Pricking-transplanting seedlings

I recently got a question about pricking seedlings. It referred particularly to Aquilegia flabellata and Capnoides sempervirens started in early February, which are now starting to look a bit unhappy. Liz (not real name) did a very good job! and notice the coir fiber pot used for Capnoides (it can be planted as a whole in the ground).

This is a good occasion to talk about if, when and how to prick out seedlings in general.

So, you got your seedlings growing. What next?
Most will need to be prick out. Common saying is that this should be done after the true leaves are formed. Usually we are doing it much later.

It all depends on what species were sown, the size of pot used and germination percentage.
For species with very good germination rate, the sowing pot will get insufficient to sustain a good growing for all seedlings.
From my warm sowings of this year: Thymus zygioides, Paronychia cephalotes, Acinos alpinus…..they are all pricked out as of last week.

How to proceed? I will exemplify with pictures of Anthemis carpatica seedlings of last year.
First, let the mix to dry out; if the mix is too wet most fine roots will break when you try to separate them. The more roots you preserve, the better.
Gently squeeze the pot on all sides; the content should easily slide out (if too wet, wait a few more days).
Place the pot content on a tray, plastic sheet…then separate the seedlings. Ideally, the roots should easily come loose when trying to separate the seedlings.

It is quite amazing how many seedlings will come out from a 6 x 8 cm pot! Lower right corner – Silene suecica before pricking out last week.

Since we are not talking nursery production :) it is best to not prick out individual seedlings, especially for species with fine seedlings (discard the very week or the ones with broken roots). I usually make bunches of 2-3+ seedlings and repot them together in a pot with fresh potting mix. By transplanting in bunches you obtain a nice clump-like looking plant fast. Large seedlings are best potted only 1-2/pot (Centaurea, Eryngium, Helleborus….).

Various pricked out seedlings; choose the size of the pot accordingly with your needs: Oxyria dygina, Centaurea orientalis and Acinos alpinus

Water thoroughly.
Wait 1-2 days before placing the pots again under the lights (if outdoors – keep them out of direct sun for few days).

*Various Fabaceae may not react kindly at transplanting and it is best to do it fast before the roots grow too long. Same applies for the true alpine species, which grow up very long roots although the aerial growth seems small.

It is good to learn from mistakes, so I will show a Lupinus breweri seedling of last year: I waited too long for transplanting, that’s for sure! The plant survived but later slowly disappeared. Most Lupinus species are prone to do this and are best sown directly in the garden or pricked out very, very young.
The same goes for Astragalus, Oxytropis and other ‘legumes’.

What happens if you don’t transplant the seedlings?
In some cases, the young plants will stop growing because of lack of nutrients and space. Especially in small pots all potting mix is ‘consumed’ by the roots which will became entangled at the bottom. In most extreme case the seedlings may perish or get sick.

We can learn again from my mistake. Last year I failed to prick out all seedlings (again). In the plate below, I show 3 species I transplanted only in October. Notice the root system of Anemone caroliniana after growing in a small pot from May to October!. Being too late for the roots to have time to re-establish, I transplanted the Anemone and Clematis in larger pots without separating the seedlings.

!Various species seedlings do not need to be pricked out and react badly if you try to do so.
I already mentioned this for Arisaema species, Roscoea, most Liliums, Fritillaria spp., Podophyllum, most Iris; in general any rhizomatous/bulbous/tuberous species (Allium, Calochortus, Crocus, Gladiolus,….). They are all best grown in the same pot for 2+ years.

If you realize the sowing pot is too small to ensure good growth, the best option is to transplant the whole content in a larger pot. This can be done at any time during the growing season (Lilium philadelphicum 2 years old seedlings transplanted as a whole in a larger pot shown above).

Another option is to wait until the seedlings go dormant and repot the little bulbs/tubers in new pots, keeping the same depth where you found them. Problem is that in many cases they are tiny, and most likely some will be lost in the process (I’ve been there).

Good luck and keep growing!