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Hagman et al. 1975 Found that the upper third of the regrowth has the highest alkaloid concentration overall. [There were points it was only as strong as the middle third but these were the low values. (Regrowth in the middle third did show a substantial increase in alkaloids.)]

They reported a mean concentration of 12 P. arundinacea clones grown in a greenhouse versus those grown in the field.

Part	% total alkaloid	by dry weight.
	Greenhouse	Field
Leaf tip	0.29	0.27
Blade base	0.23	0.26
Leaf sheaths	0.07	0.10
Stem	0.04	0.11

Marten et al. 1973 reported the following average alkaloid concentrations in P. arundinacea [Using only regrowth and harvesting when the plants were at 20 to 60 cm tall and still in vegetative stage]:

• 0.29% in upper half of leaf blades
• 0.23% in lower half of leaf blades
• 0.07% in leaf sheaths
• 0.04% in stems
• 0.05% in inflorescences.
• and when above ground parts was 0.19% the rhizomes was 0.01%.