Friday’s seeds – or is it a fruit? Triosteum

Sometimes we refer to ‘seeds’ without actually realizing that we are talking about the fruits.
This is the case of dry fruits like achenes, caryopses, samaras…, which tightly enclose the seed(s) and it would be practically impossible/or at least highly impractical to try to ‘extract’ the seeds.

So, why do we care if we sow seeds or fruits?
Knowing that we actually handle fruits, helps understanding why certain treatments are needed for the storage/germination process. Also, because in these cases we cannot see the actual seeds, we only make the assumption they are inside the fruit and will germinate in due time. Which perhaps they will, but sometimes there is no one there to do it!
To understand what I mean, you can have a look back at two notorious examples:
False assurance – Linnaea borealis
The Beauty and the Parthenocarpy – Acer triflorum

In the Caprifoliaceae family there are also species with dry fruits which we treat as seeds, like Morina and Triosteum. In both cases, they have hard teguments which play a role in retarding/obstructing the germination.

I wanted for a long time to have a closer look at Triosteum aurantiacum. I found no reliable info regarding its germination but someone who bought ‘seeds’ few years ago got back to me saying that by filing the fruits tegument, followed by GA3 and/or cold-moist stratification obtained good results.

So, I placed the fruits in warm water for a few days in an attempt to soften their teguments before I proceed to dissections. In Triosteum – and I refer here to Triosteum aurantiacum – the fruits resemble coffee beans, and only by looking at them one can imagine it will take a lot of time for them to disintegrate naturally in the soil.

Even after keeping them in water for few days I had to use a cutter to slice through them. The wall of the fruit is extremely thick and the seed is fused to it.
Here’s a plate showing the whole story in pictures:

I managed to extract one seed intact – inside, the embryo is invisible with the naked eye because of underdevelopment, pointing to the requirement of at least one period of cold/moist stratification.

Conclusion: these are the options to hurry up the germination for Triosteum – first, by filing the hard tegument with a metal file almost until reaching the seed, followed by cold/moist stratification 3 months.

Second, by nicking the end of the fruit (I used this myself for T. pinnatifidum), followed by cold/moist stratification for a few months. In this case, take care not to harm the seed when nicking the end and best to keep the fruits in water for a few days to somehow soften them.

A suplimentary GA3 treatment coupled with the cold/moist stratification may have some effect or not; I will try it this winter and we’ll know for sure.

About Morina next time…