Friday’s seeds – Dalea purpurea

Back again with the hugely (un)popular Friday’s seeds, by necessity.

In the first week of March I used the HWT on a small lot of Dalea purpurea, purple prairie clover ‘seeds’. Using the whole dispersal units (calyces containing the pods with seeds), I didn’t see how much the seeds have imbibed (a sign that the seedcoat was fissured). It would be tedious to remove the seeds by hand, so, those who purchased Dalea ‘seeds’ also received the whole calyces, which together with the pods and seeds inside are the plant’s ‘dispersal units’ (larger seeds companies will separate the seeds with a machine).

I sowed them the next day; on the same day, I also sowed a small pot with untreated calyces. In both cases the germination was been poor, to use a nice term; only 1 seedling on each pot. 

For this reason the situation begs further study.

For Dalea purpurea, until you see the actual seeds, it is not easy to guess being in the legumes family (Fabaceae). The seeds remain enclosed in 1-seaded pods and these are in turn included within the persistent, fuzzy calyces. As a whole, again these are called dispersal units. Some are wrongly calling them fruits.

Where are the actual fruits? And how do they look? By gently squeezing a dry calyx, the seed enclosed in a papery outer covering comes out. It doesn’t look like a pod, but that’s what it is: a pod with a very thin fruit wall, as seen in the image below.

Now that we deciphered the Dalea fruits-seeds dilemma, back to the HWT yesterday, using cleaned seeds this time. This is how they looked today; about ½ have imbibed well and were already sown.

Possible reasons for the poor germination in the first attempt:
A single HWT treatment wasn’t enough to break the seedcoat (for genera like Hedysarum and Astragalus the seeds need 2-3+ treatments with hot water); it is also be possible that the presence of calyces impeded the process.

Second reason: the temperature at which the pots are kept is +/- 21 C daytime. I found a study that indicates 25C as a good temperature for germination. It is likely that more seeds will germinate in time, but we aim for a more uniform germination.

I’ll update the germination info on the product page, as soon I have more data. Keep in mind that scarification can always be employed instead of HWT, I just do not like to use it, especially for small size seeds.