Passiflora x 'Silly Cow' on the walls of the Laboratory building at RHS Wisley

Passiflora x 'Silly Cow' is a recently introduced hybrid from well-known passion flower breeder Myles Irvine. Named in honour of his friend Jana-Marie Štípská', the words 'Silly Cow' in this instance are used a term of endearment rather than a derogatory comment. While it is always an honour to have a new species or hybrid named after you I am not so sure that I would admit to this one.

Growing both in my garden, I can say that my own 'Silly Cow' specimen starting flowering a good month later than the regular Passiflora caerulea, and only then sporadically, usually three or four blooms every couple of days. Each flower only lasts a day and while the flowers are indeed superior to P. caerulea, the lack of blooms means that it does not perform as well. Even though insect pollinators visited the blooms no fruits were set.

A regular Passiflora caerulea
Sadly stock of this gorgeous hybrid is few and far between, in fact I am only aware of two nurseries who can supply Passiflora x 'Silly Cow'. However as a specimen climber it is definitely one to consider. It is vigorous in growth and extremely floriferous, with 5 inch wide blooms emerging with a vengeance in June followed by a constant few until November. What really sets this cultivar apart is the pronounced navy-blue corona filaments which look almost jet black from a distance. To the artistically minded, they can take on the appearance of large, dilated eyes staring back at you.

While the parentage of  Passiflora x 'Silly Cow' appears to be a closely guarded secret you can't deny that it looks like a Passiflora caerulea on steroids, which is kind of what it is.

While regular species of passionflower contain two sets of chromosomes, Passiflora x 'Silly Cow' is listed as being a polyploid complex. This means that it is a hybrid of interrelated and inter-breeding plants with chromosomes numbering more than 2 per cell.

Polyploid plants tend to be sterile which would explain why Passiflora.'Silly Cow' rarely sets fruit. Be that as it may the plant itself is as tough as old boots able to withstand winter temperature down to -8 degrees Celsius.

Grow Passiflora x 'Silly Cow' outside on a sheltered, south or west warm wall. The top growth can be damaged by seasonal frosts, but new stem will arise from older wood in the spring. It can be grown in any ordinary, well-drained soil in full sun or partial shade. In colder areas of northern Europe it may be worth protecting Passiflora x 'Silly Cow' with brushwood or polythene sheeting for the first year or two until it becomes established.

In February or March, thin out any overgrown vines back to ground level or to a main stem. Spur back lateral shoots to 6 inches at the same time.

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