Potatoes Growing Potatoes Potatoes were first grown in Peru over 2000 years ago, long, long before the Irish ever got their hands on them! Aside from dairy foods, potatoes are the most commonly eaten food in the western world. QUICK GUIDE POTATO Latin Name Solanum Tuberosum Type Half-hardy annual Site and Soil Sunny, well-dug and composted. Do not add lime. Plant to Harvest Time From 13 to 17 weeks How Many? Earlies, 1kg (2.2lb) per 3m (10ft) row (75cm or 2ft 6in wide). Slightly less for maincrop. Up to the 1800s, growing potatoes was only for the poor. Their nutritional value and taste has been appreciated more over the last 200 years and the humble potato has now become part of the standard diet of the UK and Ireland. Growing potatoes takes up a large amount of your garden space, so think carefully before planting. It is best to concentrate on the early potato varieties and those maincrop varieties which are unsuitable for commercial growing. This article concentrates on how to grow two varieties of potato; "earlies" (known as new potatoes) and the "maincrop" potato. Both types of potato are planted in a similar manner and nearly at the same time; however they are harvested at different times. There are of course intermediate varieties which can be harvested between the two main varieties. Position A potato plant will grow in most soils as long as it has been well dug. The soil should be clear of large lumps and stones. Add as much compost as is available, or bonemeal (or similar) at the time of digging. It is a good idea to prepare the soil in mid November or December to allow it to settle before planting and let the compost begin to break down. Although not fussy about the soil type, the potato prefers a slightly acidic soil, so do not add lime before, during or after planting. Potato plants take up a lot of room! Choose very carefully! The ideal position for potatoes is a warm and sunny site with little or no shade. Do not grow potatoes in the same soil for two or more years in succession, this will increase the risk of disease. For the same reason do not plant potatoes where tomatoes were grown the previous year. Both are from the same family and will readily transmit diseases to each other.
When and How to Plant Potato Seed Potatoes are grown from 'seed' potatoes which grow better if they are allowed to 'sprout' before planting. First purchase the seed potatoes in late January. These are available from seed catalogues or your local garden centre. Look for seed potato which is certified as free from disease and select healthy looking examples about the size of an egg. The disadvantage of the catalogues and garden centres is that the number of potato seed varieties is very limited and they are only sold in large amounts. If you only want more variety and to buy several varieties in small amounts, the solution is to go to one of the many potato shows around the country. In mid February, place the seeds in boxes (for small amounts, cardboard egg boxes are ideal) in a light airy position at a temperature of roughly 10 C / 50 F. See right. The potato seed should be positioned so the sprouts are uppermost and the 'stalk' end (where they were severed form the parent plant) is at the bottom. Sometimes this is a bit difficult to judge, but if you get it wrong, and the potatoes sprout from the bottom end, simply rub off the sprouts and turn the potato to the correct position. The picture below shows the stalk end of a potato which should be at the bottom when placed in the egg boxes. As the potato seed produce sprouts, remove all but the topmost four to ensure that they receive all the goodness of the seed potato. The ideal sprout length at planting time is 2.5cm / 1in although this is not critical. What is critical is that the sprouts are green and not white coloured. White sprouts are caused by not enough light. If the sprouts appear too early for planting the potatoes outside, simply rub them off cleanly and they will re-sprout in a couple of weeks time. Research has shown that the sprouts can be removed five times without any ill effect on the sprouts which will replace them. Mid March is the ideal time to plant the sprouted potatoes in the open ground. Plant 'earlies' about 30cm / 12in apart from each other, in rows which are 60cm / 2ft apart. Plant main crop potatoes about 35cm / 15in apart, in rows which are 75cm / 2ft 6in apart. Where you are planting
more than one row, the rows should (ideally) run from North to South to allow each plant its full share of sun. Dig a trench about 10cm / 4in deep, placing the potatoes in it with the sprouts pointing upwards. Fill the trench over the potatoes trying to avoid damaging any sprouts. Scatter bonemeal or similar long lasting fertiliser over the top soil and rake it in. Potato plants produce good sized tubers in 65 to 100 days depending on variety. The 5 phases of potato growth 1) During the first phase, sprouts emerge from the seed potatoes and root growth begins. 2) During the second, photosynthesis begins as the plant develops leaves and branches. Growth stages 1 and 2 takes 30 to 70dys. 3) In the third phase stolons develop from lower leaf axils on the stem and grow downwards into the ground and on these stolons new tubers develop; swellings of the stolon. This phase is often (but not always) associated with flowering. Tuber formation halts when soil temperatures reach 26.7 C, hence potatoes are considered a cool-season crop. Takes about 2 weeks 4) Tuber bulking occurs during the fourth phase, when the plant begins investing the majority of its resources in its newly formed tubers. At this stage, several factors are critical to yield: optimal soil moisture and temperature, soil nutrient availability and balance, and resistance to pest attacks. Lasts up to 3 months. 5) The final phase is maturation: The plant canopy dies back, the tuber skins harden, and their sugars convert to starches.
Caring for Your Potatoes Frost damage is the first concern in the early stages. If shoots emerge above the soil level and frost threatens, draw a little soil from the bed edges over them. (Earthing up) After the potatoes plants have grown to about 20cm / 8in pull up the soil in between the rows around the plants leaving a few centimetres still showing. Repeat the exercise in two to three weeks time. The diagram to the right shows the ideal end result During the growing season, ensure that weeds are removed and apply some long lasting fertiliser again around mid-august. A month or so after planting, the dense foliage of the plant should then block out sufficient light to deter all but the most vigorous weeds. As the potato plant grows, do not remove or 'stop' the foliage, it is supplying food to the tubers. However, remove any flower heads or buds which appear because these will produce potato seeds which will divert energy from the potato tubers. How to Harvest and Store Potatoes Flowering potatoes above Potatoes are ready for harvest when the foliage first starts to die and turn yellow. Early (new) potatoes can be lifted earlier (no earlier than June) to get the very tastiest potatoes. In this case, harvest them about a week after the potato plant flowers first appear. New potatoes only produce a couple of handfuls of potatoes per plant, so dig up the whole plant. Main crop potatoes will be ready for harvest in mid-autumn (start of September at the earliest). For all potatoes, dig them up from the side of the ridge (a fork or spade are both fine) to avoid damaging the potatoes. See the diagram on the right. The foliage can be placed on the compost heap only if its completely free from disease - if not, burn it. If you don't need all the potatoes from a plant at one time or if you want a few early in the season, simply burrow around the roots with your hands and remove the potatoes you need. The remaining potatoes will continue to grow. Remove any soil clinging to the potatoes and leave them on the soil for a few hours to dry out - if they are stored damp, they will rot. Leaving them on the soil surface in the sun will harden the skin slightly, doubling the storage time - this is especially important for main crop potatoes. Store the potatoes in boxes or sacks, checking them every few days, removing all but those in good condition. Damaged or blemished potatoes should be eaten immediately. One word of caution, some potato flowers may well turn to berries which are definitely poisonous. Eaten in sufficient amounts the berries can be fatal. You may wish to remove them if children are likely to see them. Other Methods of Growing Potatoes There are two common alternate methods of growing potatoes by the amateur gardener. The first is container growing. This can produce a surprisingly amount of potatoes and is great for very small gardens.
How to Grow Potatoes in Containers This is something the most amateur gardener can do with success. It's also an excellent way of growing potatoes in a small space. Because the potatoes are grown in a container of fresh multipurpose they are very unlikely to be affected by any soil borne pests and diseases. The only care they require is earthing up a few times and to be kept watered and fed. Our step by step guide takes you through the process with pictures. What You Will Need 1. A container to grow the potatoes in (see main article below). 2. Enough multi-purpose compost to nearly fill the container. 3. Between one and three seed potatoes (see main article below), preferably sprouted. 4. Concentrated liquid tomato feed for use later in the season When to Plant Seed Potatoes in a Container The average time for planting potatoes in the open ground in the UK is around mid-march, a few weeks later in colder areas, a few weeks earlier in warmer areas. When you grow potatoes in containers you can plant them a few weeks earlier as long as you make sure they are in a relatively warm position. For example, near the side of a house wall out of strong winds is a good position. The Container Any size of container can be used from 30cm (1 ft) wide and deep up to a full-sized dustbin. They can be rigid plastic, plastic sheet (as above), dustbins, almost anything. The only requirement is that they have good drainage holes in the bottom. We used a reinforced plastic container specially designed for growing potatoes in. From experience we know these will last several years. The Seed Potatoes Planting the Seed Potatoes The seed potato on the left has been chitted or sprouted Chitting is not necessary but it will give an earlier crop of potatoes. Depending on the size of the container you will need between one and three seed potatoes. For a 30cm (1ft) container use 1 seed potato. For larger containers use two to three seed potatoes. Don't use more than three.
Fill the bottom of the container with about 10cm (4in) of multipurpose compost. As you add it to the container, break up any lumps. This will allow the potatoes to grow more easily and bulk out the compost. Place the seed potatoes on the top of the compost with the side that has the most sprouted eyes uppermost. Complete the Planting With the seed potatoes in place add another 10cm (4in) of multipurpose, breaking down any lumps as you go. Water the container well and then mark it up with the variety of potato being grown. Place the container in a light and airy position out of any chance of frost. Earthing Up the Potatoes After a few weeks shoots will begin to appear from the compost. When they reach about 15cm (6in) above the soil level, add about 10cm (4in) more multipurpose compost so that only 5cm (2in) of the shoot is above soil level. Repeat the above process until the shoots reach above the top of the container. Care of Potatoes while growing The main care required is watering and feeding. Water when the compost starts to dry out. Check it by uncovering 10cm (4in) or so of compost and checking if it is drying out. The weight of the container will also indicate if the compost is drying out. Feed every couple weeks with a concentrated tomato feed, diluted as per the instructions on the packet. If the potato plants start to produce flowers then pinch these off to encourage the plant to produce larger potatoes and not seed. Harvesting the Potatoes Potatoes are ready for harvest when the foliage starts to turn yellow. Maincrop potatoes especially can be left in the compost for several weeks longer. Early potatoes can be harvested before the leaves turn yellow for small tasty new potatoes. Sometime in early June, carefully feel through the soil to judge the size of the potatoes with your hands. Harvest the by twisting and pulling gently. The remaining potatoes will continue to grow. Pests and Diseases Potatoes grown from stock certified as free from disease and planted in soil not occupied by potatoes the previous season, are relatively free from pests and diseases. The most common ailments to affect potatoes are potato blight (see next paragraph), scab, slugs, and wireworm. There is little protection available that can effectively solve these problems. Potato blight has two phases - the first attacks the leaves, the second attacks the potatoes themselves. If your potatoes are attacked by the blight, there is no cure. However, cut the foliage back to 5cm (2in) from the ground at the first signs of infection. This will prevent the blight from
getting to the potatoes themselves. With no foliage, the potatoes will not give of their best, but they will continue to grow for a month or so. Which Varieties of Potatoes The potatoes in the table below are all recommended varieties for the home gardener. Potatoes are affected by the type of soil in which they are grown, so try a couple of varieties before deciding which is correct for your garden. Name Skin Flesh EARLY Maris Bard COOKING New Boil Steam Mash Chip Saute Bake Roast White White Y Y Y Y Y Winston White Cream Y Y Y Y Rocket White White Y Y Y Y MAINCROP Estima Yellow Yellow Y Y Y Y Y Valor White Cream Y Y Y Y Y Y Y Desiree Red Yellow Y Y Y Y King Edward SALAD Red/ White Cream Y Y Y Y Y Y Y CharlotteYellow Yellow Y Y Y Nicola Yellow Yellow Y Y Y Y Y New varieties of potatoes are constantly being introduced. The aim of potato breeders nowadays is to maintain a good taste, but make the potatoes resistant to slugs and blight. This is where the 'Hairy Bolivian Potatoes' make their comeback! Many of our potatoes today originate from potatoes from Bolivia. These potatoes were capable of growing on the snowline of mountains at very high altitudes. They survived through these cold conditions because the foliage was covered with fine hairs. This gave the leaves an insulating layer to protect them from frost. Potato breeders are inter-breeding these old original potatoes with our new varieties to get the best taste and also better frost resistance. Another benefit of the layer of hair on the leaves is increased resistance to 'blight', the major potato disease. Blight is an airborne disease where the blight 'spores' are blown by the wind onto the leaves of potatoes. Here, they send out little roots which enter the potato leaves and infect the entire plant. With the layer of hair however, the spores land on the hairs and have to send out their little roots much further to infect the leaves. In most instances, the spores are so exhausted by the time they reach the leaves that they die before infecting the plant. So, if you notice that new varieties, after 1990, have hairier leaves, don't worry, it's the latest in potato fashion. The second method is to cover the planting area for early varieties with black polythene, simply held down with earth or bricks. The potatoes are planted at normal depth by cutting a '+' shaped hole in the plastic and planting with a trowel. The advantages are that the soil is warmed by the black polythene, giving the young plants protection from frost. The potatoes should be ready for harvest a couple of weeks earlier than normal.