Potatoes are one of the most satisfying crops a home gardener can grow, emerging from the soil, each one a tasty surprise. Plant now for a late summer harvest to be enjoyed long after the garden has been put to bed for the winter.
Introduction to Planting
Last year, we were introduced to the potato in the Ask A Master Gardener session “Seed Potatoes vs Potato Seeds”. This week, Susie Everding leads us through her 20 year potato planting journey.
It all begins with a tuber – a swollen modification of a stem, lurking underground, and used by the plant to store nutrients. Tubers that are to be used as seed potatoes the following season are harvested when immature. Small but vigorous, they contain all that is needed to produce a plant that is identical to the parent.
Potato plants will flower and produce seed, but due to the rather complicated nature of their genetics, the seeds may or may not be viable and may result in some unusual offspring!
Choosing a Variety
Did you know that there are over 5000 varieties of potato? Susie’s favourites include:
- Banana fingerling – creamy variety good for boiling, baking and frying; excellent salad potato.
- French fingerling – great when boiled or roasted
- Purple Peruvian – a splash of colour with high nutrient value
- Yukon Gold – bred at the University of Guelph, popular for a creamy consistency and rich buttery flavour
Don’t limit yourself! Many options, some organically produced, are available from online suppliers (see resource list) and at local nurseries. Buying from bulk bins is less expensive than pre-packaged, and if you have any of last year’s harvest leftover, those can be planted as well.
Some gardeners prepare to plant seed potatoes by “green-sprouting” or “chitting” them, placing them in a cool lighted area for several weeks and waiting for the tubers to break dormancy and sprouts to appear While this may produce a crop a little more quickly, it is optional.
Simply let the seed potatoes warm up for a few days, cutting larger ones into golf ball sized pieces. Small ones can be planted whole. Each piece should have several ”eyes” which, when planted, will face upwards (cut side down). If cut, allow them to dry for a few days before planting, which will seal the cut side, reducing the likelihood of disease.
Planting can be done once soil temperature has warmed to at least 10C. Some use the appearance of dandelions as a guide!
Potatoes like full sun and well-drained, slightly acidic soil, although they are adaptable to poor soil conditions. In fact, according to some reports, the Shakers would use potatoes as a first crop to break up previously uncultivated garden plots.
Susie’s planting technique is based on advice from well known organic gardener Eliot Coleman, who advises planting each tuber at a depth of 3 inches, spaced 12 inches apart in the centre of a 3 foot wide bed. Cover with soil, tamp lightly and water. Provide 1 inch of water per week (adjusting for rainfall) and more once the potatoes have flowered and the tubers are actively growing.
When sprouts emerge, cover with an inch of compost and then with 6-8 inches of straw. Alternatively, potatoes can be hilled by adding soil to cover the stem as the plant grows.
Potatoes are produced underground along the stem of the plant. Hilling encourages more potatoes to form above the already formed ones beneath. In addition, hilling prevents the tubers from being exposed to light and developing a green tinge (due to chlorophyll). While chlorophyll itself is not harmful, it may signal the presence of solanine, a glycoalkaloid which is toxic, and should not be consumed.
Mulching keeps the soil beneath the straw moist and regulates temperature extremes, thus reducing stress on the plant. There is some evidence that it may also lead to a reduction in the numbers of Colorado potato beetle as mulch may house beneficial insects that are predators of larval beetles.
Once the plant is flowering, the potatoes are between quarter and golf ball sized, and can be harvested if you just cannot wait! However, those that are left in the soil will continue to grow if undisturbed. Generally collection of mature tubers is done 4-6 weeks after flowering is complete and the top growth has died back. Simply remove the soil or mulch and use a spade or fork to gently lift out the crop. Leave them on the surface of the soil to dry for a few hours, turning once, and then brush off the excess soil (do not wash). Store at 5C in the dark, or if you lack cold storage, a bin on a concrete basement floor will suffice.