Overall plant density in vertical tower systems
Plant density in your system is driven by 3 factors
- Spacing between Towers
- Number of pockets per row
- Height of the Towers
The space between towers and the number of plants per row will be driven by the size of the plants you want to grow. The height of the towers themselves will be driven by the vertical space available in your growing area and if you are willing to lift towers out for harvest and replanting.
Tower spacing controls the horizontal growing area. Pocket spacing controls the vertical growing area.
For example if you apply pockets to your tower using the "tic tac toe" pattern (which puts 2 plants on one row and then one plant on the next row), the rows with 2 plants will need more space between towers than if you only applied one pocket per row. Although the single pocket per row pattern still puts the plants slightly offset left and right, they face more forward and hence need less inter-tower spacing.
Tower spacing can vary
If you want to grow both large plants that have relatively low plant density and smaller plants that have much higher plant densities you can have some towers close together and others farther apart on the same frame. For example, 2 towers can have close spacing of say 8 inches on center for strawberries, then 2 towers 12 inches on center for standard lettuce and herbs, and then 2 towers that are 16" on center for very large greens.
Pockets on towers
Multi-Row tower installations
The final factor that contributes to plant density is the actual height of the tower. If need to pack in as many plants per square ft as possible you can use 10ft pipe. To avoid ladders you can lift the tower out and lay it down for harvesting and replanting. If you want to avoid having to lift the towers out, keep tower height to less than 6ft. In the US, pipe comes in 10 ft. sections so splitting the pipe in 2 provides 2 (5') towers with no waste.
Mounting frame factors in tower height
You will need to keep in mind that you need at least 6" (150mm) of additional clearance for your frame and irrigation system on the top. You will then need at least an additional one foot for drains. You may need more depending on the height of your reservoir. So, for example a 5 ft tower can easily require 6 and 1/2 ft of ceiling height.
Number of rows per tower
Each pocket is approximately 6" tall (150mm), and you will need allow 6" (150mm) of blank space for irrigation considerations. This means a 5ft piece of pipe will have 9 rows of plants and a 3ft piece of pipe can hold 5 rows of plants.