Wednesday Vignette – what does drought tolerant mean?

Euphorbia rigida - heat stress

There are two Euphorbia rigidas in this planter from last year. Whatever water was doled out should reasonably have reached their roots in equal measure – yet they look so different! Not the best illustration of my point, but you get the idea. One did great – one did not. Why is that?

Several blogger friends have recently been writing Winners and Losers posts, touting the virtues of plants sailed through this summer’s adverse conditions, and lamenting which ones didn’t (here and here). Heaven knows it’s been a hot summer, and our spring was so miserably dry. Today, I had a very interesting conversation with Tamara of Chickadee Garden fame. We were talking about how – although some plants are listed all over the internet as “drought resistant” they truly aren’t holding up at all, without some liquid help. For example, Susan (in the first link) remarked that Echinaceas don’t at all live up to their reputation of purported toughness. This prompted the thought that lots of things have changed since the internet (which we now all rely so heavily upon) was first instigated back in the early 90’s. Maybe Echinaceas truly were drought tolerant back then. I mean, before our summers all of a sudden had 30 days over 90F, and we had to water excessivly in June. Tamara, who is of the organized sort, added support to this notion. She had looked in her garden diary, at an entry from 2015, where she had jotted down that we had just broken a heat record with 15 (I think it was) days over 90F. That was only three years ago, and this year, a mere 15 days of that kind of heat sounds quite benevolent, by comparison.

I wonder what this means? At the rate we’re going, maybe by 2023, we’ll have 60 days over 90. And, in another ten years, maybe any summer temps under 100F will feel cool? I don’t know, but my point is that the concept of “drought tolerant” likely is a moving target. Today’s Manzanitas might be tomorrow’s pansies? Well, hopefully not, but you know what I mean.

About annamadeit

I was born and raised in Sweden, By now, I have lived almost as long in the United States. The path I’ve taken has been long and varied, and has given me a philosophical approach to life. I may joke that I’m a sybarite, but the truth is, I find joy and luxury in life’s simple things as well. My outlook on life has roots in a culture rich in history and tradition, and I care a great deal about environmental stewardship. Aesthetically, while drawn to the visually clean, functional practicality and sustainable solutions that are the hallmarks of modern Scandinavia, I also have a deep appreciation for the raw, the weathered, and the worn - materials that tell a story. To me, contrast, counterpoint, and diversity are what makes life interesting and engaging. Color has always informed everything I do. I’m a functional tetrachromat, and a hopeless plantoholic. I was originally trained as an architect working mostly on interiors, but soon ventured outside - into garden design. It’s that contrast thing again… An interior adrift from its exterior, is like a yin without a yang. My firm conviction that everything is connected gets me in trouble time and time again. The world is a big place, and full of marvelous distractions, and offers plentiful opportunities for inquiry and exploration. I started writing to quell my constant queries, explore my discoveries, and nurture my curiosity. The Creative Flux was started in 2010, and became a catch-all for all kinds of intersecting interests. The start of Flutter & Hum at the end of 2013 marks my descent into plant nerd revelry. I occasionally contribute to other blogs, but those two are my main ones. For sure, topics are all over the map, but then again - so am I! Welcome to my blogs!
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25 Responses to Wednesday Vignette – what does drought tolerant mean?

  1. bergstromskan says:

    Interesting and logical point. Also a scary view.

  2. Peter Herpst says:

    Interesting that two of the same plant responded so differently in the same pot. On the positive side, I’ve always wondered what it would be like to live in California. At this rate, we’ll soon know.

    • annamadeit says:

      Isn’t that weird? Yeah, I think we down here in Oregon are closer to CA conditions than you guys are. We were in Seattle a week ago, and were marveling at how pleasant walking around the city was. That 10 degree (or so) difference is just magical!

  3. Not to contradict, but the record for 2015 was 29 days over 90, and that’s the record we just broke with 30. So while the pattern of more heat does seem to be the way of the future hopefully we aren’t going to get there as fast as you fear. Hopefully.

    My WV…

    • annamadeit says:

      You know, that contradiction of yours just made my day! I bet I just misrepresented what Tamara told me, and apologize for doing so. I suppose we’ll get there in the end, but I SO appreciate a slower pace. Phew!

  4. Kris P says:

    I think you’ve hit the proverbial nail on the head, Anna. I’ve long contended that what’s considered drought tolerant in one area (like the PNW) isn’t so much so in another (like SoCal). However, it appears that horticulturalists and botanists are only just beginning to evaluate the degree of drought tolerance. I think of Olivier Filippi as a pioneer there and now it seems that entities like UC Davis and the California consortium that’s assembled the “Water Use Classification of Landscape Species” (WUCOLS) have moved that effort forward dramatically. WUCOLS already rates selected plants by level of drought tolerance for specific areas within California but I suspect it’ll be a LONG time yet before plant growers and sellers get on board to publicize these classifications. In the meantime, labels can only be seen as a starting point in individual gardener assessments.

    Here’s my WV featuring what’s proven to be a drought tolerant plant here:

    • annamadeit says:

      Good to learn about WUCOLS here – thanks Kris! I’d never heard of them before, but will keep an eye out now. If I ever move, drought tolerance will be at the top of my list for plant criteria. My current garden is as flamboyant as can be in terms of water use. Its creation has been ALL about learning about what plants do, and how far into shade I can push sun lovers. I will graduate to water use next. 🙂

  5. Alison says:

    I was really surprised when I read Susan’s post about her Echinaceas not being drought tolerant. For me, they are. I have some in my garden that are fine and I haven’t watered them at all this summer, not once. Not by sprinkler, not by watering can, not by handheld hose, not even my own sweat or spit. They’re flowering in western sun and the foliage is not the least bit brown or crispy. We’ve had a few days over 90, not as many as Portland, but some (I haven’t kept track). I have some enormous clumps of Panicums in the same bed that are about to flower that have been similarly abused.

    • annamadeit says:

      That IS interesting, but then again – like you said – we are a lot hotter and drier down here. I bet that’s what’s hanging in the balance. It will be interesting to watch the development as things increasingly heat up and dry out in summer and get wetter and windier during winter. We need to come up with some really great way of capture/mediate the intense rain falls we get WHEN we get them. Not fond of either of these extremities…

  6. Tina says:

    Of course, I garden in such a different climate, but our Echinaceas are good in our long hot summers. The go dormant and any premature deaths seems to be more about soil than heat. That said, I know what you mean and your point is valid. I think we’re at day 49 of over 100 and while everyone always thinks, “oh,Texas is always hot” that’s not really true. Yes, there were usually, not always, a couple of days over 100–in August–but now, each summer is a scorcher. Grim, indeed.

  7. Evan says:

    There are so very many factors involved in plant performance, including how they perform in drought. Air and soil temperatures, soil type. water table, rainfall patterns, how well-established a plant is. What is drought tolerant in one part of the country, like Echinaceas in the Midwest where they have scorching but humid summers with thunderstorms, may not be on much of the West Coast, where we don’t just have drought, we have a natural summer dry season. Even along the West Coast, the cooler areas, especially if they have a high water table, a soil type that allows a plants roots to reach further and faster, higher fertility, etc. can consider plants drought tolerant that the hotter, drier parts of the west cannot. My echinaceas are hanging in there for now, but none of them are in the driest parts of my garden and they’ve all received at least some water. Still, the leaves of several are crispy and most of the flowers are browned around the edges. It might be more useful to think in terms of “climate-adapted” plants rather than “drought-tolerant” plants. We should be seeking plants adapted to our summer-dry climate, instead of the more nebulous “drought-tolerant” label. Unfortunately, that requires more homework and knowledge of where plants grow in their native habitats.

    • annamadeit says:

      It is indeed more complex… You’re right, of course… climate adapted sounds like a far better term to use. Get this – I even started watering my huge Southern Magnolia. I like to think it drops less leaves after I did, but I could totally be imagining that.

  8. FlowerAlley says:

    This has been my hardest summer ever as a gardener. I am older. My garden is more complex. BUT there is more to it than that. Lord help us.

  9. Pingback: Wednesday Vignette(s): Don’t make me miss winter! | A Writerly Garden

  10. Well I am late to this party but I wanted to pop in about the Echinacea since it seems to be one of the most notable surprises. That poor plant is located right at the drip line of my 50-year-old Cornus florida, so it’s very likely that root competition is a significant factor. I have another Echinacea – one of the hybrids with white flowers – which made it through the summer much more easily – it’s not in a root competition zone and I also threw a bit of water at it.

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