Understanding drought and drought tolerance

I have grown a lot of plants that claim to be drought tolerant.  About 95% of them die in my conditions.  For a person living on the 'wet' west coast, it is discouraging that not even drought tolerant fruit and veg can survive here without excessive watering.  And yet, other plants said to be high water users, do just fine with little or no irrigation.

Looking at drought tolerance, I realized that this means many things to different people.  But that's okay, I thought, because everyone knows what 'drought' means, so we'll start there.  It means more than two months without rain, right?

Apparently not.  

It is surprising how many definitions of drought are out there.  The Dry Gardening Handbook by Filippi talks about drought as "hydric deficit" when the plants "loses more water by evapotranspiration than it can absorb through its roots."  (p40).  Others talk about drought as "a prolonged period of abnormally low rainfall; a shortage of water resulting from this." (google).  


What do we mean by drought?  More importantly, what do we mean when we say a plant is "drought tolerant"?  

I wonder how long after planting do your plants die?  Dought tolerance typically applies to plants that are well established, with deep roots, not to newly planted.

About the only type of plant that can survive for long, before it has had a chance to send down deep roots, are your succulents, Cacti, etc.

I think it is a lot more complicated than being well established and their root system.  Although, that is part of it.

My own plants start dying about 2 to 3 months after the rains stop.  Some, however, last the full summer without rain (roughly 6 months).  Some are annuals, some perennials, some shrubs, some trees, some fruit, some veg.  Some have been established for 10 years, some only in the ground a few months.  

However, I've noticed that the title "drought tolerant" has nothing to do with the survival capabilities of the plants.  I now grow winter squash, amaranth, sunflowers, and even beans without water or rain.  It looks like this year I should get a cucumber and hot pepper crop as well.  These aren't 'succulents, cacti, etc.'  These are all crops that are said to be not-drought tolerant.  And yet, when I grow so called "drought tolerant" plants, they can't take it.  


What I'm looking for with this thread is a more general discussion on what drought is and what makes people call a plant 'drought tolerant'.  

Amen to this topic. I've been thinking about this recently considering we are in the midst of a hot-spell where everyone is complaining about their plants.

r ranson wrote:
What I'm looking for with this thread is a more general discussion on what drought is and what makes people call a plant 'drought tolerant'.  

What is considered a Drought?

I can give you what I would call "a farmer's perspective" from the stories I've been told of yesteryear. A drought to a farmer in my area might be one where there was a bad or failed crop, due to little or no rain. Example: in 2002 there was apparently a drought bad enough that made the pasture grass go dormant and every farmer with cattle in a 20km radius had to move them to a local pond because all the streams and dugouts dried up. They also had to feed the cattle last year's hay for the entire summer and then buy hay from out of province just to get through the winter that year. Here's an Article about that year's weather.

Based on that loose definition, if any plants could survive that scenario and produce value by the end of the season via money/sustenance, they'd probably be considered a drought-tolerant plant.

We could also come up with a % system, since we are talking about tolerance and not resistance, where if there was only a certain % of rain compared to the yearly average, it would be considered a drought. For example, if I get 27cm of rain in an average year, we could say anything below 5.4cm(20%) of annual rainfall is a drought. This means that any plants that survive at or below the 20% mark can be considered drought-tolerant.

2017 example of drought-tolerance

In my area this year:
May = 0.9cm of rain
June = 4.6cm of rain
July = 2.6cm of rain

To put that into perspective, in August of 2016 alone, there was 10cm of rain. I would say that if in August 2017 we get no rain, this would be considered a drought year - if only a minor one.

I didn't water my plants from May 14th until around June 25th when I noticed I was starting to lose too many of them for my liking. Since July was pretty brutal with almost constant 30'C temps, I've softened up and watered the plants once every 10 days. By comparison, the native serviceberries, chokecherries, hawkthorn and crabapples are all producing in abundance despite the lack of water - they were even early to fruit this year.

I think drought is always going to be relative. Drought in western Washington is different than drought in western Texas. To me, drought (which really looks weird written out to me, drowt? drout?) means a growing season that has significantly less precipitation (maybe 30 or 40%?) than usual for the area. As such, a 'drought tolerant' plant would be a variety that can withstand 30-40% less precipitation than its peers. So a drought tolerant sunflower and a drought tolerant melon are going to have vastly different requirements. Also, a drought tolerant annual is going to have different characteristics from a drought tolerant perennial. Ultimately I think that it is just a relative term so if you are planting 'drought tolerant' varieties from vastly wetter environs they may not do near as well as non-drought tolerant varieties from your area.

What seems to happen a lot is people take 'drought tolerant' plants that grow natively in sandy soil, plant them in clayey soil, expect them to remain 'drought tolerant', and then are surprised when they wilt and die.  This is actually a pretty predictable outcome, and you only need to appreciate a few things to understand why:

First, realise that the texture of your soil has a massive impact on water availability to the root system.  Water moves very slowly through clay and very quickly through sand.  Roots can't take up more water than has reached them.  It doesn't matter how much rain falls on the surface — it's how much has percolated down to the root system that matters.

Second, remember that short/light showers (or an equivalent irrigation regime) will only provide water to the top few cm of soil and thus the top few cm of roots.  The same layer is extremely prone to evaporation and drying, so sunny dry days will quickly warm the soil and evaporate the water and get you close to (or below) the wilting point.  Long showers, whether light or heavy (or an equivalent irrigation regime) will give time for water to percolate deeper into the soil, supplying moisture to deeper roots, and bank up moisture in an area that is less likely to dry out the moment the sun makes an appearance.

Third, appreciate the fact that sand has large macro pores between grains, thus allowing root systems to grow into them quicker and, when they are filled with water, absorb more of the water faster. Clay has much smaller macro pores, which retards the rate and extent of root growth, and also limits the amount of water that can be absorbed when they do fill up.

So, 'drought tolerant' plants are simply those plants that are able to get their root systems into parts of the soil profile that contain moisture — despite relatively moisture-free above-ground weather conditions — and are able to extract that moisture at a rate that is adequate for their needs.  If those plants evolved on sandy soil, then they are adapted to quickly penetrating large macro pores with their roots to create a large moisture catchment area, and are tuned to quickly absorb large amounts of water from infrequent rain events.

Humans see a plant growing in a (sandy) desert that obviously experiences frequent droughts, simplistically label it 'drought tolerant', and then naively assume that they can grow it in completely different soil and it will remain 'drought tolerant'.  That's just not true.  'Drought tolerant' plants that evolved on sandy soil are fundamentally different to 'drought tolerant' plants that evolved on clayey soil.

I agree with the definition of drought that says around 20% less precip than normal for several months. About soil types, yes roots may grow slower in clay soil, but clay with good humus content stores an amazing quantity of water.

About drought resistance --don't under estimate soil pH. The proper pH is key to a plant's ability to use the water in the soil. Locally adapted seed strains are much hardier because of this. Saving our own seed year after year has been key to drought resistance as the strains adapt to our soil conditions. I suspect many nurseries or seed co's call things drought resistant if they will survive 2 weeks without water. That is the Eastern US definition of a drought for ag purposes.

Weeds tend to do fine.  Amaranth purslane have zero issues.

This is very interesting about soil types and drought.  I never thought about clay as I have silt in one area and I have something that is a mix of dust-like sand and rocks (glacial deposits).  The clay seam is about 12 feet down from the valley surface, so I just pretend like it's not there.  Improving the organic matter in the soil is an important part of my plan to grow without irrigation.  


But mostly, I'm still having trouble understanding drought.  For example...

George Hughes wrote:I agree with the definition of drought that says around 20% less precip than normal for several months.  

What is 20% less than zero?  My normal rainfall is zero from about May 1st to about October 15th.  If zero is normal, does that mean I have no drought?

Kelly Osborn wrote:Weeds tend to do fine.  Amaranth purslane have zero issues.

Mine are starting to die off in the dryer parts of the property, late this year because of the wet spring.  However, the grain amaranth I've been acclimatizing to my conditions is still growing strong.  

For the arid west, I think we need to adjust how we think of precipitation. Instead of thinking of it as water that falls from the sky on our crops, we need to take a longer view and think about the whole water year. Specifically, I'd pay particular attention to snow water equivalent (SWE) and depth of snowpack in the mountains in May. SWE will dictate how much water percolates down the mountains throughout the summer, while the depth of snowpack will dictate how long the water percolates down the mountains throughout the summer. Everything in our climate is built on this cycle of storing water in snowpack during the winter and spending it all summer as it slowly percolates through the mountains. Rotten logs on the forest floor absorbing water in November  might still be increasing the humidity of its surroundings come August if the snowpack was well structured like it was this year. Better snowpack means higher rivers, means higher groundwater levels, means wider floodplains, means increased humidity, means higher chance of thunderstorms in the summer. It's why Sacramento, which is hundreds of miles from the Sierras, gets greener in summers with better snowpack the previous winter. And why my lake has just started to go down in level, despite not really getting any significant precipitation since May. The snowpack is a giant water battery, and for the west, it's how we get most of our water in the summer.

So when I think of drought in the arid west, I think about bad snowpacks — either the winter wasn't cold enough or there wasn't enough precipitation. We've been getting a lot of AR events the past few years, which are super bad for snowpack — it melts snow in the middle of winter, wasting our battery right when we don't need it (plants are dormant, the ground is already wet). For other areas of the world, the hydrologic cycle is different, and they would interpret drought differently. I think "drought tolerance" is a similar idea — it's relative to whatever standard hydrologic cycle the seed breeder comes from. A drought tolerant Juniper might be adapted to conserve water and survive 5 years without adequate water, but a drought tolerant butter lettuce is probably just going to have a deeper root system that allows it to get a few more inches into the soil, allowing it to survive a week or two without surface irrigation.

In my view: there are many different types of drought, and many different types of drought tolerance. Junipers have adapted leaves that reduce the amount of evaporation, allowing them to survive on less water. Cacti have adapted trunks that can literally store water, allowing them to bank it up in wet times to save for the dry. Drought-tolerant Apple rootstocks have deeper root systems, allowing them to harvest water far below the surface. Drought tolerant grasses go dormant when it gets too dry, and wait for wetter conditions. I would qualify each of these plants as drought tolerant but each has a very different strategy for solving that problem, and each is adapted to a specific type of drought.

For the United States we have a site called the United States Drought Monitor that I find to be useful in understanding how to define droughts. See the attached image taken from the site showing the categories they use to classify an area as being in drought or not.

This site uses a combination of methods to classify droughts including soil moisture levels, temperature (above or bellow normal), stream flow data, precipitation levels, etc. Click here to go to the page on the site that has information about how they measure drought but really the gist of it is that it is very complex and tries to take into account much more than just precipitation for the given month. It is aimed more at farmers and foresters than smaller scale operations but I still find it useful.

So right now my area is setting records for the most days straight of no rain but at the same time we are not in a drought and are just starting to be classified as abnormally dry. This is due to how much rain we got earlier in the year up through June. Despite no rain in July and so far none in August we are still not reaching the D0 or abnormally dry classification used by this site. But this does not mean that my soils on my land are full of water but it does mean that the healthy forests around me and water bodies / rivers are all doing fine overall. If my place was fully established with food forests and healthy rich soil I don't think this dry spell would be any concern for me but as a new system I have had to water some plants. But I have noticed that plants that were planted no later than April and were given a very good layer of mulch are doing fine and have not needed any watering.

My soils are all clay and where I have not placed mulch it is just rock hard and grey (looks almost like concrete) but the areas I have improved are still moist and the plants are doing great with no watering.

I kinda think less in terms of drought - I let the scientists decide that based on all the factors the site I shared takes into account - and instead compare the amount of rain I'm receiving to the amount of recommended watering for a specific plant. This means that during the summers where rain is fairly rare here (average of 1.57" in total July through August but tending to be lower in recent years) I would need to water fairly often if I followed the normal recommendations. But my focus is instead on how much water I can bank from our wet season (every month except July and August most years) in my soils or in above ground storage. I'm focusing all my projects right now on building up the organic content of my soil to hold water. So far the native plants that I planted in January as bareroots have needed no watering (even some sensitive ones are having no issues) and have put on 2-4 feet of growth upwards and far more in volume. My non-natives are also doing great but only if they were planted no later than April and got a good mulch layer. I have had to water some plants that I planted in May and June to keep them going but even these I'm only occasionally watering to hopefully harden them off.

Looking at how everything has done this year at my place I have decided to follow a set of rules that I think will eliminate my need for watering.
- No plants planted after April.
- No plants planted in an unmulched area.

Bit simplistic but these have been the two biggest takeaways for me this year. Of course some annuals currently need to be planted later due to frost danger but I'm going to try to setup some season extenders so I can get all of my annuals in the ground by the end of April to eliminate any need for watering them too. I may do some annual planting in July or late summer to get the next harvest going for late summer, fall and winter but I'm still hoping that a good mulch layer and planting in established (at least 2 years old) hugel beds can minimize the need to water these plants. I may setup a rain water catchment system and just store the water from the spring just to help these late plants out. But my aim would still be to only need to water for the first couple weeks after planting the late plants.

As far as drought tolerance goes as a plant characteristic I don't really pay much attention to that. Instead I prefer to look at the habitat type that the plant naturally lives in and where that habitat is located - where is the plant native? Now for a lot of our cultivators this info is not really available due to how much we have changed the cultivated variety compared to the wild type. But I have still found you can get a sense of is this a plant that would naturally grow in a forest, on a forest edge, in a meadow, in an arid environment, around or in wetlands, next to rivers, etc. If you can get information about the soil type the plant normally grows in that is also great. There is a local nursery in my area that specializes in native plants and I really like their species descriptions. Here are a couple from their website:

Populus balsamifera (trichocarpa)   Black cottonwood
Exposure: full sun to partial shade
Soil moisture: saturated to moist
Transplanting success: high (both container-grown & live stakes)
Growth rate: rapid
Form: deciduous tree to 160 feet; roots are fibrous and branching, shallow or deep, and extensive

Pinus contorta var. contorta   Shore pine
Exposure: full sun to partial shade
Soil moisture: wet to dry
Transplanting success: high
Growth rate: rapid
Form: coniferous evergreen tree to 60 feet; tap root

Pseudotsuga menziesii   Douglas-fir
Exposure: full sun to light shade
Soil moisture: moist to dry
Transplanting success: high
Growth rate: moderate to rapid
Form: evergreen tree to 200 or 300 feet; tap or modified taproot, shallow or deep, widespread root system

With this basic information I can readily determine the general type of habitat that the plant will do well in and while Douglas-fir and Shore pine are both commonly listed as drought tolerant I find the exposure and soil moisture information far more helpful. But even though these two are very hardy trees I would not plant them later than April and I would much rather get them in the ground in January or February. For my restoration work (day job) I try to do as much of my planting as possible in October to give the plants all the time possible with only bareroots being planted in January and February (can't get those from nurseries until then).

If a nursery does not give this type of information then I will often look at the USDA's site (I'm sure there are other good sites out there) or an agricultural extension office just to get a bit more info beyond "drought tolerant."

I have planted in the last year close to a thousand trees and shrubs on my property and have only watered about a dozen of them. Out of the ones I have not watered I have only had them die when I did not give them a good mulch layer. I also have potatoes, zucchini, beans and annual flowers that have gotten no extra water and are growing great - well the beans got munched by some deer but still growing and producing with no extra water! Plus a good garlic harvest that I hope to expand next year. This is all in very poor soil that has almost no organic content and is mostly all clay - but using hugel beds, a good mulch layer and planting most of the plants very early in the year has worked great - I have not added any compost or amendments to the soil. Overtime, my soil should just keep getting better as the mulch and hugel beds age and the trees and shrubs get going.

Key to understanding what constitutes drought is what your normal climate is. As important as how much and how often rain falls is when it falls in the year.  The warm-temperate and subtropical zones of the world tend to be strongly seasonal as to rainfall, with a pronounced wet season and dry season.  The two common patterns are monsoon climate, where the bulk of the rain falls in the warmer months of the year (southern Florida and parts of the Southwest fall into this category) and the Mediterranean climate, where most of the rain comes in the colder months (mostly California and marginally further up the West Coast in North America).  Both plants (and sometimes varieties) and strategies well adapted to one of these climate patterns rarely do well in the other.  
     Another thing to remember is evapotranspiration is related to temperature.  I find that many things that need irrigation every other day at 95 degress will need it daily at 105.

Around here, drought tolerant is treated like xero scaping, which means once established doesn't require additional water, which often means natives, but many trees and shrubs can be adapted this way. I feel like landrace crops would provide a good understanding of location specific drought/low water tolerance. Once established, I have various roses, citrus, yarrow, salvias, trees, which require no additional water, including the drought years. So much seems to be dependent on what the plant is used to. I'm aware that some Californians trees suffered when they stopped watering their lawns, but, once again, because they were used to summer irrigation. I know of at least one northern california grain farmer who is doing dry farming, so it is possible. I would plant things and see what works, take seeds from what works, etc. Good luck.

I love all the ideas and tips in this thread for dealing with low and zero water situations.  Thanks so much for joining in.


I'm still a bit confused by this definition of drought.  There seems to be a theme that 'drought' means below 'normal'.

If we go with this definition, and my normal is zero, I'm not sure how to get less than zero precipitation.  So I don't get 'drought' in the summer?  Maybe there is a different word for this?  Please let me know what it is so I can use it when buying new breeding stock.  


Or maybe I'm asking the wrong question.  

I want to buy seeds that will survive to reproduce in my conditions.  If I can do that, then I can use them as a start of a landrace breeding project.  Even just plants that can produce pollen - that would amazing.  I'm just getting tired of spending money on 'drought tolerant' plants that can't even make it to June before keeling over.  This made me think that drought is not a standard term, or maybe it's not the right term for what I want.


I heard on the radio yesterday that due to unexpected heat, this one farm growing drought tolerant veggies only has to water an inch, every third day.  If 3 days makes a drought then I am seriously confused about what this word means.  

Kyle Neath wrote:For the arid west, I think we need to adjust how we think of precipitation. Instead of thinking of it as water that falls from the sky on our crops, we need to take a longer view and think about the whole water year. Specifically, I'd pay particular attention to snow water equivalent (SWE) and depth of snowpack in the mountains in May. SWE will dictate how much water percolates down the mountains throughout the summer, while the depth of snowpack will dictate how long the water percolates down the mountains throughout the summer. Everything in our climate is built on this cycle of storing water in snowpack during the winter and spending it all summer as it slowly percolates through the mountains. Rotten logs on the forest floor absorbing water in November  might still be increasing the humidity of its surroundings come August if the snowpack was well structured like it was this year. Better snowpack means higher rivers, means higher groundwater levels, means wider floodplains, means increased humidity, means higher chance of thunderstorms in the summer. It's why Sacramento, which is hundreds of miles from the Sierras, gets greener in summers with better snowpack the previous winter. And why my lake has just started to go down in level, despite not really getting any significant precipitation since May. The snowpack is a giant water battery, and for the west, it's how we get most of our water in the summer.

This is a great factor to think about.  I wish I my watershed included snow.  It always amazes me that snow from the Rockies can flow all the way to the Atlantic.  It really puts water into perspective.

I think that the term drought is in reference to climate, not short-term weather, so a drought is a lower than usual annual rainfall. Where I live, it also doesn't rain from May to October 15, and I don't know of any annual vegetables that can be planted during this time and not require additional watering. If I look out in nature, some things will stay green until it gets hot, but by now, everything is "California brown", except for trees. I do have some squash and tomato volunteers that do not get direct watering, but they are somewhat shaded. I am planning on saving seeds from them.

I would water sparingly, save seed, and in subsequent years, further cut back on water to see how little you can give them for them to still produce. Other strategies would be short season plants allowed to get a foothold prior to rain stopping, and then allowed to finish up without additional water. And any kind of hugelkultur, whether with trees or straw, so as to conserve the water in the land.

Sounds very like here.  The world is going very brown except in the remaining dew pockets.

Do save the seeds from the volunteers, that's where I started with the squash then I found some varieties that would cross with it that have success with germinating in cold soil.  I kept adding genetics from there, now I'm selecting for taste and ability to survive with neglect.  

I don't know of any annual vegetables that can be planted during this time and not require additional watering

I think vegetables, as they are sold in the store these days, can't.  But there is evidence they used to be - There are historical accounts of farms in my part of the world that did it.  

With a bit of earthworks to keep the winter moisture in the soil and some inspiration from this forum about landrace plant breeding, I have success growing winter squash, sunflowers, and amaranth with no water.  This is year two for those crops, with absolutely zero water in the dryest part of the property.  Last year was a dryer summer.  This year had a wetter spring but hotter summer.  It looks like I'm not far away from breeding beans, peppers and hopefully tomatoes that can grow in our summer with no irrigation, in the next year or three.  This is all from experimenting to see what works.  

Here are a pictures from last week.  It's early morning so the leaves aren't droopy yet.  They wilt something terrible in the heat of the day but recover over night.  The close up of the squash is from the last week of July.  

To me, these are drought tolerant because they don't die after two months of no rain (when the main part of the soil dries out) and can still produce a crop after several months of no rain.  I think this is where my problem comes from.  Maybe what I'm calling drought is different than what other people consider drought?  Or maybe I'm using the wrong word?

This is a great topic. It's one I think often about. I'm still trying to find answers, myself.


I see all sorts of plants, including natives, peddled as drought tolerant, yet they die even with moderate irrigation. I even contacted a supposedly landrace seed grower to ask about how little irrigation I could get away with. I won't name names, but their response was that they don't know, as they irrigate heavily in order to promote beautiful fully developed seeds.


I've even seen prickly pear die in Portland because of drought.

If anyone has new thoughts or experiences to add to this thread please let me know

James Landreth wrote:I even contacted a supposedly landrace seed grower to ask about how little irrigation I could get away with. I won't name names, but their response was that they don't know, as they irrigate heavily in order to promote beautiful fully developed seeds.

That's the same answer that I would have given. I live in the deep desert. My garden receives no rain during June, July, and August. There are currently no warm-weather annual vegetables that can survive those conditions. I'm not interested in trying to develop varieties that can handle drought. My community had the foresight to locate itself in a location with abundant water, and put in the investment to make a reliable water storage and irrigation system. My varieties are selected to withstand super low humidity, and blistering sun, but not drought. I have abundant irrigation water and use it well.

There are winter-hardy crops that grow well here without irrigation. But they are not drought tolerant either, they are drought avoidant, growing during cool weather, when rain/snow is occurring regularly.

There are fruit trees that grow here without irrigation. Most of them have the good fortune of being planted near natural swales or catchments that concentrate the scarce rainfall. It's rather a lark of topography that they survive, not necessarily due to being drought tolerant.

I once asked my next-door neighbor how often she waters her garden.  She said, "As little as I can get away with."

I thought, "Good answer!"  (Laugh.)

I would find it very valuable to be able to quantify drought tolerance myself, as I live in the high desert, and I want to be able to dry farm everything, or at most water sparingly only with rainwater and snowmelt I capture during late fall / winter / early spring.  It's useful (if frustrating) to hear that the term is thrown around to mean a wide range of things that may not be relevant to my situation.

That said, even asking a landrace grower exactly how often they watered their crops may not be as relevant to your situation as you might hope.  For instance:

- How much rainfall do they get during the growing season?

- How high is the water table in their area?

- How efficiently did they water their plants?  (Drip irrigation is very efficient.  Drip irrigation buried under deep mulch is hyper-efficient.  Sprinklers waste a lot.  Flood irrigation wastes even more.)

- How hot is their growing season?  (Relevant to transpiration rates.)

- How many hours of sun on average did their plants get?  (Relevant to transpiration rates.)

- How deep of a mulch did they use?  (Relevant to soil evaporation rates.)

- How much water can their soil hold?  (I don't just mean sand versus clay.  I also mean how much organic matter is in there.  If they're using hugelkultur, for example, the soil may be able to hold a lot more rainwater than it would normally.)

This is one of the reasons why swapping seeds with fellow gardeners whose growing conditions you already know match yours is of special value.

It seems there's no real answer to this question, as it's all relative. I'm wondering if all we can do if we want to grow with no or minimal water is experiment like crazy with different growing conditions, and start with as diverse a gene pool as we can then landrace. But even a neighbour who also doesn't irrigate will have different soil conditions, different shade, different wind, so her landrace seeds might not enjoy my garden, and vice versa.

The things that work well for a PNW summer-drought/winter-rain garden probably won't work for my 1"-a-month-all-year-round garden with frequent but very light rainfall. I am realising mulching heavily will probably be a disaster for this garden as the rain won't ever reach the soil. But incorporating way more organic material into the soil, planting in ditches rather than raised beds, using dappled afternoon shade to reduce evaporation -  these techniques might work for me. Then hopefully I can develop the landraces that enjoy my conditions, starting with as little watering as possible and reducing watering season by season as the plants get better adapted.

As it happens, my neighbour with the stunningly beautiful and productive garden who is keen to help me start a garden on my property irrigates hers a lot more than I will be able to, so starting with her seeds is not the best place to start a minimal-irrigation garden. But at least it IS a start!

I think, provided we have space to grow in, we need to try to get as many different seeds of a plant from all over - local seeds, seeds labelled drought-tolerant, seeds from seed producers who irrigate heavily, and let the genetics sort themselves out over a few generations. If we do this and get no survivors, maybe that's not a plant that will grow without some additional water. Some just won't, n matter what we do. Then if it's a plant we really want to eat, maybe that's one for near the grey-water outlet or close to the kitchen door so it's easy to give a bigger share of our precious water supply.

Raven, I love your non-irrigated veggie photos! Your garden I think would work very differently to mine -- I am guessing you store up water over the wet winter and hold it in with heavy mulch? -- but unwatered and nicely productive plants like that in August are impressive!

I'm fortunate enough to live in an area that gets a fair amount of water over the entire growing season. We might get stretches without rain, but usually it is easily mitigated.

The way that I figure out if my area is in drought conditions is that I wait for the area farmers to start getting nervous. You might get chatting in town and the subject of drought conditions will inevitably pop up. I think this thread is excellent because... what is a drought really?

I view drought-resistant plants as plants that can thrive in high heat environments with minimal water. For me, that means watering every other time that I might water what I consider ordinary plants.

In a similar west coast climate, I think our heavy rains in winter may end up reducing drought tolerance for some plants on poorly drained soils. Flooded, anaerobic conditions  in heavy clay seem like they could kill deep roots of plants intolerant of wet feet. Then when our dry summer hits, the topsoil dehydrates along with the surviving roots of anything that couldn’t handle wet feet for up to half the year. It seems like organic matter should help, and root pulsing from living plants would be a way to get that deeper over time as roots grow and die back.

Another factor for drought tolerance seems to be plants adapted to reduce evapotranspiration when needed through closing stomata and having waxy leaf surfaces.