loose and drain better, and sandy soils hold more water.

In addition to water retention, garden soil is unlikely to contain the optimum level of nutrients. The soil will also contain seeds, which will likely germinate when brought to the surface.

However, the big advantage of garden and allotment soil is that it is available. For this reason, it can be good for mixing with other media to help them go further. The mixture can be used from the base of the pot upwards. For the top 3 inches, or 8 centimetres, using fresh compost as the top layer will help suppress any weed growth.

Compost (shop bought or homemade)

Fresh compost is different to garden soil as it has recently been made from a rich mix of organic matter that has been broken down by organisms. The high level of organic matter means that it is rich in nutrients that can help plants grow stronger. In addition, compost contains material like wood chippings to bulk it out. This contributes to the crumbly texture of compost, giving good drainage and aeration that makes for healthy roots.

Shop bought compost has the advantage that through controlled manufacture it should be weed free. There are two disadvantages to shop bought compost: the cost of buying it, especially if you have a lot of pots to fill; the weight (and messiness) of transporting the compost home from shops.

Homemade compost is easy to make, but is a process that can take many months (six months or more). To get the optimum consistency, shredded cardboard or wood chips need to be added. It is also likely that homemade compost will contain weed seeds, even after it has rotted down.

Many gardeners choose to use shop bought compost for germinating seedlings to take advantage of it being weed free. Mixing homemade compost with normal soil for the base and mid layers of pot growing helps save money. A layer of shop bought compost as the top layer will reduce the likelihood of any weeds growing.

Well Rotted Manure (shop bought or homemade)

animal waste in straw
Horse bedding before composting

Manure is made from animal waste (non-meat eaters like cows and horses) mixed with dry material like straw. It is very rich in nutrients, making it an ideal ingredient to include in growing media for hungry plants like squash, rhubarb, courgettes, and tomatoes.

Manure is sold in bags from shops, just like compost. Some allotments have a relationship with a local stables to provide a supply of horse bedding, which is left to rot down before use by plot holders. It is important that the manure has been well rotted and broken down, rather than used fresh.

Well rotted manure looks very different to fresh animal bedding, having an appearance more similar to compost - but somewhat stickier. Well rotted manure should not smell.

well rotted manure
Well rotted manure

Natural fibre (coir or coconut fibre)

coco fibre brick

An alternative to using garden soil or compost is to grow plants in natural fibre. Coir is manufactured from the hairy husks around coconuts, and has excellent water retention and aeration properties that make it an ideal media for growing plants.

Coir is commonly sold as bricks, which are very light to carry as they do not contain any water. To use the bricks, they need to be placed in a large container and mixed with the specified quantity of water. The result is an almost perfect growing media.

coco fibre brick after mixing with water

I like coir for two reasons:

  • It is not messy - hands do not get dirty touching coir
  • It is much lighter to bring home from shops
    (and is suitable for postal delivery)

There are disadvantages to growing with coir:

  • It is a little more expensive that buying compost
  • It does not naturally contain nutrients vital to plant growth
    (although it is possible to buy coir with added nutrients)

The lack of nutrients is potentially a big issue for growing vegetables, but this can be mitigated in the following ways:

  • Germinating seed does not require nutrients, making coir a mess free replacement for seed compost
  • Supplementing coir with nutrients by mixing with compost (homemade or shop bought), well rotted manure, or adding nutrient solutions when watering (ie tomato plant food)

I see coir not as a replacement for traditional growing media, but as a useful supplement. For germination, or for plants that do not like dry conditions, using coir on its own or mixed with other types of growing media can be helpful.

How To Protect Your Plants

There are a wide variety of insects and animals that want to eat what you grow, and when they find a food supply, they usually do not stop until everything is gone. For a gardener this can be hugely frustrating. There are numerous techniques that are claimed to stop or reduce attack, but below are the ones that I have found to work best for me.

Create A Moat

Despite their apparent lack of athleticism, slugs and snails are excellent climbers, and can easily scale the outside of a pot to get to plants. They are active from early evening until dawn, providing plenty of time to make the journey to your plants and back to where they hide in the day. However, I have found a water barrier to be extremely effective at preventing slugs and snails reaching plants. It is also stops ants too, making it an effective way of dealing with an aphid attack (aphids are often farmed by ants).

The trick it to use a tray much wider than the base of the pot, and ideally with a high lip. A high lip is better as it gives a better depth of water, which is good for watering plants from their base, and is less likely to dry out in hot weather. The protective moat will only work if the tray is constantly filled with water.

If you have a lot of pots to protect, you could consider creating one large moat using pond liner supported by a wooden frame or similar. All the pots would stand inside this.

Use A Net

protecting seedlings in a container with a net

A net stretched tightly over plants stops animals eating your crop, whether that be mice, rats, badgers, squirrels, or most commonly pigeons. The net needs to be secure at its base to prevent animals burrowing underneath. Tucking the net underneath the pot is a good way of doing this, or alternatively, weigh the net down with bricks or other heavy objects.

Use A Plastic Cloche

protecting seedlings in pot with a plastic cloche

Young plants are particularly at risk of being eaten, as their flesh is thinner, tastier, and easier to bite through. When the plants are small, one attack at night can destroy the crop. The risk decreases the larger the plants get, as the skin on the stems and leaves becomes thicker, and if a plant is attacked, hopefully enough of the plant will be left to enable you to correct the problem and save the crop.

Plastic cloches are ideal for protecting small plants at this critical stage. Ensure the base of the cloche is buried in the soil to prevent anything getting under it. The cloche will provide a warmer environment for young plants too, helping them to mature faster.


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