(Editor's Note: This article was originally published on November 26, 2007. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
Hi, my name is Mark Fox and I hold the NCCPG National Collection of Crocosmia in the UK. My friend Pat Gunter and I have written this very shortened story of where Crocosmia come from and a rough guide on how to identify the main species that are available. There are actually nice species but most modern hybrids are bred from the common four in this short history.
Crocosmia are a genus of Southern African bulbous plants that spread by producing what are called corms. A corm is a fleshy underground stem that is similar to a bulb but stores its food as a stem tissue and has fewer and thinner leaf like scales. All of the species grown in the UK come from 'summer rainfall areas' of South and Southern Africa, and the varieties offered have been bred from these, and it is this that makes them suitable for growing outdoors as late summer and autumn flowering perennials in the UK. Most Crocosmia are quite drought tolerant however all benefit from being given plenty of water during their growing season.
There are chiefly four species that have been used in the horticultural development of this genus. These include Crocosmia aurea, Crocosmia pottsii, Crocosmia masoniorum and Crocosmia paniculata, the first two have smooth leaves (see above photos) and the latter two species can be easily recognised by their pleated leaves (see below photos). There have been many crosses between them. The main cross that many of you will know is between Crocosmia pottsii and Crocosmia aurea, as it was this cross that produced the common montbretia.
Crocosmia aurea, which can be quite a large-flowered species, is chiefly a woodland plant, and comes from more temperate and tropical areas. Thus it is less hardy and in nature is given protection by the trees it grows under. The trees also provide shade and a more organic soil. Montbretia that have larger flowers than normal have more Crocosmia aurea blood in them. Thus with a few exceptions they need to be treated differently that those with smaller flowers as they can be more tender and need different requirements. Indeed, some of the larger-flowered Crocosmia definitely benefit from being given a little shade, 'Emily McKenzie' especially.
Crocosmia pottsii is found in the open along the banks of streams in its natural habitat, and thus prefers moist conditions in full sun. However, that said it is very tolerant of a range of conditions. The true species is grown in the UK but there are many hybrid forms of it, and these are so vigorous that it is very difficult to get rid of them once you plant them. So really this small flowered species should only be grown if you have room for it, or you have a difficult spot in which to plant. This plant is very much a survivor. However, there are some very good garden worthy forms of C. pottsii.
Both of the species mentioned above are also supplied with ample nutrients in nature, C. aurea from the decomposition of vegetation in its habitat, and C. pottsii from the nutrients that it is supplied, found growing along streams.
The other two species, Crocosmia masoniorum and Crocosmia paniculata can be dealt with together as they originate from more mountainous areas of South Africa. Because of this they are more frost hardy than the other two species. Hybrids from these now represent quite a proportion of what is being offered commercially. I fully recommend their culture in colder planting zones. The most common of these offered is Crocosmia 'Lucifer' but there are also many other good varieties, these differ in both height and flower colour. To generalise if you see a listing of Crocosmia and you don't see ''x crocosmiiflora'' in the name then it is likely that what is offered is a hybrid between one of these species, e.g. Crocosmia 'Walberton Yellow', which is a Crocosmia masoniorum hybrid.
Anything tall, such as 'Lucifer' or 'Zeal Giant' will have some Crocosmia paniculata in its blood.Crocosmia paniculata was once known as Curtonus, and Antholyza, which gave it its common name "Aunt Liza."
We can conclude from this that smooth-leaved Crocosmia (montbretia) require warmer, more organic, moist, nutrient rich soils; and that those with pleated leaves (Crocosmia masoniorum and Crocosmia paniculata hybrids) are less fussy and more tolerant of various conditions and locations. This is, however, a generalisation.
If anyone wants to contact me with any questions, please post a thread to this article.
Written by: Mark Fox (Mr_Kodak) and Pat Gunter (FlowrLady)