Three Sisters Planting - for superior Sweetcorn, Squash & Bean crops•
Posted on 9 May 2021
When most people think of companion planting it is usually to add crops that smell strongly and deter predators. So planting mint beside lettuce to keep snails away, marigolds with tomatoes etc. But there are other reasons for planting different crops together. The Three Sisters planting method is a great example of this.
Its an ancient practice. Native American tribes such as the Iroquois and Cherokee grew Three Sister Gardens. This allowed them to successfully grow 3 crops in the area of one. A concept the is as important now - with shrinking garden sizes and water retention increasingly important - as it was back then.
How Does the Three Sisters Method Work?
The Three Sisters in question are - sweetcorn, beans, and squash. If you think of a jungle or even your local woodland then this will be made up of many different plants growing under, over and around each other. Each plant has its place and thrives without a gardener wringing their hands and fretting about how to keep pests away.
So the first of our Three Sisters is sweetcorn which grows tall and strong and provides a structure for the beans to climb up. You can also use sunflowers as your uprights if you don't like corn. This will have the advantage that it will attract lots of lovely pollinators and give you sunflower seeds at the end.
The beans return the love by stabilising the corn so that it doesn't snap in the wind. They also fix the nitrogen into the soil that the other plants need and take up space between the corn stems reducing the space available for weeds.
Lastly the sprawling squash plants block sunlight on the soil, effectively creating a living mulch. This helps reduce soil temperatures, minimise moisture loss and suppress weed growth.
How much space do I need for the Three Sisters Method?
Ideally, you need an area a minimum of 3 x 3 metres (10 x 10 feet) although a single 3 Sisters Mound could fit into 1 x 1 m (3 x 3 feet)
If you do 3 Sisters Method on a smaller scale it is advisable to either do more than one mound or avoid sweetcorn as you need 10 to 20 plants to ensure full pollination and get full cobs.
Most people choose to arrange their plants with a ring of sweetcorn surrounded by a ring of beans and on the outside a ring of squash. The traditional mound is described below. To ease picking this mound can be replicated as many times as you like in a single or double row.
How to plant the Three Sisters Method
Getting this method right is all about timing. Your uprights i.e. the Sweetcorn or Sunflowers need a two or three week head start so that they are strong enough to support your beans. You can plant all the seeds direct into the ground but the method we outline here uses Rootrainers to ensure a super strong root system for the plants and guarantee you don't have any holes in your planting scheme from seeds that fail to germinate. The good thing about 3 Sisters is that you can use one set of Deep Rootrainers for all three crops in turn.
How to Plant 3 Sisters
Make a mound of soil about 10cm (4") high with a small well in the centre. Repeat this at 1-1.2M (3-4') intervals for as many mounds as you want to construct.
For each mound - plant 4 corn seeds in Rootrainers and wait until they are about 12cm (5") tall. Then move 4 plants to the top of your prepared mound and plant there15cm (6") apart.
Once the corn is in the ground, plant 4 beans seeds in your Rootrainers. When your beans are large enough to transfer, plant them halfway down the sides of the mound at least 7cm (3") from the corn plant.
The beans will grow slowly at first as they will be shaded by the corn but this is a delay rather than a full stop and they will catch up and make a spurt in growth as the sweetcorn matures.
Finally use your Rootrainers for 2 squash seeds. Once these are large enough to transplant plant them opposite each other 60cm (24") from the centre of the mound. Squash plants need as much light as they can get, hence planting on the outside of your arrangement. Unless you are gardening in a stately home then choose a compact variety and leave some natural paths so you can reach the inner plants to pick them.
If you don't like squash then, whilst not quite as leafy and prolific, courgettes, gourds or even watermelons would fulfil a similar role around the outside.
The good thing about this method is that it is actually good for the soil and works best if you don't do crop rotation. The breakdown of the bean roots from last years crop fixes the extra nitrogen that the corn needs into the soil.
What varieties to choose
The corn should be a tall variety so that it gives the beans somewhere to climb. More compact varieties are usually grown here but look for the taller varieties otherwise you may find the beans overcrowd the corn.
Beans must be pole or climbing rather than bush beans. Non-vigorous and bushy-pole varieties are best so that they don't smother the corn plants. Climbing French Beans, Lima, Runner Beans and Borlotti Beans all work really well.
If you have limitless space then winter squashes will work., otherwise stick to summer squashes which are a little more contained. And as mentioned above you can sub in watermelons, gourds or courgettes.
We'd love to see it if you plant a 3 Sisters Garden. Please tag us on Social Media if you decide to try it.
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