Boraginaceae: Borage Family — Popcornflowers
Popcornflowers are extremely challenging to identify in the field. All of them have very similar white flowers, varying only in size and in the appearance and color of the “appendages” (at the base of the corolla lobes, sometimes yellow, sometimes white and occasionally completely absent). Too much reliance should not be placed on the color of the appendages as these can often vary on the same plant or even in the same flower head. The growth habits, size and hairiness of the plants cover a wide range, and it can be hard to make a determination based on these given how variable individual plants can be, even within a particular species. The key distinguishing characteristic is to be found in the nutlets.
First, the distinction between Cryptantha and Plagiobothrys is that the inner surface of Cryptantha nutlets has a distinct longitudinal groove. Plagiobothrys nutlets lack this groove but instead have a distinct attachment scar below the middle of the inner surface.
Secondly, especially within the Cryptantha, one has first to ascertain the number of nutlets (between 1 and 4) and whether they are rough or smooth, and then examine their individual shapes. The problem is that the nutlets are all small, sometimes very small, and it is almost impossible to come to any conclusions without the aid of a microscope.
With Plagiobothrys, one can narrow the choices by seeing whether a plant has any opposite leaves. One of the most common, the Rusty Popcornflower (P. nothofulvus) has another unusual characteristic — the calyx is circumscissile in fruit, meaning that the top separates from the base like a lid. Nutlets are generally 4 in number, variable in their shape and appearance.
Enjoy these pretty little flowers but be warned that you will need the aid of a proper botanical key, a microscope, and a good deal of practice if you want to identify individual species with confidence. This page illustrates a small number of species, more to show some of the variations than to act as a guide to identification. The fingernail is included in some of the photos for scale; it is exactly 1 cm across at its widest point.