How to grow food in a sunken container garden

Growing in small spaces may require you to grow your vegetables, herbs and fruit in pots or containers, but have you ever thought about the benefits of growing you food in sunken pots/containers? A sunken container vegetable garden is an excellent choice that doesn’t require much preparation, requires less space than a raised garden bed, and allows you to grow many different kinds of edible plants for your kitchen garden. This post walks you through the benefits and simple steps you can implement to set up and start growing food in a sunken container garden.

There are many benefits to growing in pots – you can check out my blog post on growing food in small spaces using pots and containers here. However, there is also one major draw back. Container gardening in pots means that they don’t retain moisture well, and dry out quickly in warmer months, especially the black plastic pots that are often the cheapest and most readily available option to gardeners.

In our current rental, we actually have a fair bit of space to work with. I had a go at setting up in-ground gardens using the no-dig method which worked really well in our last rental, but this one was quickly overrun by invasive grasses. I went ahead and build some raised bed gardens, which I absolutely love, but I didn’t want to go overboard with constructing any more garden beds that would have to be moved in a couple of years time, and I didn’t want to invest too much money. I wanted to use some pots that I already had, so I felt that I needed to get creative with my thinking.

I wanted to plant some tomatoes along a fence line, but I didn’t want to plant them directly into the ground as the grass is so invasive that it would engulf the plants in no time. So, I thought, how can I grow in pots but retain enough water to have a successful tomato crop?

This is when a sunken container garden popped into mind!

What is a sunken container garden?

A sunken container garden is exactly what it sounds like – a pot or container that you partially sink into the earth. The container may simply be a pot like mine, our you could get creative and use whatever you might already have access to such as buckets or large ice-cream containers with holes in the bottom. You could even go big with your sunken container garden and use an old bath tub or laundry sink to act as your sunken container. I always encourage you to use what you already have, or find some reclaimed materials rather then buying anything new (if you can help it).

What are the benefits of a sunken container garden?

The major benefit of sunken container gardens is the ability to retain water for a longer amount of time than if the pot was simply placed on the ground. When you water a sunken pot, the water moves through the pot and out the drainage holes at the bottom, where it is held for a period of time. This means that it remains available for the plant to use rather than it just running away. Another benefit of this method it that the pots don’t heat up as they do when they are above the ground. The typical black plastic pots absorb heat so easily, and this may negatively impact your plant’s roots inside.

Plant roots are able to grow down through the holes in the bottom of the pot to continue to access nutrients from the soil below. This has happened on many occaision with my sunken container garden. Roots find their way down through the holes in the pots. The roots are then able to access moisture and nutrients further down in the soil profile, making them more resilient to infrequent watering or fertilising. This also means that beneficial organisms such as worms can enter the pot and work their magic on the soil.

Sinking the pot or container into the earth creates a border/boundary between the plant within the pot and the plants outside the pot such as grasses or weeds. This was a huge bonus, as the grass in our yard is super invasive and really takes over when given the opportunity. The boundary allows us to mow/brush cut around the edge of the pot to stop grass engulfing the plants. The time saved on weeding has made working in my sunken container garden so much more enjoyable. Not having to constantly battle weeds and grasses has really made a difference.

Which plants grow best in a sunken container garden?

Any plant that grows well in a pot will grow well, if not better, in a sunken container garden. Some examples of these plants include:

• Tomatoes
• Broccoli
• Cabbage
• Kale
• Beans
• Peas
• Herbs
• Beetroot
• Cucumber
• Eggplant
• Capsicum/bell pepper
• Lettuce and other leafy vegetables
• Garlic
• Onions
• Strawberry plants

For my garden, I found that growing tomatoes along a fence line in sunken containers especially effective as the fence then acts as a trellis structure to stabilise the plants. This set up would also be perfect for cucumbers, beans and peas, with the fence offering the perfect structure for these plants to climb up as they grow.

Which plants don’t grow well in a sunken container garden?

There are a few types of plants that I’ve tried to grow in my sunken container garden without much success. These include:

• Pumpkins
• Zucchinis
• Melons

These types of plants have very large root systems that like to grow deep and wide. They don’t enjoy having their root growth restricted, and this may result in poor growth and very little or no fruit. If you wish to grow these crops, then I recommend saving some space for them in your in-ground garden or raised garden beds.

Be mindful when growing root vegetables in pots/containers or sunken container gardens, as root crops such as carrots require deep but well draining soil. It may be best to save the space in your in-ground garden or raised bed garden for crops such as carrots and beetroot.

Is a sunken container garden the best option for my space?

There are some limitations to using sunken container gardens which will need to be considered.

A sunken container garden is best for spaces where you can dig holes deep enough to place the pot at least 2/3 of the way into the ground. This may be along borders, in narrow spaces, or in amongst existing garden beds. If you have the space and ability to dig but don’t want to set up any permanent structure, then a sunken container garden may be perfect for you.

What materials do you need to set up a sunken container garden?

Fortunately, you really don’t need many materials to start your sunken container garden. This makes it a great option for those who wish to get growing but don’t want to invest too much time or money into creating their garden. Check out this list of required items/tools below:

• Shovel
• Pots or containers with holes in the bottom
• Potting mix/compost/soil
• Mulch
• Seed or seedlings
• Garden hose or watering can

Important: Make sure your pots are the right size for the type of plants you’re growing. Larger containers are great for plants such as tomatoes and smaller containers will work well for leafy greens or snow peas. You just need to ensure that your plants have enough room for their roots to fully develop. If you wish to grow vegetables such as corn, you may need to choose a dwarf variety that is suitable for growing in pots/containers.

If you’re not sure what size pot is required for growing vegetables and herbs, you can download my FREE pot size guide below!

How to set up a sunken container garden

1. Decide on the location for your sunken container garden. Ensure that your chosen location offers adequate hours of direct sunlight to your plants.
2. You need to be able to safely dig a hold approximately 2/3 of the depth of the pot/container.
3. Mark out where your pots are going to go.
4. Start digging your holes, measuring the size as you go to try and make it the same size as your pot. Dig the soil out and save it for another use, or keep it somewhere to replace into the holes when you’re finished with your sunken container garden. If you soil is particularly dry or hard, you may need to soak the are with some water prior to digging.
5. Level the bottom of the hole so that the pot sits flush on the base of the hole. I like to add some compost and/or dry leaves/grass clippings to the bottom of the hole to encourage worms to the area. This will offer good drainage and add organic matter to the soil below for when the plant roots start to grow down into the soil below the pot.
6. Place the pot in the hole and fill with your desired growing medium. It’s add a handful of dried leaves or dry grass clippings to the bottom of your container. I like to fill my containers with a combination of organic potting mix/compost/aged cow manure. You can add some blood and bone fertiliser and worm cast to give the soil a boost.
7. Rest you soil for 7-10 days, watering every couple of days to keep the soil moist and boost the soil biology.
8. Plant your seedling or sow seeds and water in well.
9. Mulch around the plants to help retain soil moisture and protect the soil.
10. Water and fertilise according to your plant’s needs.
11. If you plants require trellising, ensure you set this up in advance so that they can begin to climb as soon as they are ready.

How to maintain your sunken container garden

The maintencance of a suken container garden can be done in a similar manner to that of a raised bed garden, in-ground garden of regular container garden. Between at the end of the growing season, or between crop rotations, it’s a good idea to amend the soil with good quality compost, aged cow manure, blood and bone and worm cast. Boosting organic matter using these methods feeds the soil biology and will give your new season plants a great head start.

In between seasons I also like to remove the pot from the ground and brush cut around the back of the sunken containers as there is usually a lot of grass that grows in that space. (You don’t want to go removing the pot from the ground while your plants are growing, as this will disturb any roots that have made their way down through the holes of the pot and this may send your plant into shock).

My frugal tips for setting up a container garden

• Borrow equipment – if you don’t own a shovel, you don’t need to go out and buy one straight away. It always pays to ask around and see if you can borrow one from a friend, neighbour or collegue.
• Source pots second hand – check out Marketplace, trash and treasure shops, or the local tip shop to see if you can find some pots cheaply, or even free. Many kinds of plastic containers will work well, I find that old buckets are perfect for sunken container gardens.
• Use old buckets – we managed to find some buckets in a skip out the back of a local pub, these were the perfect size and just needed some holes drilled into them to create drainage holes. Free is always good!
• Sourcing soil – when filling your sunken pots and containers, you will need to use a combination of compost, potting mix and/or soil and aged cow or sheep manure. You can make your own compost to save money, and you may be able to reuse some of the soil you removed when digging the holes if it is good quality.

Let me know how you go!

Please leave a comment below and let me know how you go. I’m happy to answer any questions you have. I look forward to hearing from you 🙂