Cattail (Typha) morphology [part 1]

The intention of this post (and a future one) is to provide a short introduction to the morphology of cattails (genus Typha). Part 1 focuses on reproductive structures (flowers and seeds) and describes one of the most important characteristics for species identification, the gap between the inflorescences.

Cattails (other - sometimes ambiguous - names include bulrush, reedmace and cumbungi) are perennial plants from the family Typhaceae (together with a second genus, Sparganium). They generally can be found in or near water in natural wetland ecosystems or artificial habitats like drainage ponds or ditches. They are quite interesting as on one hand, they follow the strategy of pioneer plants with the mass production of small seeds to colonize new habitats as fast as possible. On the other hand, they are able to outcompete other plants and establish persistent populations by spreading vegetatively with their rhizomes and building dense stands.


The gap between the inflorescences?

When IDing cattails, I often mention "the gap between the inflorescences" and here I want to explain what this actually means. The flowering shoots consist of the two different types of inflorescences (also called spikes) at the end of a stem. The male (or staminate) inflorescence is located above the female (or pistillate) inflorescence. Depending on the species, there can be a gap of varying length between these two or it can be absent (see the pictures below).


picture 1 (left): graceful cattail (Typha laxmannii) with a gap between the inflorescences; picture 2 (right): Typha shuttleworthii without a gap between the inflorescences

These structures are not a single flower but rather consist of a high amount of very small flowers. The male flowers produce pollen which is dispered by the wind, and the female flowers turn into diaspores after they are pollinated (see the chapter "Diaspores and seeds" below). Note that in the second picture, the term "inflorescence" for the female spike is actually not correct anymore because the flowers have already turned into diaspores which means that the plant is fruiting and the term infructescence (or seed head) should be used.

After spreading the pollen, the male flowers often fall off the stem which makes it harder to spot if a gap between the inflorescences existed before or not. Pictures 3 and 4 below will hopefully illustrate the difference in an understandable way. In the left picture, you can see that the part of the stem directly above the female spike (= the gap) has a different color than the rest of the stem above that part. The light green color is the same as the color of the stem below the female spike. The part of the stem where the male inflorescence was located has a light brown color and the surface is not as smooth. In contrast, there is no bare part of the stem above the female spike (= no gap) in picture 4. This means that the male inflorescence was directly adjacent to the female one.


picture 3 (left): narrow-leaved cattail (Typha angustifolia) with a gap between the inflorescences; picture 4 (right): broad-leaved cattail (Typha latifolia) without a gap between the inflorescences

As mentioned, the length of the gap (or the distance between the inflorescences/spikes) varies and in some cases, especially for hybrids, it can be very small (as in picture 5 below).


picture 5: hybrid cattail (Typha × glauca), the hybrid between T. angustifolia and T. latifolia

Species that usually have a gap between the inflorescences are:

  • T. angustifolia / narrow-leaved cattail
  • T. domingensis / southern cattail
  • T. laxmannii / graceful cattail
  • T. minima / miniature cattail

Species without a gap are:

  • T. latifolia / broad-leaved cattail
  • T. orientalis / eastern bulrush
  • T. capensis / cape bulrush
  • T. shuttleworthii

It is important to know that there are exceptions! The gap of species from the first group can be (almost) absent (this is quite often the case for T. domingensis) while species from the second group can sometimes have a small gap between the inflorescences (although it should not be longer than around 0.5 cm). Here is an example for T. latifolia.




On average, the distance beween the inflorescences is larger for T. angustifolia compared to T. domingensis.




Last but not least, there are hybrids with intermediate characteristics and the gap can be present or absent and the length can vary, even between shoots of the same plant or population. This feature can be used to identify a hybrid because the length of the gap is usually more or less consistent in a population of the parent species. Therefore, it is important to take photos of several different flowering shoots with spikes (especially in the area around the Great Lakes in Canada and the United States where the hybrid between T. angustifolia and T. latifolia, T. × glauca, is very common).



Diaspores and seeds

Diaspores are structures which are responsible for the dispersal of the seeds. For cattails, each diaspore consists of a single seed and perianth hairs that support the transport with help of the wind (picture 7). The seed is around 1 mm long and the whole diaspore around 7 to 13 mm (the values vary depending on the species).

Each spike (or seed head, picture 6) contains a very large amount of diaspores, even the smaller ones usually more than 100,000. Under windy conditions, they can travel long distances and establish new populations far away from their origin.



picture 6 (left): fruiting spike of the graceful cattail (Typha laxmannii); picture 7 (right): diaspore of the narrow-leaved cattail (Typha angustifolia)



Other characteristics

In a future journal post, other characteristics like the color of the fruiting spikes, bracteoles in the female inflorescence, the length and width of the leaves, mucilage glands on the leaf sheath and the lower part of the leaf blade, the shape of the sheath margin, rhizomes and clonal ramets will be discussed. Some of these features can be useful to distinguish the species.



Further information

Posted by pastabaum pastabaum, August 13, 2021 14:36

Comments

No comments yet.

Add a Comment

Sign In or Sign Up to add comments