The influence of transplanting depth of head lettuce on size and shape of head
Three separate experiments were conducted to determine the influence of depth of transplanting on the size and shape of head of crisp-head lettuce. A hotbed experiment was conducted in the winter of 1950-1951. A greenhouse experiment was conducted in the spring and early summer of 1951. A final experiment, which was a modification of the other two, was conducted in the field in the early summer of 1951. The variety of lettuce used was Imperial 44 for all three experiments.
The lettuce was seeded in a seed flat and transplanted to Bird-10 Vita-Bands 1 ½ inches by 1 ½ inches in size. The plants were then transplanted into the growing areas at shallow, medium, and deep transplanting depths.
The hotbed and greenhouse experiments were inconclusive in their results but were of value in giving practice and growth information which made the field experiment more satisfactory in results.
The results of the field experiment showed that deep transplanted lettuce produced heads more conical, more compact, and more curly leaved than lettuce transplanted medium or shallow. The core length of deep transplanted lettuce was shorter than the core of shallow or medium transplanted. The heads from all three transplanting depths were the same in height but were significantly different in width. Heads from the deep transplanted plants had the narrowest width and were definitely more concial than the shallow or medium transplanted. The heads from the three transplanting depths weighed the same, which indicated the deep transplanted heads were smaller because they were more firm.
The shape of head was influenced by the added mechanical pressure of the soil around the plants. The compactness of head and conical shape of the deep transplanted plants appeared to be the result of soil pressure around the plant. Very compact heads, as observed on the deep treated plants, are undesirable where the lettuce is to be used as a garnish or in a sandwich because it is difficult to remove a leaf intact from such a head.
The results of this experiment indicates that deep transplanting of crisp-head lettuce should be avoided, and that the more shallow the plants are transplanted the more desirable the size and shape of the heads will be.