ID tips for wee, annual Crassula species of western North America

In western North America there are two widespread, tiny, annual Crassula species not restricted to aquatic environments: Crassula connata and Crassula tillaea. This journal post is a summary of basic info on the two species, and ID tips for telling them apart.

What's similar about them?

Where they grow

C. connata and C. tillaea have very similar habitat preferences, and often occur on mostly bare, sandy soils with low organic content. Often you will find both species growing at the same locality. Localities with this type of soil will often be relatively flat. Good places to look for them include compacted soil of unpaved roadside turn-outs, infrequently used hiking trails and margins of more often used ones, footprints of razed structures, and other areas that lack a recent history of soil build up. These species are essentially early colonizers of bare habitats, and are not competitive with more robust plants that move in later in ecological succession. If there is extensive, taller vegetation, you are unlikely to find them. These species can also be found associated with vernal pools, but will not typically be found growing as a submerged, fully aquatic plant, though at least one other wee, annual Crassula species can be found doing so.

Example of Crassula connata growing in sandy, low-organic soil. Notice also the long internodes on this mature individual (relevant for ID, discussed below).

When they grow

These species are annuals, and can first be found emerging in January, although they are very small and hard to spot at first. They grow steadily into late spring, and by the time that the heat of summer arrives, they are largely cooked, dead, and gone.

What they look like at a glance

Both species are small, succulent (duh), and start their life green, becoming redder in age. If you aren't looking closely at the plants, then they will look more or less identical. When you are familiar with their differences, though, they can look pretty distinctive even at a glance.

How to tell them apart

1. The flowers of Crassula tillaea have three petals/sepals, whereas the flowers of Crassula connata have four petals/sepals. That is hands-down the best way to get the ID on these wee Crassula species. If you see a wee Crassula with five petals/sepals, see the last section of this post.
2. The foliage of Crassula tillaea is quite bushy/mossy, whereas the foliage of Crassula connata is quite sparse, so that the internodes are usually conspicuously easy to see.
3. Crassula tillaea flowers are usually very inconspicuous, hardly noticeable, whereas you can usually spot flowers on reasonably matured Crassula connata.
4. Color can also be helpful. Both species start green and age red, but Crassula connata pretty much always has some level of red spotting pattern, which is most apparent on still-green tissues, whereas Crassula tillaea is usually without spots, and usually gets to be a more even and total ruby red color eventually.

It can be helpful to look at specimens with a magnifying lens, or take a close macro photo, but it is not strictly necessary. All of the features outlined above are visible without aid of magnification.

Below is an example of the 4-sepal, 4-petal flowers of Crassula connata. Notice also the clear red spots on the green tissue here. Photo taken by Ron Vanderhoff.

Below is an example of the very inconspicuous, 3-sepal, 3-petal flowers of Crassula tillaea. Notice also the lack of any clear red spots on the green tissues here. Photo taken by Ron Vanderhoff.

Below is an example of a fairly mature C. tillaea, showing an even, ruby-red color. Photo taken by Keir Morse.

Finding these species without breaking your back
If you are curious and want to see these wee Crassula species in the wild, it can be a little tricky to find them, as they are so very small. In many cases you will have to walk slowly in likely habitat and stare down at the ground hoping to spot them; a rather uncomfortable endeavor. However, if you search for them in the morning, or late afternoon, when the sun is low in the sky, you will have better luck, as the red color really stands out when the plants are hit with sunlight mostly from the side. I have often spotted populations while riding in a moving vehicle, at speed, based on this visual queue. The wee Crassula species can be quite numerous and locally abundant where they occur, and their color in aggregate can be very helpful for finding them. One thing that often causes a false alarm for this kind of search method are the Erodium species (usually Erodium cicutarium), which can also be very low, and very red. However, Erodium species are actually pretty good indicators of habitat suitable for these Crassula species. Anywhere where you will find these wee Crassula species, you will probably also find Erodium cicutarium, however, the reverse isn't as reliable in my personal experience, as Erodium cicutarium grows well on a broader range of soil conditions, including those that aren't suitable for wee Crassula species.

The third wee, annual Crassula species.
A third species, very similar to Crasulla connata and Crassula tillaea, that can be found in much the same types of habitats, but over a much smaller range in North America, is Crassula colligata ssp. lamprosperma. This species is a recent introduction from Australia, having arrived possibly as late as after the turn of the century. This species is currenlty fairly well restricted to the lowlands, and foothills along the southern edge of the San Gabriel Mountains, with only a few localities known elsewhere in SoCal (one in Orange County, and one in the Los Angeles Basin). It is rather abundant in some habitats within this range, however. The species is probably more widespread in Southern California than we understand, so please keep an eye out for it, and tag/at me if you do think you found it! See separate journal post here (https://www.inaturalist.org/journal/grmorrison/76131-aussie-pygmyweed-in-southern-california) for info on that species.

Glen R. Morrison
14 March 2023

Posted on 14 March, 2023 20:15 by grmorrison