Suck it Up - Phytoremediation

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Organic Ade

Suck It Up!
(AKA Phytoremediation)

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Witch Hazel
the "easy organic"

So you've had your soil tested and you're in trouble. Somehow, somewhere, chemicals have gotten into your soil. A burst septic system, a chemical spill, arsenic treated wood, lead paint, blasting powder from well digging, or a stump hole has poisoned the soil in your yard. 

And, here come the experts, telling you the only way to have a garden you can enjoy is to remove all the soil and replace it with new. So there goes your garden budget anyway. Right? 

WRONG!  Read on...

Welcome to the wonderful world of Phytoremediation (break it down fight-o-remeedee-ay-shun). Using plants to fix soil is an old, old tactic, but one that has somehow been lost to the average gardener or farmer. Plants can clean up pesticides, heavy metals, explosive and oils, among other things, and keep those contaminants from being washed down into the water table. The plants can do this by one of three ways. They can store the chemical in their roots, stems and leaves. They can change the chemicals into less harmful chemicals within themselves. Or they can change them into gases, which are exhaled and reduced to harmless trace amounts when combined with the air. Also, if you have inoculated your plants before planting them, the fungi that live on and near the roots of the plants can break down the chemicals, or just concentrate them and stick them to the roots of the plants, to be pulled from the soil later. 

The benefits to phytoremediation are obvious. It is letting nature take care of our slip-ups. In some cases the absorbed materials can be extracted from the plants, reutilizing them so that further mining isn't as necessary. Some of the down sides are that it takes a little time, and effort on the part of the property owner. It may appeal to some to just have someone come in and remove the polluted soil. But that isn't fixing the problem; it is only moving it from one place to another. 

In some areas, the toxic accumulations are a part of the natural flow. Evaporation of underground water can bring toxic amounts of selenium and boron, nickel and other materials to the top of dry soils in the form of salts. Since this is a recurring problem, a cyclic planting of absorptive plants can be initiated. Every four to ten years a crop of hyper accumulators could be planted instead of the favored crops, thus loosing one season of crops, but ensuring the continued viability of the soil for future plantings.

When trees are used for phytoremediation, they are for the most part left in place to stabilize the contaminants and to change them into harmless gasses but if you have a use for a specific area, annuals and herbaceous perennials might be your way to go. The previous seasons growth can be cut and disposed of properly (not in a compost pile) to disperse the contaminant. There are specific plants for specific contaminants, and I hope to hit a few here for you, and show you what to look for. Remember, after a season of phytoremediation, get your soil tested again, to see if you need to kick it up a notch, or if the soil will be safe to work with.

The Best Suckers for...        

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Brake Fern sucks up arsenic

Arsenic: One of the best hyper accumulators of arsenic in the soil and in ground water (from treated wood) is the pteris vittata, a Brake fern that sucks arsenic from the soil at an amazing rate. This fern can also be grown hydroponically to cleanse water sources. The fronds should be cut in the fall and disposed of safely. Brassicas, particularly Indian mustard, are also hyper accumulators of arsenic and other metals, if you need a sunny patch cleared up. 

Leachate: The nasty liquid that percolates from landfill areas can be safely contained and controlled by rapidly growing poplars. These poplars then exhale them as gasses into the air, and transform them. They are short lived, however, so it is advisable to plant longer living trees, like mulberry and Osage orange, amongst them. They are capable of breaking down some of the most toxic and persistent poisons, including PCB's. Got a new house on an old landfill? Start planting. 

Benzene: Alfalfa grass and poplar trees can remove not only benzene compounds, but also ethyl benzene and other chemical compounds from the soil. Again, cut the grass and dispose of it the first year.

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Sunflower and Cabbage
 suck up metals

Heavy Metals: Plants can't do much about the music, but the actual metals in your soil, like zinc and cadmium can be absorbed by Alpine Pennycress and cabbage. For those of you who are thinking that these beneficial plants are looking distressingly like a lot of weeds, take heart. The Pelargonium Geranium is also a hyper accumulator of heavy metals, and are excellent at treating CCA (chromium, copper, arsenic treated woods…you know…your deck?), and lead in soils, including the lead that is in gasoline. Sunflowers are also a heavy metal accumulator, so you can have your cheery garden while healing the soil.

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Sunflower sucks up radiation

Radiation: Okay, so this isn't your average problem with soil in a garden. But folks who live in the desert near where testing has occurred can find that their soil has suffered fallout and contains radioactive materials.

Pigweed (amaranthus retroflexum), though it may seem to be just another noxious weed, can remove radioactive cesium from the soil. In a heavily contaminated area, pigweed can remove three percent of the cesium in three months. In a lightly contaminated garden, it could clean it up in one or two growing seasons, planted two or three times a season. And here is where sunflowers shine again, as lovely plants with a purpose. They are used to absorb cesium and strontium from soils.

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Alfalfa sucks up petroleum

Petroleum: Picture this…your husband or teenage son has been working on your car, changing the oil. The pan is left in the way a little to long, and WHOOPS! Into the garden or yard it goes. Not a good scene. But never fear! Fescue and Bermuda grass, clover and alfalfa can stabilize that oil and keep it from killing off the garden. The microbes used to inoculate the clover and alfalfa are better at stabilizing it faster than the other grasses, but either will work. One season should do the trick, and you can go back to planting there next year.

Explosives: Okay, well, again, this is not a problem for most folks, unless, like my family, they have some hicks in the woodpile that went fishing with dynamite when they were young, drunk and stupid. Or maybe you have a kid who is into the whole evil genius scene. In any case, if you have TNT, RDX or any of the other explosives chemicals in your property, parrot feather, reed canary grass, water star grass, and elodea could be your answer.

Nitrates: This is not generally a problem in soils, but in water, nitrates can build up and cause problems. Nature has given us the right idea where water is concerned. She filters her waters through bogs and marshes, slowly easing the water through a myriad of roots, leaves and stems to make sure that what flows into the sea can be assimilated by the life already there. Plants such as bulrushes, water lilies, arrowhead, cattail, sweet flag, and water hyacinths can absorb the extra nitrates along with moderate amounts of heavy metals and even chlorine to cleanse the water and make it safe for wildlife and humans alike.


Best Plants

Heavy metals

(e.g. benzene, toluene, zylene)

Alpine Pennycress, Barley, Cabbage, Crucifer, Dandelions, grass (Rye, Fescue, Bermuda, Sorghum), Hop,  Indian Mustard, Nettle, Pelargonium, phreatophyte trees (poplar, willow, cottonwood, aspen), Rape Seed, Stone cress (Thlaspi caerulescens), Sunflowers

Wood Preservatives
(e.g. arsenic, PAH)

Brake Fern, Indian Mustard, fibrous rooted grass (Rye, Fescue, Bermuda, Sorghum), phreatophyte trees (poplar, willow, cottonwood, aspen)

(e.g. PCBs, pesticides, herbicides)

grass (Rye, Fescue, Bermuda, Sorghum), legume (Clover, Alfalfa, Cowpea) Mulberry, Osage Orange, phreatophyte trees (poplar, willow, cottonwood, aspen), 


Indian Mustard, Pigweed, Sunflower


Alfalfa, grass (Rye, Fescue, Bermuda, Sorghum), Hybrid Poplar, Indian Mustard, Juniper


elodea, grass (Rye, Fescue, Bermuda, Sorghum), legume (Clover, Alfalfa, Cowpea), parrot feather, phreatophyte trees (poplar, willow, cottonwood, aspen), reed canary grass, water star grass 

(agricultural runoff)

grass (Rye, Fescue, Bermuda, Sorghum), legume (Clover, Alfalfa, Cowpea), Indian Mustard, phreatophyte trees (poplar, willow, cottonwood, aspen),

Bullrush, Cattail, Coontail, Pondweed, Arrowroot, Duckweed; Algae, Stonewort, Parrot Feather, Eurasian Water Milfoil, Hydrilla, Sweet Flag, Water Hyacinths, Water Lilies

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