Growing potatoes can be quite rewarding, especially when you eat your own home-grown potatoes fresh from the garden. This blog post will help you producing a nice crop of good-size potatoes, perhaps even more than once a year!
What? - What should I use as seed potatoes
In theory you can use any potato to start off a new potato plant. However, the best potatoes are those that are not too big or too small, come from a healthy potato crop, look healthy, and don't have any cuts or other blemishes.
Most people buy seed potatoes from nurseries or hardware stores. That is fine and not expensive. The bags are most likely from Tasmanian potato farms. Potato farmers sell their large potatoes to supermarkets. The small ones are sold as seed potatoes. Food gardeners don't really want large seed potatoes, so everyone is happy.
Most potato farmers are very aware of the diseases potatoes can have. They would not knowingly pass on diseased potatoes to food gardeners because that would further spread a disease.
Some people use supermarket potatoes as seed potatoes, but they are definitely not always disease-free, so you are taking a risk. These potatoes will only be marginally cheaper than seed potatoes bought at a nursery or hardware store, so it is not really worth the risk.
You could use potatoes from your own crop from last season. I do this for one variety of potato that I can't buy. However, only use your own potatoes if you know that your crop was healthy and if you rotate your crops (see below).
Cuts and blemishes in potatoes can cause a spud to rot if the ground is wet. Large potatoes can be cut in two or three, and the parts can be planted separately, but if you want to do this, let the cuts dry before planting, to lower the chances that the spuds will rot in the ground.
Some potato varieties are good for roasting, others for chips, others for mash, others for salads. A Guide to Potato Varieties on this blog will help you choose the potato variety you want.
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| a Kipfler (on the left) and a Bintje (on the right) |
When? - When to plant and harvest
Tasmanian nurseries begin to sell bags of seed potatoes in April. Far too early for most gardens. If you never get frost in your garden, by all means buy your seed potatoes at that time, and plant them soon after.
If you plant your seed potatoes early and there is a frost or two or three in July or August when young lush foliage is just above ground, that foliage is likely to get burned by the frost and go black, and that will set back the plants a lot. Really, there is no need for so much hurry. You don't gain a lot by planting early because plants will grow very slowly in winter.
If you couldn't stop yourself and planted your spuds early, and there is a forecast of frost in your area, cover the young foliage with straw, other light mulch, hessian bags, or a tarpaulin before the frost happens. It may help avoid frost-damage.
It is much better to plant when the chances of frost have passed. This season I bought seed potatoes at the end of June, not because I wanted to plant them then, but because I know that when I need them (late August) nurseries will probably have sold out. I store these seed potatoes in the vegetable tray of my fridge. If they have begun to sprout at planting-time, perfect!
Chitting is the term used for encouraging seed potatoes to sprout before planting. The seed potatoes are placed in a tray in a light and cool place until sprouts emerge. They will take less time to emerge above ground if you chit them. In areas with late frosts, chitting tubers before the last frosts can be a great way to get faster germination when you finally plant. I don't need to chit my potatoes.
In Tasmania you can plant seed potatoes as late as mid January. A mid-January planting will give you a crop just before the cold season starts. In many parts of Tasmania you could have an early crop (planted mid Aug, harvested end of Dec), and a late crop (planted up to mid Jan, harvested mid May).
When are potatoes best harvested? Wait until the foliage has died down. At that stage you can leave some in the ground for a month or two, so they remain fresh. Don't do this if there is a lot of rain and the soil is sodden. If, at the end of the season, you leave spuds in the ground too long, they will begin to re-sprout in the ground, and not be as nutritious.
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| A nice crop of Pink Eyes |
Can't wait to taste your first new potatoes? Some people indulge in bandicooting. It is the word used for carefully digging out one potato per plant before digging out the whole plant many weeks later. Don't bandicoot too enthusiastically. It is best to wait until the foliage has died down.
How? - How to plant and look after spuds
Early one season I carefully dug out one potato plant: |
This photo shows the original seed potato - the one put in the ground by me - and what happened after that. The seed potato has formed a stem and foliage above ground (not in the photo) and is now beginning to form new potatoes above the original seed potato. Potato plants always grow new potatoes above the seed potato!
The photo below shows two seed potatoes that were planted way down a deep hole. The white stalks have just reached the surface and are now 30 cms long.
I plant my seed potatoes around 20 centimetres deep, with around 30 centimetres between spuds in my rows and around 30 centimetres between rows. If you have plenty of space you may choose to make the distance between rows 40 or 50 centimetres.
New potatoes that are formed at or above ground level and that are exposed to air go green. Green potatoes are somewhat poisonous and should not be eaten. This is yet another reason why it is best to plant potatoes deeply. Alternatively, hill your potatoes.
Hilling is the practice of adding soil or compost or mulch to your rows of potatoes to make sure that new potatoes are not exposed to the air and go green. Hill potatoes once their foliage is above ground and before the plants become large and unruly. If you plant your seed potatoes deeply you can get away with little or no hilling.
Potatoes need regular watering, but do not over-water because that could lead to rotting.
Potatoes do not need to be fertilised.
Healthy potato foliage looks like the first photo in this blog post. Foliar spray with seaweed extract dissolved in water if the leaves of your potato plants go a bit yellow. Repeat weekly if needed.
Where? - where in my food garden should I plant potatoes?
Potatoes are a cool-climate crop. This is why in Australia the best potatoes are grown in Tasmania. Potatoes originally come from South America. There they are grown in the foot hills of the Andes where it is not so warm.
Potatoes need slightly acid soil (pH 6 - 6.5) that is well-draining and not too nutrient-rich. A potato crop grown in soil that is too rich can be a real disappointment: tall stems, lots of leaves, but few potatoes in the ground, because the plants focused all their attention on forming foliage.
It is good to fit potatoes in a crop rotation system, so they aren't planted straight after fertilising your soil. The Importance of Rotating Crops on this FGG blog discusses an easy-to-follow system of crop rotation that includes potatoes.
What does all this mean for growing potatoes in containers - grow-bags or pots?
Growing potatoes above ground-level in pots or bags is not preferable to growing them in the ground, but it can be done. Keep the new potatoes that form out of the light by using non-transparent bags or pots, keep the soil moist but not wet at all times, and keep the soil cool. Some people use containers on wheels and move the pots in and out of the sun as required. You will need to plant your seed potatoes deep and hill them as the season progresses.
How to best store potatoes?
Ideally, once the foliage has died down, you leave potatoes in the ground until they are needed in the kitchen because that way they will be at their freshest. However, when left in the ground too long they will begin to rot or re-sprout. Re-sprouting potatoes can still be eaten, but will not be at their nutritional peak and may have a glassy appearance when you peel them.
After digging up potatoes, remove most of the soil and leave them to dry on the garden bed for a few hours. Then, without too much cleaning, put them in a crate or basket. The best storage method is the one where the potatoes don't touch each other, where there is plenty of ventilation, and they are kept in a cold, dark, but not frosty, environment.
In the photo above I used a black plastic storage container with dry sand and old fridge baskets for a layer above the bottom layer. On top of the basket goes an old blanket that puts the spuds completely in the dark. I store these baskets under our house where it is cool and dark most of the time.
Another method, where you can put more spuds in one basket is to use newspaper between layers of potatoes (see below).
Whatever method you decide on, check the potatoes about once a fortnight - remove spuds that have gone mouldy and remove shoots.
This system allows you to store potatoes until around mid August. By then you really can't stop the tubers from sprouting.
Long term storage of large amounts of potatoes is a challenge, but not in our house-hold, because we always have eaten all our spuds well before it is time to plant the next lot.
Happy spudding,
Max Bee
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