Vertical garden in a PVC pipe

A vertical garden in a PVC pipe uses an upright pipe as both the structure and the channel. Lettuces grow from openings along the pipe, one above another, while a pump circulates a nutrient solution (water with dissolved nutrients) from top to bottom inside it. It is a form of hydroponics: the plants do not depend on fertile soil, because the nutrients arrive with the water.

How it works

Play with the drawing: switch the pump on and off, try the timer, move the days forward and click the parts to see what each one does.

1. The pump lifts the solution. A submersible pump in the reservoir pushes the nutrient solution through a hose to the top of the pipe.
2. The solution trickles through the substrate. The pipe is filled with an inert material such as sand, gravel or carbonized rice husk. It holds the roots and keeps some moisture as the solution runs down by gravity.
3. The roots feed along the way. Each seedling sits in a side opening, with its leaves outside and its roots growing into the moist substrate.
4. The excess returns to the reservoir. What is not absorbed drains from the base back into the reservoir, and the cycle starts again.

The pump does not need to run all the time. In the trial described below, it ran on a timer: 15 minutes every 2 hours.

What a field trial showed

Agronomy students at ICA/UFMG, in Montes Claros (Minas Gerais, Brazil), grew lettuce in upright PVC pipes 15 cm in diameter, filled with substrate. According to the published report:

• Sand, gravel, carbonized rice husk and a commercial substrate all worked. The choice can follow whatever is cheapest and easiest to find locally.
• Seedlings were transplanted at about 20 days, and the harvest came 45 days after sowing.
• The pipes allowed about 28 plants per square meter, against about 9 in conventional cultivation.
• With the nutrient solution prepared according to the manufacturer's recommendation, there was no need for pH and conductivity meters, which are expensive.

These are results from a local trial, with that place's water and climate: they are a reference, not a guarantee.

Common variations

• Hollow tower with net cups. Instead of substrate, the seedlings sit in slotted cups fitted into the holes, and the roots hang inside the pipe, wetted by the solution trickling down.
• Soil-filled pipe, watered by hand. No pump and no nutrient solution: the nutrients come from soil and compost, and watering is done from the top. It is simpler, but the soil dries faster and the water is not reused.

Cautions

• The system depends on the pump. If it stops for long, the substrate dries out and the plants suffer.
• Opaque, covered reservoir. Light reaching the solution encourages algae.
• Very hard (calcareous) water makes the solution harder to balance. That was exactly the challenge of the Montes Claros trial.
• Materials. Prefer a new pipe and food-safe parts that have not held chemicals.
• Light and heat. Lettuce needs good light, but very strong heat tends to harm it.

Authorship

This is a widespread technique, with many variations and no identified author. The trial cited tested the system; it did not invent it. If you know the origin of a variation and have a source for it, use the report button below to let us know.