Wisteria that doesn’t send runners
I have a 5 year old wisteria that looks healthy and blooms nicely, but since reaching the top of our arbor the first year, it hasn't sent out any runners, so the arbor remains entirely uncovered. The plant just gets bushier without getting larger or spreading. How do I encourage runners? My other two, same age, in the same backyard, are doing nicely and sending runners just fine.
Thanks for the follow-up. Unfortunately, I don't think it's either insect damage or any of the issues referenced in the links. And we are not in a particularly windy place and, if anything, the problem wisteria is more protected than the other two.
To add to the details--The three Wisteria plants I now have growing are the third try at this endeavor. The first two plantings of three plants, all of them had this same phenomenon--no runners after their initial growth to the top of the arbor. Some of those were there for over 10 years and only ever had bushes at the top of the arbor, never any runners or spreading. I eventually became convinced that the issue was drainage, so the third try I raised the root ball into some very large pots with the bottom cut out so the root balls should never be saturated, but the deeper roots can go where they please.
One of the three new plants started sending runners the second year, the second started sending runners the third year. I was hoping the pattern would continue and the third plant would send runners the fourth year, but now it's the fifth year and I'm getting anxious. I've tried various fertilizer combinations but to no avail.
Not every plant will grow at the same pace. Is wind a factor on this corner? Have you inspected the vine carefully for any signs of insect damage?
I have listed a few links that may help you pinpoint an issue.