A small survey of white oak (sect. Quercus) acorns in Whitney, CA
On 9/8/2024 I visited a park in Whitney and was intrigued by the various different acorn morphologies I found on the white oaks. There were only two species present, Q. lobata and Q. douglasii, yet I found 6 different "groups" of acorns. In this journal post I'm going to go over the differences between the groups and ID them to the best of my abilities.
Out of 17 Acorns I collected, 6 groups can be made. I named these groups A, B, C, D, E, and F.
Group A
4 Acorns were collected from group A. The acorns are 39-45 x 11-14 mm with a cupula that's 14-18 x 17-21 mm. The acorns are narrow with a blunt tip. The scales are large at the top of the cupula and get smaller towards the open end. The scales at the open end are long and bristle-like. These appear to come from Q. lobata.
(Both observations are of the same tree)
https://www.inaturalist.org/observations/240650943
https://www.inaturalist.org/observations/240648702
Group B
4 Acorns were collected from group B. The acorns are 43-53 x 11-18 mm with a cupula that's 13-15 x 16-19 mm. The acorns are long and narrow with an obtuse tip. The scales are large at the top of the cupula and get slightly smaller towards the open end. The scales form spirals that look like rings. These appear to come from Q. lobata.
https://www.inaturalist.org/observations/240650820
Group C
2 Acorns were collected from group C. The acorns are 42-45 x 20-21 mm with a cupula that's 16-21 x 27-32 mm. The acorns are wide with an obtuse tip. The scales are large at the top of the cupula and get smaller towards the open end. The scales are larger and darker than in any of the other groups. These appear to come from Q. lobata.
https://www.inaturalist.org/observations/240650988
https://www.inaturalist.org/observations/240650782
Group D
4 Acorns were collected from group D. One acorn's measurements will be put into parenthesis due to it being an outlier . The acorns are (29) 40-43 x (15) 17-22 mm with a cupula that's (6) 6-8 x (12) 16-19 mm. The acorns are wide with an obtuse tip. The scales are large at the top of the cupula and get smaller towards the open end. The cupula much smaller than is expected from pure Q. douglasii. These appear to come from Q. x eplingii.
https://www.inaturalist.org/observations/240650236
Group E
2 Acorns were collected from group E. The acorns are 55 x 21 mm with a cupula that's 15-18 x 22-23 mm. The acorns are wide with a blunt tip. The scales are large at the top of the cupula and get smaller towards the open end. The scales are lighter in coloration than in the other groups. These appear to come from Q. x jolonensis.
https://www.inaturalist.org/observations/240649866
Group F
1 Acorns was collected from group F. The acorn is 56 x 18 mm with a cupula that's 15 x 22 mm. The acorn is narrow with an acute tip. The scales are large at the top of the cupula and get smaller towards the open end. The scales towards the open end have small bristles on them. This appears to either come from Q. lobata or Q. x jolonensis.
(Unfortunately I didn't get photos of the original plant)
https://www.inaturalist.org/observations/240683164
Comments
@alexbinck @yerbasanta @carexobnupta @jonaskat Ya'll might find this interesting. Let me know if I missed anything important.
An interesting comparison. I do not recall seeing filiform tubercles previously in the Dumosae. Overall, this population appears to be an old intergraded three taxa population and a mirror of the Pepperwood oaks.
As a not to my identification priority, I give the largest weight to the acorn and cupula over leaf morphology. The reason is that it appears to be a stable feature and it is the tissue of the mother tree.
I have not analyzed the collection of acorn and cupula observations. This observation set adds to the set of features that should be considered.
One feature worth mentioning is the Q. garryana feature where the tubercles change from the base to the distal edge. This gives the distal edge a banded appearance and is a change of the proximal tubercles being cornute to scale like at the distal edge.
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