New/more sowing advice for small & fine seeds
Happy New Year to all!
I will start 2021 with more sowing details for small/fine seeds.
This post was inspired by an inquiry about Parnassia germination. Parnassia species have simple physiological dormancy and they should germinate well after a proper cold/moist stratification.
However, as said elsewhere, the devil is in the details and many things can go wrong. So, although they may seem child-like directions, please read this post and have a look at the pictures; maybe there is something you can change in your sowing method.
But first, your seeds may not germinate simply because they weren’t sown at the proper time.
If you plan to sow in January and beyond, please review this post: Practical considerations for sowing in late fall-winter.
With the mild winters experienced in the last years, it is very improbable that sowing species with a requirement for cold/moist stratification (3+ months) in mid to late January will result in germination by spring (in many locations). Some may germinate since there is a fine line between 2 and 3 month requirements, but no one can say precisely which ones needs what.
Usually species that don’t germinate in the first spring may germinate in the second year, after more cold is provided by the second winter. Species like Gentiana, Saxifraga, Swertia, to name the first coming to mind, germinated for me in the second spring after sowing in the last years.
Besides bad timing, I will bring to attention what else can go wrong with the small/fine seeds sowing & sowings
Sowings of small/fine seeds are among the hardest to manage over 2-3 years for a few reasons:
First, these seeds (supposedly) sown superficially, due to repeat watering, are easily exposed at top of the potting mix and they desiccate easily. I personally think this is the main reason for germination failures for small/fine seeds, either in the first or the second spring.
The second reason is the reverse, when the seeds are sown a bit too deep and they may start to ‘slide’ lower and lower in the pot during watering.
What can be done to prevent this?
Sowing technique speaking, I already gave tips on sowing fine seeds in this (updated) post: Kernera and a trick for sowing fine seeds.
But let’s exemplify the sowing process for Parnassia palustris. I will keep the pot in the garage for 1 week, and then place it outdoors. We’ll see the result in the spring. Again, I personally don’t sow cold germinators in January anymore (except Primulas which most do well with only 1-2 months of cold stratification and other species with GA3 treatment).
1. For outdoors sowings, use a slightly ‘heavy’ mix for sowing; it remains moist without huge variations dry/wet (like it happens with too much peat); simply mix your regular ‘sowing mix’ with any 3-1 planting mix or black earth (2 parts to 1 usually is good); 2. fill the pot and tap the mix well; 3. add the label and a fine layer of vermiculite (perlite) + few drops of water; 4. spread the seeds (they will stick to the moist verm.; 5. add another layer of vermiculite (perlite); 6. place the pot in a container filled with water and let stand until the pot fills ‘heavy’ (you may need to add more water).
After sowing and watering (always from the bottom) enclose the pots in a plastic/Ziploc bag or a plastic box with a clear lid (shoe boxes are perfect). Keep the sowing in the house/garage (1-3 weeks; small seeds imbibe quickly) and then place outdoors.
This is an older picture taken one year in early spring
In the spring:
Open the bags/box gradually or just for a part of the day starting in early spring; monitor the humidity all the time.
Don’t forget to keep/move the sowings in a part shaded location in the spring! Even if the March/April sun seems weak to us, it is not the same for tiny, newly germinating seeds/seedlings. As the seedlings appear, remove the pots from the bag/box. Needless to say, be careful when watering very small seedlings!
If no germination happens by late May, add one more layer of mix (or fine gravel, grit) of on top the pots and move them in a shaded location (not enclosed in bags). This way you won’t have to worry about watering too often. I know that taking care of ‘empty’ pots during a whole season when so much else is happening, is hard but if you let them dry out completely at some point there is nothing to expect in the following spring.
Note: for alpine plants – add one more part of vermiculite to the sowing mix for good drainage, mix all well. For indoor sowings, just add vermiculite (or perlite) to the regular sowing mix (no black earth ot 3-1 mix).
Stay tuned for more new & ‘old’ seeds on Friday.
