Drought friendly watering techniques

Considering that our California drought keeps getting worse, I’m looking for ways to use as little water as possible on my trees. I have a small urban yard in Berkeley, CA with 12 fruit trees: 8 planted last year, 2 established, and 2 in pots.

My yard is heavily mulched and that goes along way, but now that it’s been almost 6 weeks since the last rain (and 3 months since a real storm) the soil is getting a little dry. I already save my shower water while it’s warning up in a 5 gallon bucket but that really doesn’t generate much extra water.

I’m looking into:

  1. Laundry water discharge systems which can be installed without a permit in Berkeley. I could probably get about 60-80 gallons per week from this but it sounds involved.
  2. Rain barrels. Obviously this only works if we actually get rain, and even then it seems like an extra 200 gallons or so wouldn’t last very long over the long dry season.
  3. Long, deep soaks. I already do long deep soaks separated by long periods without water following suggestions I’ve read elsewhere. Seems to be moderately effective. Last year I could go over a month between waterings.
  4. Another option I remember reading about but haven’t been able to find information on again. I’ve read about people drilling holes along a length of wide PVC pipe and burying it vertically in the soil. When it’s watering time they pour water into the top of the pipe at ground level so the water is able to penetrate deeper thereby being less susceptible to evaporation and encouraging deep root growth. Anyone heard of this?

Anyway, just looking for the most cost effective and simple solutions out there. Appreciate any thoughts you all may have.

Chris, I’m down in S. California, where the drought is worse, and temps are hotter for longer. Yes, mulch is essential. I run my drip systems under the mulch to reduce evaporation as much as possible. As to long, deep soaks - you have to know where your tree’s feeder roots lie. If you’re running your water to soak down 5’, and your feeder roots reside in the first 2’ of the soil, then you’re just wasting water. Commercial citrus growers figured this out, and now recommend 18" of soak penetration. If you can recycle your grey water, that will go a long way. They make it ridiculously difficult here in California to recycle grey water, while talking out of the other side of their mouths about water conversation. I find this baffling. If you do opt to recycle grey water, take into consideration what you put down your pipes with regard to soaps/detergents. They should be bio-friendly or biodegradable. Easy enough to find with laundry detergents, as a lot of folks are using laundry grey water these days to recycle to their yards. Just remember to divert to waste when you use bleach in your laundry. It probably is the most promising of all water conservation techniques you could use. Trying to capture our elusive rain water would require some significant tanks to really capture enough to be of value, and that would also entail a filtration system, and a pumping system. Very, very expensive to retrofit into a home (we looked into it).

HQ - regarding gray water, I’m most interested in the laundry specific system because Berkeley doesn’t require a permit for them. Whole-house gray water systems appear to cost in the 10-15k range from the little I’ve read on the subject and rules it out for me.

Regarding deep watering… Your comment is interesting. I’ve read several other places that slow drips for an hour at long spaced intervals are much more effective than shorter intervals aimed at just the top layer of soil. I suppose it’s a question of how deep is deep enough. I’ve just been following time suggestions I found online and don’t know how deep it’s actually penetrating. Maybe that only gets me a couple feet down.

One more follow up… How deep are the roots of an established tree? I would have thought the roots would be far deeper than 2 feet.

In my place in the country I have the drain from the washing machine running directly out to my pecan trees. They do really good that way. I also have a friend that uses the PVC pipe buried like you talked about and he said it works really well. He just fills it up to the top and then lets it soak out and his trees do really good.

Insteng - Good to hear I didn’t make that up! Do you know how deep and how wide the pipe is? How many pipes are around the trees and how far from the trunk?

Chris, “deep watering” is relative. It depends entirely on the trees you’re watering. Citrus trees, for example, even mature ones have feeder roots that reside in the top 18" of the soil. Their tap roots will go down deeper, but their feeder roots are in the first about 2’ of soil. So, it depends entirely on whatever rootstock your stone/pome fruits are one. If you deep water beyond the feeder roots, you’re simply watering your water table :confused: So, do a little homework to see where those feeder roots reside, then start testing how long it takes to get the water deep enough to the lowest feeder roots, but not much below that. You may need to water longer during the hotest summer months, and of course, much less during the winter.

Patty S.


I agree generally with your advice but the tap root will have feeder roots as well. If it didn’t it would die or at least not be functioning. All functioning roots have feeder roots at their tips.

That said if heavily mulched to control losses to evaporation then wetting to about 18 inches is a good way to go. Pushing the water deeper on a regular basis invites losses below the root zone. Hopefully winter rains will refill the deep profile and flush out salts.

If soil is free of rocks the depth of water penetration can be determined with a metal rod. Right after irrigation wet soil will be soft and the limit of wetting will be like hitting concrete.

The upside of limiting water as much as possible is sweeter fruit for species with some drought tolerance like citrus, stone fruit, figs, and grapes. Berries don’t generally fit that group.

Fruitnut, the 18" is based on citrus roots, not stone/pome fruit roots. Citrus feeder roots the vast, vast majority are in the 18" of the surface soil. Many studies support this, and the new thinking with “deep watering” of citrus, based on UC Riverside’s research is to only take water down to 18-24". Water is so extremely precious (and expensive) here, it is good to know just how deep to water. Now, for stone/pome fruits, this depth may be different. And, it will be for sure based on rootstocks. So, back to what I said - do the research - know where your feeder roots reside, and water accordingly, but not beyond. I just a cheap plastic covered plant stake or a piece of skinny rebar to check my soil moisture. Not fancy, but it works well. And yes, my soil IS concrete is not moist, lol! And, I don’t adjust my stone fruit watering times as I head into my warmer spring/summer, which is my water of slowing water restricting my stone fruits as they ripen. It has worked very well. My fruit is very sweet and rich. I just have to watch not to over do it, and water stress my trees. If I have a heat wave during that time, I will increase my watering just a bit. I have it dialed down pretty far right now, so going down daily and looking at the trees. And, we can’t count on winter rains, sadly I had one really good soak. The rest of our rain was pretty light. And, citrus does not seem to respond well to water restrictions. It causes dried out fruit vesicles. Icky.

a source of free and clean water that many people dont even know about is your central heating and air conditioning system. Actually any AC system for that matter or de-humidifier. All central AC systems have a coil that condenses water and usually drains to a near by drain. I set up a system to collect that water and was catching at least 4-5 gallons of water per day that would normally go down the drain.

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Let me make sure I’m understanding that the laundry gray water is ok for my plants? Will it change ph?

That’s the idea. From what I’ve read as long as you don’t use bleach and stick to the natural/biodegradable detergents you’ll be fine. The only caveat I’ve seen is that it shouldn’t go on the edible parts of veggies and whatnot growing in your gardens. In the root area is fine though.

Not sure about the pH aspect. I think someone said it might not be great for blueberries etc. On the while it didn’t seem like people have issues with it.

Patty didn’t you talk about citrus surviving nearby without irrigation due to deep water? If that’s the case the feeder roots would be deep where the water is. Many trees can survive fine with no rain or irrigation if there is a water table in the root zone. Natures version of a self watering container.

Some cover the surface of self watering containers like Bill’s Figs. I imagine you’ve seen his setup. Feeder roots in his setup would be in the capillary zone above the water table not in the surface soil.

So yes feeder roots are mostly in the surface soil because that’s what we wet when we irrigate.

Sadly, A/C condensation can contain heavy metals such as lead. Hard to say to what degree. To be safe, I use it only on ornamental plants.

My pool, lawn and fruit trees all need water. There just isn’t any way around it. I maximize water usage as much as possible. Mulching is the biggest help, water very early in the morning, etc. For thirsty veg & melons I use EarthBoxes, which I fill solely with gray water. The EBs lose very little water to evaporation.

Starting this year in the raised veg beds I’m going to use ollas. I picked up three this past weekend:

Dripping Springs OLLAS (Clay Pot Irrigation)

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Yes, an aquafer that runs behind my house, but I wouldn’t say it’s “deep”. It is the natural drainage area of the 157 acres behind my house. And, plants will try to find that water, so I’m betting that that section of the orchard probably has abnormally deep roots. Just to survive. But, truly, if left to nature’s design, citrus trees have shallow feeder roots. This has been studied ad nauseum in the state of California because of the cost of water. So, we’re not artificially causing feeder roots to remain shallow. They simply are, naturally with citrus :slight_smile: Just like avocado trees.

Rain falls on surface, roots start from surface equals more feeder roots in surface layers. It’s that way for most everything.

Well, sort of :slight_smile: Rain falls abundantly in certain areas. Such as the tropics and sub-tropics, so plants that naturally grow where water is abundant tend to develop more superficial feeder roots. Such as citrus and avocados. Plants that grow in areas with less frequent rain tend to grow deeper feeder roots. Like an Oleander. If anyone has attempted to dig up an Oleander has found out.

In emergencies, light waterings are actually more effective than deep ones as far a bang for the fluid ounce. You can keep trees alive with less water by applying more frequent light waterings.

I don’t use a lot of laundry water since switching to a front loader that only uses a few gallons a load. My dry well stopped working years ago and although I’m not careful about bleach or using natural laundry products, the fruit trees with roots in the area where this water floods are the most vigorous on my property and were even when they were being doused with a couple hundred gallons of grey water a week.

I think P content can be a problem if the grey water completely saturates the soil . You might want to be sure to use low phosphorous detergents but I doubt it is necessary to go all natural unless you want to.

Anyone can attach a hose to a washing machine outflow outlet and simply move the hose around or put it in a storage container. You don’t have to be at all handy to set up such a system.

Laundry discharge “systems” are common here where (until 2017) everyone has been on septic systems. Most people simply have pipes that divert laundry discharge into their yards in some random place away from the house (my neighbor to the south has created a “swamp” behind their house…).

I had a plumber come in and fit a pipe through the exterior laundry room wall for an alternate drain which leads outside to a valve that either sends the water into a 32 gal trash can or via pipe to a hidden french drain I dug down the middle of my net-house where I grow blueberries and raspberries in containers.

So far so good. Then we got new appliances. Now we use about 32 gal/wk (just two of us here) for laundry, bleach load included. I use a liquid “eco” detergent from Trader Joe’s and standard chlorine bleach. This water I distribute (by hand). It does not go far (obviously).

For people thinking about piping this water directly to the plants, be aware that you need really good filtering. I use a fine paint strainer bag on the discharge pipe (which I have to clean every week) and still my watering cans clog up periodically.

As to the bleach, we have a retired Ag prof here in our CRFG chapter who has used laundry water (all of it) on his orchard for many years with no ill effects on the trees (or him!). I would not use such water on pH sensitive plants like blueberries.

So I use the water now mainly to try and keep some beloved ornamentals going (food for the soul, rather than the body) and to supplement drip irrigation for new little trees. But as I said, thanks to technology, there’s not much water to use :disappointed:

Collecting other household grey water is quite a task involving replumbing and permits which may become easier to get in California as this grim drought progresses. Then, since grey water does not store well, you also have to look at a good distribution system (other than a watering can…) to get it where you want it.

We all will need to rethink a lot.