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Week 2 - Plant of the week - Crocosmia
Our plant of the week for week 2 is Crocosmia, not all of which are as aggressive as Montbretia!

Here's the handout:



GARDENING FOR PLEASURE

Plant of the Week

Crocosmia : Family : Iridaceae

Crocosmia, is so named because the dried leaves smell of saffron when rubbed, and after the Greek words, krokos for saffron and osme for smell .

Crocosmia come mainly from South Africa but they also exist in Malawi, Zimbabwe, Swaziland, Mozambique, Lesotho, Madagascar and Tanzania. All of the species grown in the UK, and the varieties derived from them, come from summer rainfall areas of South and Southern Africa. There are four species that have been used in the horticultural development of this genus. These are Crocosmia aurea, Crocosmia pottsii, Crocosmia masoniorum and Crocosmia paniculata. The first two have smooth leaves and the latter two species can be easily recognised by their pleated leaves, and there have been many crosses between them.

The corms are unusual in forming vertical chains with the youngest at the top and oldest and largest buried most deeply in the soil. The roots of the lowermost corm in a chain are contractile roots and drag the corm deeper into the ground where conditions allow. The chains of corms are fragile and easily separated, with each corm capable of producing a new plant, a quality that has enabled some species to become invasive and difficult to control in the garden.

Over the past few decades crocosmia have undergone a renaissance and are presently high on the "most fashionable plant" lists. The common Montbretia, (Crocosmia x crocosmiiflora) was the first hybrid Crocosmia and was bred in France in 1879 by Victor Lemoine of Nancy, and introduced to Britain in 1880. It was named after Antoine Frans Ernest Conquebert de Monbret, a botanist who accompanied Napoleon on his Egypt campaign in 1798. It was bred by crossing Crocosmia pottsii (a species that grows near streams) with Crocosmia aurea (a woodland species). This is why most Montbretia prefer a little shade, lots of water, organic matter and nutrients. Most hybrids bred before the Second World War were Montbretia hybrids.

The common Montbretia and a few other varieties have given the genus a bad reputation because they spread so vigorously and have become weeds throughout the world. Other vigorous spreaders are some horticultural forms of Crocosmia pottsii including 'Red King' and 'Red Star', Crocosmia x crocosmiiflora 'Meteore' and Crocosmia 'Marcotijn' which is usually sold as Crocosmia masoniorum.

Most Crocosmia are quite drought tolerant, but all benefit from being given plenty of water during their growing season. They prefer drier soils during the dormant winter months. They tend to be hardy down to -5°C but with good drainage will stand lower winter temperatures. The yellow and apricot varieties can be more tender.

As a general rule, Crocosmia prefer well-drained soil and full sun. Certain varieties are more suited to shadier places – those varieties with larger downward-facing flowers are usually related to the wild woodland-dwelling Crocosmia aurea and they tend to perform better in part shade. Crocosmia masoniorum and Crocosmia paniculata originate from more mountainous areas of South Africa, and are more frost hardy than the other two species. Hybrids from these now represent a significant proportion of what is being offered commercially. The most common of these offered is Crocosmia 'Lucifer' but there are also many other good varieties, and these differ in both height and flower colour. 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. Anything tall, such as 'Lucifer' or 'Zeal Giant' will have some Crocosmia paniculata in its blood.

As a generalisation, smooth leaved Crocosmia (Montbretia) require warmer, more organic, moist, nutrient rich soils; and those with pleated leaves, the Crocosmia masoniorum and Crocosmia paniculata hybrids, are less fussy and more tolerant of various conditions and locations.

Crocosmia are wind tolerant and salt tolerant except in extreme places, and they are left alone by rabbits and deer. There are varieties suited to the front, middle and back of the border and they combine well with grasses, mixed perennials and other summer/autumn plants such as Coreopsis, Kniphofia, and Helenium.

Crocosmia are also superb when grown in patio containers but make sure that you protect the pots in severe winters as the corms are more exposed to the cold when grown this way and split the clumps every few years as a crammed pot will eventually produce more leaf than flower. Even Montbretia bear much larger flowers if grown in pots with plenty of organic matter and feed, and they make superb specimen plants for containers on the patio.

Crocosmia can be planted directly into the border. A few minutes extra work before you plant will pay benefits. Dig a 12” deep hole and add at least 4 full handfuls of grit to the base of your planting hole particularly if your border does not drain well. Plant your crocosmia with the corms set at around 5” and incorporate plenty of organic material such as composted bark or well-rotted manure. A sprinkling of general purpose organic food will help them to establish. Gently firm the soil around the clump but be careful not to damage the fragile new shoots that might be emerging beneath the surface. Finally apply a good 2-3” layer of mulch to the surface – this can be bark or well-rotted compost and will act as a ‘duvet’ to your plants in the winter, protecting the corms and young shoots from winter cold.

Crocosmia will generally not require staking with the exception of taller varieties such as ‘Lucifer’ and paniculata which sometimes fall away towards the edge of the clump (this can be resolved by lifting the clump in the winter and planting 6-8” deeper). Each autumn it is a good idea to protect the plants by applying a good 3” thick mulch of bark or compost over the crown of the plant. You can leave the old leaves in place for added protect and cut them back in early spring, being careful not to damage any newly emerging shoots.

The main complaint about the plant from those who grow it is that its flowering diminishes year by year. Eventually the preponderance of green leaves far outweighs its vivid flowers. Action is then needed. In the wild, or where it has naturalised, crocosmia moves into new ground so that the fresh rhizomes can feed themselves and break away from the older bulbous roots. In garden conditions, however, room for expansion may be limited or non-existent, so it may be penned in and starved. Chains of roots increase, sitting on top of one another in a congested mass until all the soil is eaten up. Clumps of starving rhizomes manage to produce a few leaves and little else.

Lifting is best done in autumn, but can be undertaken at any time during their dormant period providing the weather is mild. Never lift or replant crocosmia in frosty conditions. Usually, by late October, foliage has turned brown. Crocosmia can be propagated by division in spring. Dig to a depth of 12in to avoid damaging the corms and use two garden forks, back to back, to prise the clump apart. The chains of corms can be replanted intact or individually separated off. There is evidence that the younger corms derive some vigour from the older corms so maintaining the ‘chains’ intact may be the better option.

Discard wizened or diseased corms and trim off old leaves to a stump. Replant sections at the same depth in rich, moisture retentive and well-drained soil. Some crocosmias, such as Crocosmia ‘Lucifer’ and C. x crocosmiiflora ‘Jackanapes’, produce underground stems (stolons). These new shoots can be detached, along with fibrous roots, to produce new plants. Crocosmias flower profusely when crowded so do not divide clumps too often; every two or three years should be enough. A few cultivars of C. x crocosmiiflora can be invasive, so reduction is essential to maintain control.

Flower colour is on the hot side of the spectrum, from scintillating oranges and reds to subtler warm yellows. Some are marked or flushed with red, in others the colouring is pure and solid. Heights vary between 18in and 4ft. Some flowers are dainty and rounded others are large showy stars.

Crocosmia 'Lucifer' is a very popular and reliable variety bred by Alan Bloom. Aptly named, its flowers are flaming red. It is the earliest to flower and its great pleated leaves are an architectural feature in their own right. The seed heads provide further decoration. It is also extremely hardy.

Crocosmia 'Solfatare' is a glorious combination of amber flowers and bronze grassy foliage. It may need protection in colder areas.

Crocosmia 'Emily McKenzie' is one of the most flamboyant varieties. The large deep-orange flowers are splashed with sealing-wax red both inside and out.

Crocosmia 'Citronella' (syn Honey Angels) has fresh green leaves and small, soft yellow luminous flowers. Easy to grow, hardy and upright.

For planting combinations, try Crocosmia 'Citronella' with Imperata cylindrica 'Rubra' and Rudbeckia fulgida. The undercurrent of the rich-crimson grass gives the pretty pale crocosmia flowers added appeal. Crocosmia 'Star of the East' in front of Euphorbia characias or any of the glaucous spurges looks good. The blue-grey euphorbia leaves intensify the vivid orange of the crocosmia flowers. Use Crocosmia 'Lucifer' with Dahlia 'Bishop of Llandaff' and the acid-green bracts of Euphorbia schillingii or E. palustris for undiluted zing.

Although crocosmia can be planted in clumps and patches it looks best in broad swathes, intermingling at the edges with other herbaceous plants of similar height. This kind of ribbon planting exploits its colonising tendencies and makes it flow.


Jo Hanslip
April 2009

Sources include
The National Collection Holder, M A Fox, 9 North Street, Caistor, Lincolnshire, LN7 6QU
Tel: 01472 859269 / 07971 006 462:
http://www.simplesite.com/CROCOSMIA/5330361

http://www.trecanna.co.uk/

http://www.johnjearrard.co.uk/plants/crocosmia/crocosmia.html

http://www.theafricangarden.com/

Royal Horticultural Society
http://www.rhs.org.uk/advice/profiles0905/crocosmia_dierama.asp

Suppliers
Holden Clough Nursery Ltd, Holden, Bolton-by-Bowland, Clitheroe, Lancashire, BB7 4PF
Telephone: 01200 447615
http://www.holdencloughnursery.com/

Trecanna Nursery, Latchley, Nr Gunnislake, Cornwall, PL18 9AX Tel: 01822 834 680 http://www.trecanna.co.uk/

Proper Plants, Penknight, Lostwithiel, Cornwall, PL22 0JD Tel: 01208 872291
http://www.properplants.com/

Avondale Nursery, Avondale Nursery, at Russell's Nursery, Mill Hill, Baginton, Coventry, England CV8 3AG Tel: 024 7667 3662
(no mail order, but good-sized show gardens)
http://www.avondalenursery.co.uk

Bali-Hai Mail Order Nursery, Mrs M.E. Scroggy, Bali-Hai Mail Order Nursery, 42 Largy Road, Carnlough, Ballymena, Co. Antrim, Northern Ireland. U.K. BT44OEZ. Tel/Fax.: 0044(0)28 28885289
www.mailorderplants4me.com


The National Collection Holder also has plants and seed for sale.




And here are the images at Photobucket:

Crocosmia


Aren't they gorgeous?

Jo