New fieldguides are out!

Two updates fieldguides are just published and can be downloaded for printing - at no cost!

Field Guide to Weedy Plants of Eastern US

Weedy Grasses and Grasslike Plants of Eastern US

Print the first guide at 100% on LEGAL paper, double-sided, then fold in 4 parts.

Print the Grass guide on LETTER paper, double-sided and fold in 3 parts.

How to identify weed species

To be able to identify plants to a certain species, you will need a good flora, a handlens, and a little patience while you learn the botanical terminology that describes plant features (stipules, petiole, sepals, and things like that). 

Some plant groups are a lot harder to identify than others, like the Polygonum genus in the rhubarb family Polygonaceae for example (see photo above). For them you will have to look at tiny hairs and glands through the handlens, but for many others it is enough to compare the photos in a photo flora.  It depends. But to be sure, then you need a book (flora) that includes all the species in our area and usually something to magnify the plant with.

If you find something that looks unusual, you can always press and dry it and show it to a botanist later for confirmation.  A photo is often helpful, but many species you can't tell apart from photos.
[photo by Vilseskogen, Flickr, Creative Commons]

Species: Yarrow and nosebleeds

The weed yarrow is a native here in the US, but it is also present in Asia and Europe.  It has been used medicinally for a long time.  Its botanical name, Achillea millefolium (Asteraceae), is of course after the Greek god Achilles, and millefolium after a 'thousand leaves' since the leaves are so finely dissected. 

When I was a kid in Sweden, they told us stories how in the old times, school kids would take a piece of the leaves, which have sharp tips on each little leaflet, and put it in their nostrils before a boring class at school.  A while in during the lesson, the kid would just slightly touch its nose, and a profuse nosebleed would start, and wow, the kids got immediately excused from class.

Yarrow is also cultivated here in the US, so it is one of those weeds that the horticulturalists can't really decide if it is good or bad.  Maybe it is just an interesting plant?

Species: Yarrow (Achillea millefolium, Asteraceae)

[Image from Lindman's Bilder ur Nordens Flora (Swedish), public domain]