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.

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.

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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.

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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.

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Amorpha regrowth 2: the results

Frost came and the Amorpha is done growing for the season. Check out this year’s growth.

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Visually impressive I know. It’s actually lacking 2 ft of what I expected. If you’ve read Dealing with deficiency earlier this summer, you probably noticed this season wasn’t stellar for lush growth.

Compared to the nearby cherry that yellowed and lost its leaves several months ago, the amorpha did quite well, remaining green and vibrant, growing for a lot longer than other plants in the food forest. Early September even it slowed down and aborted its growing tip, calling it quits for the year.

Last year it grew right until frost in October. If the same had occured this year, I suspect it could have grown that extra 2 ft and more.

I plan on coppicing again next year. A lot of my seedling Amorpha I coppiced lightly this year though, just removing a branch or two to which they responded well. So I may have more genetics in different locations to compare with next year. I’ll keep you posted.

Dealing with deficiency

One of my three sweet cherries in the food forest has for the last two years lost its leaves a little earlier than the other trees. A slight difference, I dismissed it as stress from converting its nitrogen source, as it came in soil filled with synthetic N from a nursery unlike my other trees that were bare root.

Trees seldom turn colors - let alone lose their leaves around here -in August. The tulip poplars and my sweet cherries in particular are turning color and losing leaves while other plants seem to be alright.
Trees seldom turn colors – let alone lose their leaves around here -in August. The tulip poplars and my sweet cherries in particular are turning color and losing leaves while other plants seem to be alright.

This year, it happened far earlier and another, the healthiest of the three that was planted bare root, began the same yellowing, browning, curling, and dropping of leaves from oldest to just sprouting.

Potassium deficiency seems to be the culprit, as the leaf loss began mid season, about July for the one, and August for the other, accompanied by lack of rain.

It’s not so much deficiency so much as unavailability. You see, potassium is naturally in the soil –in most cases a lot of it, but it’s chemically bound as rock to other elements. Rain and to a small extent plant roots use acids that slowly free up the potassium, making it available for use. When rain stops falling, the supply of acids goes down, without the acids there’s no release of potassium.

We have been without rain for several weeks now. And before this lack of rain we had too much –daily rain for several weeks. This actually makes the problem worse because sodium becomes more active when there’s too much potassium, and just like drinking sea water causes dehydration so active sodium makes water unavailable to plants. So no wonder I’m seeing a deficiency.

Other plants need high amounts of potassium for good health such as clover, which also browned and dried up in that part of the food forest, whereas ragweed (Ambrosia) is just getting really happy, as it likes a low potassium environment.

Of course, several chemicals may be at work showing the same symptoms, but they do fit the bill for potassium. Whatever the culprit, the remedy, as far as I am concerned, is about the same.

The weathering of rock releases plenty of nutrients including potassium. Once released, organic matter and humus grab hold of these released nutrients and hold them with a weak bond plants can access. When organic matter is lacking, these nutrients leach, or get bound up as this quote from a study in upper New York points out:

Only a trace of acid-soluble phosphorus occurs in the plow layer and upper B horizons. At lower depths, the phosphorus content is as much as 12 ppm. The pH increases with depth from 5.3 in the surface soil to 5.7 in the B a. Nitrogen averages 0.13 percent in plow zones, while organic matter averages 4 percent. As expected, organic matter is closely related to nitrogen in these soils. It is also related to exchangeable potassium: the amount of mineral colloidal matter in coarse sands is too meager to have much effect on the supply of potash [the usable form of potassium] in ionic [usable] form. Hence, most of the available element is held on organic colloids.

 

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Organic colloids is organic matter and humus, aka decomposed mulch or compost. You get a higher yield of humus from woody material containing lignin than green lush material, hence my interest in woody N fixers.

IMG_0484 The stick behind the Amorpha is the healthier cherry. Notice the Amorpha is fine. In fact, this is the one I hacked of just this spring. Amorpha have very deep roots.
The stick behind the Amorpha is the healthier cherry. Notice the Amorpha is fine. In fact, this is the one I hacked off just this spring. Amorpha have very deep roots.

Thankfully, my oldest Amorpha is right by the healthier cherry tree, so help is on the way.

Adding a few more mulch makers around the tree would in the long run benefit this supply of organic matter. Comfrey would be especially good for this as its roots go deep to where potassium and phosphorus leaches, as the quote infers. Comfrey is also said to accumulate more of these elements than most plants, which when cut would decompose along with organic matter.

 See this study on the effectiveness of buckwheat for scavenging and making phosphorus more available. Some study organizations such as this one suggest it affects more than phosphorus. Rye is mentioned here for nitrogen and potassium scavenging.

This spring I added more swales in the food forest –just small ones that I dug with aIMG_0486 shovel. These allow more rainwater to soak in, releasing more nutrients for a longer period of time. I’ve noticed this is only slightly longer though, if wilting is any indicator. The greater benefit plants get is more water when it’s around, which does boost growth noticeably. More growth makes more mulch, which makes more humus, hence water and nutrient retention is improved by swales in a direct as well as roundabout way.

So this is the plan I have for now. I’ll keep you posted on its effect.

Amorpha regrowth

So I introduced you all to my oldest amorpha last year with this picture:

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I included a small picture in the previous post of the six foot specimen just a year later. I lately coppiced it.

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This is about 3 weeks after coppicing. I left about 8-10 inches of branch above the ground, and about every inch sprouted a new shoot. As of taking the picture many of the shoots were 6-8 inches long.

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We’ll see how much growth it makes before frost.

N fix 2: Amorpha fruticosa

The most used nitrogen fixer in my food forest? Amorpha fruticosa. There are myriad reasons why: PCD3947_IMG0034 First and foremost, because it is easy to grow from seed. No scarification. No hot water or acid baths. It doesn’t even need stratification. But it grows. I planted a small handful of seed this spring, and I couldn’t even get around to potting up all the sprouts. Thankfully they didn’t all come up at once, giving me a larger span of time for transplanting. IMG_1939 For such convenience, there is hardly compromise in quality. The USDA puts Amorpha fruticosa in the “medium” nitrogen fixer category, meaning it has 85-160 lbs per acre nitrogen fixing potential. This is very good for a native.

Being native, my seedlings found the right bacterial clients without any inoculation. For anyone not in its native range, it would be wise to inoculate to be sure you have them. I started finding nodules within eight months from planting the seeds.

I imagine having or not having the bacteria would explain why some people think of this plant as slow growing. My established plants can grow as much as six feet from the ground up in one year. In their first year from seed, the fastest growing plants grew to just under three feet. Even in its native range the ground might not have the right bacteria. So if your plants grow much slower, perhaps consider getting some inoculant.

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A three year old A. fruticosa. The taller branch in the middle is the last three years growth. This fourth year it sent up the branches you see at the base, most of which were just under six foot tall by frost.

Such fast growth doesn’t equate to a huge plant. It only grows to a maximum of 12 feet. Most people cite 6-10 feet as a more average height. But again, maximum benefit will be achieved from coppicing. So it shouldn’t ever get over 6 ft, right? It has no complaints being coppiced either. An experiment in the southeast US was able to coppice the plant four times a year.

This management conveniently keeps the plant from setting seed, from which it propagates very well, as I mentioned. I plan to coppice mine just once a year, in late May. This is right before the flowers bloom so it doesn’t make seed, and makes for the best mulch material, since flowering time for a plant is when the most nutrients are active in its upper parts.

If you want to keep the above ground growth, such as for letting the plant establish, I have been successful just popping off the blossoms by hand, since the plant doesn’t rebloom.

I wouldn’t pluck them too early though, as the flowers are really very beautiful. On top of that, I have a love affair with healthy legume foliage. So between that, the flowers, and all the uses, there’s no wonder why I can’t get enough of it.

False indigo
Top photo by Benny Simpson, above photo by Bruce Leander, found on wildflower.org