The potato tuber is a fleshy, food-storing swelling at the tip of an underground stem, also called a stolon.
Originating from Central and South America, potatoes were brought back to Britain it is said by Sir Walter Raleigh around 1586.
Since then breeding programmes have produced hundreds of different varieties.
Some varieties have white, brown, purple or red skins, coupled with either white or golden flesh.
A few different Varieties
They are classified as early, second early or maincrop potatoes which refers to when the crop is ready for harvesting.
- Early Variety; normally these are ready for lifting approximately ten weeks after they emerge from the soil.
- 2nd Early Variety: take 16 to 17 weeks to mature after planting.
- Maincrop Variety: these are usually ready 18 to 20 weeks after planting.
Potatoes like plenty of sun, and adequate moisture throughout the growing season to swell the tubers.
Normally good soil preparation coupled with rainfall will suffice.
Failing that manual watering will be required to ensure the tubers get sufficient moisture.
- Early varieties; do not store well and should be eaten soon after lifting.
- Second earlies; generally store quite well.
- Maincrop varieties; are deemed to be the best varieties for storing.
Order seed potatoes if you have not already done so.
When ordering one can estimate the quantity needed by remembering that six potatoes weigh approximately 0.5 kg (1lb).
Alternatively if you have created a planting plan you can calculate the number of seed tubers you will require.
The advantage of calculating your needs in this manner caters better for varieties that have either large or small seed tubers rather than relying on the number to weight ratio mentioned above.
That is, subject to size there can be more than or less than six tubers to the 0.5 kg (1lb) and you could end up with too many or too few tubers to suit your needs.
Planting distance is 300mm (1ft) apart for earlies, and 400mm (16") inches apart for maincrop, in rows 600mm (24") apart.
When the tubers arrive set them up, rose end uppermost, in shallow boxes or trays, and put them in a light, airy, frost-proof place to chit.
Chitting is a means to encourage the seed potatoes to sprout before planting.
Sometimes it is difficult to determine the rose end.
This can be made easier by locating the point where the tubers was connected to the root system (stolon).
Once located this will indicate that the rose end is at the other end of the tuber.
The chitted tubers are ready to be planted out when the shoots are 20-25mm (¾"-1") long.
Take care they do not get the tubers chilled, or for that matter too warm, a temperature of 4°- 8°C(40°- 45°F) should suffice.
Chitting potatoes is not essential, the practice is mainly a time saving technique to grow the crops quicker, i.e. it gets the plants off to an early start.
Plant two or three potatoes in a 250mm (10") pot to get an early catch crop.
Alternatively, plant two or three chitted seed potatoes (tubers) in large purpose made bags obtainable from many reputable seed potato merchants or garden centres, one tuber should be sufficient in smaller bags.
Cover the tuber/s with compost.
Water regularly and never let the compost dry out.
Potatoes sown in Bag
As the leafy green shoots (haulms) grow taller, gradually unroll the top edge of the bag and fill in around the plant/s with compost.
Continue with this process until the bag is full.
Continue watering regularly, adding a liquid feed once a week.
Different potato varieties mature at different times, with early ones ready in mid to late June, and later ones will carry on developing into July and August.
If an early variety is being grown then they are usually ready for harvesting when they come into flower.
With second early or maincrop varieties wait until top growth starts dying back.
Ready for Harvesting
Check over seed tubers that are already sprouting and dust/spray with insecticide if aphids are spotted.
In poor light the shoots may become drawn these should be rubbed off to encourage more to develop, or cut them back to a leaf joint near the tuber.
Be on the look out for rodent damage as this can make the tubers susceptible to disease.
Any seed tuber showing disease symptoms should be removed and burnt promptly to prevent further spread.
Prepare ground, if conditions are suitable, if this was not done at the back end of the previous season.
1) Excavate trench
2) Add manure to tench
3) Cover manure
4) Completed bed
If weather and ground conditions allow, plant out previously chitted early varieties.
Form drills 150mm (6”) deep in fertile, humus-rich ground, rose end / chitted end up, 300mm (1ft) apart in rows 600mm (24") apart, cover with a layer of compost or soil, then add a general fertiliser.
Fill in drills so that rows are slightly mounded.
Alternatively use a bulb planter to form holes and pop one tuber in each hole.
Maincrop potatoes can be planted from now to until early May if weather and ground conditions allow.
Form drills 150mm (6”) deep in very fertile, humus-rich ground.
Set previously chitted tubers, rose end up, 400mm (14”) apart along the row, cover with a layer of compost or soil, then add a general fertiliser, rows should be 750mm (30") apart.
Fill in drills so that rows are slightly mounded.
Earth up potatoes when the haulms (tops) are about 150mm (6") tall.
Pull the soil up to the height of the uppermost leaves it doesn't matter if the lower leaves are buried, or if in fact you completely bury the haulm/s
Keep an eye open for signs of potato blight (Brown blotches on the leaves).
If any signs are found treat accordingly.
If the weather has been particularly dry maincrop varieties will benefit from a heavy watering every seven to 10 days,
Give them a good drench so that the water soaks right down to the roots - frequent sprinklings will just wet the soil surface and potentially create the conditions suited for the formation of blight.
Signs of Potato Blight
Check early varieties by digging up a root, and if of a suitable size commence harvesting.
As a rule of thumb early varieties are generally suitable for picking about ten to twelve weeks after they have emerged from the soil (fourteen to fifteen weeks from sowing)
Most early varieties do not store for long, so it is sometimes better to pick as required.
As a guide, 2nd early varieties mature approximately 16-17 weeks after planting, and maincrop, approximately 18-20 weeks from planting.
Week 28 - 32:
Now is a suitable time to prepare to grow fresh potatoes for your Christmas dinner.
Use specially prepared cold-stored tubers, as home-saved tubers can suffer from pests or remain dormant, the choice is yours!
Plant up three tubers to a 250-300mm (10"-12”) pot/bucket containing potting compost. (see Week 5)
Place well rotted manure or garden compost in the bottom third of the pot, for moisture retention.
Do not plant the tubers directly on to the manure / garden compost.
Just cover the tubers with about 50mm (2”) of potting compost.
Plunge the pots out in a well lit or semi shaded spot, grow on, and check periodically to ensure they don't dry out.
As foliage develops, earth up the potatoes with more compost until the container is full.
Keep well-watered and use a general-purpose liquid feed.
Lift a root of maincrop potatoes to check on size and suitability for harvesting.
If you spot any sign of blight, remove all foliage and stems immediately to prevent it reaching the tubers.
Once maincrop potatoes have stopped growing, cut back the haulms (top growth) if you have not done so already, and harvest the tubers for immediate use or storing.
Burn all foliage suspected of blight infection, and only store unblemished tubers, and discard all green (poisonous) and undersized tubers, and set aside damaged ones for immediate use.
When harvesting the crop use a broad-tined fork.
Push the fork vertically down into the soil for its entire depth, this will hopefully avoid spiking tubers.
Ease the shaft back towards your body and this will expose the root and tubers.
Idealy choose a fine dry day to lift your potato crop, and leave the tubers on the surface of the ground for several hours to allow the skins to harden.
If this is impractical due to the weather allow them to dry off under cover.
Before transferring the crop to paper or hessian sacks, select a few healthy egg-sized tubers to use as seed tubers the following year.
Store them in a dark, cool, and frost-free location.
Selected Seed tubers
Prepare ground for next years potato crop by digging liberal helpings of well rotted farm yard manure or garden compost. (See Week 13)
Leave the top of soil rough, winter weather will break it down to a suitable tilth.
Potato tubers in containers for cropping at christmas, should be moved to a frost-free area.