Crocosmia × crocosmiiflora
Crocosmia" × "crocosmiiflora, montbretia, is a garden hybrid of "C. aurea" and "C. pottsii", first bred in 1880 in France by Victor Lemoine. The name "montbretia" is often found in horticultural literature. Description. "Crocosmia" × "crocosmiiflora" grows to 90 cm high with long sword-shaped leaves, shorter than the flowering stem and arising from the plant base, ribbed and up to 20mm wide. The base is a corm, a swollen underground stem lasting one year. The flowers are up to 5 cm long and coloured deep orange. Cultivation. In the United States, "Crocosmia" × "crocosmiiflora" is  considered suitable for planting in hardiness zones 5–9, but in more northerly locations it can be planted in the spring and the corms dug out in the fall. The corms should be planted in a well-drained garden soil in a full sun to partial shade. The hybrid will set viable seed that can be grown from seed as soon as ripe, but as a hybrid will not breed true. In Belfast, Northern Ireland it is recorded as well-established in a wide range of locations. There are over 150 named cultivars within "C." × "crocosmiiflora" including: Those marked have  received the Royal Horticultural Society's Award of Garden Merit. Invasive species. "Crocosmia" × "crocosmiiflora" is deemed an invasive plant in New Zealand, common on roadsides in the northern parts of the West Coast of the South Island. The New Zealand Department of Conservation classes it as an environmental weed. The California Invasive Plants Council (Cal-IPC) lists "Crocosmia × crocosmiiflora" as an invasive plant in California, with limited concern / distribution. It is widely naturalised in England and Scotland especially along the western seaboard from Cornwall north all the way to Sutherland.