Potato blight is a serious disease that can destroy whole crops. For organic growers there is no treatment other than cutting off and burning the tops and hoping that blight has not got into the tubers.
There are many varieties around that claim to be blight resistant but a new strain of the disease, known as Blue 13, has changed that. Varieties that had shown reasonable resistance are now far more vulnerable.
When we moved to Derbyshire in 2003 we tried several varieties but they all succumbed to blight and harvests were small. It was at about this time that a new, very blight resistant tuber came onto the amateur market. We trialled two varieties; Sarpo Mira and Sarpo Axona and while both were extremely resistant we settled on Sarpo Mira because we liked it and it gave higher yields.
For the past few years we have only grown ‘Mira’ in the beds. Each year the yield has been between 77kg and 91kg (170lbs and 200 lbs) from two beds 1.2m x 4.6m (4ft x 15ft.) There are two rows per bed with 10 tubers per row.
When Sarpo was first trialled as a members experiment by HDRA (now Garden Organic) some people reported that the spuds were flowery; we have never found that and think it is down to over cooking! We find that Sarpo is an excellent all rounder, steamed, baked or roasted so do not be put off by what you hear.
Other qualities include long storage at ambient temperature – ours usually last to the following April/May when stored in hessian sacks on the floor of an unheated garage.
The tubers also have moderate resistance to slugs.
Some notes about growing them.
- If you get brown spots on the leaves do not automatically assume that it is blight! See my blog post of 19 July 2009. It is more likely to be a nutrient deficiency.
- If they do get blight do NOT cut off the tops. I saw a trial in Wales this year where Sarpo were the only variety left standing when everything else had been wiped out by blight. They had some patches of blight on the leaves but the researchers say that the plants can continue growing for ~3 months after infection. The blight does not seem to go down into the tubers so the harvest is not affected.
- ‘Mira’ is a very heavy cropper so needs feeding throughout the growing season.
- The tops do not die off after flowing like other varieties so do not wait for that to happen before lifting. (They can continue flowering for weeks!) Check regulalry and harvest when the tubers are the size you want. I would advise against leaving them into the ground until autumn as the tubers can become massive and hollow.
Read more about the Sarpo story here.