About the Riverside® Passiflora

Simply the best

The history of Passion flower hybrids

The earliest known Passion flower hybrids were created in the early 19th century. Since that time hundreds of hybrids of these fabulous flowers have been created, of which sadly many have been lost over the years. Few are hardy however and fewer still are polyploid, Polyploidy means having more than the usual two sets of paired chromosomes. It is one of Nature’s ways of speedily adapting to environmental change. Our advanced breeding techniques are now starting to produce polyploid Passion flowers with three or even four sets of chromosomes per cell. This gives easy to care for plants with increased vigour and larger, stronger flowers which often stay open for several days.

Riverside® Hybrids have the following advantages for both nurseries and home gardeners:-

Free flowering

All the selected Riverside® hybrids are free-flowering, producing flowers at every node over a period of many months, often May-November.

Riverside free flowering


The solidity of the striking polyploid flowers lends itself to more intense colours that stand out strongly against other plants around them.

Riverside striking colours

Size matters

All Riverside® Hybrids compare favourably with Passiflora caerulea, producing bigger, stronger longer lasting flowers.

Riverside size advantage


Hardiness is approximate but these should survive occasional dips down to -8°C, 18°F or USDA zone 8b.

Riverside hardy hybrids

Some relevant articles both by and about Myles Stewart irvine & the Riverside® Hybrids: 

‘Plants that excite!’

Hardier Passiflora. The captivating flowers of Passiflora make them desirable plants, especially given an increasing range of fairly hardy selections. An article that I wrote for the RHS ‘The Garden’ magazine June 2020 issue. Download PDF

Hardy Passiflora The Garden

‘Pure Passion’ Plant Profile

Myles Stewart Irvine, Riverside® Passiflora breeder,
by Philip Clayton
The Garden (RHS) Volume 135 Part 9 September 2010
Download PDF

Pure Passion RHS The Garden

Investigation of Passiflora hybrids using flow cytometry

L.A. King and M.S. Irvine
Passiflora (2010), 20(1):pp. 5-11
Download PDF

Passiflora hybrid cytometry

‘Breeding hardy Passiflora by Myles Irvine, Riverside® Passiflora breeder.

The Plantsman (RHS) New Series Volume 9 Part 3 September 2010
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Passiflora RHS PLantsman