Practical Permaculture – Plants and Phytoremediation

Plant identification is an art in itself and honestly has to be taught by physically seeing the plant, I have been to a million lectures with someone flipping through slides and talking about different plants, and I can say without a doubt that I learn very little. I prefer my plant introductions to be in person, I like to be able to touch, smell and when applicable taste the plant. Just as with humans plants have a first and a last name, the first part of the name is the genus and the second part the species. Common names I feel are just as important due to the fact that I find when I am asked questions, they usually go something like “Ever hear of cheeseweed, if yer chickens eat it it’ll make er eggs taste like cheese” really… Learn as much as you can about each plant you come in contact with, if nothing else Wikipedia the hell out of your garden, know what makes each plant tick.

Plant selection for permaculturists is really an art form that not only encompasses, but embraces biodiversity. Plants are the multi-tool in the permaculture world completing tasks such as attracting beneficials, repelling pests, soil remediation, soil stabilization, tillage, moisture control, living trellis, and as companions to one another often just simply enhancing flavor or improving one another’s health. An entire family of plants noted for their ability to fix nitrogen in the soil are the Legumes which include beans, peas, alfalfa and lupines as well as trees like locusts and redbuds.

I find that one of the most commonly mis-understood tools is the role of the legumes. Most legumes are sort of nitrogen hoarders in a way, fixing nitrogen for themselves and storing it for use inside the plant. Legumes don’t really “fix nitrogen in the soil” as much as they “fix nitrogen in the plant”, the green part of the plant is the key to nitrogen fixation. In order for the nitrogen to be fully utilized, the entire biomass of the plant needs to de-compose in place replacing the nitrogen into the soil. Another one of the commonly mis-understood ideas is that legumes fix nitrogen through out the entire life of the plant, this is simply just not true. Plants have changing nutrient needs as they progress through their life, plants use the most nitrogen during vegetative growth before flowering. Once a plant starts flowering, potassium requirements spike followed by phosphorus during fruiting. In order to maximize the nitrogen potential of legumes cut them before they go to seed and let the entire biomass of the plant break down in place.

Green manure is a cover crop grown to add organic matter and nutrients into the soil. Green manure is almost essential in a sustainable annual cropping system often being grown during the fallow period in winter and then tilled into the soil in the spring before flowering. Heres a quick list of plants used in green manure cover crops – clover, vetch, fava beans, mustard, buckwheat, lupin and alfalfa. Time energy and resources are required to grow and use these cover crops effectively, timing is everything and the window for planting is easily missed. Make sure that your planting dates allow enough time for your cover crop to get well enough established to over-winter.

Just in case you weren’t familiar with this next term I would like to introduce you to a guilty pleasure of mine called “fruit porn”. Oh you know you are into it, in fact, i’d be willing to bet your mailbox is filled with it during winter… Mine is! I sort of have a little problem with fruit porn, hoarding it, often finding old issues hidden in boxes for no good reason. All that I am going to say is be carefull, it is super easy to get “the bug” and order one of everything. I have seen this happen more than once and the end result is usually one or two absolutely perfect plants and a whole bunch of dead stuff. Instead pick one or two types of plants and get a bunch of one variety of each, this will allow you to familiarize yourself with that variety.

Urban lots are tricky in that they offer little space compared to a food forest or permaculture farm. When growing for more than just personal consumption you won’t be able to fill every square inch with every type of fruit tree, berry bush and vegetable you can get your hands on, instead pick a cultivar of apple and buy a few of them, and do the same with say blueberries and raspberries. This doesn’t mean you can’t plant a few specimen plants here and there and have a little fun with design. I am just trying to stress how nice it is to grow enough of one type of berry to be able to share or sell it.

I want to stress the importance of planting things other than food bearing plants and trees… I’m talking about bio-diversity here people, permaculturists work with EVERY facet of nature. Large trees create bird habitat and shade for the plants and people underneath them as well as something for the vines to climb on. The list of herbs that benefit other plants is absolutely enormous, common sage Salvia officinallis is one of my all time favorite herbs to use in the garden and landscape, when it blooms in early summer you can not get close to it because of the bees and is considered a companion to rosemary, cabbage, beans and carrots.

The idea of soil remediation or “phytoremediation” is nothing new, mankind has been using plants to repair soil for thousands of years. I always get a kick out of people referring to permaculture as “new” when in reality it is the cutting edge of a 10,000 year old idea… What we call organic, natural or sustainable was at one time simply called “FOOD”, it wasn’t until recent decades that we started having to specify the manner in which it was farmed. I have problems with the fact that foods are labeled organic as I feel the term is getting watered down as farmers test the limits of the rules, makes you wonder whats next… Morganic – Our veggies are morganic than the competition. Plants have been used to remove heavy metals and toxins from soil for years and a lot of research is currently being done on the subject.

Phytoremediation of leaded soils is a subject that is very near and dear to my heart, out of 10 lots soil tested last year here in Wilkinsburg I found only two that were within reasonable lead levels. Under 99 ppm is acceptable for lead levels in gardens growing veggies, we had samples test as high as 1558 ppm. Lead is commonly used in water and sewer pipes, roofing, cable coverings, paints, gasoline, insecticides, gold production, hair dyes, stained glass and photography to name a few. Lead is a moderately active metal that dissolves slowly in water and most cold acids, it does not react with oxygen in the air, and does not burn. Lead causes both immediate and long-term health effects and should be avoided at all costs. Lead is commonly remediated using indian mustard, ragweed, hemp dogbane and poplar trees which sequester the lead within its own biomass. Phytoremediation works as a multi-year tool for toxin extraction requiring a little planning, every effort helps though.

Here is just a small example of hyperaccumulators…

Arsenic – Sunflower or Chinese Brake ferns both store arsenic in their leaves.

Cadmium – Willow which is also an accumulator of zinc and copper, willow has a high transport capacity of heavy metals from root to shoot coupled with a huge amount of biomass production.

Cadmium and Zinc – Alpine Pennycress is a hyperaccumulator of these metals at levels that would be toxic to other plants, although the presence of copper will often inhibit growth.

Salts/salt tolerant – Barley and Sugar Beets are used for the extraction of sodium chloride to reclaim fields flooded with sea water.

Caesium 137 and Strontium 90 – Sunflowers were and still are being successfully used in the phytoremediation of the land around Chernobyl to absorb the radiation in the soil…

It is important to mention that phytoremediation is not an overnight solution to your soil woes but with some carefull planning and consideration of time constraints, soil can almost always be remediated using plants… I could ramble on and on about plants so this may have to turn into a multi-part section of this series, we will see…

peace – chriscondello

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