Roscoea Germination techniques?

Submitted by Tingley on

I am new to the group, and am slowly trying to build a collection of Roscoea species and hybrids. R. purpurea grows well for me here in southern Nova Scotia, but there are very few Roscoeas available in the local nursery trade. I now have seedlings of Roscoea alpina, but am wondering if the other two species (R cautleyoides and R. humeana) ought to be exposed to moist chilling prior to germination. The alpina seedlings were planted kept in darkness, at no greater than 70F. The other two species were given the same treatment, but there is no sign yet of any growth. Perhaps I'm a bit impatient, but I'd like to be sure I am doing the right thing to insure the best chance of germination.


Submitted by Middleton on Wed, 01/09/2013 - 17:30

My newly acquired Roscoea humeana seeds sown last February 12 in an unheated greenhouse germinated April 21st/12 in a pot & plastic bag bag environment. 
I followed the instructions according to the Ontario Rock Garden & Hardy Perennial Society Germination instructions of 4 degrees Celsius x 3 weeks then 20 degrees C.  I assume this species of Roscoea need a cold chilling stratification period!
Good Luck

Submitted by deesen on Thu, 01/10/2013 - 04:42

I seem to have had reasonable success with Roscoea seed using my normal seed sowing regime which is: sow them in Autumn (in 7cm square plastic pots in a gritty, well drained seed mix) cover them with grit, and leave them exposed to all the weather can throw at them. 

Submitted by Tingley on Thu, 01/10/2013 - 08:55

Thank you both for your help. The Roscoea humeana flats have gone into the fridge for a few weeks to see if that will trigger some action. I may try the same with the pot of R. cautleyoides seed.

Submitted by Mark McD on Sat, 01/12/2013 - 08:58

I have had good luck sowing R. cautleyoides seed when harvested late summer/fall and direct sowing in the garden near the mother plant, and they come up thickly in spring.  I received seed of several different species from various seed exchanges, and tried the same technique (direct sowing in the garden), labeling the spot, but had no germination; thus mixed results.

Submitted by Tingley on Sat, 01/12/2013 - 09:34

Thanks, Mark. I just discovered the other Roscoea thread - under 'Woodlanders" on this forum, and am impressed by that R cautleyoides of yours. There are few if any representatives of the genus available in the nursery trade here in the Maritime Provinces. I brought our R. purpurea with us when we moved from Vancouver BC in 2009. Seems to me that the genus is only now starting to catch on in Canada.

Reading about your love/hate relationship with the genus has me wondering if the plants would be a bit stockier and more resistant to collapse if they were given a bit more sun. Our plant flopped in BC when it was only getting a short amount of sunlight each day. Now it gets plenty more sun, and only collapses late in the season when frosts or strong winds cut it down.

Submitted by Mark McD on Sat, 01/12/2013 - 09:49

While my photos of the current spot for R. cautleyoides look shaded, it actually does get direct sun for 5-6 hrs and then becomes shaded by the house.  But, as you suggest, maybe I should move some of the seedling plants out to a full sunny spot and see how the growth behaves.  

I've never dug up or moved Roscoea, seems like the roots go deep, do you have any experience moving or dividing them, and if so, when is the best time to do it?

Submitted by deesen on Sat, 01/12/2013 - 12:23

McDonough wrote:

I've never dug up or moved Roscoea, seems like the roots go deep, do you have any experience moving or dividing them, and if so, when is the best time to do it?

Hope Maggi and Ian see this thread, I'm sure they could contribute. I'll be interested too since I have changes planned for the area they currently grow in in my garden.

Submitted by Tingley on Sat, 01/12/2013 - 14:28

Mark and David: I  can't speak with any experience about Roscoea cautleyoides, but if it is similar to R. purpurea root wise, I'd dig them in the autumn, after top growth collapses for the year, or early in spring before they start into active growth. I actually lifted my clump of Roscoea purpurea this past autumn, once all the top growth had withered. I used a garden fork to do the loosening and lifting, figuring it would do the least mount of damage to the storage roots. Each of the old growths of R purpurea led to virtually independent root crowns, so separation was only a matter of teasing them apart. Hopefuy the situation is the same with the other species of Roscoea.

Submitted by Tingley on Sun, 02/03/2013 - 13:30

Just giving a status report about the Roscoea seed trays:
Roscoea alpina- 11 seedlings, some now sending out their second leaves. These were sown in late December at 65 to 70 F and given a few weeks of darkness by covering the tray with cardboard. They germinated within a week or two after being returned to light.

Roscoea cautleyoides - sowed initially at the same time as the above, after 2 weeks of warm & dark, no show, so they were moved into the fridge. Flat came out Wednesday, Jan 30th, and now showing six seedlings breaking the soil surface.

Roscoea humeana - received the same treatment as R. cautleyoides, flat came out of fridge on January 30th, no sign of growth as of Sunday, February 3rd.