Robin Gale-Baker, from Sustainable Macleod, discusses growing potatoes. This is one of a series of articles she has written about growing various veggies (see right hand sidebar). She has also written a number of articles about growing various herbs, growing various fruit trees and general growing techniques.
- Grow in rich soil in full sun.
- Grow in well drained soil.
- Leave potatoes beneath ground for good storage.
- Start harvesting when plants flower.
Potatoes thrive in very rich, well-drained soil, in full sun. In these conditions, potatoes are both easy and satisfying to grow. One advantage of growing your own is that you can harvest them as required.
It is important to only plant certified seed potatoes as these will be disease and pest free. Seed potatoes are known as chats. Small chats – egg size – can be planted whole but larger ones can be cut into sections each containing an eye. If doing this, then allow the cut surface to dry out for a few days before planting. Also, knock off all but one shoot from each potato or section. Leave whole potatoes in the sun for a week before planting to harden them and to initiate shooting. At planting and flowering times, feed with a seaweed solution.
Potatoes come in determinate and indeterminate varieties (just like tomatoes):
- Indeterminate potatoes grow along the stem. As such, they benefit from being ‘hilled up’ with soil to keep the potatoes from exposure to the sun and to cover surface roots. They are deemed slow growers and mature in 16-19 weeks. Indeterminates include Brownell, Dutch Cream, King Edward, Nicola, Pink Fir Apple, Russet, Salad Rose, Sapphire, Sebago and Up to Date.
- Determinate potatoes grow beneath ground essentially at the depth they were planted. As such, they do not need hilling up. They are deemed fast growers and mature in 10-13 weeks. Determinates include Burgundy Blush, Carlingford, Kennebec, Kipfler, Pentland Dell, Pink Eye, Purple Congo, Red Pontiac, Russian Banana and Spunta.
For both determinate and indeterminate potatoes, make your own mix of compost and straw mixed with either well rotted cow manure or well rotted chicken manure plus a generous amount of blood and bone. Dig down about 15–20cm into your garden bed, fill up to 10cm with your mix plus soil, plant the potatoes 25–30cm apart, and water in.
For indeterminate potatoes, make sure that they are planted in a wide trench, with the soil from the trench hilled up on either side for later backfilling. If planting several rows, these should be, say, around ½ metre apart to provide the space for the hilling up. Once the potatoes begin to shoot, backfill with around 10cm of soil and continue to do this when the shoots re-appear until the trench is filled. If exposed to light, chlorophyll will develop which is accompanied by a toxin called ‘solanine’ that causes potatoes to turn green rendering them poisonous. Peeling the ‘green’ from the potatoes makes no difference to their toxicity.
How do you know when to harvest your crop?
For new potatoes, harvest when flowering begins and the lower leaves are yellowing. For old potatoes, wait until the plant has died down. In both cases, the best place to store the spuds is in the ground. For new potatoes, feel down around the roots and remove the number that you need for each feed; for old potatoes, dig up one plant at a time.
If you do dig up more than you can use, do not wash the potato. Rather, leave as much dirt on them as possible and store in a dark, cool, airy place.
Potatoes like a pH of 5.5-6 as do other members of their family such as tomatoes, capsicum and eggplant. Crop rotation is important so do not grow spuds where other family members have been growing and choose a new spot to grow them each year for a 4 year rotation. They are frost tender so, should frost threaten, cover them with a cloth of any description the night before. If they are hit by frost, and you can hose the frost from them before the sun strikes the foliage (very early in the morning), they will survive.
If you lack garden space for potato growing, potato bags are available from nurseries or you could use a hessian sack. These can be placed on a balcony, a porch or anywhere in the garden. Adapt the soil mix described above (potting mix is not a suitable medium as it lacks sufficient nutrition). Adhere to the spacing guidelines, which may mean as little as one seed potato per bag. This will, however, still give a good return especially for a single person or couple and you could fill several bags with different varieties.