Dear Sue,

Thank you for contacting us. The thimbleberry is a North American native. The fruit falls from the shrub easily and deteriorates quickly after harvesting. As a result, there is not much research on them. 

We previously received a similar question which received this response:

Lack of fruit can be the result of many issues, from few pollinators or a freeze that kills the flowers... They need slightly acidic soil -- a pH just below 7.0

The thimbleberry shrub (Rubus parviflora)... will bloom and fruit on 2nd and 3rd year primocanes. So if you've been seeing new canes one summer, it should bear fruit for the next two summers.

When pruning your thimbleberry shrubs, be sure to retain the older canes. They produce the best yields on mature canes that are 2-3 years old. Enhance the soil with finished compost or manures. Doing so encourages vigorous flower and berry production.

I hope this information is useful. Please write again anytime you have garden questions.