Great work
@Transform !
I’m impressed you went to such effort to sift the fine sand out.. attention to fine details like that really will make a difference in the seedling’s early development, which will ensure it gets to as mature a stage as possible before the next winter.. you really want them to pump out as much growth as possible before those cold UK temps set in..
Interesting idea about germination inhibition.. I’m not sure why they germinate erratically.. but it’s pretty normal with a lot of Acacia seeds and can take anywhere from 48 hrs to a few weeks.. if they take too long you can let them dry and then just sow them into your medium and water it to swell them again.. maybe a little less likely to rot that way. Some native nurseries use this approach. I also forgot to mention, any seeds that float to the surface are likely not viable. No harm in leaving them in of course but you should count the floaters so that you have an idea of your germination rate.
You might find interesting
this research paper on Acacia seed germination from Cambridge university, which says:
The seeds of most Australian acacias have pronounced physical dormancy (PY). While fire and hot water (HW) treatments cause the lens to ‘pop’ almost instantaneously, for many Acacia species the increase in germination percentage can be gradual. If PY is broken instantly by HW treatment, why is germination often an extended process? Control and HW treatments were performed on seeds of 48 species of Acacia. Seeds were placed on a moist substrate and imbibition was assessed by frequently weighing individual seeds. In the two soft-seeded species all control seeds were fully imbibed within 6–24 h, while in hard-seeded species very few control seeds imbibed over several weeks. In 10 species over 50% of the HW-treated seeds imbibed within 30 h, but mostly the percentage of imbibed seeds gradually increased over several weeks. Some seeds in a replicate would imbibe early, while others would remain unimbibed for many days or weeks then, remarkably, become fully imbibed in less than 24 h. While HW treatment broke PY almost instantaneously, it appeared that in many Acacia species some other part of the testa slowed water from reaching the embryo. This process of having staggered imbibition may be a way of ensuring not all seeds in a population germinate after small rain events. Thus it appears the lens acts as a ‘fire gauge’ while some other part of the seed coat acts as a ‘rain gauge’.
In my experience most seeds if healthy will germinate within the week with the wet towel method.. sowing directly can be much more erratic and take some time/really require the right temperature (around 23 degrees Celsius) . Seeds from different species can behave quite differently so trial and error is usually in order. For example I have a tray of Acacia phlebophylla seeds I sowed about 7 months ago.. I sowed about 40 seeds and they only stopped sprouting a few weeks ago as the temperature dropped. About 25 of the 40 have sprouted and seem like they’ll continue once it gets warmer again if I’m diligent in keeping the medium moist. During late summer and early autumn about 3 or 4 seeds germinated each week. Some species just seem harder to bring out of dormancy. In the wild it is often bushfire that damages the coat and the rainfall afterwards causes the swell and brings them out of dormancy. Thicker seeds can respond poorly to boiling water treatment if using damp towel method.. and do better with nicking and cold water I find.
Oh and before I forget.. very important with native a lot of Australian plants to avoid too much phosphorous in your mix.. especially Acacias. Be sure to check any fertilizers used are low phosphorous and nitrogen rich. Acacia are nitrogen lovers
Scotts Osmocote Native Fertilizer is a good brand of native Australian plant fertilizer. You should be able to order it online. When you transplant your seedlings into new pots, watering them in with diluted Seasol will help with establishing healthy roots. Lastly, Acacia seedlings do well in taller tubes as the tap root grows fast.. my understanding is that in early stages, tall is more important than wide in the seedling stage IMO. I use 65mm x 65mm x 160mm forestry tubes for seedlings now and you can wait much longer before needing to transplant.
Hope that was easy enough to understand.. been a long day.
On the note of my own plants, they're all out of the greenhouse and in the garden hardening in the elements. We had our first frost the other day but my place is pretty sheltered from the extreme in the lower parts. So its giving them the chance to gradually harden instead of just being suddenly slapped by heavy frost. If it gets too cold I always have a sun room.. they can keep my salvia and Acacia simplex company.
Couldn’t resist sharing some photos and video of the wattles at night with the dew floating around them.. notice in photos 1, 2 and 10 how red the maidenii are going red from the cold. They should survive as they are the most established of my plants, and they are survivors from last winter when they were a mere 3-4 inches tall.
Photos in order:
1 and 2 - Acacia maidenii
3 and 4 - Acacia acuminata narrow phyllode var.
5. Acacia obtusifolia and phlebophylla saplings
6. Either Acacia retinodes or provincialis.. it was accidentally included in a seed packet with some floribunda seed. I also have some retinodes seed so will sow some in spring to compare to this specimen.
7. Acacia courtii
8. Acacia floribunda 'white willow'
9. Acacia phlebophylla
10. Acacia maidenii
11 and 12 - Acacia phlebophylla
