20 years ago I was enthralled with offering of eritrichium howardii seed in Jim & Jenny Archibald's North American collections list, "...Dead Indian Pass NW of Cody. 2800m. Limestone gravel patches and rock fissures... this is certainly not impossible to cultivate well... of course it needs superb drainage and protection from winter wet... Silver rosettes packed into dense cushions, to 10cm across, covered with the purest blue flowers on 5cm stems. (10 seeds @ $7)". Taking that sitting down, one packet was enough, and I don't recall any success. 10 years on I was able to germinate and plant to a tufa piece a seedling that was very vigorous and gradable, e. howardii 'blue sky'. More have followed and the plants raised from cuttings are far easier to handle. In Jim's notes there is valuable information:
- The preference for rich, limestone-derived soil ( mineral rich) and growing in narrow crevices ( keeping the crown dry and provides a cool root run).
- The location near Dead Indian Pas, though relatively high at 2800 m., is very hot in summer. This is to the good, as many eritrichium sp. are not so heat tolerant.
The notes about culture in Europe are not so useful. We can grow it outside without protection. This point was recently brought home to me when John Mitchell, the supervisor for the alpine section of RBG, Edinburgh commented on the range of plants we grow outside that they cannot, and so must grow as specimens in pots. Winter wet is the main problem. One coping strategy for such conditions is to plant directly in/on tufa, and indeed, the RBG had just bought a load for that purpose. You can still fail with tufa if you don't adjust, "radicalize", your methods. Humans are creatures of habit and we dislike challenges to our approved practices. But Jim's notes say it simply and best, "Limestone gravel patches and rock fissures". He also noted that they had collected seed from plants they had grown - a sign of hope for those of us with no experience.
In the same list was eritrichium nanum var. aretioides from both Colorado and Wyoming. Most interesting are the different soil conditions. On Pike's Peak, soils are a "granite grit" vs. those of the Big Horn Mts., "...exposed, stony ridges on hard limestone". My recollection is masses of e. nanum growing on fertile, rocky pastures on Hunt Mt. in the Big Horn's. The soil was actually a heavy, silt/loam and would grow an excellent vegetable garden. The two collections are not so different as the soil data would suggest. I have plants of both and they grow equally well. As Jim notes, "...While more difficult than e. howardii, the N. American races seem easier than those from the Alps... the classic arctic-alpine of the N. hemisphere. Purest blue flowers on silver-haired cushions." I have only been growing them for ~ 3 years, but in a narrow, elevated clay crevice, the plants have grown much better than I expected, with 3 of the 7 seedlings surviving both summer and winter. Though e. nanum is more sensitive, I think that we will find a hardier plant among all the seedlings we grow much as what happened with e. howardii 'blue sky'. The sight of masses of e. nanum growing with dodecatheon conjugens, douglasia montana and aquilegia jonesii , essentially in what is used as pasture for sheep, is much different idea than we might imagine, but so it is. At least here, one can see the plant's need for a richer soils and its acceptance of some competition - it may be that there are co-operative benefits involved too. Often, I think, we treat plants as solitary specimens/individuals when they more likely need the benefit of association. Currently, I grow eritrichium using 2 methods. With freshly rooted cuttings, a compact "brush" of roots radiates from the lower stem. In this case, it is easy to drill a small (12mm) hole in tufa to a depth ~ 4cm. with the cutting in place, the hole is filled with Spanish River Carbonatite which provides nutrition, and the top part is capped with clay to prevent wash-out. The clay does not bother the stem and preventing wash-out is important. One may also "smear graft" a rooted cutting onto the tufa. It will quickly root into the stone. The tufa does slow down growth, but the plants are quite healthy.
The other method applies to any flat-surfaced stone - in my case it is tufa that is layered like sandstone and splits easily on those reed lines. Two or more perfectly aligned pieces are made. A thin layer of clay is trowelled onto one side. The plants, either seedlings or cuttings are set on the clay with the roots splayed out. The pieces are pressed together so that there are no air voids, and then set into the garden or trough. The caveat being to create a thin crevice no more than 12 mm wide. The plants grow faster with this technique, but still remain in character - thinner is better.
So, with reasonable success with these 2 species, I'd like to try others. The Chinese chionocharis sp. in particular are what I have in mind. So far, the problem has been germination; i.e., none! While it's easy to play "blame the seed collector", John Mitchell said his experience has been the same _ none, nihil _ even when they brought back plants from China with seed attached. I have no idea what the problem is, but hope we overcome it. John said that the chionocharis should grow as easily as e. howardii. We owe a lot to the seed collectors who endure many hardships for little financial gain. They are modern day hunter/gatherers. If it weren't for the self-rewards they receive, we would be limited to selective breeding programs and have very little really new plants to excite our minds.