Taphrina johansonii Sadebeck

Aspen tongue

About plant names...

I was long perplexed by these miniature bunches of stunted bananas. The leaves of the tree are quaking aspens Populus tremuloides, but aspen catkins are green and narrow, not swollen and bright yellow. Was this some weird cultivar?

Turns out that Taphrina johansonii, a fungus, sometimes infects the green catkins, causing the individual flowers to swell and turn yellow. (Yes, those are flowers, though they lack petals.) These fungi are ascomycetes, or sac fungi. I was not able to determine whether they pose a significant threat to the tree.

Online References:

Forestry Images

4/21/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 6 × 4" (15 × 10 cm)

4/21/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 7 × 4½" (17 × 11 cm)

Taphrina johansonii description by Thomas H. Kent, last updated 25 May 2020.

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This catkin is normal, mostly unaffected by the Taphrina. · 4/21/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 9 × 6" (22 × 14 cm)

4/21/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 6 × 4½" (14 × 11 cm)

4/21/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 5 × 8" (13 × 19 cm)