How to Grow Potatoes
How to Grow Potatoes
Potatoes are one of the easiest vegetables to grow and they need only need limited attention during the growing season. There are a few simple tips when growing potatoes; it is a good idea to earth them up, (see below) water if dry and feed them, if you have time. If it is a reasonable summer with no blight, potatoes will grow with little attention. The main problem when growing potatoes is blight which is described below. Essentially it is an air borne fungus which will strike if the conditions are right, generally warm and damp, and cannot be cured.
Best tips when growing potatoes
1. Always earth up potatoes even if you are growing in pots
2. Take great care not to damage the top growth especially when earthing up
3. Water well, potatoes need a good amount of rain to grow well and feed regularly.
4. If you live in a blight prone area, see below, grow the blight resistant varieties of Potato.
This is one of the first steps when growing potatoes. Several weeks before you want to plant out the Potatoes, put the potato tubers in a light cool room (image right, ) allowing shoots to form for about 5-10cms. A good way of chitting the tubers is in an egg box or seedtray and out of direct sunlight. The best time to do this is in February, for planting out in March, but it's not essential if you don't have the time. There is much debate whether chitting potatoes makes any difference and commercial growers manage well without doing it. Advise on how to grow potatoes often recommends chitting, but there seems to be an equal, informed opinion to the effect it makes little or no difference to the crop whether the tubers are chitted or not.
When to plant potatoes
As a rule of thumb, plant out early potatoes, which include the new potato varieties in March/April; Second early April; and Maincrop later in April. Potatoes are frost sensitive and need some frost protection.
Potatoes do take up a lot of growing space and unless you have a large veg plot you may want to save space and grow potatoes in containers.
Potatoes grow well in large containers, place 3 or 4 tubers in each pot with 15-20cms of good compost in the bottom and cover with 10 cms of compost. If you are planting in the vegetable plot, plant the potatoes about 13cms deep and 30cms apart. If you have chitted the potatoes handle carefully so as not to damage the shoot and plant with the shoots upwards, if possible.
It is advisable not to grow Potatoes in the same ground each year or where you have grown tomatoes previously (which are the same family, Solanum) because of the risk of blight which has been a problem given our wetter summers. Blight causes the foliage to turn yellow and collapse. Potatoes grown earlier in the year are less likely to be effected, which are the earlies and salad potatoes.
When growing potatoes if you plant out early or we have late frosts you need to protect the top growth, called haulms, from frost. Potatoes are not frost hardy (What does "frost hardy" mean?) which means early in the year the top grow needs protection from frost. As soon as the shoots appear earth up or cover the growth by adding more soil in the pot.
"Earthing up" is important, which means as the top growth appears, extra soil is added to the pot, or scraped up around the potatoes if in the ground, to form a mound and continue with earthing up as the potato grows, (see image left.) The potatoes form under the soil beneath the plant so a good depth of soil or compost is need to for the potatoes to grow. If the potatoes are in the veg plot, earth up to create raised ridges up to 30 cms. Earthing up will help to increase crop yields and offer some protection against blight. The only maintenance is to water the pots in dry spells.
Potato Blight is the main problem when growing potatoes. It is an air bourne fungus type disease which attacks the foliage (and later the tubers) causing it to collapse. It commonly occurs in wet, mild and humid conditions and is difficult to manage. It will affect tomatoes as well, although if they are grown in a greenhouse this will afford some protection as it is mainly, but not exclusively, a disease which affects out door crops. It starts with brown marks on the leaves, image left and quickly spreads so that all the foliage turns brown or black collapses and the plant looks patently sick; it cannot be missed. Once it takes a hold there is not much that can be done as it spreads rapidly.
Good air circulation can help which means not planting the tubers too close together and following crop rotation. This means never growing potatoes where they were grown the previous year, especially as the fungus can overwinter in any tubers left in the soil which if they are allowed to grow the virus can spread from there. This means when clearing the veg plot at the end of the season it is very important to remove all potatoes including any very small ones. In addition you can grow Blight resistant potato varieties, which does not guarantee that Blight will not visit, but very much reduces the chances. Late varieties of potato are more prone to blight so growing earlies and salad potatoes may escape as the warmer humid temperatures are more likely later in the year. In the eastern parts of the UK and drier areas it is less of a problem. It is the humid warm air which allows the pathogen to spread, and it can destroy a crop in a couple of weeks.
If the plant becomes badly infected the only possibility is to cut off all the infected leaves close to soil level and be careful to pick up all bits of infected leaves. If the blight has not reached the tubers they can still be harvested later, if the blight occurs later in season, so the tubers have grown sufficiently to make a decent meal.
There are also varieties offered for sale by garden centres and on line which are more resistant such as Sarpo range and it certainly worth looking at this range if growing maincrop which will mature later.
Potatoes also suffer from keeled slugs which live underground and bore into the tubers, which damages them and makes them prone to rotting. Because this form of slugs lives so far underground slug pellets are not effective, nematodes are a better suggestion.
Potatoes also get scab which makes them look unattractive but they are edible and not noticeable when peeled. This tends to be more of a problem on thin chalky soils which are prone to drying out the addition of organic matter will reduce the risk of scab.
Suggested potatoes to Grow
Which potatoes to grow is always a question of personal choice and space. Potatoes take up a lot of room even in containers. There are several different types of Potatoes, first and second earlies, Salad potatoes (harvest June onwards) and Maincrop (harvest later in the season).
Earlies, which as the name suggests mature more quickly, so you can harvest sooner.
Earlies take about 16-17 weeks to mature, maincrop 18-20 but can be left in the ground until October and generally store well.
Earlies are slighly less prone to blight, Maincrop take up more space and for longer so there are advantages each way.
For main crop, when blight is often a problem a good choice would be organic Potato 'Sarpo Mira' in an attempt to beat the blight later in the year. They are said to be one of the most blight resistant potatoes.You may have a personal preference, if not a good starting point is to look at varieties which have the RHS garden merit award
In 2013 the RHS did a trial of first earlies and best early salad potatoes grown in containers. Those varieties which gained or retained the award were: 'Casablanca' a waxy white fleshed potato, 'Golden Nugget' waxy, 'Sharpe's Express', 'Maris Beard' 'Lady Christi' 'Jazzy' 'Vales Emerald' and 'Charlotte' worth checking them out.
Blight resistant varieties : 'Sarpo Mira' (Maincrop) 'Orla' (First early) 'Carolus' (Early Maincrop) 'Athlete ( Second Early)
It is possible to plant potatoes in August for harvesting later in the year for Christmas dinner. Buy seed potatoes sold as Christmas or winter potatoes and they are best grown in containers so that you can bring them into a greenhouse to protect from frost. These potatoes do not need to be chitted before planting.
Plant into the container in the usual way and the best time is late August /Early September. Use the same type of container and compost as you would normally, water in dry spells direct to the plant avoiding as much as you can the leaves, as that antagonizes the blight which can be around late September/October if it is warm and wet.
The top growth is frost sensitive so you will need either to protect with a fleece or bring under glass into the greenhouse. These potatoes will be ready to harvest about 12 weeks after planting.
Potatoes are an ideal container crop. As with all container grown plants or vegetables, because they are in a container they need a little more attention in terms of watering as they are more vulnerable to drought and drying out.
When to Harvest Potatoes
Check once the plants are flowering, this is a sign the crop is ready. If you have planted in the ground take care when you harvest not to spear the potatoes with the fork and to clear them all out of the ground, including the tiny ones, to prevent week seedlings growing the following year.
Earlies can be lifted as soon as the flowers appear as can salad potatoes.
Maincrop can be left in the ground much longer even after flowering. Towards the end of the season cut off the top growth from maincrop, leave for about 2 weeks and lift and store somewhere cool and dark. Hessian sacks are good for storage as they allow air circulation. Potatoes need to be stored in a frost free place and it is important to exclude light. It is important the Potatoes are completely dry before storing. Maincrop potatoes will keep and store for longer than earlies.
There are a vast amount to choose from in the garden centres and seed catalogues including many well known names available such as Maris Piper, King Edwards Charlotte.