Chloranthus at OpdeHaar open garden

Chloranthus sessilifolius Domino
Chloranthus sessilifolius Domino

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Chloranthus in Asia

Chloranthus are woodland plants which, while fairly well known in Japan and S.E.Asia, are as yet rarely encountered in European and American nurseries. As I write these lines in 2015, the most comprehensive review of the genus as a garden plant is that published by Tony Avent of Plant Delights Nursery in USA. Tony’s succinct text sums up the genus beautifully:

Tony Avent of the well-known Plant Delights nursery in USA summaries the genus Chloranthus characteristically succinctly:

Chloranthus, a genus of 17 species of easy-to-grow Asian perennials, are among the most esoteric perennials we grow. They are valuable for their bold texture in the woodland garden and really funky flowers in late spring. Chloranthus plants produce dark green leaves that in some species are reminiscent of hydrangea. The leaves, held on 2-3′ stems, are topped in May with a spike of small, white, bottlebrush-like flowers that are fragrant in the morning.

In China, chloranthus flowers are added to tea to impart a unique sandalwood-like scent and in south-east Asia the leaves are also used to make tea. Chloranthus is considered by palaeontologists to be one of the basal angiosperms…in plain English, they think chloranthus represents one of the earliest, most primitive flowering plants. So now you know enough about chloranthus to enthral people at your next dinner party…trust me, you’ll be a hit.

Chloranthus prefers a part shade site with well-drained, consistently moist soil. This is a very easy plant to grow, and you certainly can use it to fool your know-it-all plant geek friends, too.”

For people who are looking for more botanical details, there is an interesting table in Flora of China which guides one through identifying the different varieties of  Chloranthus.

Chloranthus fortunei “Domino” or Chloranthus sessilifolius “Domino”

Our first encounter occurred one spring about 3 years ago when a plant with shiny, black leaves almost called out to us across one of Bob Brown’s poly-tunnels at Cotswold Garden Flowers nursery in UK. It was labelled Chloranthus fortunei “Domino” but current thinking is that it is actually C. sessilifolius “Domino” and the picture on our website shows it growing robustly in a moist spot  which gets mid to late afternoon sun in our garden.

Apparently, C.fortunei is growing on the rockery at the RHS Wisley Garden in UK which maybe indicates that at least some members of the genus are comfortable in sunny conditions – I hasten to add that I’ve not seen the situation myself. I do know that my own plant lets me know when it is getting a bit dry so the “photosynthesis-transpiration compromise” is probably an issue with the plant. As the season progresses, the spectacular dark leaf colouration of Spring gradually reverts to dark green.

Our plant gave us a generous crop of seed in September and these have been freshly sown here and portions given to two plant nurseries; if we get successful germination(s) then details will be posted.   Recent queries (August 2015) around the nursery trade here in The Netherlands revealed that propagation work is going on with at least two Chloranthus species – C.oldhamii and C.fortunei. I have small plants of both these species from Dutch nurseries and need to be sure that they are what they say they are in the light of what I just said regarding the “Domino” variant. While our plant vindicates Tony Avent’s remark about being very easy to grow, propagating the plant by division is reported not to be easy in the sense that a high proportion of the plants die. I don’t have more details but the reports were enough for me not to try splitting my single specimen.

Ironically, just as I was resigning myself to having a plant that probably wouldn’t have commercial appeal to my nurseryman friends, I came across a nursery in The Netherlands which seems to have resolved any propagation problems and offers small C. fortunei plants – http://www.kwaliteitsplanten.nl/chloranthus. Lovely quality plants were sent by mail towards the end of August and have since grown robustly to the extent that I have had to re-pot them at the start of October and they will be over-wintered in a greenhouse . If they do emulate the “Domino” variant, then the nursery has a potential hit on it’s hands especially as it was said that the plants came from tissue culture propagation. The saga continues!!

Propagation from seeds

We are now at the start of June 2016 and it seems a good time to offer an update on my experiences with propagating chloranthus and let me start with the seed from my “Domino” plant which I harvested in mid-September 2015 when the seed pods only had to be touched to release them from the plant. As I said previously, the harvest was massive. Seed is easy to handle and remove from the pods and, when fresh, it has a light green colour which progressively darkens to black over a couple of days when the seed is left exposed to the air. I took freshly harvested seed and immediately surface-sowed one portion on seed compost then covered the seed with a fine dusting of compost. The other portion of seed was thoroughly washed 3 times in tap water using a bowl and a fine tea strainer and then similarly surface sown in two trays – one tray was put in the fridge for 6 weeks and the other was put alongside the unwashed seed in a greenhouse where ultimately all 3 seed trays spent the winter, exposed to daylight. It should be noted that the greenhouse was not artificially heated in the winter months but temperatures only dipped briefly below zero on a couple of occasions.

Around mid-March, both trays of washed seed gave a germination that was effectively 100% while germination of the unwashed seed remained at zero and I’ve now discarded the seed tray. These results demonstrate that chloranthus sessilifolius plants are self-fertile and tempt one to conclude that seeds are coated with a germination inhibitor which the washing removed and that extra cold stratification in a fridge is not necessary. However, one cannot definitively conclude that some sort of cold/winter period is not helpful to germination because the greenhouse was unheated. Seedlings were large enough to transplant into pots by early April. There have been no problems although it is still impossible to access to what degree the extra-dark colouration of the parent “Domino” plant is present in the seedlings although it is definitely present. 

Cuttings

Vegetative propagation is the only way to ensure that one obtains a clone of a variant such as “Domino” but experiences on splitting an existing plant are reported to have a high mortality rate (Bob Brown, Cotswold Garden Flowers). In early April I therefore decided to try taking cuttings of my plant and took off 5 outside stems by carefully probing down to the root and removing stems at this juncture. I put the stems into a proprietary potting compost in a pot which was subsequently enclosed in a plastic bag to ensure a high humidity until the cuttings were rooted after about 3 weeks. (The standard trick of watching for signs of new leaf growth as an indication that roots are forming failed for me and I will return to this again later in my story. That said, it was very easy to see signs that the cuttings were “flagging” when the bag was removed to ensure that any bacterial or fungal rot was absent and stems remained firm and erect after 3 weeks.)  I will only proceed to re-pot these cuttings once signs of growth are present.

Plant identity

Earlier in my saga I commented on my other efforts to obtain chloranthus species and in particular 3 cuttings of what was stated to be Chloranthus fortunei (Kleine Plantage, Eenrum, Netherlands). These 3 plants basically sat in their pots not growing very much and were over-wintered in a greenhouse at temperatures no lower than around 5 deg C and only dropped their leaves in February; new growth started fairly soon and I re-potted them. To cut a long story short, they don’t appear to be in any hurry to develop into substantial plants in the way that recent plant introductions such as Begonia grandis or Impatiens omeiana do. My other source of Chloranthus fortunei from tissue culture (Kwaliteitsplanten.nl, Netherlands) initially served to deepen the taxonomic question of the correct identity of what I’m growing here. As I said earlier, these plants developed robustly from seedlings and had to be re-potted in the Autumn. They were over-wintered alongside the other chloranthus cuttings and lost their foliage about the same time. They are forming healthy looking plants BUT they lack any of the dark pigmentation present in the other chloranthus. The mystery is resolved when one views the plants from above as in the accompanying photograph.

Chloranthus fortunei (left) & Chloranthus sessilifolius(right) (2)
Chloranthus fortunei (left) & Chloranthus sessilifolius (right)

The plant with the darker pigmentation lacks stems at the base of the leaves while the other has short but distinct stems. In short, the pigmented plant is Chloranthus sessilifolius and the green variant is indeed probably Chloranthus fortunei. I use the term “probably” because I’m not a trained botanist, let alone, taxonomist but the comments on pigmentation are in accord with data presented in Flora of China. 

Summary

The decorative value of Chloranthus sessilifolius is clearly enhanced by the dark foliage colour which contrasts well with the white flowers and this is maximised in selections such as “Domino“. Propagation of the sort is easy from seed . An open question remains on the subsequent rate of plant development which in cuttings seems to be slow. 

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