Wisteria floribunda Seeds | Japanese Wisteria
LATIN NAME: Wisteria floribunda
COMMON NAME: Japanese Wisteria
Plant Profile
Japanese wisteria is a woody climber that twines clockwise, seen from above, a direction that separates it from the Chinese species, which turns the other way. The racemes can reach a metre in the best forms and hang like bunches of grapes, opening from the base towards the tip over several weeks.
It grows in the woods of Honshu and Kyushu and has been trained over pergolas in Japan for a thousand years, at temples such as Kasuga and at the wisteria tunnels of Ashikaga. The plant is long-lived, and a specimen can cover a quarter of an acre after fifty years.
Science & Biotechnology
Wisteria floribunda flowers as the leaves expand, while Wisteria sinensis flowers on bare wood, and that difference in timing is the quickest way to tell them apart in spring. The Japanese species also has longer racemes and more leaflets, nineteen against eleven, and its flowers are more fragrant.
The seed is poisonous. Wisterin, a lectin-like compound, and a resin glycoside are present in the pods and in the seed, and a handful can cause vomiting and abdominal pain in a child. The pods are attractive and they hang on the vine into winter, which is when children find them. The vine also fixes nitrogen through rhizobia, which is one reason it grows so strongly on poor soil, and the same vigour is what makes it a weed in the right climate.
Uses & Benefits
The plant is grown for its flower and for the structure it makes over a pergola, and named cultivars are sold by flower colour and by raceme length. The wood is hard and was used for small implements in Japan, though the plant is not grown for timber.
The seed is not edible and the pods should be cleared from the ground. In Japan the flowers are sometimes pickled or blanched for tempura, and the practice is traditional but the quantity is small and the flowers are cooked, which is not the same as safe.
Growing from Seed
Soak the seed overnight in warm water and sow at one centimetre in a pot, since the hard coat delays germination otherwise. Seedlings take ten to twenty years to flower, so buy a grafted or cutting-raised plant if flowers are the point.
Plant in full sun in soil that drains, and give it a frame strong enough for the weight of fifty years of wood. Prune in winter, cutting the long whips back to two or three buds from the main branch, and again in summer to shorten the new growth. Without pruning the plant makes leaves and no flower, which is the usual complaint. The plant also layers itself where a runner touches the ground, so a vine left unchecked will travel along a fence line for twenty metres.
Our Take
The wisteria with the longest racemes and the sweetest scent, and the one to plant if you have a strong pergola and a pair of secateurs. Keep the pods off the ground.
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