Water is one of the limiting factors for growth in gardening in the dry summers of the Pacific Northwest. Though it is possible to dry farm (grow with little to no irrigation), if you have limited space, irrigation is necessary.
Drip irrigation is the most efficient and works great if you plant in rows and do not need to disturb the tubing/emitters. If you have a low producing well or live in a drought, this is a great option. I use this for my food forest. Fertigation is another option (spraying the plants with compost tea or a fertilizer water mix).
The traditional method is overhead sprinklers. These ideally have overlap to avoid blind spots. I currently use 4 of these — one in each corner of my garden. Each has a good deal of overlap. Since my irrigation well is low production, I purchased a triple timer and a single one and time them to wait an hour between watering again for the well to fill again. It has not dried up yet, so I recommend this method for low production wells. I have a 1hp pump with built in pressure tank that I purchased for around $120 and I dug a 1” line about 250’ from the well to my garden. This has worked great so far. Overhead irrigation is less efficient and wastes more water than other methods. So if water is expensive or limited, this is not ideal.
I also have a raised bed with small sprinklers along one edge. This works well also.
Using automatic timers is a great way to save the hassle of having to remember to turn on sprinklers manually and can keep your garden alive when you are on vacation. Keep an eye on your irrigation though as I have had a couple instances where my timer was not setup or working properly putting my plants back quite a bit.
1-2” of water a week is the rule of thumb. Place a small bucket if you use overhead sprinklers to see how long you need to irrigate. With drip irrigation, read what your emitters advertise in gallon output and research what your plants require.
If you live somewhere with dry summers, one of these irrigation methods is a must. If you live somewhere summers are wet like the East coast, irrigation can still be important but no where near as essential. Keep an eye on your plants for wilting and occasionally feel the soil. Mulch can make your watering go further.
So you want to grow a food forest but know that most the plants you are planting in it need water. Sure mulch can help to reduce or eliminate the need for watering, you can probably get better production with at least some irrigation.
Make sure to mulch even if you do have water. If no water, like I said this is your best option short of only planting drought tolerant plants. Wood chips will be around for a long time and fertilize and retain the water as well as reduce weeds competing for soil nutrients from your plants. If you do not have access to wood chips, compost, leaves, grass clippings, etc.
How big a food forest are we talking? Do you need to have water rights for your property to water it? If you already have water rights, all the better as you can irrigate however you like as long as it is according to your water right regulations.
Many commercial orchards use large sprinklers to irrigate all throughout the property. This is also the least efficient way to irrigate and will use a lot of water.
For a small food forest, you could water by hand, but this can be a problem if you have limited time or plan vacations without a family member or friend to help. I hope to automate as much as reasonably possible.
Drip irrigation is the method I chose. This is the most efficient way of watering and allows you to only water the plants you desire to grow. This can help reduce weeds and not run your well dry.
How far is your food forest from your house? Do you need to run a long hose or PVC out to it or can you pump from a nearby well or a creek? Or can you use rainwater collection in tanks (drip works great for this too)?
Once you know where you are getting your water, you must decide what supplies you will need. I purchased a drip irrigation kit with quite a bit of what I needed as this was the most economical route and gave me spare parts to add in as my food forest expands. I then purchased 500 feet of 1/2 inch drip line, 250 feet of 1/4 inch line, more 1/4 inch male to male connectors and 50 mini sprinklers (starting with 2 per fruit tree for now). I got this all on Amazon as that was convenient and competitively priced. Make sure to research that all the parts work with each other or purchase all from the same brand. My RainBird kit worked with many other companies’ supplies, but I saw in the comments that other brands were not interchangeable (You can tell by the actual dimensions of the tubing and by reading reviews).
I have 13 trees so far and plan to add a few more soon, so I bought extra supplies as I expand. I also have grape, raspberry, and kiwi vines, strawberries, beans, squash, hopniss, huckleberry shrubs, thimbleberries, and yacón in my food forest so far. This calls for a lot of emitters.
First I stretched out my 1/2 inch line starting from the hose bibb. As I layed it out I used some long metal staples to hold down the hose without puncturing it. I used a zigzag pattern as this was most efficient, but if it is too long, you can lose some pressure toward the end, so you may have to loop back the end to the beginning to equalize the pressure. You can also run a loop around your food forest and T off from the loop across it for a similar result but fairly equalized (requires more 1/2 inch connectors though).
I then punctured the 1/2 inch line with the 1/4 inch connectors wherever I needed mini sprinklers for the fruit trees. I liked the mini sprinklers because they are adjustable in distance/amount of water. I am placing one on each side of the roots. I may have to add more as the tree grows.
Making the puncture was difficult after my hands got tired. I found the bottom of the sprinkler stake punctured much easier without breaking connectors. For getting the tubing on the connectors, you can heat it up, but I just twisted them on a few at a time.
For raspberries, I stretched some emitting tubing from the kit with emitters every several inches to water them all along the trellis row.
Since I only have a few grapes, I just added sprinklers to these, but any emitter will work too. The kit included many different emitters for more gallons per hour to experiment with.
I attached the tubing to the hose bibb with the kit’s adapters and will hook this onto a timer for automating the watering. You may have to run it for hours depending upon what emitters you are using. If you really want to get fancy, they make timers that can run certain lines at different lengths of time for precise watering. Since I used mini sprinklers, these can be adjusted to provide more or less water depending upon how the plants respond.
Once you are confident your watering is set up, you can mulch over the top with wood chips to cover up the lines so they are not tripped on. But take a mental note of where it is in case you have to add more emitters or dig near it.
Every few days at the start, check on your plants and feel the soil before the next watering. Does it feel too wet or dry? Or is it moist and just right? You can get water gauges for this, but you can learn the feel of how wet soil should be. It should be clumpy but not soupy. Swap out emitters or adjust them if possible to water all along tree or plant roots. Emitter tubing is a great option for running through large areas of plants. You can even zigzag or coil it up around something in need of a lot of water.
And just like that the food forest is watered! This setup should take little maintenance and keep your forest lush and producing juicy fruit and veggies through the dry seasons.