Potatoes require a fairly long growing season. Potatoes are grown from seeds, which look like small, soft potatoes which sometimes have ‘eyes’ on. There are four main types of seed potato available:
- Salad potatoes: Known for their firm, waxy flesh and unique flavour, these are ready relatively early in the season.
- First Earlies: These are the very first potatoes to be ready in the year, maturing from as early as May when planted in February. These are often known as ‘new potatoes’.
- Second Earlies: These follow-on from the first earlies and are usually ready to harvest from June as well as being suitable for storing until August.
- Main crop: Ready to be lifted from September to October, these can be eaten straight away or stored for up to three months.
Site and soil: 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.
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.
How to grow potatoes from seeds When to plant: Salad potatoes: March – April First Early potatoes: February – April Second Early potatoes: March – May Main Crop potatoes: March – May
Harvest time: Salad potatoes: June – July First Early potatoes: May – June Second Early potatoes: July – August Main Crop potatoes: September – November
Preparation: 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 main crop 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. Thin, 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 in plots A few days before planting, fork over the plot, incorporating some fertiliser in the top few inches – our pre-planting potato feed is ideal. 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.
First Earlies, Second Earlies and Salad varieties should be positioned 30cm apart and 10cm deep in rows 45cm apart; Maincrop varieties should be spaced 40cm apart and 10cm deep in rows 60cmapart.
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 20cm high.
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. An occasional heavy watering is better than little and often as this does not get down far enough and encourages shallow rooting.
Harvesting: 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.
First Earlies are best harvested in small quantities and eaten straightaway when fresh in June and 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 the potatoes are lifted – cut the foliage down to stop continued growth, lift in September and store as per Main crop varieties.
Main crop varieties can be lifted from September onwards and stored as long as the tubers are lifted in dry conditions or are dried properly before being put away. Store in a cool, dark, frost-free area.
Storing Maincrop varieties can be lifted from September onwards and stored as long as the tubers are lifted in dry conditions or are dried properly before being put away. Store in a cool, dark, frost-free area..
Potato Pests and Diseases
Potato Blight – Worst in warm, moist conditions from mid-summer onwards. Brownish black spots appear on leaves and stems and eventually spores from these spots can wash into the soil and effect the tubers. You can reduce risk by wide spacing or growing in Gro-Sacks, as this reduces the risk of infection from one plant to another. Remove and destroy effected leaves and leave the potatoes in the ground for three weeks before lifting, so that the spores on the soil surface die.
Potato Cyst Eelworm – This is a widespread problem in soil where potatoes are often grown. The plants’ growth is stunted and the leaves turn yellow and die. Your yield of potatoes will also be reduced. Unfortunately there isn’t a lot that can be done about eelworm, apart from to avoid growing potatoes in affected areas.
Virus diseases – Potatoes are susceptible to several aphid-borne virus diseases. Leaves become mottled and the plants stunted. Any diseased plants should be lifted and destroyed. Preventative measures include: buying new seed rather than saving your own, bin old tubers instead of adding them to the compost heap.
Potato Blackleg – Leaves become pale and curly inwards and the stems begin to rot at the base. Affected plants should be dug up and destroyed.