Written by Dale Richardson - Updated: June 23, 2023
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How deep does the soil need to be to grow sweet potatoes? This is an important question if you want to cultivate sweet potatoes in a planter or container. It is also important to know how deep to prepare your garden bed before planting your slips.
The minimum soil depth for sweet potatoes is 30cm (12inches). This will give the plant sufficient space to send out roots and grow tubers.
Sweet potatoes are a long-season plant that needs plenty of warmth while growing. They also need adequate soil to support the plant and provide enough space for proper tuber growth. We will talk about proper soil depth for sweet potatoes in the garden, in containers, and in grow bags.
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Heavily compacted or shallow soils will impede their growth and the tubers will be bent and stunted. You can also hill soil into mounds to plant the slips in to increase soil depth and improve drainage.
When preparing the garden bed for sweet potatoes, it is ideal to loosen the soil to 30cm (12inches). Sometimes, working the soil to this depth is not feasible. In this case, try to loosen the soil from 20cm to 25cm (8-10inches). This is will give the roots and tubers sufficient space to spread without contending with compacted soil.
Image by Carmen Edenhofer
Once you have prepared an adequate depth of fine tilth soil, you can further benefit your sweet potatoes by deeply loosening the subsoil. Loosening the subsoil to a depth of around 60cm (24inches) will greatly improve aeration, water drainage, and allow the plants' roots to reach nutrients deep in the soil.
The broadfork is a great tool to loosen your subsoil without having to mix the soil layers through tilling. The broadfork, looks just like it sounds: a wide, giant fork. You step the broadfork deep into the ground and rock back and forth to break open the deep soil layers without bringing them to the surface. You can do a similar type of sub-soil loosening with a standard garden fork, but it won't penetrate as deeply or as thoroughly.
Hilling your soil into berms or mounds after you have tilled it can also greatly benefit your sweet potatoes by giving them extra soil to grow. Make your berms about 25cm (10inches) high if possible to add extra depth, and plant your slips on top of the berms.
Once you have your soil prepared to the right depth, you can read about growing sweet potatoes in your garden in this article .
A container needs to be at least 30cm (12inches) deep to properly grow sweet potatoes. Don't forget to make sure that the container is also wide enough to allow the roots and tubers to spread.
Sweet potatoes grow very well in containers. It not only allows you to grow this root vegetable if you have limited garden space, but you can take the plants inside at night if frost is threatening. If you do grow them in containers, it is even more critical that you provide adequate depth for the tubers to develop properly than it is in a garden bed.
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Image by Carmen Edenhofer
If your soil is too shallow, the roots of the plant will quickly reach the limits of their growing space and will start circling around the container in search of more soil. This will not only deprive your plant of nutrients but can ultimately kill the plant. If the plant does manage to sustain itself, it likely won't produce any sweet potatoes for you to enjoy. Any sweet potatoes that do grow will probably be bent or stunted. Not at all the harvest that you desire.
If your soil is too shallow, the leaves of the sweet potato vine will often start to yellow due to a process called chlorosis, which is caused by insufficient nutrient absorption.
You can also grow sweet potatoes in grow bags. Grow bags come in a variety of different sizes, and it is important to get one that is big enough. As with containers, make sure that the grow bag will allow you to provide at least 30cm (12inches) of soil depth for the sweet potatoes. Many (if not most) grow bags are designed for potatoes, and these should all be adequate for your sweet potatoes as well. Many also come with a convenient door on the side of the bag for easy harvesting.
If you cannot decide on which size to get, remember that in this case more is always better.
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