October is potato planting time in the Southern Hemisphere, so it seems like a good opportunity to share with you an in-depth "how to" guide for growing the humble spud. For those of you that haven't signed up to my newsletter yet, this is an example of the seasonal garden deep dives I take each month, showing you how to grow an edible crop, straight to your inbox. You will also be the first to receive new recipes before they go up on the website, as well recommendations, inspirations and other kitchen garden bits and bobs. If this sounds like a bit of you and you would like to sign up you can do so here.
But for now ~ lets talk potatoes!
Homegrown potatoes have far more flavour than some of the watery specimens we pay for in the supermarkets, and being that they are an simple and fun crop to grow, there really is no excuse for at least giving them a go, even if it is just in the form of sticking one or two at the bottom of an old bucket. As long as you understand what conditions they need and how they grow, there are many different ways you can grow them.
Growing conditions
Potatoes are frost sensitive plants that require plenty of warmth and sunshine to thrive, so if you are somewhere prone to spring frosts, wait until you are absolutely sure the weather has warmed up before planting them.
The heavy feeders do best in slightly acidic soil that has previously had plenty of compost and organic matter dug in. Chicken manure is great here as the plants like the added calcium, but do make sure it is well broken down. I usually add this to the garden over the winter so it has had plenty of time to weather in, but not to worry if you haven’t ~ just make sure the compost you are adding now is well rotted.
As far as soil goes, a light sandy loam is best for potatoes, but most soils will do, providing they are slightly on the acidic side. Potatoes despise alkaline soil. Because of this, you never want to add lime to your potato bed, in fact avoid planting potatoes in any garden that has been limed within the last year. If you think your soil is alkaline, you will need to incorporate lots of organic matter in the form of wood chips, grass clippings, leaf mould and well composted manure to raise the acidity.
The other thing potatoes don’t like is soggy stagnant soil, so ensure your garden bed has adequate drainage. Once again, adding plenty of organic matter is a great way to combat this problem, with untreated sawdust and fine wood chips being a brilliant soil conditioner. If you have clay soil that is very wet and heavy, you might want to consider raising your garden beds up, or you could plant your spuds no-dig style, using organic matter to mound them while building up the soil at the same time. I explain how to do this further down.
Never grow potatoes in the same spot year on year, or where tomatoes have previously been, as they are both from the nightshade family and are prone to spreading disease.
New Potatoes
There is nothing quite as wonderful as the first new potatoes of the season, so young they haven’t formed a skin yet, and so tender and sweet they only require minimal cooking time and even less seasoning.
If you are hoping to grow a bowl or two of buttery gems for Christmas day, plant Rocket or Swift; under the right conditions these fast growing varieties can be ready to harvest in 8 - 10 weeks. If you get them in the ground within the next week or so and give them plenty of nourishment they should be good to go.
New potatoes don’t store well, but like many other summer delicacies, the short season only adds to their appeal.
Container grown new potatoes
The easiest way to plant new potatoes is in pots or buckets with holes punched in the base, and with the school holidays in full swing here in Aotearoa, what better outdoor activity to do with the kids or grandkids?
Place each pot in a sunny, warm position and fill the bottoms up with 15cm of friable, compost enriched soil. If you are using a regular 10 litre bucket, place just one seed potato in the bottom. If you have a wider, deeper vessel, you can get away with putting 3 potatoes inside, giving each one an equal amount of growing room. For potatoes that have been already been chitted (pre sprouted), face the new growth upwards.
Cover with another 10-15cm of soil and water in. If you have it, add a bit of seaweed fertiliser, comfrey liquid or worm juice to your water first.
Once the potatoes grow through the soil, let the foliage get 10cm high, then cover it with another layer of compost. Keep repeating until your pot is full. Mulch the top with straw or grass clippings to lock the moisture in, and keep the pots well watered over summer ~ potted edibles need more water than ground grown plants.
Begin harvesting either when the plant flowers, or for non-flowering varieties, once it has been growing for 8-10 weeks. You can test how the spuds are going by reaching in and feeling around in the soil ~ you should be able to harvest one to see how big it is. If you think they are ready, harvest the whole lot by tipping the bucket or pot out!
Some potato varieties don’t flower, such as Swift, Rocket and Nadine, so these should be harvested once they have been in the ground for the set amount of time.
Growing newbies in the garden
For a larger harvest of new potatoes you may want to plant some into the garden. If you don’t have much room, you can just pop them in amongst other plants where you see gaps ~ being new potatoes they will only be in the ground for a couple of months. To do this, dig a hole 15 - 20cm deep. If the soil needs it, you can add a trowel full of compost before placing the potato into the hole, sprout side up. Cover over with soil and allow to grow. As with pot grown spuds, as the foliage grows, keep covering it with any organic matter you can find ~ garden soil, compost, hay or grass clippings are all good options.
If you want to grow a large amount of new potatoes, follow the directions for planting maincrop spuds, but place the new potatoes closer together at 30cm intervals, and harvest as explained above.
Don’t be scared to pop new potato seeds anywhere there is a gap in your garden ~ there is a saying that once you plant a potato you will never get rid of it, but personally I don’t see this as a problem. I love the surprise harvests throughout the year that the odd wayward potato produces.
Maincrop potatoes
Maincrop potatoes are the keepers, the ones that develop thick skins suitable for storing over winter. My favourite variety is Agria ~ I find the deep rich flavour far superior to any other maincrop potato, and the floury consistency makes them highly adaptable in the kitchen. Agria also crop heavily, making them suited to container growing. Rua is my second choice. They are a flavoursome variety that keeps well, producing large crops in most soils. If you are after the quintessential waxy potato that will hold its shape for summer inspired potato salads, then Nadine is a good option, or you might choose Desiree, which is a red skinned all-rounder suitable for all applications. Personally I use Agria over everything else regardless, but that is just because I enjoy the flavour so much, and for me the less waxy the spud the better ~ this is just personal preference.
Growing potatoes in a garden bed
Begin by breaking up any large clods of dirt with a hoe or similar, and remove any big pieces of bark or stones you come across. Then, if you have untreated wood ash from a fireplace, you can sprinkle a decent amount onto the garden bed, raking it in well. This is not imperative, and I know not everyone has this option, but the potash will help to improve the flavour of your potatoes and the yield of your crop.
Dig trenches around 20 cm deep in rows a pace apart using a trenching shovel, a long handled hoe or a regular shovel. If you have a wide garden as I do, place a plank down to stand on while you work the ground, so as not to compact the soil.
If you have it, add a layer of organic goodness along the bottom of each trench. This could be in the form of sheep pellets, homemade compost, well rotted chicken manure, or even a thick layer of fresh comfrey leaves. Anything that will feed the potatoes nutrients from underneath as they grow. Potatoes are big feeders, and the more goodness you can put into your soil at planting time the better.
Place you seed potatoes ~ sprout side up ~ in the trenches 50 - 70 cm apart, pushing them in slightly. You can put them closer together if you are short on space, but keep in mind that maincrop spuds need room to produce high yields. Sometimes if I want to give the plants an extra boost, I put a small handful of blood and bone under each potato as well.
Gently rake some soil back into the trenches so the potatoes are covered by about 10cm ~ there will be a dip where the trenches were but that is ok, because over time you will fill that in, and in the meantime the dip will help the potatoes to retain moisture.
Let the plants grow, and once the foliage is 15-20cm tall, mound soil up around it, so just the top leaves are poking out. Continue mounding soil around the foliage as it grows. In the early stages the aim of mounding is to promote tuber growth, but as the plants grow it will prevent the swelling tubers from going green (which they will do if exposed to light).
Once you run out of soil, give the whole bed a thick mulch of straw, grass clippings, compost, or any suitable organic matter.
Maincrop potatoes can be “tickled” to harvest a few new potatoes off each plant as soon as they begin to flower. Gently feel underneath for baby spuds, and carefully pick one or two ~ don’t be too greedy though! It’s just a teaser.
Harvest your potatoes once the tops have fully died back in autumn. The longer you leave the tops to die off the longer the potatoes will store, however you must make sure you are harvesting them during a dry spell. As you dig them up, put any damaged ones aside for eating straight away.
To store for winter use, place your potatoes unwashed in a single layer in a dry, cool, shady place such as a southern facing deck or shed, or even a basement if you are lucky enough to have one. It is important the area gets good airflow and has low humidity so the tubers can dry out properly ~ the aim is to extract moisture from the potatoes and to harden the skin. They should have finished curing in a couple of weeks, at which time you can store them in sacks or crates, away from light, in a cool dark airy place.
Check the potatoes regularly, discarding any that show signs of damage or rot.
The No-Dig Technique
You can use potatoes as a means to build up and break in heavy garden soil, but this is only really an option if you have lots of organic material on hand. Begin by spreading a thick layer of straw over the area you want to plant in, then cover that with a 10-15cm layer of broken down compost or top soil. If you have sheep pellets or some other composted manure add it here too.
Place the potatoes on top, 50-70cm apart (or less for new potatoes), and cover with another layer of straw. As the potatoes grow, add more layers of organic material such as straw, grass clippings, or compost, mounding around the foliage as you go.
Harvest by pulling back the layers of mulch ~ by now the worms will be working their magic and the soil underneath will be more conditioned. Plus all that organic matter will be actually be beginning to turn into soil. Once you have harvested, fork the bed over, and plant a different crop straight in ~ I find garlic is a good crop to follow potatoes.
Good luck with all the potato planting - it really is a satisfying and exciting crop to grow, and it is a pretty special feeling digging edible treasure up out of the garden:)
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