Potato Growing Masterclass: My Tips for a Bigger, Better Harvest

, written by Benedict Vanheems gb flag

Harvested potatoes

Let’s go on a deep dive into the wonderful world of the humble spud. We’ll explore what to grow, how to get the biggest, best and most blemish-free harvest possible and, if you haven’t got much ground space, we’ve got growing potatoes in containers covered too!

Types of Potatoes

For the gardener’s purpose, potatoes are classified according to how long they take to go from planting to harvest. Early season or first earlies are the quickest off the blocks, taking as little as ten weeks. They tend to have thinner skins, which means there’s no need to peel them. Many salad potatoes sit in this category.

Mid-season spuds, or second earlies, take a little longer – around 12 to 14 weeks – and are enjoyed from around the middle of summer.

And then we have late cropping or maincrop potatoes. They need a touch more space than the earlies but compensate by giving generally chunkier tubers that store really well for months. They’re ready to unearth from late summer onwards.

Type Growing Time Harvest
Early Season / First Early 10-12 weeks Early Summer
Mid-Season / Second Early 12-14 weeks Mid to Late Summer
Late Cropping / Maincrop 14-20 weeks Late Summer to Autumn

With literally hundreds of varieties to choose from within these categories, my advice is to kick back with a nice cuppa to study the variety descriptions with care. Pick ones according to whether you want fluffy, floury spuds for mashing and baking, firm and waxy potatoes that will hold together well for boiling or enjoying in salads, or perhaps an all-purpose potato – perfect if you don’t have the space to grow lots of different types but want it all!

I also like to look for varieties promising good resistance to diseases and pests such as slugs or nematodes. This year I’m opting for a blight-resistant maincrop variety called ‘Sarpo Mira’, along with some quick-growing first earlies to plant under cover now.

Chitting potatoes
Chitting potatoes gives a slight head start on the growing season

Chitting Potatoes

You’ve probably heard you need to sprout, or ‘chit’ your potatoes – but is it really necessary? It does give your spuds a slight head start early in the growing season, when soil temperatures are still quite low. By getting seed potatoes to sprout in advance of planting, they’ll be maybe a week or two ahead of unsprouted spuds when planted, and in the fairly low temperatures of spring, that can make quite a difference.

Chitting’s very simple. Lay your seed potatoes out so that the ends with the most eyes (the little dimples from where the shoots will emerge) face upwards. Larger seed potatoes can be cut in two or even three, so long as each section has at least two eyes on them. Keep your potatoes in a bright, cool but frost-free place, such as a bright windowsill. I leave mine in the greenhouse, but if a frost threatens I’ll bring them indoors. Avoid keeping them in the dark, as they’ll produce long and spindly shoots that easily snap. Short and stubby shoots are what we’re after.

The number of sprouts you leave on your seed potatoes is inversely proportional to the eventual size of your spuds – the more sprouts you have, the smaller your spuds and vice versa. Lots of modest-sized potatoes is fine by me, but if you’re after fewer but larger tubers, take some time to cut out most of the eyes or sprouts like this, leaving just a couple intact to grow on.

Get on and chit your potatoes the moment you get hold of them, keeping them in that bright, cool position til it’s time to plant.

Indeterminate potato varieties tend to produce a heavier crop

Determinate vs Indeterminate Varieties

Did you know that – just like tomatoes, to which they’re closely related – potato varieties are either determinate or indeterminate? I didn’t until recently I have to admit, but knowing what type you have will play a big part in how you grow it.

Determinate potatoes produce their tubers in a single layer just below the soil surface. They’ll benefit from a layer of mulch as they grow to help shade any tubers that break through the surface and prevent them from going green in the light. Indeterminate potatoes on the other hand form tubers more vertically. Because of this they tend to be far heavier cropping and, in most cases, will need extra soil drawn up against the stems to give plants more space to form and swell those tubers.

Once you’ve got your head around this it’s an absolute revelation let me tell you! Here are some common varieties, showing which type they are:

Determinate Potatoes Inderminate Potatoes
Anya Cara
Carlingford Desiree
Estima Kind Edward
Kestrel Nicola
Pentland Javelin Pink Fir Apple
Rocket Rooster
Vivaldi Sante
Wilja Valor
Potatoes in sacks
Potatoes planted in containers need extra attention paid to watering

Planting Potatoes in Containers

The most accessible way to grow potatoes is in large containers, which means anyone can grow spuds, even if you only have a small outdoor space.

Choose a large container – I like to use tubs that are around 30 litres (8 US gallons) to give the tubers loads of room to grow and to help retain moisture for longer. Potting mix isn’t cheap, so you can keep costs down by blending it with screened garden compost and/or used potting mix. You can also add a little organic fertiliser, for instance a specific granular potato fertiliser, or blood, fish and bone. Mix it all together thoroughly.

Next, fill your container to about a third of the way up. Pop two seed potatoes on top, then add another third of your mix. Add another two potatoes, staggering the position relative to the first layer so that the foliage isn’t all growing in the same position. Then fill the container to the top with your potting mix.

Determinate potatoes are a good choice for container growing, because you can grow multiple layers in one container. If planting an indeterminate variety (and the majority of late cropping or maincrop varieties are indeterminates), plant just two potatoes in the bottom. As they grow up, they’ll initiate and swell tubers right the way up the full height of the container, so there’s no need for two layers.

Water your container, and then top it off with a mulch such as old straw, old, dry grass clippings, or leaves. This will help insulate them and lock in valuable moisture.

Planting potatoes
Traditionally, potatoes are planted in trenches, but they grow just as well when planted in holes

Planting Potatoes Early

Potatoes are usually planted in early to mid-spring in most areas, but if you have a protected structure like a greenhouse, or if you garden in a warmer climate, then you can certainly give early planting a try. Just watch out for frosts and, if one threatens, pick your potato pots up and move them somewhere warmer, or throw over a few layers of garden fleece or similar to insulate the container, because potatoes do not like the cold.

Move potatoes started in the greenhouse outside later in spring. With any luck, you should get a really early harvest, perhaps even before the end of spring.

Planting in the Ground

Once the time comes to plant potatoes outdoors, prep your soil with a good layer of compost, ready for your chitted seed potatoes. Space your potatoes 14-16 inches (35-40cm). Dig a hole for each potato, aiming for a depth of around 6-8 inches (15-20cm), pop the tuber in, and cover it over. Nice and easy! This spacing is perfect for early to mid-season varieties (first and second earlies). For late-season or maincrops, space them 18 inches (45cm) apart to give them extra space to grow bigger tubers.

You can also plant into trenches cut into the soil, or even grow beneath straw.

Hilled-up potatoes
Hilling up earth around the stems gives indeterminate potatoes more soil to swell their tubers in

Earthing Up Potatoes

For potatoes grown in the soil, there’s the question of whether to ‘earth up’ your spuds. Again, it depends on what you’re growing.

Determinates simply need mulching. I like to use a combination of dried grass clippings, leaves and straw for this. There’s no need to do anything else because, if you remember, the tubers will all form in a single layer, so all you’re doing is making sure any that poke proud of the soil surface are kept covered and sheltered from the sun.

Indeterminate potatoes, however, produce their tubers in a more vertical formation, so the more space you can give them to grow, the bigger and better your harvest. This is where earthing up comes in. Just draw up soil around the stems as they grow to increase the volume for those potatoes to grow into. You should only need to do this once, perhaps twice, until such a point that you can no longer draw up soil or the foliage closes over above the rows. Try earthing up in the morning, when plants will be fuller with water and so standing upright, which will make the job a lot easier.

In all cases, thrusting your seed potatoes down into the soil, nice and deep, should give more opportunity for those beautiful tubers to grow.

Potato blight
If blight strikes, act fast to prevent it from reaching the tubers

General Care

Wherever and however you’re growing your spuds, be sure to keep everything nicely watered. This is especially important for container-grown spuds. Moisture evaporates faster from container plants, and pots can get pretty warm, so you may need to move them into dappled shade in hot weather.

Aim water close to the base of plants to avoid wetting the foliage, which can create humid conditions that open plants up to disease such as blight.

Potato blight, also known as late blight, is the biggest worry for potato growers. There are a few simple strategies we can take to avoid this fungal disease. The first strategy is to grow earlier maturing potatoes that will be in and out before the disease typically appears from around midsummer. The second strategy is to plant blight-resistant varieties, which is why I’m opting for ‘Sarpo Mira’ – it’s claimed to be one of the most blight-resistant potato of all, although there are others that show reasonably good resistance too.

If blight does strike, act quickly. Chop foliage back to ground level, but don’t dig up your tubers for three weeks. This gives enough time for any spores still hanging about to die off so they don’t infect the tubers. You can add blighted foliage to the compost heap, but make sure you bury diseased material to prevent the spores from travelling.

Storing potatoes
Once harvested and cured, potatoes will store for months in a cool, dark place

When to Harvest Potatoes

Harvest your early potatoes while the plants are still green and lush, typically when they start to flower. Containers can just be tipped up onto a tarp and the spuds gathered, but for in-ground potatoes, extra care is needed to ensure those precious potatoes aren’t accidentally spiked by your fork! Start from the outside and – carefully – work your way towards the centre of the plant. I like to grab the foliage of the potato if it’s still intact, get the fork in underneath, rock it back and forth, and then lift up. Handle those nuggets of pure joy with care so you don’t bruise them, and enjoy them as soon as you are able.

Late season or maincrops are harvested later in summer as the foliage yellows and dies off. A few weeks before harvesting, ease off the watering. This will help the skins on the tubers below ground to start thickening and toughening up so they’re in good condition to cope with long-term storage.

Cut back the foliage if there’s lots of it so you can get in there and see what you’re doing, then dig up your spuds. Cure them by leaving them to dry on the soil surface for a few hours. Store only firm, blemish-free potatoes in breathable sacks such as burlap or hessian. Only store perfect potatoes – any that have been speared with your fork, burrowed into by pests, or which have green parts should be stored separately and used up as soon as possible.

Keep them somewhere cool but frost-free, dark, and well-ventilated. They’ll stay in good condition well into winter.

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Show Comments


"Awesome information! I did not know there were determinate and indeterminate varieties of potatoes like tomatoes! Thanks for sharing!"
Mindy (The Off Grid Barefoot Girl) on Wednesday 6 March 2024

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