6 MASS. EXPERIMENT STATION BULLETIN 418 



of rooted plants is to be obtained. On the other hand, growth may be too vigor- 

 ous, and excessively vigorous shoots do not root as well as do those of moderate 

 vigor. Plants may be set in the fall, if available, provided that severe winter 

 weather is not probable. Spring setting is satisfactory, but it should be done as 

 early as one can manipulate the soil. Care during the summer should be the 

 same as with other nursery stock. 



In the spring of the second year, the shoots are cut near the base, care being 

 taken not to damage the shoots. A few to several shoots will start from the 

 crown of the plant. As soon as the new shoots are about 4-6 inches tall, moist 

 earth is hilled up around the bases covering the basal half of the shoots. It is 

 important to start hilling up while the bark is soft and green. This is repeated 

 about twice as the shoots grow until there is a layer of 4-6 inches of moist soil 

 around the bases of the shoots. The soil must be placed by hand, care being 

 taken to spread the shoots to make a rather wide row. A plow or celery hiller 

 may be used to throw up a ridge close to the row of plants and the mound com- 

 pleted by filling in between the shoots. 



The production of shoots and the proportion of them dev^eloping roots varies 

 with soil, rootstock, and season. In most years nearly all the medium-sized 

 shoots form roots. A transplanted shoot having very few roots will often live, 

 but the more roots it has the better it will grow. 



If a newly set stool bed does not show vigorous growth following setting, it 

 may be advisable to allow the plants to grow for a second season before hilling up. 

 In such cases, the sacrifice of one year's crop will be amply returned by better 

 crops in later years. Too much vigor is also to be avoided as very vigorous shoots 

 do not root as well as those of moderate vigor. 



The rooted shoots may be removed in late fall, but our experience is that it 

 is better to wait until early spring. As soon as frost is out of the ground the 

 mound is leveled off and the well-rooted shoots cut off as low as possible. Very 

 weak shoots may be left for another year until they become well-rooted plants. 

 Strong shoots not rooted should be removed or else laid down as discussed later. 

 After removal of the shoots the bed is kept well cultivated until new shoots start 

 from the crowns when the hilling process is repeated. Most shoots come from 

 dormant or adventitious buds in the stem tissue but some rootstocks will produce 

 new shoots from the roots. Effort must be made to keep the crowns as low as 

 possible or they will get so high as to make hilling difficult. 



A stool bed once well established will last for many years, yielding a crop of 

 rooted shoots each year. If the plants lose vigor, a coating of well-rotted manure 

 or a commercial fertilizer may be expected to invigorate them; but a good start 

 in the early years and good physical condition of the soil are more important. 



A somewhat different method of growing clonal rootstocks is called layering. 

 This differs from stooling in that the plants are set a little farther apart in the 

 row and in a slanting position. Instead of cutting off the shoot the next spring, 

 the shoot is pegged down in a horizontal position. Any long branches are tipped 

 back and the little tree covered with an inch or so of soil. The buds break and 

 push up through the thin layer of soil. They are then mounded as in stooling. 

 This method is used with rootstocks that do not root very freely and may some- 

 times be used in stool beds to fill vacant places where plants have failed, though 

 it is probably better to fill in with new plants from lined-out stock. The laid 

 down shoots may produce new shoots for a second or third year, but they soon 

 fail and new strong shoots must be laid down from year to year. 



Yields vary greatly with soil, stock, and season. Mailing IV, VII, XIII, and 

 XVI seem to be the most productive types. The others are less productive or 



