Potato Magazine 1(1): 6 (June 1918)
When to Plant Potatoes
Results of Experiments in Canada—Dates when Tubers Were Planted in Provinces and Results Obtained—Simple Rules for Planting
W. T. Macoun
Dominion Horticulturist

ONE of the several important factors in the production of large crops of potatoes, is the time of planting. Perhaps in no part of Canada has the crop suffered more from not being planted at the best time than in the Province of Ontario. There it is customary with most farmers to plant about the last week of May or early in June. Because of the importance of planting some other crops early and because a fair crop of potatoes can be obtained by planting late, earlier planting may not seem desirable.

However, experiments both at the Central Experimental Farm, Ottawa, and at the Agricultural College, Guelph, Ontario, and the experience of many growers, have demonstrated the importance of much earlier planting than this, if the largest yields are desired. In 1917 the yield per acre of Green Mountain potato planted on May 12 at Ottawa was at the rate of 352 bushels per acre; May 26, 295 bushels per acre; June 9, 242 bushels per acre: June 23, 59 bushels per acre, and these results are typical of those obtained in other years. A very striking difference in favor of early planting was shown in 1915 at Ottawa, when the Irish Cobbler, planted on May 15, yielded at the rate of 425 bushels of marketable potatoes per acre, and planted on May 29, only 250 bushels, a difference of 175 bushels per acre. At Guelph the following results, being the average of six varieties, were obtained in 1915: Planted May 3, 201.3 bushels per acre: May 17, 169.6 bushels per acre; May 31, 123.1 bushels per acre; June 14, 72.1 bushels per acre; June 28, 31.9 bushels per acre.

Evidence is strongly in favor of planting potatoes for maximum crops not later than May 15 in Ontario, except in the northern part where the time of planting has to be governed by the time the land is in condition.

From the results of experiments which have been made earlier planting than has been the custom would be desirable in the prairie provinces if larger crops are desired. The following were the average results for three years at the Experimental Farm, Brandon, Man., from planting at different dates: May 1, 288 bushels per acre; May 14, 285 bushels per acre; May 28, 253 bushels per acre; June 4, 188 bushels per acre. At the Experimental Farm, Indian Head, Sask., the best results have been obtained from planting

May 20, than from later dates, though earlier planting has not been thoroughly tried. At the Experimental Station, Scott, Sask., the best results, taking an average of three years, have been from planting about May 8, even though the tops are sometimes frozen badly after the potatoes are up. At the Experimental Station, Lacombe, Alta., the average of a two years' test was as follows: Planted April 28, 350 bushels per acre; May 26, 206 bushels per acre; June 9, 192 bushels per acre; July 6, 19 bushels per acre. It will thus he seen that where the spring (s early, and where frost comes relatively early in the autumn, early planting gives best results. On the south eastern coast of Vancouver Island it is necessary to plant during the latter part of March or early in April, to get the best results owing to drought in the summer. In the valleys of the upper country in British Columbia early planting is very desirable where autumn frosts come earls', whereas in the warmer valleys where there is irrigation, and where autumn frosts do not come early, it is not so important to plant early.

In the maritime provinces, owing to the lateness of the spring and the coldness of the soil, planting during the first two weeks of June gives the best results. The late spring in these provinces is compensated for by a long autumn without frost, ensuring the development of tubers at a time when in other parts of Canada the plants are dead. The lower St. Lawrence region of the Province of Quebec has climatic conditions somewhat like those in the maritime provinces, and June planting gives good results. In parts of Quebec where spring is relatively early, but where early frosts occur, early planting is desirable. In northern Quebec doubtless it will be found desirable to plant as soon as the soil is dry enough, risking injury from spring frosts so as to have the crop well advanced before autumn frosts.

From the results obtained under different climatic conditions in Canada, the following general recommendations are made which should apply both in Canada and the United States:

Where the spring is early and autumn frosts early, plant early.

Where the spring is early and summers are hot or dry, plant early.

Where the spring is late and autumn frosts late, and the summer relatively cool, early planting is not so important.

Where the spring is late and autumn frosts are early, plant as soon as soil is dry enough.

The variation in tuber productiveness of seedling potatoes is a constant source of interest to the plant breeder. This particular seedling plant produced 244 tubers weighing 6 pounds 7 ounces, and 213 seedballs weighing 2 pounds 11 ounces. The production of such a large number of seedballs is very unusual.