It’s been over a decade since we first began germinating peony seeds from open and controlled crosses. This has been with varying degrees of success and one learns with time of course. We shall not discuss all the details of hybridizing and germinating peony seeds, there’s already an excellent article on the site here from Nate Bremer. What we have done this year is a little experiment to find out which substrate is best to germinate peony seeds. To take a slide from the article just mentioned, this shows some substrates often used to germinate peony seeds:
In the past we have germinated peony seeds in outside garden soil, potting soil, coarse river sand, compost and perlite. We actually only use indoor germination as outside germination is slower and, at least we find, is quite erratic. Compost and potting soil gave different results one year to the next and was quite a gamble. We don’t seem to have a green thumb as so many other people have… Last year we used perlite and it turned out this was far better than potting soil and also much easier to work with. However some germinated seeds showed some damage on the roots that appeared and a few of those even rotted. It’s however very easy to give a certain amount of water when you start from fresh dry perlite. So we intended to try different treatments this year and see if we would get different results. Someone in the hybridizer’s corner with a whole lot more mileage in hybridizing suggested me trying vermiculite as that is his preferred substrate. I’m not someone to take good advice lightly and thus I’ve bought a large bag of vermiculite to incorporate it into my experiment.
So, how did we go about it? At the middle of August we harvested some open pollinated seeds from an easy seeding cultivar, in this case Just Peachy. From previous experience we knew it germinates quite well. We threw away the cracked already ‘open’ seeds which are shown in the next image so as to have only perfectly round seeds. The ‘floaters’ were also thrown away as all others that seemed to be somewhat ‘different’. This to have somewhat comparable seeds for the different treatments. Seeds were then randomly allocated to the following:
Three different completely dry substrates with different amounts of water added. Coarse river sand (10 and 25% water (volume/volume)), perlite (0-5-10-15-20-25%) and vermiculite (0-5-10-15-20-25-30-35-40-50%). In practice we simply took a water measuring cup, filled it to the right volume and then added the amount of water needed. For example 1 litre of vermiculite received 0,25 litre of water to have a 25% water content. The vermiculite absorbed all the water, so the total volume remained at 1 litre in this case. This was also the case with all other treatments, only with vermiculite at 50 % water, could we see that this was above the saturation maximum and some water remained floating in the ziplock bag. Each different treatment had 20 seeds of Just Peachy which seemed like a good number to work with.
Now this was all done mid-August. The ziplock bags with the substrate and seeds were placed in our greenhouse and then all we had to do was wait. It has been an exceptionally warm Autumn and many of our other seeds already germinated by the beginning of November. Thus we have opened our ziplock bags with the Just Peachy seeds as well, searched for the seeds and sorted them in one of five categories: large roots (5 cm +), average roots (2-5 cm), short or beginning roots (0,1-2 cm), no roots but still good seeds, and finally rotted seeds.
Let’s have a look at the results:
|% water||Long roots||Average roots||Short roots||No roots, good seeds||Rotted seeds|
|Coarse river sand|
|Total always 20 seeds per treatment. Numbers with orange background had some rot at the end of the roots. Green background shows the best treatment.
Seeds harvested August 11th. Treatments started August 12th. Opening of ziplock bags November 10th.
Some insights can be had from the numbers in the table. Keeping them dry (0% water in perlite or vermiculite) results in nothing, as would be expected. But, unexpectedly, if the substrate is too wet, this also results in nothing. The 50% water in vermiculite did not result in all rotted seeds, but they came out perfectly sound. Coarse river sand is immediately too wet it seems, even at 10% none of the seeds made any movement towards germination.
From the three substrates, vermiculite is clearly the best, followed by perlite and then, with no germinations, coarse river sand. Some treatments resulted in germination and roots but the substrate was too wet for them to remain healthy and some rot showed up at the root tip growing points usually (those have been marked by an orange background). Many of the rotted seeds also showed the beginnings of germination but the roots had rotted soon after breaking through the seed coat. Apparently the most rot occurs when the roots start growing and it’s less the seeds themselves that start to rot.
The best treatment needs a lot less water than what we oursevels expected initially. My standard treatment for all other seeds this year was 25% water in vermiculite. As can be seen, this is too much humidity for them. The most germinated seeds with the longest roots can be had from vermiculite with only 10 % water added (shown in a green background). As we all know, some seeds are simply inclined to rot, no matter what treatment you give them. But in this case we have 14 germinated seedlings, 2 that might still germinate later on and 4 that had rotted. This is 70% germination and is the best in the table.
Seeds from other crosses and harvested at other times will give different results of course, but the general message is clear: use vermiculite with only 10% water in ziplock bags for the best germination of your peony seeds!
As always, all errors are only to blame on ourselves and your own experiences or questions are most welcome in the comments section below. To conclude a few images from some of the different treatments.