Thimbleberry, Rubus parviflorus
After the arctic raspberry, this might be the next cold-hardiest of the blackberry/raspberry group. And, I mean… the fruit looks like a thimble. How cool is that?
- Cold hardiness zones: 3 – 7 (can withstand cold to -40° F, -40° C)
- Soil PH: 6.0-7.0
- Watering needs: Medium-low. Don’t overwater. But do keep them evenly moist long enough to help them establish.i Drought tolerant.
- Blooming Season: Mid-spring to mid-summer, sometimes 2x in a year (spring and fall).
- Harvest season: June-August
- Fruiting age: 2 – 3 yearsii
- Average mature yield: Unknown.iii For fruit, don’t cut back canes. Fruit tends only to grow on canes that are a year (or more) old. Individual canes on the plant live 2 – 3 years each.iv
- Pollination for Fruit: Thimbleberries are self-fertile, so they don’t need a second plant to get fruit. However, more plants will yield more fruit on each plant.v
- Size at maturity: 8 foot tall, 3-6 foot wide (2.4 by 1 – 2 meters)
- Sun needs: Full shade to full sun
- Preferred habitat: Margins of moist, shaded forest.vi Native to Canada, western United States, and Alaska, they like the high, cold forest.
- Growth rate (vigor): Moderatevii,
- Natural reproductive rate (and methods): High, through rhizomatous root spreading.
- Propagation method: Separating root sprouts, rooting branch cuttings, and by layering (burying part of a branch with a nodule, which then roots, and can then be divided from the mother plant). Though more challenging than other propagation methods, seeds can remain viable for 5 – 10 years if kept refrigerated.viii
- Average life span: Unknown. Cousin species’ (blackberries, raspberries, etc) have lives between 10 and 15 years.
- Plant family: Rosaceae
Not to be confused with the flowering raspberry, Rubus odoratus (which is also sometimes called thimbleberry) Thimbleberry is a berry that looks like a bowl-shaped raspberry, and is closely related to the raspberry, but more hardy. Once the roots get established, it spreads, forming thimbleberry patches in shady, cool areas.
Though all seem to describe the taste of thimbleberries in positive terms, there seems to be enough diversity in their descriptions to suggest that different plants will have slightly different-tasting berries. Actually, this doesn’t surprise me much. In the mountains near my home where they grow wild in large patches, the diversity of the leaf-shapes of the different individual plants suggests a genetic diversity that would lend itself well to cultivation of different varieties of thimbleberry. I found thimbleberry leaves that were almost heart-shaped, others that were very simple, others star shaped, and still others almost maple-leaf shaped.
Flavor can also be effected by how soon/late you harvest. With most berries, early harvests yield tart fruits, and late harvests yield sweet or bland tastes, while the perfect ripe season will often have a subtle blend of mild, sweet, and tart. This may be so with the thimbleberry. But one thing seems clear: thimbleberries can be used in the same way you would use raspberries.1