Solanum tuberosum, better known as the potato, plays a leading role in our kitchens thanks to the thousands of ways in which it can be used. Native to the Andean area of central-southern America, potatoes are related to tomatoes, peppers and aubergines. The potato reached Europe around the 16th Century but only began to be appreciated as a vegetable two hundred years later.
Cultivated in a vegetable garden in the ground it’s fairly easy to grow and crops well, however it’s difficult, if not impossible, to grow potatoes on a balcony or using unconventional methods; to obtain acceptable results you need to use sacks.
Soil and Sacks
Potatoes need deep soil (at least 60 cm) so use jute or synthetic sacks that are at least 80 cm tall. If possible use soil that’s siliceous, loose and light, slightly acid and rich in nitrogen and potassium. These characteristics can easily be obtained by adding well matured manure to the soil used for previous crops such as cabbage and legumes, while it’s not a good idea to use soil that’s clayey or comes from pots in which other solanaceous species (for example tomatoes, peppers or aubergines) have been grown.
Sowing or Planting
It’s not really correct to talk about sowing potatoes, in fact the plant is normally propagated agamically by planting tubers from the previous season that are sprouting, or pieces of them, or by using seed potatoes that have been bought specifically.
Potatoes are “sown” when the moon is waning and the period in which they are grown, generally speaking, goes from spring to the beginning of winter. Mild climates make it possible to plant them in the winter and harvest until late spring, in this case early varieties are recommended. In areas with harsh winter weather potatoes must be planted in the spring and harvested towards the end of the summer.
If the temperature drops to below freezing the crop can suffer irreparable damage, especially during the initial phases, which require a temperature of at least 5 °C. The return of cold weather (below 2 °C) during spring can be harmful, so, before you plant your tubers, take a look at the weather forecast!
During the productive phase, the growth of potatoes slows down considerably if the temperature is below 8 °C or above 25 °C.
Place not more than 4-5 sprouting tubers in the bottom of the sack that you’ve prepared with 20 cm of soil, cover them making sure that none of the shoots are in the open-air and spray water evenly over the surface. Leave the sack indoors if the minimum temperature outdoors is still below 10 °C.
As soon as the shoots show above ground, move the sack to a spot with plenty of light and let the potato plants grow to at least 10-15 cm.
When they’ve reach this size, cover them with soil again leaving just the first leaves above ground, if necessary unroll the edge of the sack to gain height. Repeat this operation until your sack has reached a height of roughly 60 cm – 70 cm. In this way your plant will have the depth required for a good harvest.
Now place the sack in a well lit spot on your balcony and leave the plants to grow normally.
Potatoes need plenty of water during the first phase of cultivation, in which the plants must grow, but they don’t like to get waterlogged; when the time for harvesting is drawing near you must drastically reduce the amount of water you give them, to avoid that the tubers are attacked by rot or other pathogens, the right quantity to use is just enough to keep the soil cool. Jute sacks, in particular, will help you control the humidity and keep it constant.
Potatoes don’t like environments that are too dry or sunny so, when summer is drawing near and the weather gets hotter, choose an area of your balcony that’s partly in the shade.
90-130 days after you planted your tubers you will be able to harvest your potatoes. When you see the small off-white flowers withering and the leaves loose their bright green colour and turn an autumn shade of yellow, it’s time to uproot them!
If you’ve grown your potatoes following organic rules, you can use them in recipes which include potatoes with their skin on, dishes that can’t really be made with the potatoes that you but in a normal shop or market, treated with anti-sprouting products.
You can decide to harvest early and have your own tasty new potatoes, which are now rarely found on sale.
Friends and Enemies
Potatoes intercrop well with spinach and with legumes. Amongst its best friends are flax, petunias, green beans and white deadnettle, Lamium Album, which wards off the majority of harmful insects such as the potato beetle and the cockchafer. Should you notice the presence of potato beetles, macerated onion or tomato extract will be useful.
As we’ve already said, potatoes don’t like waterlogging, damp environments or extreme temperatures; such conditions, if they last long, encourage the proliferation of diseases, in particular fungal diseases such as potato blight, which affects both the stem and leaves.
Bacteria, viruses, aphids, moths, potato plants have many enemies, but by avoiding climatic stress and watering correctly, with the right amounts and taking care not to get the leaves wet, you will help your plants grow strong and be less subject to attacks.
Photos: Tommaso Turchi
Art: Lucia Simeone