Seed Potato Planting Guide

There’s nothing quite like digging around beneath a potato plant and finding your first crop of fresh spuds.

Seed potatoes are easy to grow in garden beds, raised beds, large pots and planter bags. Choose the right variety, give them loose soil and regular water, and you can enjoy your own freshly dug potatoes from early summer right through to autumn.

What Are Seed Potatoes?

Seed potatoes are specially grown tubers supplied for planting. Despite the name, they’re not seeds at all.

Certified seed potatoes have been produced and checked under a certification programme, giving you a healthier and more reliable starting point for your crop.

Supermarket potatoes may sometimes sprout and grow, but they can carry disease, may have been treated to slow sprouting, and their growing history is unknown.

Understanding Early, Mid-Season and Main-Crop Potatoes

Potato varieties are often described as very early, early, mid-season, main crop or late crop. This tells you roughly how long they take to mature.

The timings are a guide only. Warm soil and good growing conditions can speed things up, while cold weather, dry soil or a late planting can slow the crop down.

For a longer harvest, plant more than one type. An early variety will give you the first new potatoes of the season, while a main-crop variety can be left to mature for later use.

Some varieties may sit between two groups, so always check the maturity information provided for the particular potato you’re planting.

When to Plant Seed Potatoes

Plant seed potatoes once the soil has started to warm and the risk of heavy frost has passed.

In warmer, frost-free areas, early varieties can often be planted from July or August. In colder areas, it is usually better to wait until September or October.

Potatoes can continue to be planted through spring and into early summer, although later crops may need careful watering and can face more pressure from pests and disease.

For fresh potatoes around Christmas, work backwards from the variety’s estimated maturity time. Most early varieties need to be planted during late winter or early spring.

How to Sprout Seed Potatoes Before Planting

Sprouting seed potatoes before planting is often called chitting. It gives the potatoes a head start and can be especially useful for early crops.

Place the seed potatoes in a shallow tray, egg carton or cardboard box with the end showing the most eyes facing upwards.

Keep them somewhere bright, dry, cool and protected from frost. Avoid a warm, dark cupboard, as this encourages long, weak shoots.

They’re ready to plant once they have developed short, sturdy shoots around 1 to 2cm long.

Choosing the Best Position

Choose a sunny position that receives at least six hours of direct sunlight each day.

Potatoes grow best in loose soil that allows the developing tubers to expand easily. The planting area should also drain freely, as cold and waterlogged soil can cause seed potatoes to rot.

Avoid growing potatoes in the same spot year after year. Rotating them around the garden helps reduce the build-up of soil-borne pests and diseases.

Where possible, avoid planting them directly after tomatoes, capsicums, eggplants or previous potato crops, as these plants belong to the same family and can share some of the same problems.

Preparing the Soil

Loosen the soil well before planting and mix through compost or well-rotted organic matter.

Potatoes are hungry plants, so add a fertiliser suited to potatoes or vegetables. Mix it through the soil rather than placing the seed potatoes directly against concentrated fertiliser, which can burn the new shoots.

Avoid using fresh manure immediately before planting. It can encourage excessive leafy growth and may increase the chance of rough or scabby skins.

How to Plant Seed Potatoes

1. Dig trenches around 15cm deep and approximately 60cm apart.
2. Add potato fertiliser and mix it thoroughly through the soil.
3. Place the seed potatoes into the trench with the shoots facing upwards.
4. Space them around 30 to 40cm apart.
5. Cover them with approximately 10cm of soil.
6. Water lightly if the soil is dry.

Handle sprouted seed potatoes carefully. The shoots can be knocked off, although the potato will often produce more if this happens.

Should You Cut Large Seed Potatoes?

Small and medium seed potatoes are best planted whole.

Very large seed potatoes can be cut into pieces, provided each section has at least one or two healthy eyes. Allow the cut surfaces to dry and form a skin before planting.

Cutting does increase the risk of rot, especially in cold or wet soil. If you have enough seed potatoes, planting them whole is generally the safer option.

Mounding Potato Plants

Once the shoots are around 15 to 20cm tall, begin drawing soil up around the stems.

Continue mounding as the plants grow until the ridge is approximately 25 to 30cm high.

Mounding is important because it:

• Protects developing potatoes from sunlight
• Provides loose soil for the crop to grow into
• Supports the plants
• Helps conserve moisture around the roots

Any potatoes exposed to sunlight can turn green. Green potatoes contain higher levels of naturally occurring glycoalkaloids and should not be eaten.

Watering and Feeding Potatoes

Keep the soil evenly moist once the plants are actively growing.

Regular water is especially important when the plants begin flowering and the tubers are developing underneath the soil. Allowing the ground to dry out during this stage can result in a smaller crop.

Water deeply rather than applying a light sprinkle each day. Avoid leaving the soil constantly saturated, as waterlogged conditions can cause rot.

A layer of mulch helps retain moisture, suppress weeds and protect developing potatoes from sunlight.

Apply potato fertiliser according to its instructions during the growing season. Avoid using too much high-nitrogen fertiliser, or you may end up with heaps of leafy growth and not much happening underneath.

Growing Potatoes in Pots and Planter Bags

Potatoes are easy to grow in large pots, buckets and planter bags.

Choose a container at least 35 to 40cm deep with plenty of drainage holes. The larger the container, the more room the crop has to develop.

1. Add around 10 to 15cm of potting mix to the bottom of the container.
2. Place the seed potatoes on top with the shoots facing upwards.
3. Cover them with another 10cm of mix.
4. As the shoots grow, gradually add more mix around the stems.
5. Continue until the container is nearly full.

Avoid squeezing too many seed potatoes into one pot. Overcrowding usually gives you lots of very small potatoes rather than a good usable crop.

Containers dry out quickly, so check the moisture regularly during warm weather.

When Are Potatoes Ready to Harvest?

The right harvest time depends on whether you want tender new potatoes or a fully mature crop for storing.

Harvesting New Potatoes

Early potatoes can usually be gently checked once the plants begin flowering, or once they have reached their expected maturity time.

Carefully feel around beneath the soil and remove a few usable potatoes without pulling up the entire plant. This is often known as bandicooting.

Not every variety flowers reliably, so use the estimated days to harvest and the size of the plant as your guide as well.

Harvesting a Mature Crop

For larger potatoes and better storage, wait until the foliage begins yellowing and naturally dies back.

Once the tops have died, stop watering and leave the potatoes in the ground for approximately one to two weeks if conditions are dry. This allows the skins to firm up.

Do not leave mature potatoes sitting in cold, waterlogged soil.

How to Harvest Potatoes

Choose a dry day and use a garden fork to loosen the soil well away from the plant.

Lift gently from underneath, then search through the soil by hand. Potatoes can spread beyond the centre of the plant, so it pays to check the surrounding soil carefully.

Set aside any potatoes damaged by the fork and use those first. Damaged potatoes do not store well.

How to Store Potatoes

Potatoes intended for storage should be fully mature, with firm skins that do not rub away easily.

Allow freshly dug potatoes to dry somewhere shaded and well ventilated. Do not leave them sitting in direct sunlight.

Brush off loose soil, but avoid washing them before storage.

Store the crop somewhere cool, dark, dry and frost-free. Paper sacks, cardboard boxes or ventilated crates work well. Avoid clear plastic bags, which can trap moisture and allow light to reach the potatoes.

Check the crop regularly and remove any potatoes that become soft or begin rotting.

Common Potato Growing Problems

Frequently Asked Questions

How Many Seed Potatoes Do I Need?

Allow approximately five seed potatoes per square metre, depending on your spacing and growing method.

Can I Plant Seed Potatoes Without Sprouting Them?

Yes. They will still grow, but sprouting them beforehand can give the crop a useful head start.

Do Seed Potatoes Need Full Sun?

Yes. Potatoes perform best in full sun. Plants grown in too much shade generally produce a smaller crop.

Which Potatoes Are Best for Christmas?

Choose a very early or early variety and plant it during late winter or early spring, once conditions are suitable in your area.

Count backwards from Christmas using the variety’s estimated number of days to harvest, but allow a little extra time for cool weather.

Can I Grow Early and Main-Crop Potatoes Together?

Yes. Planting varieties with different maturity times is one of the best ways to spread your harvest over a longer period.

Why Are My Potato Plants Not Flowering?

Some varieties produce few or no flowers. A lack of flowers does not necessarily mean there are no potatoes developing underneath.

Can Potatoes Be Left in the Ground?

They can remain in the ground briefly after the foliage dies if the soil is dry and free draining.

In wet conditions, harvest promptly to reduce the chance of rot, slug damage and other problems.

Can I Save Potatoes to Plant Next Year?

You may be able to save healthy potatoes, but disease can build up over time. Starting each season with certified seed potatoes is the more reliable option.

Our Final Seed Potato Growing Tip

Don’t put all your spuds in one basket.

Plant an early variety for those first sneaky summer harvests, then add a mid-season or main-crop variety for a bigger crop later on.

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