Epidemiology of spinach pt. II

Growing spinach in hydroponics is basically a race between the spinach and Pythium. Fortunately for us, the good people of Cornell have done a lot of work figuring out how to help tip things in favor of the spinach. Brief reports here.

First of all, it turns out there’s a temperature tipping point. Above it, Pythium grows faster. Below it, spinach comes out ahead. That temperature is about 20C (68F).

So, the first step to avoiding sudden death by Pythium is appropriate temperature. That’s why it’s very important in aquaponics to match species of plants and fish that grow in similar conditions. If you tried to grow spinach with tilapia– whose favorite temperature is somewhere around 30C (85F)– at least one of those species would be very miserable. On the other hand spinach would probably do very well with some freshwater salmon relatives like trout, Arctic char, or grayling. Spinach and salmonids both like their water bracing and chock-full of oxygen.

LOOK AT THAT GORGEOUS FISH! It'd be worth growing Arctic char just to look at them!

Look at that gorgeous fish! It’d be worth growing Arctic char just to look at them! (They also smoke well. All in all a good deal.)

So do sturgeon… sometimes. They tolerate cold very well but grow best around room temperature. What cold is good for with sturgeon is cuing them to begin forming eggs. Thus there may be a place in sturgeon-based aquaponics for a cool-water hydroponic plant like spinach (and other winter greens like mâche, radicchio, endive, etc). Being able to nudge a fish to begin the spawning process by imitating natural seasonal cues means that you know when it’ll be ripe. Obviously you don’t want a fish suddenly losing her eggs all over the tank because you didn’t know to milk in time. Another potential problem is that the fish simply reabsorbs the eggs when she decides the tank isn’t a good place to spawn. That can be ok once or twice, but from what I understand it can be bad for the fish’s health if this occurs too many times.

There are some other cool things you can do to help the spinach pull ahead. Fungal and bacterial pathogens grow 24/7. Plants only grow when there’s light. Drawing out the light period can do some amazing things for plant growth– as evidenced by Alaska’s annual summer takeover by giant killer cabbages.

Alaskans are very proud of their naturally enormous cabbages. Forget the supplemental CO2-- all it takes to get these beauties is 20+ straight hours of sunlight a day!

M’lady’s coleworts are going to start eating frogs and demanding Han Solo in carbonite any day now.

All it takes to grow Cabbage the Hutt is 20+ hours of sunlight a day. Piping in extra CO2 is another way to boost growth. This technique is actually pretty common in the Netherlands where they have to keep the greenhouses sealed up tight to keep the warm air in. The plants can run out of CO2 by mid-morning on a bright winter day if you don’t keep adding more.

Both supplemental lighting and CO2 are quite intensive and not something you’d do for a home garden, unless you simply have to have 93-lb cabbages for some reason. But they do speed up growth enough that they can pay off if you have the right commercial market. The Dutch have done very well for themselves by using these kinds of techniques just to increase yield on their small land acreage. There may well be a place for them in US farms close to urban markets where land is at a premium.

Well, that’s it for today. Moral of the story: spinach needs environmental conditions that push you more towards an intensive, tightly-controlled Dutch-style production model if you were to grow it in one place year-round. The US is large enough that there’s almost always someplace that’s enjoying the right weather to grow it so our markets have leaned more in the nomadic outdoor production method. American growers have been loath to adopt high-production greenhouse techniques. Now you know why you’ve never seen hydroponic spinach at the grocery store– and why that may change as transportation costs go up and local food grows in popularity.


Epidemiology of spinach

With a mascot like Popeye, you’d think spinach would be the burly lumberjack he-man of leafy greens. But you’d be wrong! It’s actually quite the diva in the greenhouse.

that awful moment when you become a plant pathologist and find out everything they told you about spinach was a lie

believe it or not, this cartoon was not entirely truthful about spinach’s magic powers.

Spinach plants’ roots are especially vulnerable to “summer Pythium.” Pythium is usually grouped in with other “damping-off” pathogens like Rhizoctonia and Phytophthora (the one that killed potatoes and indirectly also several million people in Ireland): diseases that flourish in cool, wet conditions. But it turns out there are some funny-looking stepchildren in the Pythium family that like it hot.

Like all plant diseases (or diseases period), there are certain settings where the pathogen grows faster than the host. Most plant diseases really get off on low-oxygen conditions. This is especially true of those that affect the roots. Root can’t make their own oxygen– photosynthesis is the leaves’ department!– so they have to absorb it from the outside environment to function. And, remember that the warmer water is, the less dissolved gas– like oxygen– it can hold. So the warmer the hydroponic solution, the more oxygen-stressed the roots are, the worse the entire plant’s health becomes as a result, and the more fat and sassy the Pythium gets anyway. It’s a recipe for disaster.

And in hydroponics, whenever Pythium gets a good beachhead, it gets massively ugly in a hurry. Pythium is spread by little spores that swim. In soil they can only swim so far. But in hydroponics where the water is constantly whooshing around unobstructed, they can infect the entire system in a day! You go to bed one night and everything’s all normal, and the next morning the spinach is all flopped over and crying out for morphine.

An oomycete zoospore on the prowl!  (I sorted through a lot of photos of horrifying veterinary Pythium infections so you don't have to. You're welcome!)

An oomycete zoospore on the prowl! Look at that sinister Cyclops face. Clearly this microbe is up to no good.

Growing spinach in hydroponics is basically a race between the spinach and Pythium. Even in conventional hydroponics it’s difficult to control Pythium with fungicides– you have to stop using fungicides for at least 1-3 days depending on the fungicide before harvesting the plants, and that’s plenty of time for Pythium to eat them alive. In aquaponics it’s especially tricky because most if not all fungicides are toxic to fish. You can’t use them ever.

So what CAN you do to keep Pythium at bay in hydroponic spinach? Stay tuned…

My notochord will go on

We bring you an important update in the vein of nose-to-tail eating.

True fact: modern sturgeon don’t have vertebrae.*

They do have a cartilaginous sheath around their spinal cord, called a notochord. When you’re cleaning a sturgeon, you can yank it out like a big white noodle. It’s considered a delicacy in Russia called vesiga. Not only that, but it was used on a garnish on a soup called Consommé Olga** in the last meal served on the Titanic.

Ermagerd! Spinal cord!

Do I smell… spinal tissue?

It turns out you can still get your hands on some vesiga here in the 21st century. Acadian Sturgeon— a sturgeon farm in Canada– sells not only caviar and sturgeon’s reputedly amazing swordfish-like meat, but more exotic bits as well including vesiga (labeled here as “cartilage and bone marrow”).

*Sturgeon apparently started off with a normal vertebrate skeleton eons ago, then decided bones were unnecessary and got rid of them. Their body structure is now quite minimalist. I almost said bare-bones but it’s gone rather beyond that by now….

**I had no idea, but apparently Titanic reenactment dinners are a thing? Classy recipe for Consommé Olga here. Hilarious review of soups from all three passenger classes here.

My notochord will go on

My notochord will go on

Sturgeon and hadrosaurs: Best Friends Forever

We have a four year old, so our household is experiencing an uptick in dinosaur-literacy. One day in the course of googling at said four year old’s request, I made a fascinating discovery:

Only three fossil sturgeon skeletons have ever been found.

All three were lodged inside the belly of a hadrosaur (duck-billed dinosaur).

What gives? Weren’t hadrosaurs vegetarian?


Interestingly enough, the sturgeon fossils were preserved whole and fully articulated– they hadn’t been chewed or mangled up in the dinosaur’s gizzard.

As far as anybody can tell, what happened is occasionally a hadrosaur was tooling around doing its hadrosaur thing and suddenly dropped dead (disease, starvation, getting eaten by T. rex, etc). Since hadrosaurs were semi-aquatic, whenever they died it was likely to be in or near water. So their carcass would bob along until it hit a quiet muddy bank area and ripen as carcasses do. Apparently Cretaceous sturgeon were either scavengers or enjoyed the flavor of other scavengers like worms and crabs; either way, they’d snuggle up inside the hadrosaur corpse for a buffet, get stuck, and fossilize along with their real estate.

This is basically how I see it going down (minus the Han Solo rescue operation, wherein Hoth is deprived of its best fossil ever)

This is basically how I see it going down (minus the Han Solo rescue operation, wherein Hoth is tragically deprived of a magnificent fossil)

Sturgeon don’t have a lot of bones– they’re technically in the bony fish family, but they apparently decided millions of years ago that bones are for suckers and dropped them. (They don’t even have a vertebrae! Just a nekkid cartilaginous notochord around the spinal cord– as I discovered one day whilst watching this fish-cleaning tutorial.) The only hard tissues left are a few bones making up the skull and the scutes on their skin. The rest of the fish is gooey enough that the body falls apart quickly and the hard parts scatter. That might explain why so many of the fossils we’ve found came from inside a hadrosaur corpse– it made a nice quiet nook where the sturgeon remains were protected from being knocked apart by waves or scavengers.

Interestingly, I did once see a warning to would-be sturgeon farmers to always keep ponds and tanks open and clear of debris. Apparently they don’t go backwards very well; if there’s a lot of junk on the bottom they get stuck. With so little morphological change over the last 70+ million years, it stands to reason that ancient sturgeon didn’t have much of a reverse gear either.

Moral of the story: next time you’re tempted to curl up inside a stinky dinosaur corpse, make sure you have an escape route.

Until next time…..

Farm blog, on the rocks

One very smart farm blog I’ve been following for years is Walter Jeffries at Sugar Mountain Farm in Vermont.

Sugar Mountain Farm's very own cut chart.

Sugar Mountain Farm’s very own cut chart.

A lot of farmers with rocky barely-there soil whine about it. Sometimes a lot. The Jeffries-es don’t put up with that kind of sissy nonsense. They farm free-range pigs and feed them hay in winter in a couple designated areas to make their own stinkin’ soil.

They’re also building their own USDA-licensed slaughter and butcher shop, live in a tiny little concrete cottage that they built and cement-welded to the granite of the mountain themselves, and have taught at least one of their livestock guardian dogs to speak sign language. I don’t mean the dog understands hand signs. That’s a normal thing for dogs to do. I mean the dog speaks sign language and she will sign-linguistically sass you back if you try to stiff her on treats.

Awwww, bacon!

Awwww, bacon!

Check them out for your daily dose of DIY hardcore voyeurism; and/or useful tips that will come in handy next time you need to self-build your own interstate-trade-legal meat packing facility on top of a gorgeous yet godforsaken subarctic mountain. You know, depending on where you are in life.

Keeping it cool

Scientists don't know why Suwannee River sturgeon jump. Let's say hypothetically for the purposes of this post that it's too stinkin' hot in the river. No matter the reason they can mess you up if they hit you, so let's all consider boating somewhere else during sturgeon jump season.

Scientists don’t know why Suwannee River sturgeon jump. Let’s say hypothetically for the purposes of this post that it’s too stinkin’ hot in the river. No matter the reason they can mess you up if they hit you, so let’s all consider boating somewhere else during sturgeon jump season.

I mentioned here before that our main question in the pilot scale will be temperature control. Let’s talk about that a little more.

The question isn’t whether we can keep the temperature in the sturgeon comfort range. We definitely can. The question is “Can we do it with just evaporative cooling, or do we need a chiller?”

Evaporative cooling is cheap and simple, although it can use a lot of water. A chiller is basically an air conditioner for water– the little gizmo inside a water fountain that you hear kick on if you stand there drinking for a long time is a little tiny chiller. They also make very big chillers. And if evaporative cooling alone doesn’t cut it, we’ll need one of those very big chillers. We’re hoping to avoid that since chillers are expensive equipment, they use a lot of energy, and to make them efficient you need a cooling tower. That needs a lot of water just like simple evaporative cooling. So as you can imagine we’re hoping to avoid the need for a chiller.

I’m optimistic that we can make with just evaporative cooling. The ground in Florida (under the top sun-soaked 8 inches or so) stays a steady 75F or so year-round. That just happens to be the exact temperature that we want the water to be. I’ve found that even in August down here, you can find comfortably cool spots outside. It’s always a place that’s consistently shaded, there’s some water or transpiring plants, and a breeze– even just a hint of airflow will do it. Bamboo trail at Kanapaha Gardens, I’m looking at you!

Bamboo trail at Kanapahaaaaaaaahhhhhhhh......

Bamboo trail at Kanapahaaaaaaaahhhhhhhh……  (source)

Accordingly, the sturgeon farm at Mote Marine in Tampa two hours to our south manages to keep their temperature in the ideal range just with shade and natural evaporation from the tanks’ surface. In a happy coincidence, that’s exactly the environment we’ll have in our system. Shade and water.

Unlike Mote, we’re going to flow the water through a lot of shallow beds in a greenhouse. It’s possible the water could heat up in the beds since they’re in a greenhouse and will have little evaporation because of being covered by the plant rafts. On the other hand, those beds are dug into cool-ish ground surrounded by ground cloth to keep it from absorbing too much sunlight and heat, and the rafts are made of inch-thick styrofoam. The water might not heat up much at all. The only way to find out is to try it out– hence the pilot scale.

In the end the pilot will tell us whether we need to spring for electric chillers or not. This will make a big difference when we build the full-scale system– in terms of energy supply, how you situate everything on the ground, and definitely in how much the system will cost. We’re keeping our fingers crossed for good results with evaporation alone.

Aquaponics, stewardship, and local economies: or, the Bacon Manifesto

A couple years ago somebody tried to start a sturgeon farm in Melrose near our part of Florida. It didn’t go well. From what I can tell the Water Management District authorities had been leaning on locals for years to switch to low-flow toilets and other appliances at great expense, take short showers, put in low-water landscaping, etc. This is not a problem in itself. The Floridan aquifer is indeed at risk, and our springs are drying up from groundwater overuse. The people in this area lived there because they liked the springs. They were happy to oblige.

It was when, after all that, the WMD tried to grant this fish farm close to half a million gallons/day for free that stuff got real.

Many parts of the world have a history of extractive industries. They create some dead-end jobs, foul up the land until they’ve taken all the goodies, and then leave. One of northern Florida’s most impressive current examples is phosphate mining. Phosphate mining digs up forest and farm land and turns it into impressive piles of slag and slime pits. (Seriously, that’s what the waste ponds are called. Slime pits.) Sometimes the slag piles disappear into sinkholes and everybody gets to drink it. The slime pits are supposed to turn into normal ponds eventually, but it’s a long-term process and suffice it to say we still don’t know if it really works. And most of all, phosphate mining uses so. much. water. With our nutso geology, using a lot of water makes the ground collapse and swallow up houses and sometimes the people inside them.

Blimey! What a beauty! This epic sinkhole opened up under a stack of mildly radioactive phosphate mine waste in 1994. Image; data sources here, here, here.

Blimey! What a beauty! This epic sinkhole opened up in Polk County, FL under a stack of mildly radioactive phosphate mine waste in 1994. Image source;  info here, here, and here.

My mom’s mom grew up in a dead-end coal mining mountain village in Kentucky. The only reason she got out was that she was hot and managed to marry a guy who took her out of town. The reason she stayed out is the stigma of divorce at the time meant that after the marriage fell apart she couldn’t ever come back home. It’s not a great story. It’s not exactly a tale of American Dream triumph. But that’s ok. There are worse things than being exiled from a strip-mining hellhole where you can’t work the land or drink the water anyway, and the only way to get life’s necessities is through a company store system painstakingly designed to keep you in debt slavery until you die.

So I guess what I’m saying is, I hear you. There should no place for that kind of exploitative industry. It is a waste of peoples’ talents and lives. It is a waste of natural resources that you can’t ever put back. And it’s a waste of precious time that we could be using to find better ways to take care of human needs. We can do better.


That’s why I’m really pumped to have a chance to work with a green technology like aquaponics. Good technologies use cleverness to replace natural resources. If we want to have a sustainable economy we need to start using less of what we have in short supply– water, fertilizer, energy– and more of what we have plenty of– human creativity and manpower.

Growing caviar gives us a chance to have the time and capital we need to develop aquaponics into a really effective commercial-scale system. There are still some things we need to work out, like how best to control the temperature. What the best cultivars are for each kind of vegetable. Things like that. Florida has a lot of great agricultural extension scientists who work on learning how to better grow fish (sturgeon, even!) and vegetables. But we don’t have any who deal with aquaponics. It’s up to us to work these things out ourselves. Alas, research is expensive. So in order to get aquaponics where it needs to go, we need to be able to promise people a piece of a solid pot of gold later in return for money now.

The high value of caviar isn’t all bad either. I’m really glad that with aquaponics we’re able to grow vegetables too, which is something that’s useful to everybody. But if you want to help jump-start a local economy, you might as well make something that’s going to bring home the bacon!

Ohhhhhh bacon. Reminding me that it's lunchtime. Be right back....

Ohhhhhh bacon. You’re reminding me that it’s lunchtime. Be right back….


To find more about sustainable development in northern Florida, please see the excellent goings-on here at Florida’s Eden and Gainesville Connect.