date of photo Feb 13, 2018
Long Ridge Open Space, Santa Cruz Mountains (San Mateo County, California, US)notes [For reference, in the remarks below...note that a green, leafy, stolon is visible in this photo, emanating from the right of the base of the plant, and passing behind & beyond the leaf just under the flower. For images of leaves and rhizomes see here.] |
Many of these violets were noted on a field trip with fellow CNPS members Loretta Brooks & Chuck Heimstadt...but none of us knew the species. They were growing near a creek in soil covered with leaf-litter, under the shade of a mixed-forest composed mainly of oaks, douglas fir, bay trees, and willows.
To determine the species, I began with the Jepson eFlora key to Viola, where the following characters were invoked (all visible in the photos here and/or checked in the field): stem 0; internodes 0; rhizomes not especially thick & fleshy; plants with green leafy stolons; leaves round, crenate; petals lilac.
But, as so often happens, ambiguities arose in interpreting some of the characters presented in the key. In particular, for plants of this population some stolons were green & leafy (see right-of-center here...click image after it loads to enlarge); while other stolons were paler, having no leaves and only feeble root-leaders at their nodes (see center of image here). And at couplet 3 of the Jepson key, one needs to determine whether the fruit is puberulent or glabrous...but no fruit was found. The upshot of these ambiguities was that the ID here seemed to boil down to either V. odorata or V. palustris.
To clarify the choice, I consulted the Flora of North America Viola key which went smoothly up to couplet 13, where the break involves two length ranges for the petal spur...with the cut-off of 3 mm being just about what the spurs measure here (of course! :-). Going ''both ways'' at couplet 13 led to the same candidates as in the Jepson treatment: V. odorata or V. palustris...as detailed below:
- Taking the 1st choice leads to a ''widowed lead'' at couplet 14 (i.e. no opposing choice is provided...presumably an editing error):
- On the one hand, going with (fruit) ''capsules puberulent'' leads immediately to V. odorata.
- On the other hand, the (erroneously omitted) alternative (presumably ''capsules glabrous'', leading to couplet 15) yields potential candidates selkirki and japonica...but both can be eliminated by studying their detailed FNA descriptions: e.g. due to having corolla spurs too long; lacking 'bearded' lateral petal bases (which are present here, see this photo); and being way out of range (e.g. Washington state, Yukon, the midwest & east coast, etc.).
- Next, returning to the 2nd choice at couplet 13 in the FNA key leads without ambiguity to couplet 22 which yields V. palustris, since the bracteoles can be seen to be below middle of peduncle (cf. left-of-center in this image); and the leaf blade margins are crenulate. However that couplet also indicates the leaves of V. palustris are eciliate...whereas the leaves in our plants here can be seen to be ciliate (see photo here...click after image loads to enlarge). Also, the FNA description of V. palustris indicates its petioles, peduncles, and leaves are glabrous...whereas the FNA description of V. odorata indicates its petioles, peduncles, and leaves are purberulent...which is the case with our plants (also, cf. the images here and here). Futhermore, the FNA descriptions for V. palustris and V. odorata indicate the the number of basal leaves are ''2–4'' vs. ''5–10'', respectively...which clearly points to the latter for our plants. In summary, studying & reconciling the keys & descriptions in both the Jepson eFlora and FNA treatments leads to a clear ID of V. odorata for these plants.
The location here seemed fairly wild and undisturbed, though not far (~1/2 mile) from roads and human developments (e.g. rural homes). The Flora of North America discussion states that: ''Viola odorata is sometimes found in remote locations not easily explained by anthropogenic influence'', but that ''It is native to Eurasia and assumed to be introduced in North America where it is usually found in areas associated with human habitation, including parks, lawns, and roadsides.''
Note that V. odorata does not appear in the 2011 ''Checklist of the Vascular Plants of San Mateo and Santa Clara Counties, California'' by Toni Correlli, and zooming-in on the inset map at the bottom of the Jepson eFlora V. odorata page, I saw that the nearest voucher currently appearing there is a 1975 collection from Henry Cowell State Park, 18 air miles to the SSE in Santa Cruz County. However, doing an independent search of the California Consortium of Herbaria web site, I did find a single 1935 San Mateo County record for V. odoroata from similar habitat to our site...and about 15 air miles to the northwest.
Since this species was not listed for San Mateo County in Toni's checklist, nor in the records displayed on the Jepson eFlora inset map...I decided to cross-check my ID using a number of other regional floras: In fact, it turns out that the original description of V. odorata was written in 1753 by none other than Carl Linnaeus(!)...and it's right next to the original description of V. palustris :-)
Postscript (5/20/18): Dylan Neubauer recently brought to my attention the following brief 1946 note on ''V. odorata in California'' by Violet Baird from the journal Madroño. Therein it's stated that V. odorata differs from our native species of Viola (at least those known in 1946) by having the tip of the style bent downward like a hook. That character is best seen in the last three images in this series.photo category: Plant - annual/perennial