Japanese Wisteria Has Failed to Bloom
I have a Japanese wisteria that I planted three years ago. It hasn't bloomed, ever. At first I thought it was because I pruned it incorrectly. So I bought a book on vines last year and found that was not the problem. I heard the plants need to be ten years old to flower. Is this true? Also, I'm using my grown children's T-Bar galvanized steel swing set as the support. Underneath the swing set I have enclosed the area and am using the space for my compost. Could this be the problem?
First, the good news. There is no problem growing the wisteria next to your compost pile. The sturdy swing set will make a good support and this is a great way to keep your memories a part of the landscape. Excess nitrogen from fertilizer can encourage leaf and stem growth and discourage flowering. Have your soil tested to see if you need to use a flowering plant fertilizer high in phosphorous to improve flowering. Patience is needed when dealing with wisteria. The plants need to be mature to bloom. This can take 7 years or more.
Pruning and winter temperatures can also impact bloom. Annual pruning will help keep established wisteria in bounds and the plants blooming. Summer pruning helps control growth and promote bloom. Side shoots and laterals (stems growing off the main stems) are pruned back just above the fifth or sixth bud from the main stem. In late winter these same branches are pruned back to within 2 to 3 buds of the main stem. The plant's energy will concentrate in these buds that will bear the spring bloom.
If you are a northern gardener cold winter temperatures may have damaged those flower buds. The Japanese (Wisteria floribunda) and Chinese Wisteria (Wisteria sinensis) plants are hardy enough to survive the winters in zone 5 (sometimes zone 4), but the flower buds are not. Northern gardeners should consider the Kentucky Wisteria (Wisteria macrostachys). This plant is hardy and a more reliable bloomer for northern climates. The flowers are smaller and bloom with the leaves on new growth. This wisteria also requires patience, taking up to seven years to bloom, but it is well worth the wait.
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