Gardening Illustrated and Rural and Suburban Home, 27(1392): 475 (11 Nov 1905)

POTATO CURL

ALTHOUGH the curl, as it now so often presents itself in Potato-tops, has been referred to as a new disease or trouble, yet does it seem to have been known so long ago as 1834. A copy of an article which appeared in a northern paper of May in that year, makes it clear that it was seen and known some years prior to that date. The writer states that the curl disease had so far baffled all attempts to detect and clear up its causes. But then quite recent experiments had led to the conclusion that the cause was after all the product of over ripeness of the tubers. He stated the discovery was first made in the neighbourhood of Edinburgh, where the growers were in the habit of procuring their seed tubers from moorland or cold districts. In those localities the growth was late, and frosts usually killed the leafage whilst it was still green, and the tubers being full of sap, necessarily no further ripening took place. The result of planting these immature tubers was that growth was good and healthy, no curl resulting. On the other hand, fully-ripened seed tubers planted in the moorlands still developed the curl. The knowledge thus obtained naturally led to a greater quantity of comparatively unripe tubers being planted, and it would seem as if that practice has to a large extent led to Scotch Potatoes being even now so vigorous, and when planted in the south giving such splendid crops. The curl is even now a far too common disease in the south, and especially on breadths raised from seed tubers grown on light soil in the south. But probably it is not a disease in the ordinary acceptance of the word, in the same way that the well-known fungoid disease is. Rather does it seem due to lack of sap, hard eyes, weak growths, and natural deficiency of stamina arising from these causes.

Some experiments conducted in the south this season as to what are the relative growths from well-ripened tubers and from immature tubers, have, though yet limited, so far shown that much the best results have come from unripe tubers. Now here is a matter which another year anyone who may grow even but a few Potatoes can test for himself. Let him lift of some robust variety, such as Up-to-Date, or other good one, say six roots at the end of August, whilst the haulm is still vigorous and green, and the tubers’ skins are thin and tender. Let twenty of those tubers of fair size, say 3 oz. to 4 oz. in weight, be kept in a cool place in a shallow box for the winter. Then let an equal number of even sized tubers of the same variety be got up and boxed also, after the foliage has died away and the skins of the tubers are hard set. In the spring let these tubers be planted in rows side by side, in good soil, and the results watched. We are finding year by year that fully matured, or, as we may say, over-ripened tubers that have been planted produced crops, yet when these are lifted the planted sets are found to come out hard and quite whole. That, again, is a product of high maturation or deficiency of sap. Of recent years this has become a subject of common observation and complaint. We have been advised over and over again as a corrective to cut portions off the bottom of the seed-tubers, or cut them in half. Still they come out hard and non-decomposed whether thus cut or whole, and their presence invariably means a poor crop of new tubers.

We have been realising of late more and more how vastly superior for planting and cropping are Scotch or Irish seed-tubers as compared with seed-tubers grown in the south. The diversity in production seen in such cases is indeed startling. This year with a fair trial we found Scotch and Irish tubers to give of the same variety, and from the same number planted, and lengthy rows in each case, fully 30 to 50 per cent. more of top growth, and of, tuber produce over tubers grown in three and four diverse parts of England, the southern sowed seed giving the worst crops. Here we see in the former case the products of tubers grown on cool soil, and in the moister climates of the north and the west, and, consequently, much more sappy or relatively unripe, as against the produce of tubers grown in the drier and warmer south, and therefore drier and riper. Whatsoever may be the cause to which these diverse results may be due, it is not possible to over-estimate its importance to all Potato-growers in the south.