The stereotypical garden space is a horizontal, flat, well lit area, and while that configuration is useful in many circumstances, there are also more vertical alternatives to consider. Vertical gardens tend to be the most useful in situations where space is at a premium, or when the suitable light is inconveniently located.
Sometimes there is an area that gets enough light, but may be on a hillside or other uneven terrain. Plants can often be grown even in such places by creating a series of horizontal steps much like a staircase, using a technique called “terracing” which has been practiced by farmers around the globe for over a thousand years. Another tactic involves planting in vertical or horizontal rows (erosion concerns may dictate which is best for a given soil) along the contours of the hill.
Container gardens lend themselves well to vertical arrangements. Specialty pouches and frames are made that are well suited for hanging off of the side of a fence, building, or other vertical structure. These may be single or double sided with available light generally dictating which is best for a given location. With a little modification, a wooden pallet or two can be altered to hold plants and leaned against a post or each other.
Hanging planters can be used to increase available balcony growing space, and with some macrame practice can be made at home in whatever custom configuration is desired. A plant hanger holding multiple plants one above the other was a popular method of true vertical gardening with indoor plants in the 1970’s. The tops of wooden patio awnings may well be a well lit opportunity to grow vining plants in what otherwise would be unused space. A slanted rooftop garden may have fewer obstructions shading it than a ground level garden.
Indoor vertical gardens can be used to maximize limited growing space. Racks of trays can hold many times the number of plants than a single layer does. Wasted airspace can be filled with vertical planters and turned productive. Walls lined with pouches can capture side waste light and put it to use.
There are some important considerations when vertical gardening. Outside, it may be that only the best lit side is usable, the structure itself shading the far side. Indoors, lights must be adjusted to account for the shift in canopy. Care must be taken to ensure that in the event of a nutrient leak, the solution will still not come in contact with the electric lights, which can be an issue if there are containers above lighting fixtures. It is important that the structure is robust enough to support the weight of the growing medium, plant, and nutrient solution so overbuilding tends to cause less issues than underbuilding.
Vertical gardens lend themselves well to gravity fed systems, where the nutrient solution is pumped to the top and gravity is used to distribute the solution to the individual plants. Since the uppermost plants may be out of convenient reach for hand watering, some sort of at least semi-automated watering is generally used.
Although some hydroponic methods are easier than others to adapt to vertical growing, practically all conventional hydroponic methods can be altered for vertical use. Deep water culture tanks can be stacked in racks. Water can be pumped to an elevated reservoir and connected to a gravity drip system to feed soil less pots. With some creative plumbing; a series of bell siphon ebb and flow pods can empty one into the next lower. Bubble system buckets can be hung from sturdy uprights. Individual containers can be placed on stepped platforms much like a stadium. Tubes can be set on end with openings for plants, and nutrient solution dripped or sprayed inside for a nutrient film technique or aeroponic system. The possibilities are near endless, so whatever preferred method a gardener has, there is a way to experiment and try it.
In order to accommodate the change in canopy, lights are generally placed lower than in a conventional flat garden. However, it must be kept in mind that the top surface of the leaves must be lit, not the bottoms (although some vining plants are an exception as they can turn their leaves to face the light in any orientation and therefore can be entirely bottom lit).
Since more of the area is being used, plant size becomes more critical with vertical gardening. A small error in timing or plant size estimation with a flat garden may result in things becoming a little cramped, but the same mistake with a vertical garden may well overwhelm the space. Likewise, with more plant material comes a more critical need for proper air movement and circulation.
While gardens are often thought of as 2 dimensional constructs that enter the 3rd dimension as they grow taller, vertical gardens can take advantage of all three dimensions right from the start, and in the right situations, can provide gardening space where none existed before.