Late sowing of potatoes

Today we made our final sowing of potatoes. At this time of year, the major seed merchants sell so called ‘second cropping’ potatoes; a rather silly name as they are neither cropping for the second time, nor are they necessarily one’s second sowing. However, tubers sown now – at least here in the south – should provide a crop of new potatoes towards the end of October and through November, and may well stand in the ground in good condition until the end of the year, offering home grown new potatoes for the Christmas festivities.

Many of the small, cleanly scrubbed, potatoes offered by the supermarkets that masquerade as new potatoes, are nothing of the kind in my view. A new potato has a thin skin that is easily rubbed off, and an unmistakable fresh dug flavour and texture that cannot be matched by these thick skinned counterfeits. Fortunately, depending on the blight situation and the protection that can be offered, it is entirely feasible to provide real new potatoes for 7 or 8 months of the year.

Potatoes are classified as first earlies, second earlies, and maincrop, depending on time to harvest and their purpose. It is the early sorts that provide the new potatoes. First earlies are generally ready in around 12 weeks, and some even sooner. They do not stand well in the ground, nor do they store well. Whilst some might grow on to a large size, they have neither the storage nor the culinary properties of a good maincrop sort; potatoes are best used for the purpose for which they were bred. At this time of year, a quick maturing sort is to be preferred, or the crop may be rather mean. One of the most popular varieties offered by the major seed merchants is Maris Peer, a second early, and like many of the second earlies is more of a salad potato, with a firm waxy flesh.

Stored seed potatoes ready for a late sowing

Although I have previously planted potatoes late in the season, I have never bought seed potatoes at this time of year. They are often rather expensive; checking online today I noted one company charging as much as £5.99 for 5 tubers of Maris Peer, which I do not consider good value for money. Rather than buy at this time of year, I simply store some of my seed potatoes from the spring, retaining first and possibly second earlies for this late sowing. In my experience, these can be kept very well in the salad drawer of the refrigerator, which all but stops their growth. I remove them some weeks before I want to plant, placing them rose end uppermost in egg trays to chit. In that way, I can make several sowings throughout the year. By now they are a little soft and shrivelled, but they have still chitted well, showing signs of good strong shoots forming.

This year, we planted our first crop in 15 litre pots, placed in the glasshouses for our earliest harvest. We then planted two beds successionally with a mixture of first and second earlies and maincrops. Today’s sowing, then, is our fourth and final of the year. The most significant obstacle to all but the earliest sowings is the prospect of late blight, Phytophthora infestans, spores of which can be harboured by infected tubers and debris from the previous season or, on a good clean plot, brought on the wind. Early crops tend to escape, whilst later crops run increasingly greater risk of being infected. We can usually be fairly confident of a good harvest from the pots and our first outdoor sowing. Potatoes are not ideal candidates for successional sowing; any later sowings are something of a gamble, but as we have the space I feel they are worth trying. The prospect of a continuous supply of new potatoes is very tempting, and this year the results are excellent.

The spores of late blight require damp, humid conditions, hence we have been keeping a close eye on the foliage these last couple of weeks as the rain, warmth, and humidity would seem favourable. Some control may be achieved by spraying with Bordeaux mixture or similar, but although this is approved for organic use, it is not always effective and I prefer not to. Nonetheless, all is not lost; if the signs are spotted in good time, although the infection is fatal, the haulms can be cut down and burned and the potatoes left untouched for several weeks. It is hoped that the spores have not been washed down to the tubers which, if infected, will rot in storage. The potatoes can be then the dug as usual. It is necessary to be very careful in checking that all of the stored tubers are sound, then to check periodically lest any begin to rot and the rot spread.

Late sowing of potatoes in the polytunnel bed

Last year was dreadful for blight, and even our glasshouse crop of tomatoes was badly affected. However, the potato crop, although much reduced, still provided sufficient for our purposes. The tubers were carefully screened after harvest, and no rot was observed during storage. Given the danger of blight, and the lateness, today’s sowing was made under the protection of the polytunnel. Planting was undertaken in exactly the same way as described in an earlier post, with soil ridged for earthing up the haulms as they develop and the tubers planted in the troughs. Hopefully, they will provide a welcome crop at the end of the season.

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