I realized I would not be able to physically chop the root up myself so I took it to our local equipment rental storefront!  In exchange for a small sample skein they popped the root thru their huge shredder.  I got some workable chips.  I put them in a water soak overnight and then simmered them for a couple of hours the next day.  I processed a test wool skein and two silk skeins.  They came out a brilliant yellow!

The were mordanted with alum sulfate at 10% WOF and look very much like the weld flower yellow.  I had plenty of chips to hold for a later dye pot!

I originally just did a 1:1 ratio of dyestuff to substrate.  Agarita is strong enough that I think that you can step down the ratio and still get a good strong color.

Now for some local facts:

1. •Native Americans  & early settlers used this as a souce for a yellow to tan-orange dye.
   

2. •Many groups used Berberis as a dye.  The Havasupai and Navajo dyed buckskin.  Basketry was dyed yellow by the Walapai.  The Mescalero dyed hides yellow with a mixture of root shavings from Berberis.
   

3. •Saffron-scented flowers are attractive to bees.
   

4. •Fruit is favored by humans and animals.  Apaches made a jelly from the fruit
   

5. •Source: Remarkable Plants of Texas, Matt Turner, Page 114