Archive for the ‘water’ Category

I’ve had a few conversations recently that revealed to me what a dumb thing it is to call a plant “drought tolerant”.  Wikipedia gets this right technically, but leaves us without enough to apply the information: “Drought tolerance refers to the degree to which a plant is adapted to arid or drought conditions.”

Well, okay – so when we say a plant is drought tolerant, what the heck does that mean?  It means that plant has some degree of adaptability to drought.  But here’s the thing – how much adaptability?  How do I use this information?  What does this plant do in response?

2014 mid march 040

Iris douglasiana

Saying a plant is “drought tolerant” is like saying there is a temperature outside.  Is it cold, warm or hot?   See what I am getting at?  “drought tolerant” only means that there is some degree to which the plant may tolerate (not die immediately) a shortage of water.

More information is needed: enter WUCOLS.  I won’t bore you with the details and technical stuff behind WUCOLS, they do well enough – read through their website.  Not bored yet?  Good!  Now read through the rules on WELO, the California ordinance for water efficiency in the landscape.  Bet you’re bored now.

The deal is that these classifications in WUCOLS mean something.  They quantify how much water a plant wants in a particular region of California.  This does not take into account sun/shade exposure, sun orientation, wind, soil type, or any of the other factors involved in meeting a plant’s water needs.  It is not a perfect tool, but it is the best thing we have going.  WUCOLS isn’t the only resource, you can get information from nurseries and books also, but it is the most helpful hydrozoning tool I use.

In WUCOLS, the classifications are “very low”, “low”, “moderate”, “high”, or it may say “inappropriate” or “unknown”.  This is pretty self-explanatory, but what is most interesting here is that ETo is a reference point – a baseline of sorts.  So a “high” water use classification means 70-90% of the water needed to keep a 4″ tall cool season turf VERY well watered and super lush, or to put it another way, the “high” water classification is 70-90% of a whole lot of water.

I indulged online – I pulled up an article on “drought tolerant” plants from Sunset magazine.  Of their 12 plants in my home town of Oakland, one was classified by WUCOLS as “very low”, one was “moderate”, and the rest were “low”.  Nassella tenuissima / Mexican Feathergrass is listed as an invasive plant by PlantRight and should not be used at all, but WUCOLS isn’t about invasiveness, it is about water, so shame on Sunset!

It is bad juju to mix water use classifications.  If you absolutely must, then the classifications should be next door neighbors – so “low” and “moderate” is kinda okay (provided you irrigate at the higher amount), but “moderate” and “very low” is no bueno.

Next I went to the “drought tolerant” poster child:  succulents.  Low water use, right?  Drought tolerant?!  erm…. no.  Again, WUCOLS demonstrates my point.  In the plants WUCOLS lists as succulents, the same 3 classifications are included – very low, low, and moderate (screen shot is just of the alphabetical early birds, I didn’t pick favorites here).  So much for that assumption.

succulents wucols

So really, drought tolerant is anything that will grow with less than 70% of a boatload of water.  That could still an incredible amount of water, folks.  Granted, the lower classifications are pretty good and some plants truly do have a relatively dry footprint, but all plants need extra water during their establishment period, that is a post for another day.

Oh – and about those drought tolerance adaptations emphasized in the first paragraph:  a drought tolerant plant might go dormant, drop all or some of its leaves, wilt, or shrink in size in times of stress (the drought they’re tolerating) as a way of coping …. and if not watered in time, drought tolerant plants die.  Tolerance is about not being dead yet – it has nothing to do with living well, being healthy, or looking good, it is about living to drink another day.

Thanks for listening!





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You’ve heard that you should water trees deeply and infrequently, right?  I take that approach a bit further and use it for everything – trees, perennials, roses, everything.  I’m careful with my water anyway having grown up in Los Angeles during the 70’s drought when we let our yellows mellow, removed or reduced lawns, and collected shower water.

See, we’re in for some serious growing pains while we struggle to understand and adjust to mandatory water restrictions now in 2015 – I don’t need to repeat the advice, you already know it (ditch the lawn, add compost and mulch, etc).  But what we need to be doing is more than just using less water, we need to use water more wisely – to help our plants fend for themselves better.  I see water as a training tool and my plants as smart, but slow.  They can’t fetch and training them to do much of anything takes years.

As of my last water bill, I’m down to 36 GPD (gallons per day) including landscaping.  Before you bow in awe to this amazing feat, you should know that I irrigate my garden a little differently than most and I’m not watering anything I don’t want to keep.  Let the rest die, they’re out of here anyway.  april 2014 Magnolia installedHere’s where I water differently:  I bought a 15 gal. Magnolia ‘Black Tulip’ (that baby green tree in the background left-side).  It is rated as having “moderate” water needs in Oakland by WUCOLS.  Moderate isn’t exactly water-wise, but I’ve got a theory…..  and so far, so good.  I planted the tree a year ago this month.  At the same exact time, my client in Mill Valley had three planted (guess whose idea that was).  Their landscape contractor did exactly what they usually do – they amended, fertilized, and watered the hell out of those trees.  My client’s trees bloomed and grew and leafed out beautifully, gained stature nicely.  Mine didn’t.  Luckily for them, theirs are next to a lawn that I’m sure they’ll keep as long as they can, where I have no lawn.  Below is a better shot of mine last May (1 month after planting).

may 2014 MagnoliaI planted mine with a bit of compost, watered it in well that first day, and walked away.  It looked fine for a while, then it got all stressed out and started dropping leaves.  I watered it again, a nice soaking, and it threw out some new leaves.  We did this all summer:  I kept an eye on it, watering only when I found signs of stress in the leaves, but then not again until I saw more stress.  It was nerve-wracking.  The tree did not visibly thrive, and it sure as heck didn’t get much bigger.  I’m pretty sure it would slap me if it could…. but it survived.  While it was dormant over winter and I held my breath to see how it would do come spring.  This spring when it started blooming, I was delighted with how many (albeit smallish) flowers there were on my young tree, and now it is leafed-out for the season.   I’ll be doing the same this summer, soaking the presumably larger root-zone, but as seldom as possible.  I’ll also be adding more compost on top (not working it in, that’s the worms’ job) and maintaining a good layer of mulch over that.

I believe that what I am doing will be better for my tree’s long-term durability.  I believe that I gave it reason to throw energy into its root system in search of water, and that I rewarded deep root growth instead of fast, exciting foliage and gains in stature.  Over the winter, its root system likely continued to dive and while I watered, soaking further and further down but less and less often, we’re working together to train this “moderate” water needs tree to survive more like a drought tolerant tree.   Here it is today, not much bigger, but doing just fine:

150413 magnolia tree 015I don’t water fast enough that it trickles off, doing by hand what irrigation designers call “cycle and soak”, making sure that the water goes into the soil and nowhere else.  I’m also taking advantage of the few light rains we had to water further than the rain itself went = deep watering every time.

I can’t tell others to do this, the tree looked like hell that first year of establishment and I think most people wouldn’t watch closely enough nor would they enjoy the experience (even I was a bit nervous).  We’ll see how things go this summer, but I can tell you that I don’t water much, maybe once a month?  I avoid watering if it is overcast or cool outside.  I look closely at my plants in the most stressful times – when it is blazing hot, sunny, and/or dry and windy.  If I see stress, I’ll water.  If not, forget it.  I’ll keep you posted on how things go this summer.

150413 roses and MagnoliaThe most impressive thing, though, is what I noticed in putting together this post – look how much my roses LOVE this treatment – they get watered only when the tree gets watered and I have yet to see them look even a little stressed.  You can see the change best between the second photo and the one above.  They’re the hybrid tea ‘Stainless Steel’ (my favorite).  Here’s the original one (now on the right in the photo above) blooming in my old garden in Alameda in 2010 and again in 2012:rose 'stainless steel' jun 2010Rose 'Stainless Steel' full on 2012

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