Among the glories of late spring, Wisteria produce spectacular cascades of long fragrant flowers. But be aware of exactly what you’re taking on.
Wisteria is a group of deciduous vines, producing long scented flowers in May & June. It looks spectacular when grow on the side of buildings and I’m sure we’ve all looked at them and thought I’d love one of those. However they are one of those plants that you need to be aware of what you’re taking on and be ready for the routine maintenance required.
It is a group of ten species of woody twining (not self clinging) vines that originate from China, Korea, Japan & North America. A member of the Pea family (Fabaceae), Wisteria have been around a long time, with 7 million year old fossils found in China. Several myths have grown around it.
Myth No1. Wisteria was either named by the English Botanist Thomas Nuttall, after the American physician and anthropologist Caspar Wistar (he changed the ‘a’ to an ‘e’ to sound more pleasing) or after his close friend, Charles Wister….no one is sure .
The two most popular species are the Chinese Wisteria ( Wisteria sinensis) and the Japanese Wisteria (Wisteria floribunda). Wisteria climb by twining around any available support. Chinese Wisteria twines anticlockwise when viewed from above, Japanese Wisteria twines clockwise.
Myth No2. Why these Wisteria twine in different directions is not known.
A bit of Botany……Plants are able to twine (circumnutate) because cells on one side of the stem that are not touching the support are stimulated to grow faster than cells on the other side of the stem.
Myth No3. Wisteria are always very large & heavy plants. They can climb as high as 20m and spread out 10m laterally. The world’s largest known Wisteria (a Chinese Wisteria) is in California, measuring more than 1 acre in size and weighing 250 tons. Planted by the home owners in 1894 it eventually grew so large it destroyed the home it was planted again in 1931.
Wisteria flowers turn in to seed pods, similar to those of Laburnum, and, like the seeds of that genus, are poisonous. All parts of the plant contain the chemicals (saponin) lectin & wisterin, which are toxic if ingested, causing a burning sensation in the mouth, stomach pain, vomiting, and diarrhoea if swallowed…be aware!!!
However if you select the right Cultivar, position them correctly and are prepared to manage them, Wisteria are a stunning plant.
Wisteria sinensis.
- The flowers open at once, well before the foliage appears.
- Has shorter flowers and is not as cold hardy as its Japanese cousin.
- The flowers bloom gradually over a period of weeks.
- Flowers often last longer than other wisterias.
Wisteria floribunda
- Leaves and flowers appear at the same time
- Flowers (racemes) are much longer than Wisteria sinensis and heavily scented.
- Reliably cold hardy.
- Offers the greatest color variety.
Wisteria frutescens
- Native to the eastern U.S.
- It has the shortest racemes of the wisteria family.
- Flowers are lilac-blue and bunched in 10 – 15cm wide clusters.
- Generally not as heavily scented
Wisteria macrostachya
- Native to Midwest US
- Has 15 – 30cm flower clusters.
- Is the most cold-hardy species.
- Has the latest bloom time, with flowers emerging in June.
- Often reblooms throughout the growing season.
Wisteria brachybotrys (Silky Wisteria)
- A Chinese wisteria.
- Has 15cm long flower clusters and silky hairs on its foliage.
- Blooming improves with age and regular pruning.
- White and purple cultivars available.
Guide to growing Wisteria
Correct plant – choose your Wisteria wisely. Check how large it grows. There are numerous named cultivars of all the Wisteria species. These usually have superior flowers, flower at an early age and are reliable.Ensure it’s a grafted plant and not one grown from seed (seed-grown plants take many years to flower).
Correct Position – Grow in a sunny position, ideally on a south facing wall. They won’t flower reliably if grown on West or North facing.
Correct Support – Provide the correct structure for your plant to climb up. Use strong wires spaced 50cm vertically apart.
Wisteria can also be grown as standards, using a strong central support.
Pruning – Wisteria produces lots of growth and need regular pruning during the year to stimulate flowers for the next season. In July, after flowering, tie in any new growth to extend the plant’s coverage. The objective of pruning is to build up flowering spurs: short knobbly lateral branches that will produce flower buds. This is achieved by Summer pruning: cutting back the long, thin lateral growths produced after flowering to about 15cm followed by Winter pruning: Shorten these shoots further to 1 – 2 buds. Repeat each year to build up a flowering framework.
Feeding – These are vigorous plants and need nutrients, particularly Magnesium and Potassium. Generous helping of a rose fertiliser every March will help to promote regular flowering and healthy growth.
There you are. Wisteria – a spectacular, long lived plant that will reward year after year given the correct care and maintenance.