We have a Chinese wisteria which we’ve had for 20 years. We’ve
trained it on a trellis to the side of our covered porch and then
on a rope across the front so there is a nice green, leafy fringe
along the porch front. However, this plant has never bloomed.
We have consulted with our local horticultural experts and they have suggested various treatments. The lawn care
people do not fertilize near the roots of the wisteria so it
doesn’t get too much phosphorus, we have done root pruning, we have
even hit the trunk with a board to shock it, have applied super
phosphate but no blooms. We get some pretty cold
winters, but I’ve never even seen flower buds anywhere on the
plant. I know wisterias are sometimes late in blooming, but this
is a long time to wait! The roots of the plant face east and get
lots of sun. The part across the porch is shaded in the afternoon
because we have two pine trees in the front yard. We prune off the
tendrils that form during the summer to keep the plant in check,
but what else can we do to get blooms? I know it would be a
spectacular display if it ever bloomed and have almost given up
trying. I’m thinking of hanging artificial blooms just to get the
effect!
I found quite a bit of discussion in online gardening forums about
flowerless wisterias, so you are not alone. You may find this information
from Cass Turnbull of Plant Amnesty helpful:
“THE MOST COMMON COMMENT I get at classes and at the PlantAmnesty
educational booth is, “My wisteria won’t bloom.” It is natural for these
vines to take between three and seven years to start blooming. I have
read that frequent, proper pruning may help them to begin blooming
sooner, or at least more. On the other hand, some people have old vines
that have never bloomed. I am told that these are seed grown plants or
“mules.” I have often heard root pruning recommended to force an older
vine to bloom. Basically, this means that you use your shovel to cut the
roots in a circle (or dotted circle) a foot or two from the vine. I have
also heard people recommend fertilizer formulated to encourage blooms,
(not heavy on nitrogen). However, I have been faced with such a vine and
had no luck with either technique. In that case, as with all
non-performers, removal is the best option, and no one will blame you for
it.”
Here are gardener Ketzel Levine’s comments, from her NPR.org site:
“Depending on how old your wisteria is, do know that young plants can take
up to eight or ten years before they flower, especially if started from
seed. Other reasons wisteria fail to bloom: lack of adequate sunlight
(needs at least six hours of full sunlight); too much nitrogen fertilizer
(causes more vegetative growth); pruned heavily in winter or spring (also
encourages vigorous vegetative growth); severe winter injury/cold-blasted
flower buds (though that is clearly not a problem this year) or a bum
plant. It happens.”
You could either try the method described above, of cutting a circle with
a shovel, or you could replace the vine, or you could follow through on
your artificial flower idea! (I’ve heard that Bellevue Botanical Gardens
hangs Wisteria-shaped lights from their arbor for their holiday light
show.)