[John]

For several years I visited Harry Hay's garden situated right by the M25 south of London until his death over a year ago. He was not only generous in allowing me free access to photograph his plants but was very happy to give me plants and seeds. It was a treasure trove of bulbous plants and a congested arboretum of trees and shrubs.
I love Tropaeolums and Harry did too. He introduced me to several new species. About 20 years ago on my first visit he gave me some roots of T. ciliatum for which I could forever curse him as I still have it and will probably never get rid of it. It is an impressive climber with evergreen growths to about 5m high with us. Covered in attractive yet quite sombre ochre yellow flowers in summer. It also produces copious amounts of bluish fruits which seed into everything. The underground stolons are a bit like those of bind weed but become brown with tubers forming along their length. You have been warned and I would suggest you take care when trying out an unknown species.
About 5 years ago Harry grew T. argentinum for the first time. It was a very vigourous climber and was in the same spot every year since though I don't know if it is a tuberous plant or an annual. I sowed a few seeds from him two years ago with no success but kept them moist and this year three of them germinated. I was sure they must have rotted! It has subtle soft straw yellow flowers which are quite small and fringed rather like the common annual T. peregrinum.
If and when I get pictures sorted out I will have to post one!
Many Tropaeolums are winter growing geophytes which would be well suited to the mediterranean climate especially where frost free.

[John]

Having sorted the image problem here is a picture of Tropaeolum argentinum.

[John]

I have only seen Tropaeolum tuberosum subsp. sylvestre at Harry Hay's where it grew well out in the garden and scrambled through a clipped box. Harry's garden is a cold site which regularly gets down to -15ºC. It probably has the potential to be an invasive weed but it seemed confined in his garden. I grew it from seed and have kept it in a pot. The flowers are totally vivid orange red whereas those of T. tuberosum subsp. tuberosum are two-toned.

[John]

I was just thinking that these would be better placed in the subject "Bulbs" but most of them are climbers and some don't produce tubers. T. lepidum is quite distinct with it's soft mauve flowers. Here's a picture. The only one that I know of that comes close to it is T. azureum which I believe comes in mauve as well as blue.

[Alisdair]

Tropaeolum lepidum is currently viewed by Kew as a synonym of T. azureum. What do you think, Alberto? John's lovely photo certainly makes it look quite distinct.

[John]

They are clearly related but have a totally different "feel" to each other and I would be extremely surprised if they are found to be the same species!!!!!!

[ezeiza]

Ditto, Alisdair. They look so different. There are several variants of azureum but all within the same "idea".

A famous bird painter used to say sarcastically: "You will see, Alberto, that in the long run, all Habranthi will be found to be a single species". Perhaps the same will be found with Tropaeolums!

John, perhaps those with tubers should be under "Bulbs" and those like argentinum that have normal roots in "Climbers".

Tropeolums are on the whole intriguingly difficult to grow. A few grow well in cultivation but most do not.
Argentinum was distributed by John Watson but proper habitat information is lacking. Did he collect the seed in the low land where temperatures are very mild or high in the mountains where it would be an alpine? This species behaves like an annual, can produce lots of seeds but these would not germinate no matter what is done. With us it has grown very rapidly and the fleshy underground stem was perennial(!!!) although it seems to be an annual. subsequent attempts with very fresh seed gave nil results.

[John]

I don't know the provenance but can only say the seed came from Harry Hay where he had it growing every year in a poly tunnel. Seed germination was poor though I didn't have much seed to start with. It also took two years to germinate though they were kept in frost free conditions. I had two seedlings in a pot which were doing well but started to look rough so after collecting a lot of seed I cut them down, not knowing if there would be a tuber or not. The stem has secondary thickening which made me think it would be a perennial. The one I planted in the garden at home took a long time to grow away but has now branched profusely and is over 5 m wide covered in flowers. It is growing on Euphorbia x pasteurii. I am slightly concerned about it's possible weediness as we already have T. ciliatum in the garden and it is an evergreen thug growing to over 5 m high and totally evergreen so far.

[ezeiza]

John, do you grow it outdoors in SW London? This would definitely point to it having an altitude provenance.

[John]

I germinated this one this spring (after two years from sowing) and planted it out in May. It is one seedling and it took quite some time to get going but is really romping away now. I am ignorant to it's natural habit. Is it a perennial or a strict annual? You said it doesn't produce tubers. The secondary thickening of the main stem would imply a natural perennial though it may die with us and therefor behave as an annual the same way T. majus or T. minor do.

[Jamus]

I hope no one minds me reviving this thread. I've been growing Tropaeolum for a few years now and have had mixed success with them. The perennial, tuberous species do quite well in our climate zone, but drainage needs to be very sharp and it's necessary to keep them dry after dormancy and before they emerge in mid winter. I grow them in large glazed pots and use scoria in my propagation mix, coarse sand, peat and amend the mix with rock dust, an Australian product called FCRD (Fischer creek rock dust). Many of the annual species from lower altitudes are much easier to grow, seed can be sown any time from autumn to winter and will flower in spring and summer.

Regarding the discussion on Tropaeolum lepidum, it may be a hybrid of azureum with another species as they hybridise quite readily. The pictures you posted John are almost certainly Tropaeolum hookerianum ssp. atropurpureum, which I have grown and have seedlings of again this year. There is a bit of confusion around the genus but there was an excellent article published by John Watson and Ana Flores, in September 2010 in Curtis's Botanical Magazine which is well worth getting for anyone interested in the genus.

[John]

Hi, thanks for reving this again. I do get in a pickle with the naming of some of these. I also have less than I did due to lack of space but I do love them as they have such a unique character.
There was a nice clump of T. polyphyllum at RHS Wisley the other day, see pic. I've tried this in a deep pot where it struggled to flower and then disappeared! Be warned though I know if happy it can be a (beautiful) thug.

[Jamus]

I have one small plant of T.polyphyllum in a deep pot. It's the only germination I've ever had despite sowing dozens of seeds. It's three years old this year and is just emerging now, I noticed it a few days ago. I hope it does something this year! Thug? I wish!

[John]

I've only seen it happy in the ground. When I visited Jim and Jenny Archibald's, sadly after Jim's death many plants had gone to their new homes but there was a huge bed with half Tropaeolum polyphyllum and the other half the closely related T. incisum, equally beautiful but both major colonisers!

[Trevor Australis]

Tropaeolums? Me too. I have T. polyanthum at 3 yrs too so I'd best go down to see of it is emerging. I've grown quite a few from Chile-Flora seed. Curious that quite a few prefer to grow out of the drainage holes of the pots! I have one planted out at the base of an upright Yew which is finally getting going after some years sulking. I agree they should be tried more widely in places where they can scramble upward. Their growth is so light it cannot do any harm to host plants.