The varieties listed along the bottom should be sorted all the time, instead of when I just select a single factor. i.e. if I select ONLY "alpha acid" then they are sorted numerically by %alpha acid. If I select both alpha and beta acid, the results are completely unsorted. Having a "sort by" drop down would work and add some flexibility. Having multiple "sort by...then sort by" would be ideal, but might result in a more complex interface.
It would also be nice to sort alphabetically by variety, for example.
Overall it looks pretty good. Not sure what plotting package that is...it sort of looks like RGraph bar charts to me, except I think you'd have to twiddle with the defaults a bit to get it to look like that.