Suckering
All greenhouse
cultivars have an indeterminate growth habit, but if left unpruned, sideshoots
(suckers) will develop between each compound leaf and the stem. These
suckers are removed as they develop, leaving only the main stem as a growing
point. Workers must be careful not to accidentally remove the main stem
rather than the sideshoot. If this happens, a sideshoot can be left to
form a new main stem, but yield is reduced and harvest delayed. For this
reason, sideshoots are usually not pruned until they are a few inches
long, at which time they are easier to distinguish from the main stem.
Crop
Support
As soon after transplanting as possible, plant stems should be secured
to nylon strings hung from horizontal wires at least 3 m about the ground
(Fig, 10). Horizontal wires must be study
enough to support the weight of all plants in the row, given that a plant
fully loaded with fruit weighs 7 to 14 kg. Although these wires are usually
connected to the greenhouse frame, vertical poles may be necessary for
additional support so that the greenhouse frame is not bent. Each individual
stem is clipped to a string with special plastic clips available in several
sizes. Clips can be sterilized and reused, but string should be discarded
after each crop.
In systems where the crop is to be lowered, a special string winder is placed at the top of the vertical string, next to the wire. When plants are nearing the wire, the strings are unwound from these hangers and string and plant moved sideways down the horizontal wire. This process is called "lowering" and is a delicate operation in order to avoid breaking the stems. In some greenhouses, especially those using upright bags, the vines rest on special holders designed to give additional support (Fig. 5). At the end of the double row, the vines are wound around a corner and back down the next row. Upright rods are placed at the corners to turn the vines (Fig. 10), and this is another spot where vines frequently break. Vines breaks can sometimes be successfully mended with duct tape.