The spacing of planting is one of the most important factors, which in the first place influences the yields, the quality, and quite often the earliness of the respective cultivar.
Consequently, the number of plants per unit are has an indirect effect on the production costs and profitableness in general.
Spacing is of particular importance in greenhouse vegetable production, due to the high production costs and amortization deductions.
In respect to the problem of planting distances all vegetable crops can not be appraised from one and the same point of view.
On the basis of the habitat and the biological qualities the varieties can be grouped as follows:
- Plants of horizontal growth, giving a single fruit (such as the different varieties of cabbages and salads, the tuber plants, etc.)
- Plants, growing horizontally and bearing periodically several fruits (such as melons, musk-melons, pumpkins, cucumbers, etc.).
- Plants, growing vertically, periodically bearing a number of fruits (such as tomatoes, beans, etc.).
(By 'fruit' we understand the edible part of the plant).
Theoretically, with the first group the number of plants over an unit area is fixed in accordance with the habitus of the plant, taking into account the possibilities of mechanical cultivation and fertilizing, as well as the various requirements of the different markets.
The effect of the size of the nutritive area on the continuity of the vegetation period is comparatively weak; greater is the effect on the size and the uniformity of production.
The nutritive area of the second group plants is determined mainly by the indices total yield and earliness.
The number of plants per unit area may then be of decisive importance.
In the plants of vertical growth (including also greenhouse cucumbers) the determination of the number of plants per unit area depends on a number of factors.
Besides the habitus, the individual method of growing, duration, periodicity, choice of site, etc., special attention should be paid to self-shading.
The sweet pepper, with its specific qualities, falls into the third group.
The requirements towards light intensity, the periodicity of ripeness, the position of the fruit, the quality of the yields and the productive ability of the peppers, are factors of a very great importance.
From a botanical viewpoint, the pepper plant is not adapted towards a continuous fruit-bearing for a longer period of time, without aging and decreasing the quality of yield, as is the case with cucumbers and tomatoes.
The creation of short-stalked (determinate) types of pepper varieties clearly stresses not only the problem of crop-rotation, but also that of