|Emerging Gunnera tinctoria in the wild wetland area of my garden|
Many gardeners are confused about the difference between Gunnera manicata and tinctoria. In fact, many nurseries also seem confused and many plants appear to be mislabeled. As I understand it, manicata is slightly less hardy than tinctoria. The leaves of manicata are a little larger but less textured and held in more horizontal way. Tinctoria is from Chile and is probably the better plant for our climate in the Pacific Northwest.
In any event, both of these plants are moisture lovers which seem to do better beside streams, ponds or lakes. The largest specimen I have seen was at Van Dusen Botanical Garden in Vancouver, BC. There also used to be (and it is still there) a large specimen at Heronswood Garden. On a recent stroll of that garden with Dan Hinkley he told me that that plant recieved all the runoff, including fertilizer, from the nursery, and that was why it was so large. It was also located right beside a swampy area of the garden.
Gunneras are not necessarily shade plants. I have seen slides in Dan's lectures of Gunneras growing in the wild in Chile in completely open conditions. The massive gunneras at Van Dusen were also out in the open. In fact, I have found in my own garden that gunneras do not like deep root infested shade, probably because they don't get enough moisture in competition with tree roots.
So, the best way to grow large gunneras is in good soil without competition from tree roots, in a place where their roots can get lots of water, but their crown stays above winter wet, and then to water and fertilize them well in summer. In our climate it is wise to cover the crowns in winter with straw or dead leaves or something to protect them from the cold. Unprotected gunneras will sometimes be killed by cold in this climate.
As for other species of gunneras, and I have read that there are at least 40, most of them are apparantly not hardy. I have acquired on 2 different occasions Gunnera killipiana, both times from sources in the San Francisco area. A picture of this gunnera may be found here. This is an attractive plant with red stems and large leaves but not as large as G. tinctoria. Sadly both my plants succumbed to the cold the first winter I had them.
Heronswood also carried some other gunneras including Gunnera insignis, from Costa Rica, I think. A picture of that plant may be found here. Sadly, it also is not hardy here. In addition, Heronswood also offered a hybrid of insignis and some other, more hardy gunnera, but I have also lost that plant to cold and I do not know that it is available anywhere anymore. Finally, Heronswood offered Gunnera perpensa, which is a gunnera from South Africa. I grew this one in my garden for a few years, but it was proving to be extremely invasive in a wet area of my garden over the drainfield, so I took it out. In my opinion it did not offer much except somewhat large leaves and that same look could be achieved by other less invasive plants such as Darmera peltata. There are also some very small leaved gunneras which can be found here at local nurseries from time to time. These, however, do not appeal to me--the lure of a gunnera is in the large leaves and so why in the world would I want a tiny leaved one?