Sweet potato (Ipomoea potatoes), of the family of Convolvulaceaeis highly regarded for its tubers with a sweet, more or less sweet flavor. Easy to grow, this dicotyledonous plant is however very chilly. Among the 500 existing varieties, there is a minority intended for consumption. All the others are ornamental and have no taste interest. They need a lot of heat. Also, outside the Mediterranean regions, it is essential to take certain precautions to be able to hope for a satisfactory harvest. Let’s see how to plant the sweet potato, what are the best conditions for growing it, and when to harvest its tubers.
Plant sweet potato
It’s only in May that sweet potatoes are planted in France, because the risk of frost must absolutely be avoided. In southern areas, planting can be carried out already at the end of April.
The main varieties to grow in France for consumption taking into account our climatic conditions are as follows:
- L’Evangeline : very sweet with orange flesh,
- The Purple : subtle taste of hazelnut with white flesh,
- The Bonita : large tubers with a sweet flavor and white flesh (early variety).
The sweet potato is frequently related to the potato. However, they do not belong to the same botanical family. The first is part of Convolvulaceae and the second to that of Solanaceae.
Before planting the sweet potato, it is highly recommended to sprout tubers in order to compensate for the lack of sun they could suffer in our latitudes. This has the effect of pushing the plants to produce roots but also leaves before July. It is therefore advisable to stick a few toothpicks in the tubers so that they are kept in a water container without however being completely immersed. Another solution is to buy tubers to plant in April, in garden centres, or in May, seedlings in pots.
At time plant sweet potatoes in the garden, care must be taken to space them about 30 to 40 cm from each other and to respect a spacing between the rows of at least 70 cm. This creeping twining plant whose stems can reach 3m in lengthcan of course climb on a fence or any other support, which is highly preferable in a small vegetable garden because it is necessary to reserve space for other crops.
Growing sweet potatoes
This plant particularly likes fresh, deep, very fertile and light soils. It is essential to install the sweet potato in a warm corner of the vegetable garden, that is to say well exposed to the sun et sheltered from drafts.
20°C is the temperature required for planting sweet potatoes, but the late season must also be very sunny to allow tuberculization. Indeed, it is only in September that the tubers form, when the days get shorter, and to do this, they need heat, otherwise they will not develop properly. In harsh climates, the use of a tunnel or a greenhouse is essential to try growing sweet potatoes, but the harvest will never be as abundant as in the South. Let’s not forget that this plant is of tropical origin.
The potted sweet potato cultivation is irrelevant with regard to varieties intended for consumption because the tubers will not have enough room to develop, even if one opts for large containers. On the other hand, the plant can in this way be cultivated for the beauty of its foliage and its flowers which resemble those of bindweed. It is therefore preferable to opt for ornamental varieties when you do not have a garden because they bloom profusely. It is a good solution to green your terrace, courtyard or balcony in an original way. Note the tubers of ornamental sweet potatoes are edible but their tubers do not have much flavor.
Caring for the sweet potato
As long as it benefits from sufficient heat, the sweet potato needs very little maintenance.
After planting, care should be taken to water copiously and thereafter, generous watering is essential, especially in times of drought.
We have seen that trellising sweet potato stems is not not mandatorybut saves space in the vegetable garden.
When the stems begin to take length, we proceed to hilling. This consists of bringing earth all around the foot in order to create a small mound of 20cm tall.
It is not necessary to add fertilizer during cultivation. On the other hand, the sweet potato must be planted in a soil enriched with compost.
Pests and diseases
This plant is not susceptible to pests or diseases.
Harvesting sweet potatoes from the vegetable garden
In late summer, foliage begins to yellow. It is then necessary to cut about 75% of the leaves so that the tubers can benefit from a maximum of heat in order to reach maturity, because at this time the sun declines somewhat. It is therefore better to prevent the foliage from casting too much shade to allow the soil to continue to be well heated by the sun, hence the interest of removing approximately three quarters of the foliage. After 12 to 15 days, the harvest can be done, preferably on a bright sunny day.
The sweet potato harvest therefore begins at 24 to 25 weeks after plantingi.e. between September and November during a week which enjoys good sunshine, when the ground is very dry, and absolutely before the frosts. Use a spade fork to lift the tubers, taking care not to damage them.
Once they are out of the ground, they are left in place in full sun for 1 or 2 days to give them time to dry out. All that remains is to brush them to get rid of the residual earth. They can therefore be stored in a room where the temperature is between 10 and 15°C, like a cellar for example. The tubers can be stored in dry sand and the room must absolutely be ventilated. They can be kept for several weeks to several months and consumed gradually.