Optimal planting density of crops in greenhouse conditions

The problem of planting density in the greenhouse

Excessively dense planting is a true scourge for growers of all types and schools. And greenhouse is no exception. Maintaining optimal distances between plants, while still obtaining top-quality, large specimens, is something that takes a long time to master. How to instill in oneself proper order and rigor?

Space in a greenhouse is, alas, limited by its walls and ceiling—the entire dome. This fact means there is a certain limit to the canopy lighting area, a limit to photosynthesis, beyond which we cannot go. We can only ensure that the leaf surface area coincides with the lighting area—this is considered the optimal planting density. It varies for different cultivars and hybrids.

If you want to increase planting density, fitting more bushes into a square meter, the amount of light will still be divided among them all, and no increase in yield will occur. At best, the yield will remain the same, and with further densification, it will begin to drop.

Not everyone understands this, and as a rule, owners of a single greenhouse have everything planted too closely. There is only one greenhouse, the area is small, but one wants to plant everything at once:

• about a dozen different tomato cultivars and hybrids;
• in addition to them, sweet and hot peppers;
• a few eggplant bushes;
• to tuck away "temporarily" somewhere between them the remaining cabbage transplants.

Optimal organization of the foliage apparatus

It should be clarified that the aforementioned should not be understood as a requirement for strict equality between the lighting area and the leaf area for the highest harvest. In reality, for maximum productivity, the leaf area should be twice, or even more, as extensive. Plants are capable of providing light to several "floors" of foliage simultaneously: this is achieved by the dissection of the leaf blade edges, their partial transparency, and, finally, the oscillation of leaves in the wind.

By the way, different plants have their own leaf margin irregularities. The tomato's is also special: besides the fact that a leaf swaying in the wind allows a portion of sun rays to pass through its gaps down to other leaves, the serrated edge ensures a strong interlocking of leaves among themselves. The edges of tomato leaves are like a zipper; they catch easily. This prevents tall stems from toppling over; they support each other.

Important. The tomato plant is creeping; it simultaneously spreads along the ground and develops shoots upward. This peculiarity should be kept in mind during the following operations:

1. pricking out seedlings;
2. suckering;
3. tying up adult bushes.

Their shoots do not let go of each other easily, and a rough movement can tear the leaves.

Conclusion. Dealing with various crops, a gardener, firstly, tries to plant everything densely enough so that in the height of the growing season there are visually no gaps of bare soil (which would indicate incomplete utilization of lighting). Secondly, they do not allow the foliage to grow too vigorously, pinching off side shoots in time. One cannot grow tomatoes without suckering. Just as one cannot do without pinching side shoots on melon and watermelon vines.

In a greenhouse, you can provide up to 70 cm between bushes of large-fruited tomato cultivars, as they will surely grow beyond the limits of a single-stem training. They have large leaves—well, what are 35 cm on each side to them!

Following the lead of authors of books on industrial greenhouse vegetable growing, most hobbyists plant their tomatoes in four rows (two on each bed), whereas in a small hobby greenhouse, plants would have enough space with a planting of only two rows. We mainly plant tall-growing cultivars and hybrids with very large fruits, reaching a weight of 0.5–1 kg. Such powerful bushes need space. One simply needs to use the classic training into two stems: guide one stem upward along the wall, and as it grows, guide the other toward the center of the greenhouse: that will fill all the space. In return, the plants are fully illuminated and receive plenty of nutrition until the very end of the growing season, so they will not experience a deficiency of any nutrient, and this is one of the keys to their health. In crowded conditions, however, a deficiency of certain elements inevitably arises in the second half of summer: something will run out—and that’s it; their structures are created incomplete, they break easily, and the plants become diseased.

Conclusion

When plants are crowded, they do not receive sufficient lighting, which means they have little energy for each leaf and fruit. Shoots become thin, leaves turn small, and fruit set is modest.