Wisteria is a strong plant that lives for many, many years. The ideal support is a solid wall with strong galvanised wires to guide the plant. Plants are almost impossible to move once settled, so make sure you can provide plants with the space and support they require. All of the cultivars require a position of full sun or semi-shade. A moist, well-drained soil is ideal.
The best time to plant is in spring or autumn. Before planting, improve the soil by digging in well-rotted organic matter. Ideally, plant wisteria against a wall and run galvanised wires across it in order to train the plant. Don’t try and grow plants up a pergola, unless it is very strong, as plants will twist and break weak structures. Plant at the same level as it was in the original pot and water in well. Train new growth along the galvanised wires. Wisteria can be grown in containers but they will never be as successful as those planted in the garden. Ideally, only plant in a container if the plant is being trained as a standard. Choose the largest container you can find and use a good tree and shrub compost. Water well and feed in spring.
Few gardeners propagate wisteria as the wait for flowers is too long. However, if you have the yearning then take softwood cuttings in mid spring. Cut lengths of new stem of about 15cm long, removing from the parent plant above a leaf joint. Cut the material back to about 10cm, just below a leaf joint. Remove the lower leaves, leaving about four at the top of each cutting. Fill pots with cutting compost, level and firm the compost and then water. Insert the cuttings into the pots so the leaves don’t touch and cover with a clear plastic bag. Place the cuttings in a well-lit room and ensure they don’t dry out. When signs of growth are evident remove the bag and pot on.
Why has my wisteria not flowered? is a frequently asked question. Plants take time to flower; expecting flowers before the plant is four years old may be unrealistic. Plants that are grown from seed can take up to 20 years to flower but these are rarely, if ever, sold. To encourage flowers prune twice a year (see below) and be a little patient. If there are late frosts, the flowers can be damaged. There is very little that can be done about this if plants are mature and too large to be covered with a fleece.
In spring plants will benefit from a high potash feed to encourage flowers.
Prune wisteria twice a year, in August and February. If you fail to prune plants won’t flower well and plants will become vast. For the first few years give your attention to training the plant into the support. This involves pruning very low branches out, training in strong side shoots and cutting back side shoots to five buds in early August. Throughout the life of the wisteria cut back any shoots that appear below the graft union right back to the main stem. When pruning wisteria in August, prune mature plants by cutting back the shoots of the current season’s growth to five leaves. The long wispy growth is very evident at this time and if not removed will become a nuisance. When pruning wisteria in February cut back the very same shoots but back to three leaves. Mature plants are hard to kill, so don’t worry if you get it wrong.