How can I break Tropaeolum tuber dormancy?

[Steve Garvie]

I have some climbing Tropaeolum grown from Flores and Watson seed including T. azureum, T. hookerianum ssp. austropurpureum and T. kingii. They flowered well two years ago but haven't surfaced since. I thought they were dead but on tipping out the pots today all seem to be healthy firm tubers. I am not sure but I think they were exposed to late summer moisture prior to flowering well. Does anyone have advice on how to break the dormancy of these Tropaeolum tubers?

[Neil]

Steve according to the Pacific Bulb Society "This group is notorious for staying in dormancy and skipping one or two years of growth." http://pacificbulbsociety.org/pbswiki/index.php/Tropaeolum 

[brianw]

I bought some T. brachycerus from Jacques Amand last year some time (maybe at Harlow). When I got home I realised I had some "dormant" ones of the same species. I potted the new ones up and left the pot outside in the garden. In late summer I found them climbing through adjacent plants and they grew and flowered as normal. But I still have my dormant tubers that have not flowered for some years. Maybe the dormant tubers are being kept too warm and dry in the summer. I will put the recently acquired tubers outside to see if that works again.

[Ian Y]

Steve, first thing is to be sure you have live tubers as they can look perfectly good until you realise that the skin is intact but there is nothing left inside- you state they are firm which is good.
The secret to growing them is after a dry summer water them as you would the other bulbs then it is vital that they do not dry out - if they do get dry or even slightly dry they will immediately retreat back into dormancy. Once I have waters them in September I make sure they never get dry until the growth dies back after flowering and seed set. I have found some will even start to root early if any  residual moisture is in the compost then if that dries before you water they go dormant.

[Steve Garvie]

Thanks Ian, Brian, Neil.

The tubers appear to be alive -they are heavy, firm and look like wee tatties!
I suspect that moisture is the key. I will repot in moist compost at the end of August, give them a good drench at the start of September and then keep them moist whilst in growth.

[Jon Evans]

It may be of interest that 9 of my Tropaeolum species and hybrids have put up shoots this week, unseasonably early, prompted presumably by the hot spell followed by two days of steady rain at the beginning of last week, including several which didn’t appear at all last year, even though they didn’t experience one drop of rain in the garage where they were stored (I find cool dry conditions over summer are best).  I have given them a drink now, and have put them in the coolest place I can find with some light, in a shaded greenhouse, and scattered slugbait around to give the thread-like shoots some protection.  I think I will now abandon all thought of repotting the remainder this summer, as I do not want to damage new growth.
T. kingii is particularly reluctant to produce topgrowth - mine only does so every 3-4 years, and since it grew last year, though the late spring heat burnt it off before it flowered, I am not expecting it to do so this year.  Nevertheless, along with the others it will get a drench in September, and then an occasional light watering until December, to see if I can prompt it to do so.