Hello Gary,
First, I will admit my bias... after picking wild blackberries in the woods for years and years, the Doyle thornless blackberry doesn't measure up or deliver a complex blackberry flavor. I would say their taste is average, similar to that of an organically grown blackberry found in the grocery store. I have heard similar opinions from other folks growing thornless blackberries in our area (western WI). On the positive side, the Doyle blackberry does produce a reliable crop for us, sometimes in large quantity depending on the season. The fruit is large and easy to pick and well suited for freezing whole. Nobody complains about the lack of flavor in the middle of winter. That is when we love them the most.
Doyle thornless blackberries seem pretty hardy and not heavily affected by pest or diseases for us in Zone 4. We have been growing them for at least 4 years. In the past two seasons the canes have died back all the way to the ground. But in earlier years the plants re-sprouted from the previous year of growth. Not sure if this occurrence is due to age, weather extremes or our culture, but the plants have returned every season to produced berries nonetheless. We have 4 plants and they are the only blackberry variety we currently maintain. They are planted on a northwest facing slope and don't receive much attention beyond pruning out dead canes in spring and some mulch on occasion. The plants are surrounded by
lawn. The idea was to keep their suckers in check by mowing, but they really have not been aggressive for us.
I do wonder if a focus on soil enrichment would improve flavor. I also wonder about a tighter plant community, similar to that of a woodland. Would mimicking the wild blackberry environment improve flavor? Maybe from the resiliency standpoint, I
should just plant another variety with an emphasis on flavor for fresh eating.
Becky