Knowing that the potato ( Solanum tuberosum ) is one of the favorite foods of the French, that it offers good value for money, and that it comes in many varieties to vary the ways of cooking it, it is not surprising that each French person consumes on average 40kg per year! So why not grow some in the vegetable garden?
When to plant potatoes?
Potato tubers are planted when frost is no longer to be feared because this essential vegetable, native to South America, fears frost. The earth must have warmed up sufficiently, to at least 7°C.
If you buy non-germinated plants which cost less, before planting the tubers, they must be prepared, that is to say, they must be germinated, which takes around 4 to 6 weeks, i.e. a delay to be expected before the planting dates indicated below: it is, therefore, advisable to do this pre-germination from January in regions with a mild climate, and from February for the rest of the regions. To do this, spread the tubers in crates or egg boxes, making sure to place the eyes facing up. Place them in a cool (10 to 15°C), ventilated, and bright room, without direct sunlight. Thus, they will develop short, green sprouts, which will allow them to grow more quickly once in the ground.
If you buy sprouted plants, you can skip the pre-germination step. The more you are in the south of France, in Brittany, or on the Atlantic coast where the winters are mild, the earlier you will plant the potato, that is to say from February to March, which also applies to cultivation under cover. For the rest of the metropolis, you will rather wait until the end of March and until mid-April, to correspond to the saying that we plant potato tubers when the lilac blooms! Be careful, this saying is misleading because flowering varies from year to year and could mislead you with either planting too early or too late.
Depending on the varieties, you will adapt your planting schedule: early varieties will be the first to be planted in March-April while standard varieties can be planted in April-May. Be aware that if you plant a little late, at the beginning of May, this will not be detrimental because the greater warming of the soil will compensate for the delay in the calendar: thus, at the beginning of April, emergence takes on average 35 days, compared to only 16 at the beginning of May. So no rush!
To try to increase the yield of your potato plants, you can rely on the lunar calendar and choose to plant the tubers on a root day, in the waning moon, favorable to the descent of the sap into the underground parts of the plants.
What varieties of potatoes to plant?
If you buy a bag or a tray of potato tubers to plant, you can cut the larger ones in half, lengthwise, before germinating them: you will have more plants and this splitting will be favorable to growth, particularly of early varieties.
Ideally, choose organic tubers: you will avoid already having pesticides in your plant before even having made the slightest gardening gesture!
If your garden does not allow you to plant a “field” of potatoes, share and exchange with your neighbors or friends, your respective varieties: you will be able to compare the varieties and see which ones you prefer and which are the most suitable to your soil and climate.
Among the diversity of potato varieties, you will be spoiled for choice among:
- early potato varieties (Belles de Fontenay, Aliénor, Amandine, Sirtema, Apollo, Riviera…),
- semi-early varieties (Bernadette, Bintje, Charlotte, Gourmandine, Désirée, etc.)
- later varieties (Rouge des Flandres, Bleue d’Artois, Vitelotte, King Edward VII, Up to date…),
But if you want early potatoes, which are harvested before full maturity after 90 days of cultivation, you will have to cultivate them under a tunnel to be able to harvest them from April. Don’t forget that the earliest varieties can be harvested 2 to 3 months after planting, and up to 5 months for the others.
Potato planting technique
Planting potatoes is nothing other than a kind of cutting which is done by planting the sprouted tubers. You will have to monitor the weather because you absolutely must wait until frost is no longer feared and the earth has warmed up to around 7-10°C. This will depend on the region where you are located.
The potato is grown in a sunny location, it likes deep, fertile, loose, humus, clayey to sandy and well-drained soils. You will therefore need to add compost or well-rotted manure to the soil before planting, ideally the previous fall. Remove the stones and break up the large clods so that the soil is well-loosened.
The rows must be spaced at least 50 to 70cm apart, otherwise, you risk getting smaller potatoes due to lack of space: around 50cm for early varieties, and rather 70 to 75cm for later varieties. You can dig furrows 15 cm deep and place a tuber with the sprouts upwards, without damaging them, every 30 cm, or make individual holes to place each tuber at this same distance. Then, you cover it with soil without packing. In colder regions, you can plant the tubers just 5cm deep, hilling them up 5 to 7cm at the same time.
Wait 2 to 3 weeks before you see the potato plants appear. During emergence, water supply is not necessary because the freshness of the soil will be sufficient. After emergence, watering is especially necessary when the tubers are forming, especially if it is hot and dry, taking care not to wet the foliage, which could lead to the formation of mildew.
When the plants are around twenty centimeters long, you will mound them, that is to say, you will raise the earth around each plant to encourage the formation of future potatoes. You will need to do this 2 to 3 times as the potato grows.
If you want a good combination of crops around your potatoes, place them near Fabaceae (beans, peas, broad beans, etc.), corn, cabbage, asparagus, nasturtiums, coriander, etc. Move away – sunflowers, beets, and other Solanaceae such as tomatoes, peppers, and eggplants.
Wait 3 to 4 years before replanting potatoes in the same place in your vegetable garden, for a profitable crop rotation. You can grow green manure or legumes in the meantime. Please note that it can also be cultivated after turning over a meadow.
Can you plant potatoes that have sprouted?
Potatoes from conventional farming are treated with an anti-germinative product which delays or even prevents the germination of tubers, which is not the case for organic potatoes. It therefore happens that table potatoes germinate in your reserve, particularly at the end of winter or under the effect of the heat of your home, and you wonder if you can use them to plant them in the vegetable garden as a potato plant?
The answer is yes: you will plant them according to the same principles, techniques, and periods as germinated plants purchased commercially. Choose the smallest of your sprouted potatoes, and cut the larger ones in half, making sure that each part has a sprout. This will prevent you from throwing them away and wasting them, especially if they start to wilt.
