Everyone loves freshly harvested, home-grown salad, and there is no doubt that being able to harvest & eat living food gives your health a boost. In the window garden your plants get plenty of nourishing sunlight most days of the year, but how can we make sure they get enough of that vital water as well?
Small pots are great as they don’t obscure too much of your view, plus you can fit more in a single window, but due to the smaller volume of soil they can hold, they need watering more often than larger pots. Salad greens will grow very well with a smaller root volume as long as they don’t dry out, so let’s design a simple indoor irrigation system that will ensure all your crops are well watered this summer, giving you bowl after bowl of crunchy, tasty, pesticide-free salad.
Why use drip-irrigation?
- It is more efficient, so uses less precious water
- Delivers moisture at a rate the soil can absorb so avoids any messy run-offs
- Gives plants the consistent moisture level they need to be most healthy
- you can program an automatic timer so you don’t need to remember to water every day
- You can add fertiliser and other nutrients to the supply line more quickly & easily using a Venturi Siphon
If you have ever made your own potting mix you will have found that most recipes include a lot of peat moss, which is actually quite hydrophobic. This means that it does not readily absorb water unless you add a little biodegradable detergent or use warm water. The slow & steady delivery from a drip emitter allows the water time to soak into the peat and permeate the entire medium much better than if you pour a load of water on top of the soil. Some emitters even inject water directly into the soil straight to the roots – see below.
Even though I love my plants very much, I still sometimes forget to water them. Plants enjoy consistent moisture and will do better if you never let them get too dry or too wet. In the middle of summer or winter particularly this can be diificult, but once again drip irrigation will put you in control. Automatic timers allow you to program when to switch on your drip-irrigation system. Some models allow you to control the flow to 2, 4 or even 8 different zones individually. You will have to adjust your timers or change the number of emitters in your system as we go from Spring to Fall, but you can spend the time you would historically have spent filling multiple cans of water, mixing in ferts & pouring over every plant to observe your plants at your leisure. Use this time to check for pests and adjust your irrigation system to give every plant what they need.
Pump, Gravity or Plumb it in?
Most houses have a powerful pump in the basement that pressurises the water pipes so you get a flow when you open your faucets, so this is the simplest & cheapest way to power your irrigation system. If you don’t have a pump already installed in your house you can buy one online for about $20+. Make sure to check that the pump you get can pump water up to a great enough height for your design – this is called the “head” of the pump. My window boxes were 6 feet above the pump so my pump would have needed a “head” of greater than 6 feet to get any water up to that height. Don’t make the mistake of buying a cheap pump which will not truly serve your needs, and if you can afford it, try to buy one that will allow your system to grow. Once you start indoor gardening in this style you will want more boxes!
The most natural way to power your system is with gravity. Simply fill up a reservoir above your boxes and attach the hose to your drip-system. As long as the reservoir is high enough, you should be able to get a decent flow. With such a low pressure system you will need to be vigilant to make sure that nothing gets clogged and the water keeps flowing. YOu can use a water tote with a dispensing faucet as your reservoir, and make sure you attach its shelf VERY Firmly to framing timbers in the wall – it will be very heavy once it is filled!
Don’t forget of course that you will have to lift the water up into the reservoir somehow, to give it the necessary gravitational potential energy to power your system, so you will need to do a bit of work before you can relax and watch the plants drink!
Types of emitter & dripline
- Drip emitters that emit from 2 to 8 gallons per hour (1/4 to 1 Liter per minute): these attach either directly into 1/2-inch solid tubing or to 1/4-inch tubing.
- Pressure-compensating drip emitters: these are the same as above except they will deliver the same amount of water regardless of the pressure they are at. These are intended for use in systems that have emitters at different heights.
- Flag emitters