John's advice after 25 years growing at Ashbrook allotments
Potatoes
Potatoes are one of the most popular crops for the allotment. They are categorised as:-
Obviously the above planting times might be influenced slightly by the weather. Potatoes can be further categorised as waxy (firm salad type more suited to steaming or par boiling) or floury (more suited to mashing, roasting and chipping).
The most problematic disease we experience with potatoes is blight which appears when the combination of humidity over 90% and successive night temperatures above 10C occur. At Ashbrook blight normally arrives during July although some years as in 2016 it occurred in June. At one time it was possible to protect our crops with fungicide however with the far more aggressive strains of blight that have been imported there are now no effective products available to the amateur, also many allotment gardeners prefer their crops grown without fungicide. If you find potato blight a problem there are two choices. Firstly grow varieties that will have produced a worthwhile crop before this disease arrives. Alternatively grow varieties that have blight resistance and crop later.
Because potatoes are also prone to many pests and diseases other than blight is good practice to only use certified disease free seed which is produced under very strict conditions to ensure it is clean. Your own seed saved from last year or culinary potatoes are not grown under such strict conditions and could unwittingly overwinter or import yet another pest or disease. Certified seed can be purchased from most seed companies, garden centres and DIY stores however the most economic places are local horticultural trading huts who take orders in September and October for collection the following February.
Once you have obtained your seed potatoes place them eyes up in egg cartons or seed trays in a cool, frost free, well lit area to chit. Plant into prepared ground, there are several ways to do it. Some gardeners dig a trench into which the tubers are placed, others just form a 6” hole with a trowel or border spade, some make a hole with a bulb planter, the choice of method is yours. Potatoes are hungry feeders so a dressing of potato fertiliser, blood, fish and bone or Growmore along the row will help.
Suggested planting distances:-
Planting Depth Between Tubers Between Rows
Early & Second Early 15cm (6”) 30cm (12”) 60cm (24”)
Main Crop 15cm (6”) 40cm (16”) 70cm (27”)
(Sarpo Mira) 15cm (6”) 45cm (18”) 90cm (36”)
When planting earlies and second earlies some growers reduce the number of eyes to two or three so the plant puts all its energy into fewer but bigger potatoes.
Ashbrook can be prone to late frost and potato foliage is not hardy so when growth emerges and if a cold night is forecast be prepared to protect your plants by covering the exposed growth with soil (earthing up), this also excludes light from the developing crop preventing the new potatoes going green, it also gives greater capacity of soil in which the crop can develop and to some extent reduces the risk of tuber blight. If only a small amount of foliage is showing and you are short of time a shovel full of soil or compost or an upturned flowerpot provides temporary protection until the whole row can be earthed up. Fleece can also be used but for it to be effective the material needs to be above the plant to ensure an insulating air space, frost will go straight through fleece in contact with foliage.
Most gardeners let the foliage of their plants sprawl on the ground which is fine, however some train it vertically so as to expose the leaves to maximum daylight and this should give a larger crop.
Blossom appearing on potato plants is not a sign they are ready to lift. Some growers remove blossom as it appears so as to keep the plants in vegetative state and to produce a better yield.
At Ashbrook first early potatoes planted in the ground sometimes produce a very small crop mainly due to their shorter season of growth, our soil often still being cold at planting time, then during May/June just when the crop needs moisture for bulking the ground dries out. Try some by all means but be warned. However early potatoes grown in bags produce a far heavier crop.
Good early varieties are Accent, Casablanca, Lady Crystal, Vanessa and Foremost. If planted at the correct time early potatoes should be ready for lifting before blight arrives.
- First early-normally planted mid/end March-should be ready in 10-12 weeks i.e. June/July.
- Second early -planted early April-should be ready in 13-15 weeks i.e. July/August.
- Early main crop-planted mid April-should be ready in 15-18 weeks i.e. end of August/September.
- Late main crop –planted mid April- should be ready in 20-24 weeks i.e. second half of September.
Obviously the above planting times might be influenced slightly by the weather. Potatoes can be further categorised as waxy (firm salad type more suited to steaming or par boiling) or floury (more suited to mashing, roasting and chipping).
The most problematic disease we experience with potatoes is blight which appears when the combination of humidity over 90% and successive night temperatures above 10C occur. At Ashbrook blight normally arrives during July although some years as in 2016 it occurred in June. At one time it was possible to protect our crops with fungicide however with the far more aggressive strains of blight that have been imported there are now no effective products available to the amateur, also many allotment gardeners prefer their crops grown without fungicide. If you find potato blight a problem there are two choices. Firstly grow varieties that will have produced a worthwhile crop before this disease arrives. Alternatively grow varieties that have blight resistance and crop later.
Because potatoes are also prone to many pests and diseases other than blight is good practice to only use certified disease free seed which is produced under very strict conditions to ensure it is clean. Your own seed saved from last year or culinary potatoes are not grown under such strict conditions and could unwittingly overwinter or import yet another pest or disease. Certified seed can be purchased from most seed companies, garden centres and DIY stores however the most economic places are local horticultural trading huts who take orders in September and October for collection the following February.
Once you have obtained your seed potatoes place them eyes up in egg cartons or seed trays in a cool, frost free, well lit area to chit. Plant into prepared ground, there are several ways to do it. Some gardeners dig a trench into which the tubers are placed, others just form a 6” hole with a trowel or border spade, some make a hole with a bulb planter, the choice of method is yours. Potatoes are hungry feeders so a dressing of potato fertiliser, blood, fish and bone or Growmore along the row will help.
Suggested planting distances:-
Planting Depth Between Tubers Between Rows
Early & Second Early 15cm (6”) 30cm (12”) 60cm (24”)
Main Crop 15cm (6”) 40cm (16”) 70cm (27”)
(Sarpo Mira) 15cm (6”) 45cm (18”) 90cm (36”)
When planting earlies and second earlies some growers reduce the number of eyes to two or three so the plant puts all its energy into fewer but bigger potatoes.
Ashbrook can be prone to late frost and potato foliage is not hardy so when growth emerges and if a cold night is forecast be prepared to protect your plants by covering the exposed growth with soil (earthing up), this also excludes light from the developing crop preventing the new potatoes going green, it also gives greater capacity of soil in which the crop can develop and to some extent reduces the risk of tuber blight. If only a small amount of foliage is showing and you are short of time a shovel full of soil or compost or an upturned flowerpot provides temporary protection until the whole row can be earthed up. Fleece can also be used but for it to be effective the material needs to be above the plant to ensure an insulating air space, frost will go straight through fleece in contact with foliage.
Most gardeners let the foliage of their plants sprawl on the ground which is fine, however some train it vertically so as to expose the leaves to maximum daylight and this should give a larger crop.
Blossom appearing on potato plants is not a sign they are ready to lift. Some growers remove blossom as it appears so as to keep the plants in vegetative state and to produce a better yield.
At Ashbrook first early potatoes planted in the ground sometimes produce a very small crop mainly due to their shorter season of growth, our soil often still being cold at planting time, then during May/June just when the crop needs moisture for bulking the ground dries out. Try some by all means but be warned. However early potatoes grown in bags produce a far heavier crop.
Good early varieties are Accent, Casablanca, Lady Crystal, Vanessa and Foremost. If planted at the correct time early potatoes should be ready for lifting before blight arrives.