Fustic (Chlorophoria tinctoria) also known as Dyers Mulberry is perfect for natural dyeing which can easily be added and removed from the dye bath - you could also infuse first then use the dye liquor for your natural dyeing.  Whole dyestuff is perfect also for yarn dyeing where you wish to avoid any particles remaining in the batch. 
 
Fustic yields a yellow colour depending on quantity used, the fibres used, and the pH of your dye bath too (i.e. whether you use any dye modifiers such as acids or alkaline).  With dye modifiers you can achieve many shades of yellow, golden and greeny yellows.  Mordants are not necessary with fustic, however are recommended to improve colourfastness so use Alum mordant for when dyeing animal (protein) fibres, and a tannin plus ALUM or Aluminium acetate when dyeing plant (cellulosic) fibres.
 
Smallest pack size supplied is 100g
 
Recommended use is at least 40-50% weight of fibre/fabric (WOF) to reach an intense yellow colour