A note on soil contamination

Cet article en français.

Louise:

 While reading a lot about gardening, sooner or later we become conscious about the consequences of soil contamination regarding the culture and consumption of edible plants. A lot of substances can contaminate the soil. I will skim the subject here and give a few references at the end of the article on which this text is based.

The possible presence of lead surrounding the foundation of my house didn't prevent me to garden, as long as I followed some important rules.

To my knowledge, the most common type of soil contamination around old houses made from painted wood planks is lead, since the paints, in a not-too-distant-past, have had lead in them. When paint must be redone, people generally scratched the old paint away, leaving it where it fell, getting slowly buried throughout the years.

Today, one of the modern types of contamination is arsenic, because the wood used for building porches, patios and decks is being treated with it. There's also the contamination from creosote, contained in old railway beams now used to create halfwalls, garden bed borders or walkway lining, amongst other things. And let's not forget accidental contamination, for instance in the case of an old oil reservoir that leaks.

Furthermore, the soil used to burry the basement of a newly built house could hold potentially unpleasant surprises since not every construction company thinks about the ecological impact of spreading contaminated soil practically on your doorstep.

 Finally, proximity to factories or major roads where circulation is dense can bring heavy metals via the dust carried by the wind.

When this old arch fell apart 2 years ago, we
chose not to rebuild it since the space receives a lot
of sun, which now allows me to grow some
vegetables. But since we had used wood
that was treated with arsenic, I have to grow
them in containers deposited over the ground.

In case of doubt, you can have your soil analyzed. Of course, decontamination is not always affordable for everyone (it's a pricey enterprise). But you can still garden, using techniques that circumvent the contamination problems. The easiest solution and the most radical one is to just garden in containers with new, bought soil.

Personnally, living in a beautiful, centennial victorian, I expected that old scratched-out paint to still be on site, right where it fell, sprinkling the soil with lead. But there's two good news: generally, plants don't tend to absorb a lot of lead. Furthermore, this heavy metal is stable and stays where it fell. It will not go elsewhere or spread. When plants do absorb some, it concentrates in the stalks and leaves, not in the fruits. Regarding roots and tubers, lead generally concentrates on the surface (more accurately in the soil stuck on these roots and tubers).

However, the quantity of lead contained in the fruits would be minimal if nonexistant. The warnings given by governments and universities are aimed at leaves, roots and tubers of vegetables. The plants that give fruits are thus considered fine for humans to consume. Don't forget that, in the botanical sense, a fruit is the part of a plant that bears the seed(s) and that comes from a flower that's been fertilized: tomato, squash, pepper, cucumber as well as grape, strawberry, or apple.

The University of California considered there is more risk for the gardener to inhale dust contaminated with lead while gardening than there is while consuming the vegetables if they are well cleaned. For the harvest of leaves, roots and tubers, this University recommends the following measures: 

- Use new soil in raised garden beds to prevent vegetables from getting in contact with the lead.

- Make sure the soil used is rich in organic matter, since this type of soil can imprison lead more efficiently and prevent plants from taking it.

- Add a compost rich in phosphorus and keep the pH neutral or slighlty alkalin (not higher than 7,5 however, else it may harm the plants). Avoid acidic soil since it stimulates the plants' capacity to absorb lead.

- Clean the leaves well, brush the roots to take out all traces of soil and peel the skin of tubers.

Just at the foot of my rock stairs, a tiny
watermelon of the variety Sugar Baby managed
to give me 3 melons. In the background, we can
spot some eggplant green leaves.

Personnally, I'd rather take a few more measures of safety. So, in a radius of 10 feet (3 m) around the house, besides ornementals, I only harvest plants that give fruits: tomatoes, beans, peas, groundcherries, peppers, strawberries, for instance. I avoid any kind of root vegetables even if the recommendation is to simply peel or brush them. However I'm not particularly concerned about consumming the edible flowers that surround my house. And of course, nothing prevents me from growing leaves, roots and tubers in containers.

Hélène :

I read that some mushrooms can actually absorb lead. The research on this is still young, but some scientists have figured out that mushrooms have the capacity to clean certain pollutants, not only chemical toxins but also heavy metals. This area of research is called mycorestoration and mycoremediation (you may want to consult the book I read on the subject and a Ted talk from the author, Mr. Stamets).

This cute morel grew just at the foot of a side-entrance to the house. I don't know if it absorbed any lead or other heavy metal, but I didn't take the risk. I contented myself with a picture of it...

For more details or to further your own research on the subject, here are the following references:

Documents on soil contamination (Governement of Canada) 

Lead poisoning (Wikipédia)

Home Gardens and Lead (University of California)

About the potential richness and diversity in an edible garden, part 3

Cet article en français.

Diversity is an excellent thing for any garden's health : 

Until now, what I came up with as a garden design didn't start any revolution, even if it's more audacious than what we're used to see in frontyard gardens. Nevertheless, it allows me to benefit from the advantages of biodiversity :

A small bush of Common Milkweeds (Asclepias
Syriaca) which squat my flower bed and
managed to avoid eviction up to now. I conceded 
them the victory a few years ago, but I limit them
to this very spot. The numerous shoots that I must
pull out on a regular basis to avoid invasion are a
good source of mulch. On this photo, you can see
quite a few stems laying on the ground, already
half dried up. 

- I have a lot more perennial ornemental plants than vegetables. It guarantees an aesthetically pleasing layout, at least if you like cottage gardens, overflowing with blooms from the very start of spring, up to severe automn frosts. One thing is for sure, my vegetables, drowned as they are in a sea of flowers and greenery, didn't prompt a negative reaction from any of my neighbours. In fact, the vast majority of passers-by don't even notice my vegetables. They are very surprised when I hint them in the right direction with my finger.

Common milkweed (Asclepias Syriaca), a Quebec native, is a feral plant, for sure, but it cuts a fine figure with its huge pink-ball blooms, followed by attractive seedpods. If a Monarch Butterfly passes by, its favourite plant is awaiting it. Some foragers eat certain immature parts of this plant, for instance the flower cymes and the seedpods. But caution is necessary, since in Quebec and elsewhere, there were some serious cases of  poisoning. Personally, I rather leave them to Monarch butterflies and content myself with their natural beauty.

- An uninterrupted succession of blooms provide a constant source of food for pollinator insects, which then are already in place to pollinise also any edible flowering plant when it starts to bloom. Same thing for  many predatory insects, such as ladybugs, which can eat pollen as an alternative source of food whenever they don't find any prey. This way, plant diversity creates a choice accomodation for numerous beneficial insects, which will most probably choose to settle in.

Toads are quite numerous in my
garden. They are permanent dwellers.
Here and there, I build shelters like
this one for them, if they please.

- A large variety of plants offers an ecosystem capable of providing for a large array of living beings: micro-organisms, mushrooms, insects, worms, amphibians, small rodents, bats and birds. In turn, they take care of keeping each others' populations in check and therefore, they preserve balance. Sure, bad bugs will be present also, but their predators as well, useful helpers that will work for me. As a result, I used a biological insecticide only once in ten years. By the way, it wasn't very effective. The imbalance finally disappeared for good all by itself a couple of years later. The only recurrent problem was a seasonal infestation of caterpillars that would have eaten every needle of a Mugo Pine Tree without my intervention (manual removal). In the end, I cut it down, because it wasn't in good health anyway.

A tiny spring peeper found refuge in the heart of a "Trahlyta" daylilly flower, of which the petals sports a special mix of tinges : lavander blue going to grey. Throughout the years, I also found grey treefrogs, but their presence is only occasional, just like regular frogs.  It is still impressive to find some a couple of feet away from the sidewalk on a site that was so hot and dry when I started gardening there.

This slug is in a dangerous
predicament, crossing rough cement
between two garden beds. A small tuff
of black-eyed susans waits for it
on the other side, but the though
leaves will be a disappointment...

- Another advantage of polyculture, one that's often mentionned in articles on the ecology of the garden: vegetables that are hidden amongst other plants are harder to find for pests. Of course it's easier for them to wreck havoc in a traditional vegetable garden where all the good plants are gathered together in perfect rows, like an appetizing all-you-can-eat buffet.

At the opposite of this, a diversified garden will force the pests to use a lot of energy just to find the coveted plant. Furthermore, they might not be able to find them all and while moving from one plant in search of the next, they may find themselves nose to nose with  their predator.

A grey treefrog enjoyed a spa afternoon on the top of the pool filter. It seemed to enjoy the continuous vibration of the device, completely indifferent to my presence in close proximity. This tiny arboreal amphibian has the amazing capacity to change colors in a matter of minutes, going from green to brown to grey, to camouflage itself. Apparently, it hasn't yet managed to turn a neat, plastic-white colour, else it would have made for a pretty nose!

- When perennials take all the place, weeds become less of a problem. Furthermore, established perennials mean the ground hasn't been tilled in all those years. Its structure and quality are thus greatly enhanced, simply because nature's work of cycling nutrients isn't destroyed by the blades of a tiller each spring. A surprising array of living creatures, micro-organisms, myceliums, springtails, burrowing insects of all kinds, earthworms, amphibians and even tiny rodents have a way of tilling that is far more respectful than ours. They aerate the soil, digest organic matter either fresh or already decomposing, add fertilizer by their dejections or cadavers, move nutrients around and contribute to make the soil an ecological place that is both healthy and diverse.

Two varieties of Burning Bush (Dictamnus Albus).
Their white or pink stalks give height in the garden
come May. I find their perfume simply irresistible.
The Burning Bush can live up to 60 years, but they

have a hard time being transplanted.

Maybe that's the reason why it's so seldom

seen in Quebec's gardens. Most unfortunate,

because it's a splendid plant.

- Every species of plant brings its personnal contribution to the general health of the garden. For instance, Pasque Flower (Pulsatilla), with its big tap root that digs deep down in the soil, manages to reach nutrients unavailable to plants with a shallower root system. The Pasque Flower stores these nutrients in its tissues and releases them on the surface when its aerial parts die, making the nutrients available to plants around. As for the  groundcovers, they form a protective mat that retains moisture and shelters the soil from wind and rain erosion.

Some aromatic plants, like mint or burning bush, by releasing powerful perfumes in their vicinity, hide the scent of other plants and thus protect them from pests by desorienting them. And it bewitches the human senses too.

My garden at the end of March, when I'm
almost done cutting down all the dead
vegetation of last fall. The debris are
cut short and left in place (except for seeds,
if I don't want them to sprout and give
birth to  new plants).

- All this magic happens because I leave vegetal debris on my beds in fall. Hélène does the same in her garden. When spring comes, we cut all the left over stalks and use them as mulch. The soil is fed and grows every year that way. Sometimes, we have to push aside the mulch layer to make way for the growth of some plants in spring.

Results: First, the occasional thaw-and-freeze cycles of mid-winter are not fatal anymore to some more fragile specimen. Second, I rarely have to water my perennials in summer, even in times of drought, and third, I rarely fertilize them. As for my annual vegetables, when planted in good soil and protected by a good thickness of mulch, I only have to water them occasionnally, like after many days without rain or during a heatwave.

Crocuses are among the first few plants to come out from my vegetal mulch. After a very colourful show, they will disappear until next spring, and in the meanwhile, no one will be able to guess the presence of their dormant bulbs.

- Nature spontaneously creates groupings of plants that, because of their complementary characteristics, come to cooperate and help each other out. When a garden has lots of varieties, chances that they may form beneficial companionships are multiplied. This happens  without me even being conscious about it, for the most part. Daffodils repel rodents, catmint draws... cats who, in turn, repel birds and rodents, the few dandelions that can manage to root in the garden leave a breathing hole in the soil once I pluck them out, and they leave good nutrients on the ground where I drop them to decompose. The lilac Miss Kim slows down the gushing winds that slip between my house and the neighbours. Its falling leaves are left in place and contribute to the existing layer of mulch in its vicinity.

- Since plants are complex beings, we do have to expect some measure of failure, sometimes inexplicable ones. For instance, these papavers that never managed to settle anywhere in my garden, even thought I tried and tried, and the conditions were, in theory, very adequate. And these  radishes that never amounted to anything but producing leaves wherever I tried them. I think that after a series of unsuccessful trials, it may be preferable to stop cultivating something that definitely has a hard time to grow in one's garden. The easy way to garden is sometimes synonymous with humility, wisdom and going with the general flow.

A view of my garden from the sidewalk, after the ice storm of 
December 2013.
It transformed itself into a still life. I think it's prettier than the flat
surface covered in icy snow that would have resulted from my cutting all the dead vegetation close to the ground before winter. Furthermore, a new crop of mulch is waiting to be cut down for next season. This fall, I left in place all the Black Eye Susans' dried flowers. If some neighbouring birds start to get hungry before spring, they will be able to count on their seeds to await next spring.

The most common plants may give us huge surprises, like this Geranium (Pelargonium), an annual  that  can offer us a few leaves to chop in order to add an unusual taste to a salad. 

How I pushed a little more the "edible plant" definition and the polyculture principle :

One of my favourite exploration strategies is to gather information on each one of the species present in my garden, weeds included. Internet is a very valuable source of new informations, as are some specialized books on gardening. This way, through my readings, I realized that many plants among weeds as well as ornementals, are perfectly edible, or present themselves with very useful qualities.

My fall harvest of violet leaves and
stems. I chopped, blanched and
froze them for further use in a 
spaghetti sauce (leaves) and a soup
(minced stems). Violets multiply 
themselves readily in my garden, even
forming a nice ground cover of
medium height in some spots. 
I discovered that we can harvest the 
young leaves to eat them fresh and 
raw just about any time in the growing
 season, but even the older leaves are 
edible when finely chopped 
 and cooked.

This way, I found out that daylily shoots are delicious. As for Hélène, she recently discovered that our hostas are considered genuine vegetables in Japan. All this time I was thwarted by the fact that I didn't have any sunny spot for asparagus plants. And now, I discovered that I may harvest two alternative greeneries already very well established in my garden ! Same thing for some leafy edible plants that can incorporate themselves in my salads. Here, on a regular basis, we eat the leaves of violets (Viola), Musk-Mallow (Malva Moschata) and Linden tree (aka Basswood, or Lime tree - Tilia Americana, Tilia Cordata or Tilia X. Europea). Yes, it's a tree, and quite common in urban areas. Martin Crawford, one of U.K. leading authorities on forest gardens, even refers to it as the Salad Tree.

There's also the occasional edible mushroom that may offer itself as a sampling, when we can identify it with certainty. And let's not forget that maple syrup may be harvested even in cities !

Because Blue False Indigos are huge perennials,
I've been tempted to sacrifice them. But I would
have deprived myself of first quality green
manure. All aerial parts of these plants will
end up as mulch, enriching it with all the
nitrogen that they accumulated during the
growing season. By the way, Blue False Indigos
too can live up to sixty years.

I also learned that my Blue False Indigos (Baptisia Australis), though not edible, are part of the great family Fabacea. Therefore, they play an important role in soil fertilization in a natural way and without any effort from my part.

And when I pull out a dandelion, whenever its root is fat enough, I harvest it to dry it up, because one of my favourite herbal teas is made of stinging nettle leaves and dandelion roots. This tea is recommended by herbalists for its detoxificating and invigorating effects. As Hélène already pointed out, every plant has its usefulness, even if we, gadeners, aren't always aware of it.

All those discoveries and observations made me think a lot. Why not use as many different perennials as possible as a food source ? After all, their advantages are numerous :

- Many species of perennials grow very well in part shade or even in shade, unlike our traditional vegetables.

- They require minimal maintenance, compared to annual vegetables , and many of them are not invading. Incidentally, the ones that are more agressive may be efficiently controled by harvesting them on a regular basis. It's what I do with goutweed.

- As long as perennials find what they need to prosper in the spot we chose for them, they are much more resistant to climat changes. Indeed, either in bad or nice weather, your clump of chives or your big hosta will  reappear year after year.

- If we learn to cook with edible perennials, we can vary our meals without spending one cent, as long as we're willing to get used to new tastes.

There is plenty of choice  :

If you like to aromatize your meals
with celery leaves, lovage
(levisticum officinale) may be for you.
Here, this perennial can reach 3 feet
(1m) in part shade. In Helene's case,
in full sun and during the good gardening
season of 2013, it reached 6 feet.
 Thus, one plant is enough for an entire
family.

Many perennials are edible. We can eat them whole or in parts, as vegetables or herbs, use them for their medicinal qualities or they simply make good beverages or herbal teas.

Among them, some are used as herbs : lovage, catnip, lemon balm, mint, origano, wild ginger, wild garlic, horseradish, chives, egyptian onion.

For bee balm, echinacea, mullein, plantain and the roots of dandelion, these plants can come and round up our pharmacy arsenal.



Jerusalem artichokes tubers
(Helianthus Tuberosus L.).

Helene and me both harvest the tubers of jerusalem artichokes and I will be able to harvest the immature fronds of ostrich fern (Matteuccia Struthiopteris) when they are still in the form of fiddle heads, as soon as my clumps get bigger. Watch out thought, this species have been declared vulnerable by the Quebec governement, but it's still possible to buy some in garden centers, in a respectful manner towards the environment.

Rhubarbs, when in bloom, become the showstoppers of the month, and then, I can use the stalks either in a dessert or jam or even extract their juice as a substiture for lemon juice. I never noticed any weakness in my plants if I let them flower. I use the big leaves (toxic if ingested!) as mulch directly around the plants themselves.

Amongst groundcovers that are dense but not too high, sweet woodruff (Galium Odoratum L.), with which Helene makes Maitrank. 



Goutweed (Aegopodium podagraria), 
here in its variegated form,  is a perennial
green that grows very well in part-shade
and is invasive. It's also one of the most
delicious weed. I have an isolated bunch
because it was choking every other plant
in its path. 

Here, there's a couple of common weeds I use with abandon as greens : 

goutweed gives a beautiful turn to meat dishes, sheep's sorrel (Rumex Acetosella) from which the sour leaves can be used either in soups or salads,  chickweed (Stellaria Media), that I allow to grow in my containers at the foot of the other plants and that I eat in its entirety (extremely tiny leaves, flowers and stalks) for its refreshing taste, or even common purslane (Portulaca oleracea), a little succulent plant well propagated in Quebec of which I find the leaves juicy and delicious, but that requires poor soil, a soil that's becoming rarer in my yard. I have trouble still with dandelion and plantain leaves (not my taste), but I sometimes use ground ivy (Glechoma Hederacea) as an herb, on occasion. Stinging nettle (Urtica Dioica L.), is considered by some as a super plant for the incredible array of qualities it can boast about. The leaves are good cooked, like spinach, in soups or added to some recipes. I grow it in containers to prevent its spread, since I react particularly badly to its stinging (from the "hairs" on the plant).

Then again, we can think of all the varieties of trees and bushes who give edible fruits: gooseberries and currants make an abundant harvest of berries, just like raspberries and blueberries which can also be used to make herbal teas from the leaves. Elderberries offer flowers and berries if you are patient enough to do the harvest. Roses of either Rugosa or Canina varieties give their petals and their fruits called rosehips.

Finally, we may incorporate in the garden beds some small fruit trees, cherry, apple, Juneberry and Common Sea-Buckthorn, to name a few. And don't forget that some other species of trees may be tapped, besides maples. For instance, birch trees give a syrup presenting a texture and taste a little similar to molasses, but more refined. Really delicious. This syrup too may be homemade. 

For me, the nicest part of all this adventure is that my quest for new informations is not completed yet. I did not have the time to investigate over at least half of the species present in my garden. Therefore, my fun is far from over !

My garden under a coat of ice.
Have a happy gardening year in 2014 !