Planting Seed Potatoes

Where to grow your Potatoes

Seed Potatoes grow well in most soil types but ideally they should be grown in well-drained, loamy soil that is not too heavy.  The soil needs to be deep, well dug and with plenty of well-rotted organic matter incorporated.  The plot should be cleared and dug over in late autumn/early winter so that the frost can break down the soil structure, which will make for easy planting in the spring.

Potatoes are susceptible to a fairly wide range of minor pests, and one or two major pests.  However, pests specific to potatoes have only a limited survival time if they do not have access to potatoes so it is important not to grow potatoes in the same part of the garden every year.  Ideally, potatoes should only be planted in the same part of the garden once every 7 years but, given that this is not practical for the vast majority of gardeners we recommend a minimum of 3 or 4 years.  Aim to develop the longest rotational system you can accommodate in your garden.

What to do when you receive your Seed Potatoes

On receipt, unpack your potatoes immediately and lay them out in trays in a cool, light, well-ventilated and frost-free place, out of direct sunlight.  A shed, garage or even a cool, spare bedroom is ideal.

Preparing the seed for planting

To get your potatoes off to a flying start it is often recommended that you ‘chit’ them before planting.  This allows strong chits (sprouts) to develop on the tubers before planting.  Whilst this process is not essential for Maincrop varieties, it is strongly recommended for First Earlies and, to a lesser degree, for Salad varieties and Second Earlies.

To chit seed potatoes, place them just touching in a seed tray or individually in the sections of egg boxes.  Make sure the ‘rose’ end (where most of the ‘eyes’ are) is uppermost.  It is these eyes that will form the chits.  Place the trays in a cool, light frost-free environment at a temperature of about 45oF/7oC.

The aim of chitting is to produce plump, dark green or purple shoots about 1in/2.5cm long.  Long, white shoots are a sign of too much heat and not enough light.  If shoots are slow to appear, about 3 weeks before planting move the tubers to a warmer position for a couple of weeks and then back to the original, cooler place for the final week.

Planting seed potatoes

A few days before planting, fork over the plot, incorporating some general purpose fertiliser in the top few inches.  Set the tubers in rows, either at the bottom of a ‘V’ shaped trench or in individual small holes made with a trowel.  Many gardeners aim to have the rows running north-south as this allows the sun’s rays to warm both sides of the ridges (see ‘Earthing up’ below).

First Earlies can be planted from late February in milder, frost free areas; Second Earlies from early March; Salad varieties from late March; Maincrop varieties from late March.

Spacing, depth and row width

Traditional planting distances are as follows:

First Earlies, Second Earlies and Salad varieties: 

12in/30cm apart and 4in/10cm deep in rows 18in/45 cm apart.

Maincrop varieties:

15in/40cm apart and 4in/10cm deep in rows 24in/60 cm apart.

Earthing up

As soon as shoots start to appear above the soil, it’s time to start ‘earthing up’ the rows.  This means pulling soil over the shoots from either side of the row to form a ridge.  This protects the plants from late frosts and prevents the tubers from becoming green and inedible.  Repeat this regularly until the ridges are about 8in/20cm high.

Feeding and watering

An application of a high potash fertiliser at the rate suggested on the pack will increase yields.  Avoid fertilisers high in nitrogen as these will delay maturity of the crop.

Potatoes need plenty of moisture, particularly round about flowering time which is when the tubers start to form.  In dry spells it is recommended that the crop is watered every 10 days or so.  N.B. Check for any current local watering restrictions before doing this.  An occasional heavy watering is better than little and often as this does not get down far enough and encourages shallow rooting.

Harvesting and storing

Harvest times depend on planting dates, weather and temperature at planting time, weather during the growing season, variety maturity and weather and temperature at harvest time.  However, in general terms:

First Earlies are best harvested in small quantities & eaten straight away when fresh in June & July.

Second Earlies and Salad varieties can also be harvested in small quantities and eaten when fresh in June and July.  Alternatively, if the skins are allowed to ‘set’ – i.e. they don’t rub off when lifted – cut the foliage down to stop continued growth, lift in September and store as per Main crop varieties.

Maincrop varieties can be lifted from September onwards and stored as long as the tubers are lifted in dry conditions or are dried properly.  Store in a hessian sack in a cool, dark, frost-free area.

Jane Lane Nurseries

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