Phalaris alkaloids seem concentrated in new growth.
The old entheogen review articles when Dekorne was editor mention crystals obtained from phalaris extractions, so success has been known for over a decade regarding this genus.
So many different alkaloids can be found in this species, the online version of KT's aya book :
Erowid Online Books : "Ayahuasca: alkaloids, plants, and analogs" by Keeper of the Trout
Has data from various phalaris study.
Appleseed found that taking the grass, fresh, and simmering it for 10-20 minutes and then removing it and adding new grass and repeating allowed alkaloids to accumulate in solution to an amount that is useful in extraction and pharmahuasca use, while minimizing the extraction of chemicals that caused undesirable effects, he was unable to locate a strain of grass devoid of the undesirable alkaloid effects, but did find that a shorter boiling time reduced and minimized such effects.
Harvesting whole plants of this is a watse and gives bad results, only the new growth seems useful and alkaloids seem to either translocate from old growth to new growth or they seem to degrade in old grow, while still remaining in new growth. It is also worth noting that extractions of fresh material are typically more effective and dried material, when the plants dry it seems that a large amount of the alkaloids are broken down.
Interestingly fresh juice and quids of some phalaris selections like big medicine seem to be more effective than can be explained by the known chemical data. In this regard caution is advised, while not having much alkaloid that can be extracted some strains seem to be potent enough to cause problems related to being overwhelmed due to the intensity of effects.
Phalaris in general is not for beginners in terms of extraction or experiences.