N-fix 7: Vetch

I was rather dissatisfied when finished with the Top ten ground covers for food forests series because I didn’t include an N-fix in the lineup of dynamic mulch. Vetch would be my first choice.

Crown vetch (Securigera/ Coronilla varia) is indeed the tyrannical ruler of the genus. It’s industrial grade ground cover, produces medium levels of nitrogen, stretches 3-4 feet tall, and eats as much as 60 ft of new territory in all directions via rhizome spread every year.


I’ve only seen this number in reports. I’m guessing the ground where these measurements were taken was the most fertile sandy loam on the face of the planet, or someone dropped a bag of fertilizer. I’ve never seen it spread more than four feet a year -if it spreads at all. many readers have likely seen this plant along highways where governments have seeded it. Erosion is a thing of the past once this perennial is established, so they have encouraged its use.

Once established though, they can start new colonies via seed. As a result, many governments have removed it from their official list of recommended plants.

It’s a little late. I have some patches appearing by the road at the edge of my food forest, and one of my clients has several healthy patches around their property. I have in fact installed this plant in one client’s system, because it really is quite useful, and easily controlled, if you know its habits.

The one system where I installed this for instance was a very high production food forest with long rows of shrubs and fruit trees running along swales (not my designs. I was brought onto the scene in the later stages). The owner wanted a system that could be managed by laborers simply weed-whacking the place every month or two. With this mentality, the owner had started by laying black woven plastic mulch under the plantings -despite my disapproval. It didn’t take more than two moths before weeds found their way through. He was aghast when I showed him. Finally open to my suggestions for a dynamic mulch, crown vetch was the perfect candidate.

As a dynamic mulch, it can exclude grass. Sometimes, if the grass is well established, the two may persist together. If well established, it’s nigh inpossible for weeds to get a foothold in the crown vetch’s domain.

It grows well seeded among daylilies, and most any plant that grows more than three or four feet -a food forest cover.

The crown vetch in my food forest has to creep across the upper grain patch before it can invade any of my plantings. This is one of the most poor spots in the food forest even the crown vetch can’t stomach crossing. I simply tax it for its nitrogen rich growth about the time it comes into bloom. Because it can be pulled so easily, I simply yank up whole armfuls to feed other parts of the food forest. As you can imagine, the patch is expanding at a snail’s pace.

My clients have done the same, and find their patches stay put.

Hairy vetch (Vicia villosa) and wood vetch (Vicia sylvatica) are both annuals, but have scarcely less ability to spread. Hairy vetch is used commonly used as a ground cover in vegetable gardens to be tilled in as a green manure. It and wood vetch are also medium level n-fixers. I have seen vilossa reach about four feet tall as it meanders around, such as below with wine-raspberry. Reports say it can reach as much as eight feet. So long as it doesn’t bloom and seed, there isn’t a problem.


I actually let the thing seed in my food forest because it grows right among weeds, grass, you name it -without complaint. I love it. When it blooms, I nab as many as I can for mulch, leaving the rest to seed. I really just wish I had more.

I came hit the jackpot the other day at my step-grandmother’s garden. She has the wood vetch, and a lot of it. I gathered a bunch of the pods as pictured below, which popped, flinging seeds every which way even as they sat in the bowl.


I planted them in a problematic part of the food forest to see how well they might compete with the grass. Perhaps they’ll clear the place for me in a similar way sunchokes can. in the bed I found it growing so happily, it was hardly three feet tall. I’ll just yank them up or cut them down before they make any very much seed.


The right name for Amorpha

There are many species of Amorpha. The species I most recommend to clients, and in my published works, is A. fruticosa. This is because it is hardy in much colder regions, and grows taller -hence producing more biomass, than most species.

It is also the species that is best known worldwide. Several varieties have been bred from it making A. fruticosa one of the best foundational N-fixers on which to build gardens of lush fertility.

The fact is many of the Amorpha in Mortal Tree came from a company that listed the plant as A. californica, not fruticosa. I’ve called it that after I personally identified it. Allow me to explain:

Amorpha californica, according to the literature, grows a maximum of 6 ft. tall, and is only hardy to USDA zone seven. I’m in zone five, where this plant has lived through winters that fully reach the limit of what this zone offers, without the slightest dieback. I also find the Amorpha I have quickly pass up six foot tall. I looked into this further by researching the USDA Plant Database. Here I found information that backed my theory, and even pictures of the different seeds, which look nothing alike. Mine resembled fruticosa. I took liberty of calling the plant what I thought it was ever since.

I still have not the slightest doubt this Amorpha is Amorpha fruticosa. I don’t make such decisions lightly. My rather bold statement in Growing Amorpha that the company had incorrectly identified the plant got me more flack than I had ever expected.

My motive to make this statement was of course to dispel any fears the plant this company is selling won’t live for them if they are in zones 6 and 5. They are a major supplier of this plant, and I am telling people left and right to get it. I did try twice to contact the company to talk about this discrepancy, but their contact system never worked. I figured a small blog like myself was obviously of no consequence in their minds, but I was wrong.

The owner of the company was quite skeptical of my deduction. I was quite surprised when he showed skepticism of even the USDA’s accuracy, since the pictures clearly showed the seeds were not A. californica. He was in fact skeptical of most of the internet’s images of A. fruticosa seeds when I brought them up as examples. The only authority he considered trustworthy was none other than Gerd Krussman’s Manual of Cultivated Broad-Leaved Trees and Shrubs. This of course had been out of print for years, so I wondered how I would get my hands on the volume that had Amorpha in it. Thankfully, I have connections who graciously brought all three volumes to my desk in short order.

Krussman simply confirmed everything I had read previously about the plant. But we needed to identify this plant down to the very details of the flowers before this could be resolved.

Here are the results:

Flowers laid over fruticosa illustration from Krussman

Krussman’s work was not especially helpful in identifying the seeds. The real detail that sets apart A. fruticosa flowers from californica is the width of the petal, and spots on the californica flowers for what the line drawing shows.

Petal next to californica illustration
Petal next to fruticosa illustration

The flowers from my plants grown from the companies seed have especially wide petals I could not even make lay flat without ripping. So I spread it as best I could on a pen tip to show the plush width and lack of spots. I’ll let you derive the ID. It seems quite evident to me.

In our conversation about the plant, there was of course suggestion that we had a hybrid on our hands. If it is, it does not show the attributes of californica in the least. Fruticosa has the broader range, the greater popularity, and most importantly, the greatest utility for sustainable agriculture systems. I hope what I have done helped someone find success in this blossoming branch of agriculture through confident use of this amazing plant.

Building beds with bricks

The mulch-generating polyculture for Mortal Tree’s PASSIVE garden system is going well. It’s the bed in Foundation for a future I am establishing with bricks.*

The intent for this bed, per A bit blunt method, was to shift the rocks every couple of months to kill off the grass underneath. This worked pretty well for most of the bed. I shifted the bricks in July and made a final small shift about a week ago. Above is the freshly shifted “mulch” around an amorpha.

I also tried covering a small part with grass mulch in May last year, and this took care of any weeds growing through the cracks. Below is the planting now. Like most fun times, there is a mess to clean up afterwards. This bed had a lot of fun last year. What you see is actually mulch I applied, the healthy comfrey, and some amorpha interplanted. I plucked out the little bits of green quackgrass, and look forward to some very lush, beautiful growth here come summer.

I plucked out the quackgrass when I shifted the rocks. Because they block sun and moisture loss, the rocks encourage the quackgrass to grow shallow, allowing me to just pick them up rather than pulling them. What roots did grow deeply are easily pulled because the soil is so soft under the bricks.


This soil conditioning is one if the main perks of using rocks. The soil life is everywhere, with centipedes, worms, spiders -even at this cold season. Soil between the bricks which heaved from the freezing over winter is unbelievably friable. It looks like it has been tilled.

Considering how low this soil is in organic matter, with a clay-coal base, with no amendments like sand or ever even being tilled before, I am very excited to already have such results. The moisture and soil life have brought it so far because I have created the right habitat, covering the soil. The organic matter is starting to accumulate.

Above are some amorpha leaves dropped last fall, which likely have brought in nitrogen the system formerly did not have. The plants were already beginning to nodulate in their pots when I planted them last year. If you would like to learn more about how I ensure they make nitrogen and get off to a good start, I have some notes here on Growing amorpha.

I also harvested some of the comfrey leaves last year, which I left around the plants I harvested from. This is breaking down into gorgeous soil, bringing in carbon the system did not formerly have.

Pictured is some broken down comfrey from a larger patch in the food forest. This new patch should be producing similar soil in the near future. It’s already well on its way.


*This could have been done with some large piece of canvas or the like, or a large piece of plywood. One of my clients decided to try clear plastic just to block water, which was still effective at removing the plants underneath.

Making sense of wild seeds

I’m not quite sure what it takes to sprout Turkish rocket (Bunias orientalis). Last year I posted a fairly certain observation that a couple weeks in cold temperatures does the trick, only to find in the comments from the ever apt Wooddogs3 that she had sprouted quite a few straight out of the packet in warm weather.


Scratch that idea. I figured something else must have deterred my Turkish rocket sprouts; but then, in later conversation, Heather mentioned that more Turkish rocket sprouted after the pot sat out over winter. (?)

I think the fact of the matter is we are working with fairly wild, unselected seeds. With them, variance is the standard. At the same time, it offers several little known benefits.

Varying the time of germination increases the likelihood at least some of the seeds will sprout in a ‘sweet spot’ of a season, or at least avoid catastrophes, and make it to adulthood. What if an unusually late frost hits or some animal nips off the tender sprouts?

This is a very helpful character for love-in-a-puff vine (Cardiospermum halicacabum) which I’ve grown on a large scale for the last couple years. It’s a warm climate plant, and can’t take frost. I nevertheless plant it in mid April, when we still have a chance of frost. While a few will come up as early as three days after planting and get nipped, the majority of the plants take about two weeks to sprout, and will continuing sprouting up to three months after.

Cardiospermum sprout back when I tried growing them in flats. Because their sprouting time was so varied,  I watered the flats a lot longer than expected for all the seeds to sprout. They don’t transplant very well anyway, so I now direct seed.

The mechanics that govern this variance can vary, but are usually based on the activity of certain enzymes releasing nutrients necessary to wake up and nourish the embryo that will become the new plant.

Health conscious readers may be familiar with the discussion of improved nutrition in sprouted or soaked grains because the phytates present in these seeds have been removed (see here for more info). This is because in the seed, phytates bind up nutrients -phosporus in particular- keeping them off limits for the embryo (1). Water is one factor that initiates the enzyme phytase, which is responsible for breaking up the phytates (2). In the right temperature range, phytase completes the breakdown of the phytates, releasing the nutrients the embryo needs for growth. In most cases, the need for adequate water and longer durations of certain temperatures ensures the plant can grow to maturity once it sprouts.

Of course, many of our perennial vegetables also need cold, moist temperatures, or dry and warm temperatures, in addition to a later stage of warm moisture to successfully sprout. Phytates are one example of the mechanics generally at work in seeds -enzymes releasing nutrient.* Differences in the genetic makeup can dictate the time each seed takes to activate these enzymes, and release the nutrients for sprouting. Its variance in genetics that often gives such extreme variance in sprouting time, and what conditions are necessary to induce germination.

Most of our garden vegetables were the same way at one time, with lots of variance. They’ve just been selected. If over the next ten years I only saved seed from cardiospermum that sprouted two weeks after planting, this character would soon be the norm.

Although it’s nice to have an idea what’s going on in those drab looking little seeds as they deny us a happy sprout, what can we do to improve the likelihood that we, at some point, actually get a sprout?

Heather had the right idea leaving her Turkish rocket in the pot to see if any more sprouts would show up. Just give the seeds time, and changes in temperature.

I know from experience that keeping a little empty pot of dirt safe for seasons at a time is not easy. As a first step, designate a spot where seeds are protected -by mandate of heaven -or whatever works for you. Tell this to anyone that might come along thinking your untidy plant-keeping needs tossed in the trash.

Rodents seldom care about the mandate of heaven, so cover the seeds with some mesh, or build a hanging tray well above the ground, as Martin Crawford does, to keep them out. I hung some trays in our greenhouse last year which did the trick keeping mice out of squash seeds. The only problem with hanging trays I find is their fluctuating temperature: pots placed on them can easily dry out on a hot day.


Seeds are more likely to stay moist and live if they’re in more temperate climates surrounded by bricks in a shady corner. My favorite spot for sprouting is on the east side of our garage, or on the north side of our greenhouse. I’ll bring the trays from these temperate spots once in a while to the hot greenhouse. For a short time here, I watch them, and keep them watered, while transplanting any sprouts that appear. Once the sprouts stop appearing, I move them back to the less intense climate.

This system is very effective at getting around the errant nature of our prized perennial vegetables and trees. With such complexity, it’s better to just offer a variety of situations to seeds, and wait, rather than trying to guess what’s going on in those drab little seed’s dreams.

*There are even several kinds of phytase. See here for more info.

Making friends with rodents

Blurring gray fur and tails pour like a waterfall onto the floor in front of me. A tense minute, and the place is cleared -bare, clean cement floor, and nothing but hushed scurrying sounds all around. I’d just turned on the light.

This was one summer long ago, when several old building were torn down by the Township very near our chicken house. These were an old garage, another chicken pen near it, and a large old barn. They all housed droves of rats. Where did they go when these building fell? Our place.

We had quite a clean operation. When the rats came, we cleaned it to the max, removed all the wood shavings, straw bales, any and all feed -no matter how tight its container, and even some of the chickens. Despite the cleanup, the invasion lasted for months.

They were too smart to fall for traps. Eerily, one of the traps we found set off with no rat in it, had a freshly gnawed twig from the lilac bush right outside the pen stuck in it, the bait removed. My dad stayed up several nights shooting them with pellet guns. He terminated the lives of hundreds, but only recovered a few because the rats began eating their fallen, dragging them back into their holes immediately, or gnawing into them on the spot. To say nothing of a few unfortunate chickens that fell prey when the lights went out.

The rats made this new house their home in short order -with or without resources. They dug enormous piles of soil out from under the cement flooring, brought in food from some place. We had removed everything else.

When specialists begin throwing out statements about harshly mowing orchards to keep rodent and rabbit from gnawing away bark and roots of trees, I am a bit skeptical. These creatures create habitat for themselves and are part of thriving ecologies. They are eaten by almost everything, providing a vital link in the trophic system. If you have ever studied how these systems work, reducing one part of the chain, reduces, or at least effects, all the others following. If you reduce rodents, you by default reduce potential health of the trees you’re trying to protect.

A casualty in my parent’s small orchard. This tree was about five years old when snow fell, and a freezing rain covered the snow with a sheet of ice that remained for about two weeks. Rabbits, mice, and voles ate everything they could get at, including large trees like this one. See the gnawed bark at the bottom.

Rodents feed into a very broad system. Finding examples of what happens when rodents are entirely removed is difficult because we have seldom pulled this off in outdoor settings. If we have come close, someone is also fertilizing and pruning a lot to make up for the loss.

Rodents have many immediate effects too. For one, they dig holes, which allow more air and water to percolate into the soil. This is very good for soil health.

It’s interesting to note the trees most immune to damage by rabbits, voles, etc. are single seeded species, like peach and plum. The species most vulnerable are multi-seeded species, like apple and pear. Rodents and rabbits, every couple of years when the food gets scarce, devour the bark off a couple of these trees, killing the trees. If they didn’t these multiseeded species have a higher chance of sprouting on top of each other, and choking each other out.

Only one successful seed is necessary to replace its parent. Rodents are a factor which ensures the chance any young tree grows to adulthood is very, very low. This is a good thing in natural conditions. It means trees are more likely to be well spaced.

But how do we make our tree “the one” that grows to adulthood when we’ve already taken spacing into account?

The most effective move is just installing tree guards; simple spiral guards are fine for young trees; tree guards like these are better for larger trees. Larger trees are less vulnerable to girdling, but I have seen trunks near five inches in diameter girdled to the hard wood if the snow lays thick enough long enough. For these sizes, I am not a fan of corrugated plastic pipe guards because they’re extremely hard to get on and off, often harming the tree in the process. Even covering the trunks with tinfoil or fine wire mesh is better than nothing.

Opaque tree guards also protect from sun scald: when bright sun reflecting off cold snow heats the cold tree bark, making it crack. This isn’t good. Covering the trunk helps prevent it.

Another tactic is to provide food for the rodents (No, I’m not nuts. Keep reading). The fact is, rodents and rabbits will be present whether you like them or not. If you mow the grass, they will dig tunnels. If you remove food, they will find it, and store it.

I’m not the only one recommending this. One extension service informational pamphlet extolled mowing the grass in an orchard to the finest bits to reduce cover, yet recommended throwing out sunflower seeds when the snow fell. This is intended to divert the eminent population of rabbits, voles, and mice -now forced into starvation.

Apparently the specialists are aware their mowing and trapping are only mildly effective, and that the real issue is diverting and blocking the rodents when times get tough, not killing them. Natural predators do that.

It seems most logical to just leave the tall grass and brush -at least in isolated corners, so the rodents can feed themselves.

There are also biological deterrants, such as Sepp Holzer’s bone tar. Here is a forum discussion on the subject. Sepp Holzer explains making bone tar and its use in his book. I own a copy, and quite like it. I have never gone through the trouble of making bone tar though. Tree guards have done the job for me.

There is an idea that planting certain bulbs and other plants around a tree deter rodents and rabbits -especially voles, which eat roots underground. In controlled studies, ground covers like Pachysandra species, and bulbs like daffodils are themselves very unpalatable to rodents. This doesn’t necessarily deter their cozying up to your trees.

I’ve had trees with no guard brutally stripped by rabbits, despite a ring of daffodils around it. Keep in mind, when hunger gnaws, rodents gnaw just about anything -tasty or not. While these plants might deter voles from eating roots, don’t expect these to block the possibility of girdling.

Ecosystems keep a pretty tight control on rodents and rabbits as is. If we simply focus on making a healthy, lush habitat, giving your trees the protection to make them “the one” that succeeds in growing to adulthood, the rodents can function less as your foes and more as your friends. The alternative is certainly not as pretty.

Growing Amorpha

Deep purple petal over bright orange stamens of Amorpha fruticosa melt into green, spotted little crescents of seed. These ripen in the sun to a dark brown, then white-gray and hold. I kept thinking these seeds would fall off, but even in January when I lately picked some, they were tightly attached.


They have a peculiar ability to sprout without cold -unlike most woody perennials that need months of subfreezing temps. They just need heat above 70 degrees F, and up pop little green leaves. Usually I soak the seed for a couple hours before sowing into flats. I start them in February in some years, March in others, but for my climate these both mean heat has to be provided.

I have to be careful with the dry air of indoor heating to keep the seeds wet, so usually cover with some plastic, and water often. We begin heating a small portion of our greenhouse about that time for garden vegetables, so these seedlings can soak up real sunlight from day one.

They are wise little seeds, and spacing their sprouting time -which outdoors would be a fail-safe against late frost and other catastrophes. For me, it’s a great convenience. Out of one ‘source flat’ as I call it, sprouts pop within three days after planting, but keep popping up for several weeks.

Usually I wait until the first true leaves show before I begin transplanting, then clear the flat of any sprouts with true leaves once a week.

Out of the hundreds I have grown, I find it’s best to start the seeds with potting soil, or compost with good levels of nitrogen. From here I separate into small pots or cell flats no larger than 2 inches across, filled with the same kind of nitrogen rich potting soil they sprouted in.

The heat and rate of drying in smaller pots, where the roots can quickly reach the bottom and be air pruned, has given superior results for me. They still develop very deep taproots once in the ground, but this root pruning while in the pot is helpful -in part because it stimulates more branching of the root system. Planting in extra large pots with nitrogen rich soil, many seedlings rot, and must be replaced two or three times over before each pot successfully grows a plant. On the other hand I have tried planting them this early in nitrogen poor soil, and they make little headway.


I think this best mimics the situation they would find in nature. Forests and grasslands have a thin layer of nutrient rich, fluffy soil on the surface usually, which quickly becomes clay or whatever the base soil of the area. I want to get the seedlings into nitrogen poor soil to induce nodulation (aka hosting nitrogen fixing bacteria as evidenced by the formation of little nodules). This is spurred on by a lack of nitrogen in the soil. The catch is it takes time for the young plants to find the bacteria and get the symbiosis set up.

Nature’s way seems to be nutrient rich soil at first, then less rich soil as the plant gets bigger, the roots deeper. My contrived biomimicry that gives best results is moving the seedlings once they have filled their small pots and gotten a bit root pruned (not pot bound, as in roots turning back on themselves) into larger pots of whatever size you choose, filled with nitrogen poor soil about 1/3 rd coarse sand. I usually mix nutrient-rich rock powders, such as carbonitite or granite, into this before filling the pots.

Usually I transplant into 4inch pots at this point so they are filled with their roots in a couple of weeks -about the time nodules start to form. Usually this is early June -plenty of time for establishment before fall. Those I don’t get in the ground the first year go into gallon pots by August, which they usually have amply filled by next spring.

I try to avoid keeping Amorpha in pots more than a year. They grow best put in the ground as soon as possible after they have acclimated to the nitrogen poor soil. After years of refining this method, I’ve had transplants pushing 5ft by the end of year one -well on their way to exploding every spring with growth, providing some of the best organic matter for fueling your plant projects.

Where to get the seeds? You might have a plant nearby, which I recommend you snatch some seeds from. Otherwise they’re very affordable, and widely available from Sheffield seeds (my first choice), Oikos Tree Crops (They advertise A. californica, but I’ve gotten their seed -and plants, and compared it against pictures and attributes on the USDA plant database, and they have the name wrong. It’s species fruticosa), or even Amazon if you shop there.