Greenhouses and drip irrigation are a perfect match.

Plants in a greenhouse are totally dependent on the operator for water. Forget to water once in hot weather and the stress can set plants back enough to slow growth, to drop flowers or fruit, or to reduce the ability of plants to resist pests and disease.

Drip irrigation with an automatic battery-operated digital timer (TM8) can deliver a precise amount of water as often as three times a day right to the roots. It's easy to adjust the amount of water supplied by the timer. You can choose to supply less water at the first stages of growth and more water at the flowering and fruiting period.

Automating the irrigation system takes the pressure off the operator and makes it possible to leave on vacation without the need for a neighbour to water plants in the greenhouse.

Set up of a drip irrigation system is easy. We often add a standpipe inside the greenhouse with two faucets. The drip irrigation and timer are installed on the lower faucet of the standpipe and the upper faucet is free to fill watering cans and to dilute plant food.

In a small residential greenhouse, 1/2" Tubing mainline (T2100) is often installed along both long walls and across the back wall. The 1/2" mainline can stay at floor level or can be routed up to the front edge of a bench and attached using 1/2" Support Clamps (OE3).

Of course, larger greenhouses may require a different setup, depending on where paths and aisles are planned.

Along the mainline tubing, 1/4" Tubing (T3100) branches may be added to serve a group of plants. Punch a hole in the 1/2" Tubing mainline using a hole punch (TL2) and use a 1/4" Barbed Coupler (FB10) to start the branch from the 1/2" Tubing. Use 1/4" Barbed Tees (FB9) if multiple branches are needed as in the photo to the left. A one-gallon per hour dripper (D4 or D6) is added at each container, or at each plant in a container, along with a 6" stake (OE5) to hold the branch tubing above the edge of each container and to keep the dripper in place at the base of the main stem of each plant.

As an example, in our small greenhouse we often program the timer to deliver 1/4 gallon of water per day per plant, which is 15 minutes at one-gallon per hour. That rate is the minimum water required so that no matter how hot and sunny the day, the plants have enough and never have to suffer the stress of insufficient water. The soil surface may appear dry on a hot afternoon, but the soil at the roots is always damp.

Then we mix up a dilute mix of plant food and water and add that to each plant as needed by hand each week as extra fluid, in addition to the programmed drip irrigation water. The plants we grow need food and extra water at certain stages of development. And plants love to be fed a food dissolved in water, rather than a granular food that may or may not dissolve on time.

Young pepper plants with 1/4" Tubing and dripper at each plant.