Hallo Chris,
Rhamnus cathartica ist zweihäusig.
Aber ob es eventuell Ausnahmen geben kann, das ist die Frage.
https://www.cabi.org/isc/datasheet/4699 ... vasiveness
R. cathartica is normally dioecious with 4-merous male and female flowers borne on separate plants.
http://www.blumeninschwaben.de/Hauptgru ... dorn.htm#5
"Blüten grün, 4-zählig, zweihäusig"
Ich selbst habe bisher auch nur 2 Bäume blühend gefunden, 1 mal nur männliche Blüten, 1 mal nur weibliche Blüten.
https://de.wikipedia.org/wiki/Purgier-Kreuzdorn
Der Purgier-Kreuzdorn ist zweihäusig getrenntgeschlechtig (diözisch); in den einen Blüten finden sich jeweils Rudimente des anderen Geschlechts, wobei die männlichen Blüten noch verkümmerte Reste an Fruchtknoten und die weiblichen Blüten ihrerseits noch rudimentäre Staubblätter aufweisen.
(... möglicherweise können die mal mehr als rudimentär ausgebildet sein ?)
Es gibt
andere Kreuzdorn-Arten, wo das stärker variiert.
http://www.baumkunde.de/forum/viewtopic.php?t=20669
Allgemein zu Rhamnus:
https://www.rcrcd.org/files/104290005/M ... rofile.pdf
Most Rhamnus have unisexual flowers. Some species are dioecious, whereas others are monoecious or have mixtures of monoecious and dioecious plants, however monoecious individuals are rare (Rottenberg 1998, 2000). In the dioecious R. legionensis, the ratio of male to female plants in two Spanish populations was found to be about fifty-fifty (Guitian 1995), but male plants produced more than twice as many flowers. The small flowers of R. crocea and R. ilicifolia are also reported to be unisexual (Munz & Keck 1968, Allen & Roberts 2013, Nesom & Sawyer 2018), but there may be some plants with both male and female flowers, or female and bisexual flowers (A. Montalvo, personal observation). Everett (2012) noted that there were differences between male and female plants growing at Rancho Santa Ana Botanic Gardens in Claremont California. No studies were found on the ratios of dioecious vs monoecious plants, or male vs female plants in either species. If populations are primarily dioecious, that condition would enforce high outcrossing rates. Moldenke (1976) noted Rhamnus as being self-incompatible and nearly always outcrossed, likely owing to its unisexual flowers.
