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Does it exist? Weed database as a way of soil analysis?  RSS feed

 
raven ranson
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And if it doesn't exist, why not?

A lot of the old books (pre 1930) talk about evaluating the soil composition, drainage, trace elements and it's needs by looking at what weeds thrive there. Unfortunately they assume that the reader already knows what weeds mean what conditions.

For example, dock and stinging nettle love moist, slightly acidic soil with poor drainage and thrive most of all where there is extra calcium available in the soil. Add Big Leaf Maple nearby and you know there is an excess calcium available, and knowing the root depth of the three, you can guess where the calcium is and range of the water table year round.

By looking at the other weeds around it, I can get a more complete picture of the soil make up without having to do any lab work. Probably a better picture as it also includes exposure, sunlight, &c. That is if I knew what each weed ment. I know several basic weeds and trees, but would love to know more.

Is there a book or database for North American weeds and specifically what they tell us about the soil?

Anyone else interested this method of soil analysis, or am I just the odd one out? Maybe with the mass adoption of chemical analysis, this is a skill that is no longer perceived as needed.
 
Ben Brownlow
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There's a pretty good book from the '50's called Weeds and What They Tell Us that I read at some point last year, or maybe the year before. The internet says that ACRES USA sells the book. Its probably cheaper than a soil test...

 
Lou Schultz
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I don't know of a database, but sepp holzer provides a list of about fifty indicator plants in his permaculture book. Nothing about trace elements, just the categories wet/dry, acid/alkaline, nitrogen rich, and compacted. Also, the list is European, but most of the weeds are commonly naturalized here in the U.S. It would be great to know more of them. While there's no replacing modern science, I like to stay old-fashioned whenever possible. Besides, the cost of multiple soil tests for different parts of the property gets expensive.

 
raven ranson
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These sound like great references. Thank you for the suggestions. The library has Holzer's book, so I'll start there.

How about you guys, do you have any personal experience in this area? Maybe not fully scientific, but antidotal evidence is very useful in this sort of situation. Also aware that a lot if it is influenced by location, but some info transfers well from place to place.

Another example we've had on the farm here is white clover and wild buttercups. They like the same conditions, but for some reason where one grows the other won't.

This is very interesting to us because we although buttercups grow with great gusto here, white clover won't. We plant it, we plant it, it grows for 4 months to a year, and then it pitters out. Some books suggest it's a fungus thing, but I came across a passage in a sheep nutrition book that mentioned that buttercups dislike boron (an essential trace nutrient for sheep). We took one pasture and dusted it very lightly with borax (one box per 1/4 acre). No other change to how we managed that pasture. Within a season the buttercups were almost gone and the clover had taken over as the main non-grass weed (without us seeding it). The sheep that grazed there showed less need for nutritional supplements than they do when they are munching on the other pastures.

Of course, weeds grow wherever weed seeds land, but there's a difference between growing and thriving. One glance isn't going to tell you as much as intense observation over the seasons.

As our soil improves and changes through use, the predominant weeds also change. Rocky, sandy soil with good drainage still has excess of Geranium Molle, but the parts of the same pasture that has had haylage and sheep manure mulch now rotted into it, is fiscues and grasses. I don't know if it's simply drainage as the same Geranium is also thriving in my waterlogged veggie garden.

I find this subject absolutely fascinating. Love to hear your experiences.
 
Wynn Ho
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I read that wild sorrel is high in phosphorous and so should be used for that element in our compost beds (after making sure it is dead). I would guess that it means the soil there is rich in phosphorus, too.
If you cannot find a data base, is there anyway for internet users to chime in somewhere to mutually create one?
 
Lou Schultz
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Here's an article on the subject. Unfortunately it doesn't cite any sources, but still an interesting read.

http://homestead.org/DianaBarker/LooktotheWeed/SoilIndicators.htm
 
Judith Browning
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I've run across something in printed form with a list in the past...couldn't find it now.
This site seems to be talking about a few 'weeds' http://inhabitat.com/reading-your-weeds-whats-your-soil-telling-you/

This one is about lawns, same 'weeds' though http://rivanna-stormwater.org/weeds.pdf

and this seems extensive http://back40forums.com/index.php?topic=2133.0
 
raven ranson
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I love wild sorrel. It's delicious! Interesting to hear about the phosphorous, but makes sense when thinking about where I've seen it thrive. I wonder... I can only remember seeing sorrel on a slope, I wonder what it's drainage preference is.

This is fascinating stuff reading these links. Thank you all for sharing them. If you come up with any more, please share.
 
Paul Cereghino
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Walters. Weeds: Control without Poison, has some interesting ideas. It is part of the Albrecht, Acres USA diaspora.

There are some good basic analysis about soil saturation in the wetland delineation literature.. the USDA PLANTS database has a regional wetland indicator code that is used to delineate wetlands. That is relatively data driven and based on lots of observations, and it shifts based on region.

There are indiciator species in the Veg Ecology literature... Klinka and Krajina out of BC for example has a Indicator Plants of Coastal British Columbia... http://www.ubcpress.com/search/title_book.asp?BookID=1443 nice and expensive... They only differentiated among four axes... and don't get into plant presence of vigor predicting soil composition.

The problem is that what a plant indicates differs by climate. A plant that might indicate dry conditions in the PNW might indicate wet conditions in California. Climate and resulting pH affects nutrient patterns. I have looked for the basis for all the claims of plant indicators... I've seen some of those lists, and I can't help but wonder... how do they know this? What is this based on? My faith is generally low when someone tells me of a clear cut species-soil condition correlation... there are just too many factors affecting what grows--I've seen veg structure shift so much over time through succession or based on 'founder effects' (who got there first).
 
Judith Browning
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Here is a link to a new book summary and review by Miles.... Weeds and What They Tell Us It sounds like a good book.
 
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