I only have one individual of this plant, now 2 years and 4 months old. Last year it produced just one fruit, despite the fruit coming in pairs. This year it has had eleven fruit already and is still flowering.
I bought the seeds for this plant as Metaplexis japonica from Rareplants in the Canary Islands, The plant is now known as Cynanchum rostellatum. Gagaimo is the Japanese name. The plant is found in China, Japan, Korea, Tibet, the Russian Far East and the Kuril Islands. The seed seller did not specify where the seeds had come from. However, it is most likely that they did come from Japan as the seeds are sold there. One name there is gaga-imo ガガイモ but it has many, many others.
There are now 262 species in the genus Cynanchum. Some of them have latex which will burn your skin off. Other have compounds that act like digitalis on the heart and can kill. One is a horrible-smelling weed of southern Spain that I had to chop down regularly when I was there. This one has edible leaves, fruit and shoots. The abundant flowers smell of lily and chocolate mousse. It is completely hardy, being unaffected by the long and nasty winter we just had.
Cross-section of the flower showing the complex internal structure.
When I started the seeds I thought I was doing them a favour by growing it on an upstairs windowsill. Two had sprouted and neither liked being indoors, starting to grow and dying back several times. One died and I put the survivor outside. I potted it up into a 30 cm (12 inch) square pot. I used about a sixth Melcourt coarse horticultural grit and a sixth Kaizen medium pumice with the other two-thirds FertileFibre coir compost. I then topped it with more grit to make weeding easier. I had read somewhere that it likes good drainage. It started growing a bit then died down for winter. The next year it came back in spring and romped up a small tree trunk to two metres and flowered a lot.
This year it put up 6 sprouts. I used empty compost bags to shade the sides of the pot and watered it frequently during the heatwave earlier this year. It got full sun because it was trailing up a bird feeder (which I can't use to feed birds because the walls are too close and the cats too abundant) rather than in a tree as it had been the previous year. It seemed to enjoy that and produced many more and darker leaves. They were flowering and fruiting in less than four months from sprouting. In the northern parts of its natural range it grows fast to take advantage of the short summers as much as possible. It entirely ignored the trellis that I had wired onto the bird feeder and just spiralled round the bird feeder until it got to the top.
Ants were farming aphids on the ends of the stems of both the Gagaimo and Common Milkweed earlier in the year, protecting them from their usual predators - ladybirds, hoverflies and lacewings. They were also driving off pollinators so they could take the nectar for themselves. So I put sticky traps round each stem. That stopped the ants but also trapped a bee, a couple of wasps and a harvestman. I will have to control the ants in some other way next year.
Last Wednesday (2/8/2023), I harvested four fruit to try. Each fruit was
between 7.5 and 8 cm (about 3 inches or so) long and 2.5 to 3 cm (an inch or a little bit more) wide. They each weighed about
12 grammes (just under half an ounce). Here are two of them, but photographed from each side. The squares on this old shirt are about 1cm. The white patches at the stalk end are from the abundant milky latex that these plants bleed when cut. People with latex allergies should avoid eating these plants. The Japanese Wikipedia article says that the shoots are believed to be harmful if eaten in larger quantities and the roots are not eaten at all, despite the English name "rough potato".
I harvested two fruits and removed the remains of the calyx and cut them up. As soon as their photo-shoot was finished, I popped them into boiling water and simmered them for three minutes. Though they appear to be mostly hollow they made a good few mouthfuls. Very pleasant delicate texture like a tender green bean but without any fibrous bits at all. The flavour was also like a mild green bean, delightful with just a sprinkle of salt.
They were so nice, I harvested another two fruits, chopped them into centimetre thick slices and popped them in with some pasta. 5 minutes simmering with corn pasta. Pre-cooked cannellini beans with a tomato and tahini sauce. Very tasty.
I am leaving the rest of the fruit in the hope that we have some sunny dry days to ripen them. Hopefully, I will get more seeds. Though it must be self-pollinated, so it might not have much genetic diversity. The fruit should become hard and inedible, then crack open to let the silky fluff-crested seeds fly away like dandelion seeds. I will be trying to guess when they are nearly ready and cover them with cotton reusable teabags to catch the seeds.
I do have one other plant of the Cynanchum genus. Though it is quite different from Gagaimo. It was first found in Yemen and mine is probably from there. It is a leafless succulent that just produces a tangled mass of stems. It is said to have edible flowers. I have tried a few raw and they didn't do me any harm of which I am aware. It was originally placed in Sarcostemma, like several other leafless masses of twigs from hot, dry areas but they have all been placed in Cynanchum (or Funastrum for the ones living in the Americas).
It is easy to propagate from cuttings. They might survive in an unheated greenhouse and flower in summer. Mine are kept warm and bright all year and flower regularly.
This is the entry from my as-yet unfinished book Notes on the Useful Asclepiads:
Cynanchum rostellatum (Turcz.) Liede & Khanum
Usually reported as Metaplexis japonica.
China: "luo mo".¹ ²
Japan: "gagaimo".³
Korea: "bakjugari".⁴
China, leaves eaten raw or cooked. Cultivated or collected from the wild. Used medicinally.⁵ Japan, edible leaves, young fruit and tubers.⁶ Manchuria, unripe fruits eaten in late summer.⁷
China, stems and roots vs. traumatic injury, snake bites, impotence and infantile malnutrition due to intestinal parasites.¹ China, herb or root vs. impotence, vaginal discharge, milk stoppage, cinnabar toxin, swelling sores and vacuity detriment taxation damage. Seed ("luo mo zi") vs. impotence, bleeding from cuts, vacuity taxation.² Seeds and leaves as a tonic medicine called "rammashi".³ Korea, used as a tonic and to stop bleeding.⁴ China/Japan unspecified, seed tonic, haemostatic, crushed seeds applied to wounds, ulcers and all insect bites. Considered too caustic for frequent use. Pounded leaves externally vs. swellings, abscesses.⁸
China, Yangtze River, whole plant boiled in water, cooled and diluted or solution mixed with small amounts of soap vs. aphids on soya beans.⁹
¹ Li, B et al "Asclepiadaceae" in "Flora of China" at http://www.efloras.org/index.aspx Accessed 16/11/2010
² Yan, X "Traditional Chinese Medicines: Molecular Structures, Natural Sources and Applications" (1999, Ashgate)
³ Mitsuhashi, M et al "Studies on the Constituents of Asclepiadaceae Plants VIII: On the Components of Metaplexis japonica MAKINO." Chemical and Pharmaceutical Bulletin (1962) 10(9): 811-817
⁴ International Plant Genetic Resources Institute (IPGRI) and Rural Development Administration (RDA) of the Republic of Korea "Asian Medicinal Plants" http://www.genebank.go.kr/pp_a/info.jsp Accessed 15/2/2011
⁵ Stuart, GA "Chinese Materia Medica: Vegetable Kingdom." (1911, Probsthain & Co., London, reprinted 1985, International Book Distributors, Dehra Dun, India)
⁶ Fern, K "Plants for a Future Database" http://www.pfaf.org/ Retrieved 24/10/2010
⁷ Baranov, AI "Wild Vegetables of the Chinese in Manchuria" Economic Botany (1967) 21(2): 140-155 https://www.jstor.org/stable/4252860 Accessed 24/4/2020
⁸ Perry, LM and Metzger, J "Medicinal Plants of East and South East Asia: Attributed properties and uses." (1980, The MIT Press, Cambridge, Mass. and London, England)
⁹ Yang, RZ & Tang, CS "Plants Used for Pest Control in China: A Literature Review" Economic Botany (1988) 42(3): 376-406 https://www.jstor.org/stable/4255089 Accessed 23/4/2020
