CORYDALIS

[art600]

Having received surplus seed from both the SRGC and AGS, I would like to know how to maximise my chaneces of achieving germination.  I have always understood that Corydalis needed to be planted fresh, even though they appear to then lie dormant under the soil.

Should I soak them?

[Ian Y]

Arthur
Corydalis is one of the bulb seeds that I do like to sow fresh. I normally sow them as soon as I collect them into a dry compost and keep the pots in the glasshouse through what we call a Summer here in North East Scotland. I do not Know the precise detail but I understand that the seed is not fully developed when it is first shed and it goes through a further development as it lies in the warm dry soils, any one know more of this?
Back to your seeds, I do not think it is the type of seed to benefit from a soaking. It has a very brittle apparently impervious coating which I do not think would absorb moisture like some other seeds. In fact I think it is the brittleness of the coating that often causes the poor germination of corydalis from the seed exchanges. It is so easy to damage and split the coating when you are handling the seeds and once it is cracked the seed looses viability quite quickly unless it is planted.
Arthur this is a long way of saying that I would sow the seed now, I would not soak it first but I would give the seed pot a good soaking when you have sown the seed.

[Diane Whitehead]

Which species of Corydalis did you receive? 

I have had very poor success - generally, only the woodland ones
that are going to end up seeding themselves everywhere
come up for me.

I just discovered an article about research done on C. ambigua
in Japan.
http://www.ingentaconnect.com/content/nrc/cjb/2005/00000083/00000006/art00003

Its seeds have immature embryos when the seeds are shed
in May. The embryos need some time at 25 C daytime /15 nighttime.
They start to elongate when the temperature drops to 15 day/
5 night, and continue growing as the temperature drops to 0 C.
Beginning in December, the seedcoats split, and in March the cotyledons
 emerge under the snow.

The embryos did not grow if they were kept at 5 C. from the time
they were shed. I don't know whether keeping them in the fridge
as some seed sellers do, would render them incapable of ever
germinating.  It looks like my lazy method of keeping seeds lying
about in the kitchen may be beneficial for some seeds.

Maybe I'll try some corydalis seeds once more.

[David Pilling]

There's a good germination guide on the ONTARIO ROCK GARDEN SOCIETY web site:

http://www.onrockgarden.com/

it includes several types of corydalis, generally backs up the idea of a period of warm.

[Maggi Young]

More good links,  my thanks to Diane and David

[Gene Mirro]

I have germinated three types of Corydalis, caseana, lutea, and nobilis, all using the same method.  Sow them in moist mix, place in a sealed plastic bag, keep warm (20-25C) for at least one month.  At this point, you will find that the seeds have expanded and burst the seed coats.  Then they need 3-4 months of 40F (5C).  When they germinate, they don't like high temperatures.  They grow well at 50-60F for the first month or two.  At 70F, you may lose them all. 

The high temperature requirement at the beginning of the process is confirmed in Norman Deno's books on seed germination.  A word of caution about Deno's method:  when he says 70-40-70, he is saying that this is the temperature cycle which induces germination.  He is not recommending that the seedlings be grown on at 70.  For many seedlings, this is much too warm, and they will all die.  He mentions this somewhere in his books.  And in fact, the 70F after the 40F is not necessary even for germination.  Many seeds will germinate and grow at 40F after the required chilling period.  70-40-70 is just the standard cycle that Deno uses to try to keep things simple, and because it works for a broad range of seeds.

With Corydalis, you may find that the seeds will germinate irregularly all through the warm and cold cycles.  This is very inconvenient.  I carefully dig out the seedlings before they make big roots, and plant them in small pots and grow them on under lights.  This way, the ungerminated seeds can germinate at their own pace.  I have attached a photo of two C. nobilis seedlings, one which germinated after one week of cold, and one which germinated after one month of cold.  Both have been grown under lights at 50-60F.  Seed was sown on 9/28/06.  The larger plant germinated in the first week of November, and is shown on January 24.  Quite the monster, isn't it?  I won't be surprised if it blooms this spring. 

By the way, I have C. nobilis seed from three different sources.  One vendor kept the seed in moist storage since harvest.  Only one lot of seed has shown any germination so far, and it is not the one that was kept in moist storage.  That one lot of seed gave nearly 100% germination after one month of cold.  It's all very mysterious.