Evaporative Cooling

I don’t think there is anyone who hasn’t experienced an extreme heatwave this past month. Rin, who is spending the summer in Savannah, experienced their first East Coast heatwave (with accompanying high humidity) a couple of weeks ago. Here in the West, we too have had our share of extreme heat, though not the humid kind. Our backyard weather station hit 116 degrees several times this week, and I instantly start sweating the moment I walk outside.

I have discovered recently that I am a ‘sweater.’ I don’t mean that I’m always sweating; but yes, when the circumstances are right, I will sweat more than the average person. I learned this because Tom and I have joined a local gym. The reason for joining began with injury recovery, but quickly morphed into something else - another tool to build our resilience. We are planning a month-long walking trip next summer for our 25th anniversary, so we are both working hard to build muscle, improve balance, regain agility, and increase flexibility. We’ve added all kinds of different exercises to our daily routine; simply hiking up a hill is not going to prepare us for hiking 16 miles a day for weeks on end.

So now we are in training. And man, when I train, I sweat. I mean not just in the usual places. When I’m done with, say, a spin class, my calves are slicked with sweat. And after a TRX class, my forearms are dripping. I suppose it could be embarrassing, but I don’t look at it that way - I consider it a sign of a healthy vascular system that is performing one of the jobs it has uniquely evolved to do.

Sweat is a beautiful human adaptation. Chimpanzees and macaques have sweat glands, but humans have 10 times the amount that they do and are the sweatiest among the great apes. Scientists have discovered that “the higher density of sweat glands in humans is due, to a great extent, to accumulated changes in a regulatory region of DNA that drives the expression of a sweat-gland-building gene.” This happened through repeated mutations and contributed to an evolution of higher sweat gland density in humans. We are meant to sweat! It’s our primary way of cooling ourselves. As the water in sweat evaporates, the surface of our skin cools. This is true of any evaporative cooling. A liquid will remove latent heat from a surface, and that evaporating liquid will cool the air around it.

Since most animals do not sweat, they have to cool themselves in other ways, and sometimes they too use evaporative cooling. During this heat wave, we’ve been closely watching the behavior of our backyard bees on our water fountain.

Bees use water to cool their hive. Some worker bees are tasked with finding, collecting, and bringing water back; it is spread in a thin surface over the surface of the comb and the bees then fan their wings to evaporate it. A hive may use a quart of water a day in the hot months for this purpose.

Honeybees are not the only ones who do this. Some wasp colonies (many wasps are social insects and, like honeybees, live in large groups) use water the same way. They collect it and spread it on the surface of their nests. Today, while filling the one of the water bowls at the school garden, I watched both paper wasps and yellow jackets collecting water from the edges.

This is one of the most important ways we can help insects; we can place shallow bowls of water around our gardens and yards. Put a rock in the bowl, or several rocks, so that the insects don’t drown (they have poor depth perception). If mosquitos are a worry, change the water daily or weekly (it’s good to do this anyway to keep the water clean). Birds will love this, too.

Many insects will also get water from the soil in your garden, so it’s nice to have a bare space which you keep wet for this purpose. Butterflies especially adore a muddy spot.

Another creature in our garden that appreciates evaporative cooling is the chickens. Chickens, like dogs, pant when it’s hot, and this past week they’ve been panting from dawn until full dark. I actually spray them with water, and though they seem to dislike me doing that, they really love when the ground in their run is wet. So when the temperature is over 100, I go out several times a day and spray them, and the dirt in the run, thoroughly. Immediately afterward, the chickens will congregate in the wet place, and they really perk up.

Chickens also dig holes in the dirt to find the cooler place under the surface. Many creatures do this, too. While dogs and coyotes pant, owls use something called ‘gular fluttering’ which is flapping the loose skin under the throat to move air over the throat cavity. Vultures urinate on their legs to keep cool, another form of evaporative cooling!

That last fact makes me appreciate anew the way we humans use sweat to keep ourselves from overheating.

Stay cool, everybody.

Maintenance

It’s about 80 degrees at Poppy Corners, and it’s that exact time when, every April, we say to ourselves, “Is the neighborhood pool open yet?” The season of flip flops and tank tops signals also that it’s time to do some much-needed maintenance at home. Tom and I always keep a running list, inspired by Monty Don and Gardener’s World, called ‘jobs for the weekend.’ We add to it all week and then begin to tackle it as soon as we’ve finished our coffee Saturday morning. Our list this week was literally as long as my forearm - typical for this time of year.

Luckily, I’ve already planted most of our summer veg, which I normally wouldn’t do until the temp is consistently over 50 degrees at night. But I’m scheduled to have knee surgery on May 8, so I thought it would be good to get all that done before then, and luckily everything has survived. Since we removed all the raised beds from the North Garden (to make the orchard), I used that wood to make the raised beds in the South Garden taller. We’re not getting any younger around here and taller beds will be helpful in that regard. I ordered three cubic yards of planting mix from a local nursery, and added that to the beds before planting. It’s good to have all that done.

But today, the first thing on our list was the irrigation system. Now that we’ve had the last of our (prodigious!) winter storms, it’s time to begin a regular irrigation schedule. It’s important to start out with 100% saturation in your soil; if you do that, you’ll just be topping it off every time you water, instead of playing catch-up. But the irrigation system hasn’t been used all winter, so it’s not as simple as just turning it on. Inevitably there will be some problems - breaches in the lines, clogged drips, broken micro-sprayers. Tom and I turn on one ‘zone’ at a time and go around watching what happens and making notes. Often, I’ll see an area that needs coverage, and we’ll add some lines. Sometimes an area is too wet and we’ll adjust that too. Tom always has a lot of repair work to do. It’s really good to get all that done before irrigation becomes crucial.

Can you see the swarm?

After that, Tom opened our top-bar bee hive. Two days ago, I was out running errands when I got texts from two different neighbors: “Your bees are swarming!” So I rushed home in order not to miss it and to see if I could capture it for my dad, who always wants our swarms. Alas, it was too high to reach with our ladder. I’m not even sure if they were our bees (there are many beekeepers in the neighborhood), but it was a good reminder to spend some time looking through the hive and adding bars for new brood and honey. Everything looked as it should, and Tom took a full bar of honey out for us. Opening the hive is now Tom’s job since I’ve become allergic over time; he’s gotten really good at it and never gets stung anymore. I hang back and look on longingly, peppering him with questions which I’m sure he just loves. At least I can handle the messy job of cutting up the comb and extracting the honey, though gravity does most of the work.

I also spent a good deal of time today cleaning out our enormous passionvine. It’s a Passiflora ‘Blue Horizon,’ and has gorgeous flowers and small black sour fruits. It supports a huge number of gulf fritillary butterflies every year, and is a stopping place for every curious neighborhood child in summer. I bought it as a living deer fence, assuming that it would die back every winter with our frosts (and therefore remain manageable). It’s never done that, only gotten more and more enormous each year. It’s extremely promiscuous and shows up in all sorts of places I don’t want it to, so I’m always pruning the thing. However this year, we had so many nights of truly cold weather that the vine died back, leaving a hedge of dead leaves and flowers a foot thick. That was fun to hack through and remove. Now it looks quite bare, with just foundation vines on the trellis, but it won’t be long before that monster puts out new growth and begins the cycle all over again.

Tomorrow, we plan to wash the windows and screens, a once-a-year job that we loathe but that always makes such a difference in the way the light comes in our windows, so is totally worth it.

We also have reserved time for hiking both days. After all this rain, the hills are simply covered in wildflowers. This morning, we walked up to Shell Ridge where a guy named Phil (a volunteer with the Walnut Creek Open Space) has been working for ten years to restore a giant hillside with native flowers. This year it is simply spectacular, with every kind of California native annual you can imagine. Below you can see a very small section of the hillside, covered with poppies and chia. Tomorrow, I’m hoping we will have time to go a little further afield and hike in a place where we can ford some streams, which never gets old in our normally-arid Bay Area, and see nature-planted flowers.

Consistency

The South Garden, which (also counterintuitively) gets mostly morning sun, due to middle-day shading from large trees.

According to the Oxford Dictionary, consistency is “conformity in the application of something, typically that which is necessary for the sake of logic, accuracy, or fairness.”

Consistency is something with which we struggle in our garden, even in normal years.

But what is a normal year? We haven’t had one of those for a long time now. We in the outer SF East Bay have experienced wide temperature swings. For example, last Saturday, according to our weather station, the high was 112.8 degrees (F) in our North Garden at 2:45 pm; by Wednesday morning at 6:15 am it was 53.8. it’s normal to get cool here at night due to the influence of the Pacific Ocean, but a 59 degree difference is extreme even by our standards.

And rain? Well, I’m sure you’ve heard about the lack of it; here in Walnut Creek, our local city weather station has recorded 5.98 inches this year. For comparison’s sake, let’s look at Springfield, Missouri, a city a friend of mine lives in. He’s been dismayed by the amount of rain they’ve had this year, but in actuality, it’s five inches less than in “normal years” - 2021 has recorded a total of 31.8 inches since January 1. We won’t get rain again until November, if we are lucky. Springfield will have regular rain through the rest of the year.

Living in a Mediterranean climate, we expect less rain. But we do expect about 3-4 times the amount we’ve had this year.

The combination of these heat and precipitation inconsistencies has resulted in a pretty terrible die-off in our food garden.

Dead pepper

Dead tomato

Blossom end rot. It’s on every single one of my tomatoes, regardless of variety. This is because when it’s over 100 degrees, I water them twice a day instead of just once, and tomatoes like consistent water. But otherwise they would have all died, and I just couldn’t let that happen.

Crispy hop bines

Crispy blueberry bushes

This last image is from drought.gov which is updated every Thursday. In the Bay Area, we are now in Exceptional Drought conditions. Our governor has asked for a 15% voluntary water reduction from all residents (I’m not sure what companies have been asked to do). As a family, we had to have a discussion: Which water will we give up? We’re pretty good about our consumption in the house - we have only one toilet, and it’s low-flow; we have one shower, and we’re good about keeping our time in there short; we have a dishwasher and it’s energy-and-water-efficient (which saves a ton of water over hand-washing); and our laundry washer is a tiny front-loader, which uses a lot less water. Our one big water ‘expense’ is the garden.

Unable or unwilling to let the garden die after investing work and expense to establish it, we decided that our first plan of attack would be toilet flushing. If we “let the yellow mellow” and “flush only the brown down,” we can save the 15% that has been asked of us. It’s an easy fix…. for NOW. Soon, we are going to be asked to reduce even more, and then, well, I’m going to have to make some hard decisions.

I have noticed that many things in the garden are doing well, despite the inconsistencies, and it’s no surprise which ones.

Basil, and other Mediterranean herbs

Pumpkins

Winter squashes

Native plants, like Toyon…

… and manzanita

Despite the fact that I believe I’m saving the state water by growing my own food rather than buying it at the store (consider the amount of water farms use, the amount of energy used to get the food to the store, the amount of energy I use to get myself to the store), I am now convicted that I cannot continue to grow in the way I always have. The climate is changing and even if we stop worldwide global emissions today, the effects from it are going to last for hundreds of years. This means I need to figure out how to garden for the future, not the past.

Let’s go back to that definition of consistency, which included “that which is necessary for the sake of logic.” Logically we know that the weather is only going to get more extreme as a result of climate change, so therefore it doesn’t make sense to continue doing the same things and expecting to get the results we used to get. It’s time to rethink how and which things to grow in our gardens. What does that look like? It means a slow transition (because it’s going to take both effort and money to make this change) in our yards and in our diets. We may have to choose perennial veg and fruit over annuals. We’ll have to be religious about mulching or growing plants more closely together to shade the soil. We might have to grow more at certain times of year, like spring and fall. rather than summer and winter. We’ll have to get even better at preserving what we grow for the lean months. We might even have to eat things we don’t particularly like, which might be the biggest shift of all.

Over the next year, I’m going to get serious at looking at my property in a new way, with a focus on what the next five years might look like, and make changes accordingly. I suggest you come along with me for the ride. Let’s do our part to usher in an even more conscious type of gardening, one that looks to improve our future.

Planting the Winter Garden/Thoughts on Water

We had a brief respite from the smoke this weekend and were able to get all of the north garden planted for winter. This involved taking out all of the tomatoes and peppers, amending the soil, doing a little aeration of the soil, replacing the drip lines, and planting seeds. The north garden will be home to brassicas and greens, this year. I’ve decided to skip Brussels Sprouts, as I never have much luck with them. But all the other usual suspects are in, and we’ll enjoy eating them early next year. Greens will be available to eat all winter, which we love.

The next job is to cover the hoops with row cover, to keep the birds and the cabbage white butterflies OUT!

I had mulched the tomatoes and peppers heavily with organic rice straw, and one benefit of that was that the soil level was still very much as it looked in April - still level with the top of the raised beds. I thought that was interesting. Another benefit of the straw is that I was able to move it from the beds to the chicken run, and now they have a new layer of carbon to scratch through and soil with their droppings.

In the south garden, Tom took out the beans and cucumbers and I took out the pumpkins and some cover crops. Now we have snap and shelling peas planted, which might crop before cold weather - we’ll just have to see. I’m a little early on my winter planting this year, so I’m not sure how everything will behave.

Our seed garlic will be arriving tomorrow, so I also prepared a bed for that. However, I had forgotten that we had a water issue that needed investigating. We noticed some extremely wet places in between raised beds last May, and Tom dug down to see if there was a leak in the irrigation, and didn’t find anything. We dialed down the amount of water going to those beds and decided to watch it this summer, since I had already planted the summer garden. That seemed to solve the problem, except for one very wet place in between two of the beds. So Tom dug a bunch of holes again today to see if there was a leak. Surprisingly, there wasn’t. And yet we see water seeping out the bottom of the sides of two raised beds! Tom thinks maybe the lower levels of the soil are so compacted that the water is dripping down to that level and then running off. This sounds possible to me. We are on heavy clay, and though we amend the soils each year with all kinds of organic matter, it takes a long time to change the tilth of soil. I also practice no-dig methods, which ensure that soil life is not disturbed, and in theory should actually improve the soil’s texture, but it could be that I need to add more organic matter down lower in the beds, next to the hard pan. So that’s what I’ll do.

This whole issue spurred us to discuss our watering habits more generally. Watering is kind of a crap shoot. In the summer, our plants seem SO dry and tired, and the soil seems dusty and dry, no matter how much we water. And we water a LOT. We are using a lot of resources. The general rule (and this is so general, it’s almost silly) is that plants in the ground (not containers, not raised beds) need an inch of water a week. Well, in a place that rains, that’s easy to calculate; but we have no rain nine months out of the year. So the soil is never soaked, and it is never sodden in the summer months - it is bone dry. Add to that very low humidity in the air (10% humidity is quite usual here in the summer months), and very hot temps (often over 100), and that means the plants are transpiring like crazy. And, we grow most of our crops in raised beds, which tend to stay drier anyway.

We did a whole bunch of calculations and we converted an inch of water to gallons per week, and even when we set the drips for 10 minutes a day, we’re still giving the garden more than two inches a week. You’d think that would be enough, more than enough! But in the summer heat we often drip for 15 minutes a day and the plants are still wilting and sad looking. They produce, though. So I suppose they are getting just enough. But honestly, I am just guessing.

We want to be good stewards of water, here in our dry dry dry West. And yet, we also don’t want all of our hard work go to waste - we want the plants to thrive. Growing at home is still a better use of water than buying fruit and veg from the market, so in the big scheme of things, we are conserving. It just feels bad to be using so much water. If we had a lawn, would we even think twice? Most people don’t.

Well, one thing we can certainly do is make sure that we don’t have any runoff like we did this past Spring. So, organic matter to the rescue! We are also thinking of buying a soil moisture meter, so we can start to really determine how the water is behaving deep in the soil.

Wilting Humans, Thriving Garden

Is there anything more boring than talking about the weather? It’s not really news anymore that we’re all experiencing extreme conditions. Some folks have it really bad right now - the heat in India, which is causing livestock die-off, or the persistent flooding in the midwest, which has caused farmers to loose an entire season of grain. It’s not that bad here, but it has been extremely hot for June. We humans are completely wilted; the bees are pretty much permanently bearded on the front of their hive or crowded in a ring around the lip of the water feature; the chickens are firmly planted under the quince tree in deep shade.

But the garden? The garden says, Cheers Mate, Thanks Very Much. Peaches are ripening up, peppers are reaching and blooming, beans are twining and massing, pumpkins are unfurling big leaves, and tomatoes are plumping.

There are some precautions for plants in hot weather. The most important thing is to make sure your irrigation is dialed in. Consistency is more important than volume; daily water is a must when it’s this hot and dry. We Californians don’t have to feel guilty about watering each day because we had plenty of rain and snow this past winter, but in the coming years, that might not be the case. So let’s talk about preserving moisture NOW, so you’re all set when that moment comes.

The amount of organic matter (OM) in your soil is probably the most important thing, acting as a sponge, holding on to moisture. Clay soil already has good water retention and OM can help further. Sandy soil is terrible at holding on to water, so OM will be extremely important in that situation. How to include more OM? Add compost around your plants and on top of your beds each year, mulch the heck out of everything using whatever you can find, and keep a living root in the soil at all times.

Plants pump sugars and carbohydrates (carbon) down into the soil to feed the microorganisms that live there; in turn those organisms provide nutrients to the plant. Plants do not grow well alone - they all do much better with a lot of roots in the ground around them, with a lot of diversity of species. Think of a meadow, crowded with forbs and grasses, or a forest, covered with trees and ferns. Bare space gets colonized. If you don’t want your garden colonized with weeds, be prepared to colonize it yourself.

You can kill two birds with one stone by mulching with living plants. If your cover is complete enough, it will do the job of mulch; that is, shade the soil, suppress weeds, and keep things moist under the canopy. To that end, I’ve begun seeding any possible bare space, even in my veg beds, with a cover crop of some kind. Some of the tomatoes, the ones that didn’t have basil or cilantro growing under them, just got a seven-species cover crop sown beneath them (a warm season mix from Walnut Creek Seeds). I’ve seeded buckwheat in my melons, cosmos in my winter squash, and sunflowers in my pumpkins. You may feel that this would take nutrients and water away from the main crops, but the opposite has been proven true; when there is lots of diversity under the soil (in the rhizosphere, or root zone), MORE nutrients are available.

Of course, this kind of microbial diversity takes time. I find that things get better all the time, as long as I keep as much diversity of planting as possible. Also, with this system, you don’t have to worry quite as much about crop rotation. And, there are lots of other benefits to this besides water retention and greater nutrient availability, like the attraction of predatory insects that will take care of the pests in our gardens.

I encourage you to check out the latest issue of California Agriculture from UC Davis, which has a summation of a recent study about how cover cropping/multi-species cropping can really improve soil (in conjunction with no-till practices, which of course you’re already doing, right?). The bottom line is that there is more fungal hyphae in soils that are cover cropped (and not tilled). That means there are more connections between the plant roots, working in symbiosis. Here’s a little quote, sorry for starting in the middle of a sentence:

“… allowing roots greater access to water and nutrients (in exchange for carbon). Fungi, however, are more sensitive than other microorganisms to physical disturbance. Adopting no-till as a conservation man- agement practice eliminates or greatly reduces both disruption of fungal hyphal networks and redistribution of organisms and nutrients in the soil profile. Use of cover crops, meanwhile, provides more abundant and varied sources of organic carbon.”

So this system in the soil allows for greater uptake of water and nutrients. That should be enough to get you to think about adding many plant roots to one space!

credit: UCANR

One more little thing I learned in class that might help you on these hot days. Transpiration, that is, the exhalation of water vapor through the leaves of the plants out to the atmosphere, is what pulls the water up through the plant. At night, when there is no sunlight, the plants aren’t transpiring, so they aren’t taking water into their roots. Only when sunlight hits the plant does the flow of water start from the roots to the tips of the leaves. That means you want a nice reservoir of water in the soil the moment the sun hits the plants. That’s one of the reasons why it’s best to water early in the morning, just before the sun rises. Set your irrigation for that time and your plants will be quite happy. I also try to water containers in the morning, and on these hot days, they may need water again in the afternoon.

It’s a fallacy to think that a vegetable garden uses less water than a lawn; it uses just as much. So it really is our responsibility to figure out how to keep our soil super-healthy so that it can be resilient in dry times if water isn’t so available. If we start improving it now, we’ll be ready for those times.