Growing Seed Potatoes
Growing seed potatoes is really rewarding and simple to do. There is nothing quite like the delicious flavour of home grown spuds. Use this guide to help you to get the most out of planting potatoes and what type would be best for you.
What to grow:
There are many different varieties of potato that are divided into three categories described as early, second early and main crop. Choose early varieties if you are short on space as they can be planted closer together. They are also less likely to encounter pests as they are only in the ground between 12 - 14 weeks and they are also ready to eat much quicker.
Second earlies take 16 - 17 weeks to mature after planting, so are ready to harvest from late June through to the start of August.
Maincrops are ready 18 - 20 weeks after planting, so they can be lifted usually from July through to October. Maincrops take up the most space in the garden, but tend to be the best varieties to grow if you want some for storage.
Chitting your potatoes:
Chitting is a process of exposing seed potatoes to light before planting to encourage them to sprout so they produce a greater crop once planted. Start chitting from late January about six weeks before you intend to plant out the potatoes. Each seed potato has a more rounded end that has a number of ‘eyes’. Stand the tubers with the rounded end uppermost in trays or old egg boxes in a position that has plenty of natural light. The potatoes are ready to be planted out when the shoots are 1.5 - 2.5cm (0.5 - 1in) long.
How to plant:
Plant first earlies around late March, second earlies early to mid April and maincrops mid to late April. Prepare the ground the previous autumn or winter by digging in organic matter such as well-rotted animal manure. The traditional planting method is to dig a narrow trench 12cm (5in) deep. The seed tubers are spaced 30cm (12in) apart for earlies and 37cm (15in) for maincrop varieties in rows 24in (60cm) apart for earlies and 75cm (30in) apart for maincrop. Apply a general purpose fertiliser at this stage. Handle your chitted tubers with care, gently setting them into the trench with the shoots pointing upwards, being careful not to break them.
When growth emerges, start the process of ‘earthing up’. Wait until the stems are about 23cm (9in) high and draw the soil up to the stems creating a ridge about 15cm (6in) high. As the stems grow, repeat the process. Earthing up protects newly emerging foliage from frost damage and protects the developing potatoes from light that turns potato tubers green. Green potatoes are poisonous.
Another method is to grow the potatoes under black polythene. The tubers are planted through slits in the polythene. The advantage of this method is that there is no need to earth up and the new potatoes form just below soil level which means there’s no digging to harvest them as they just below the sheet.
First early potatoes should be ready to lift in June and July, second earlies in July and August, maincrops from late August through to October. With earlies, wait until the flowers open or the buds drop; the tubers are ready to harvest when they are the size of hens’ eggs. With maincrops for storage wait until the foliage turns yellow, then cut and remove it. Leave for ten days before harvesting the tubers, leaving them to dry for a few hours before storing.
Growing in a potato barrel or a bag:
Small crops of potatoes can also be grown in large, deep containers. Growing in a potato barrel or bag means you can start off your potatoes indoors much earlier than outdoor planted ones. To get really early potatoes keep the tub indoors (in an unheated room), or in the shed or greenhouse for the first two to three weeks. Alternatively you can keep them outdoors covered with plastic to protect the tops from frosts. Chit your chosen seed potatoes as described above. You will need an 80 litre bag of good general-purpose compost. Put six inches of compost into the bottom of the barrel and plant the chitted seed potatoes about two inches deep with shoots upper most.
Feed every other week with an organic potato and vegetable fertiliser and water the compost well. When the tips of the plants start to poke through the top of the compost, top the barrel up with about another six inches of compost. Again keep the soil well fed and watered. Repeat this process of topping up with compost each time the shoots poke through the surface.
Eventually the plants will produce tiny white or pink flowers. Now is the time to check if your potatoes are ready to harvest. Lift up the slider of the barrel. You should be able to see potatoes quite clearly and if they are big enough to slide them out with your fingers. Take enough for the table and close the slider again. Alternatively if you are growing them in a bag, slide your hand down the side of the bag and feel for the potatoes instead.