Sweet potatoes are not only delicious and nutritious but also possess a fascinating root system. In this article, we will explore the depths and breadth of sweet potato roots, uncovering their growth patterns and the factors that influence their development.
Understanding Sweet Potato Roots:
Sweet potato plants have two main types of roots: fibrous roots and storage roots. While sweet potato roots are not traditionally deep-rooted, they can develop a moderately deep root system. The primary focus, however, is on extensive lateral root growth rather than significant vertical penetration.
Sweet potatoes will scramble extensively when there is plenty of rain and sunshine. It is a perfect ground cover for us here in the wet tropics of NE Australia, where it grows readily during our wet season.
It is a seasonal crop so planting it in your warmer season should gain a harvest for you; and having knowledge of the root system allows you to better understand this vegetable and improve the return from your garden and your efforts.
One of the things we personally love about this plant is that it has established itself in several locations in our permaculture system, and we can now harvest during the year when we need a few sweet potatoes for a meal.
As the vine scrambles there are locations along the vine where clusters of roots grow from. Most will supply nutrients to the vine but one or two can become the storage root we know as a sweet potato tuber.
To grow sweet potato as a planned crop, you need to give it space, or plenty of balanced fertilizer (heavy in nitrogen gives mostly leaves) if it is contained in one small location. Most of the visible growth is above the surface in the form of leaves and vine stem, and depending on the soil type and condition you will get plenty of tubers or very little.
Factors Affecting Sweet Potato Root Growth:
The depth of sweet potato root growth can vary depending on factors such as soil conditions, moisture availability, and the specific cultivar being grown. Loose, well-drained soils encourage deeper penetration, while compacted or clay soils restrict downward growth.
Just because the ground is hard and dry, it is still possible to collect a few good potatoes, although they can be woody and dry at times. We have a wet season that runs for 3-4 months each year, and this allows us to neglect this plant as the natural conditions suit the sweet potato well.
As it grows, the lateral roots of sweet potatoes will spread extensively and cover a significant area around the plant. It will even grow tubers beneath pathway pavers and garden wall blocks. These can cause some damage it you are not careful, so keep an eye on your vines as they spread.
Depth and Spread of Sweet Potato Roots:
On average, sweet potato roots extend from 6 to 18 inches below the soil surface. Under optimal conditions, they may reach depths of up to 3 feet. However, it is important to note that the lateral roots play a crucial role in sweet potato plants.
These roots spread extensively, allowing sweet potatoes to efficiently absorb nutrients and moisture from the surrounding soil. The lateral root system contributes to their ability to withstand drought conditions and compete with weeds.
We have not had to dig any deeper than 12 inches to harvest tubers, simply because we prefer not to till the soil where possible. We will till the soil in the raised garden beds if we have one spare for this plant.
If you don’t till deeply, the tubers tend to stay near the surface and are easy to find. We can pick a few at a time without disturbing the entire garden patch. Leaving the vine in the garden year-round also allows us to propagate cuttings for extra locations or for other people if they require some. More on how we approach this can be found here.
This technique is also far better for building and preserving soil life, so we try to look after this side of the growing cycles carefully.
Cultivation Techniques to Promote Lateral Root Growth:
To promote the extensive lateral root growth in sweet potatoes, it is essential to focus on creating favorable soil conditions. This includes preparing the soil with organic matter to improve drainage and provide a loose growing medium.
Additionally, mulching the soil surface with organic materials can help retain moisture and suppress weed competition, further supporting the lateral root development.
We have areas in the yard where we don’t have time to mulch every year, and these locations still produce the odd tuber. The best location, meaning the most productive, is actually in partial shade under a mango tree. Info on growing this vine in shade found here.
The soil is deep and rich from many dressings of mulch and shredded mango branches. We have two varieties that like this location and even with the soil depth, the tubers rise to the surface, making the harvest fun and easy.
While sweet potatoes are not typically deep-rooted plants, they possess an efficient root system that emphasizes extensive lateral root growth.
Understanding the factors that influence root growth and employing cultivation techniques to promote lateral root development can optimize sweet potato crop yields and contribute to sustainable soil management. The information above should be helpful if you wish to grow sweet potato as a companion plant in your garden, but there are things to be aware of about this vine to consider before jumping into that method of gardening. More can be found in this article here.
If the soil is fertile and not heavy in nitrogen, is well mulched and kept moist during the growing season, there is no reason to dig deeper than the tines of a standard garden fork at the very start of the season.
The vine will spread and set roots that will in turn produce tubers. Each variety has its quirks with lighting and sun requirements, and these will be discovered along the way as you get to know this wonderful plant.
Unveiling the depths and breadth of sweet potato roots allows us to appreciate the remarkable underground world that fuels their growth and nourishes their harvest.
Article by Tim Blanch for TheTropicalHomestead.com. He is a qualified Permaculture designer.