Hi Susan! Well, I am afraid what I said might be a little misleading, as I have a couple of them.

I have gotten about ten packets of different species of Corydalis over the past few months in trades. Very excited to expand my few into a collection! So in the next year or so (if they all germinate, cross my fingers) I should be able to give a good comparison of them. I have done a good deal of reading about Corydalis though (much more interesting than some books I have had the misfortune to pick up recently, lol). There are hundreds of species, so this is something I can just keep on collecting for awhile.

Most Corydalis are spring ephemerals, which go dormant or partially dormant after they bloom. One that has a longer (if not the longest) bloom time is C. lutea. It is covered in bright yellow flowers from spring until frost (if you snip back spent flower heads). I have had mine for several years and just adore it. It is wonderfully hardy and tough. I even planted a seedling in a crack by the sidewalk and it has survived, even when the rain floods the area and freezes.

Almost all blue colored Corydalis are known to be less than vigorous growers. The only exception that I know of (only read this, not sure for certain yet as I have only just gotten seed of it) is C. linstowiana. I think Arrowhead sells the C. linstowiana under the name 'Du Fu Temple'.

Another Corydalis that is generally considered a vigorous grower is C. solida. It is a very hardy alpine plant native to Scandinavia and parts of the Balkans. The color ranges from pale purples, pinks, to a few near red cultivars like 'George Baker'.

The only downside to Corydalis is that most reseed extremely well. Some gardeners find it to be a problem. I don't since it is so easy to pluck out any unwanted ones. I think the dry/less than perfect soil over here also keeps it from reseeding as much as it could. So richer soils would incourage more germination I imagine.

Sorry I could not give you a real review of the performance of them, since I don't grow many. Hopefully I can give more info (and seeds!) when my plants grow up.

I have some Corydalis lutea seed if you would like to try them. I would be happy to send you some, along with those pink poppies. Send me an e-mail if you are ;-)
CMK

I have white corydalis - Corydalis ochroleuca - and I love it. BUT it does seed around like crazy! It is easy to remove if necessary. It's almost evergreen - it's green as soon as the snow goes away and is blooming by mid-April - and still blooming in November! My neighbour planted the yellow type two years ago and last year I started to see yellow ones appear in my garden, so I have to pull any I see or else I suspect they will out-compete the white ones. They are becoming a groundcover/filler plant in much of the shady backyard garden. Since green and white is the basic color theme of the shade garden, they are a great addition to it. Here they are in the bottom righthand side of this picture with the variegated Japanese maple we planted last spring:
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Thanks so much for all the great info. I didn't realize they were big reseeders, but that hasn't ever really stopped me before. How exciting to have all of those different seeds to try this year. That should be interesting to see how they all do. Isn't it fun to have something to collect in the garden?!?! It's always exciting to have a quest when thinking about the garden!

Du Fu Temple is what Arrowhead has on their 2010 cover. I think I will try it!! And I think I'll also order the C. Solida.

I'll email you on your offer for both the C. Lutea and the poppy seeds!! Thank you!!!

Glad I could be of use. I have a bad habit of collecting things I like, lol. That is why I have Geraniums and Geum popping up all over the place! I can't stop myself.

-woodyoak, I don't have the C. ochroleuca. If you ever happen to collect seed from it I would love to do a trade, if you are interested ;-)
CMK

CMK - I never collect seed from them - never even noticed when they set seed! But there are gazzilions of seedlings each year and friends and neighbours who like it never go away empty-handed! If you're in the neighbourhood sometime..... :-) It's a nice plant; get some if you can... I've tried a couple of blue ones but they never 'took' for me and I've now concluded that I prefer the white ones anyway so I've given up trying for blue.