Rheum delavayi 4 Baimashan, Yunnan 110710 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum rhaponticum 2 Copenhagen Bot Garden 130611 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 1 Copenhagen Bot Garden 080513 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 4 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 5 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 6 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 7 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 8 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 10 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 11 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 7 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 8 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 9 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum wittrockii 1 Bergianska 060620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum wittrockii 2 Bergianska 060620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum x rhabarbarum 2 Copenhagen Bot Garden 130604 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum x rhabarbarum 3 Copenhagen Bot Garden 130604 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum x rhabarbarum 4 Copenhagen Bot Garden 130604 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum x rhabarbarum 5 Copenhagen Bot Garden 130604 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum delavayi 1 Baimashan, Yunnan 110710 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum delavayi 2 Baimashan, Yunnan 110710 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum delavayi 3 Baimashan, Yunnan 110710 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum rhaponticum 1 Copenhagen Bot Garden 130611 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum rhaponticum 3 Copenhagen Bot Garden 130611 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum rhaponticum 4 Copenhagen Bot Garden 130611 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 2 Bergianska 060620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum tibeticum 3 Bergianska 060620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 1 Bergianska 060620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 2 Bergianska 060620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 3 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 4 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 5 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum undulatum 6 Bergianska 150527 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Rheum x rhabarbarum 1 Copenhagen Bot Garden 130604 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).