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A yellow sweet pea at last?
 

This new sweet pea from New Zealand is probably the closest to yellow that we have

For decades – centuries, even – breeders have been working to develop a yellow flowered sweet pea. This one is the closest we have.

Lathyrus x hammettii 'Primrose'Mostly, the approach has been to start with cream-coloured varieties of traditional sweet peas, Lathyrus odoratus, and to try to select for richer and richer colour.

But Dr Keith Hammett, who developed ‘Primrose’, pointed out the problem: “The significant point is that flowers of cream-coloured L. odoratus cultivars open darker and then fade.” So however dark they are in bud, the colour lightens.

‘Primrose’ has very different origins. It includes blood from the red-and-yellow flowered species, L. belinensis, discovered in 1987, as well as traditional sweet peas. The hybrids, first developed by Dr Hammett, are known as L. x hammettii and, he tells me, “cream coloured selections of L. x hammettii darken with age.

“The cross that created ‘Primrose’ was made in 1994/1995,” he said, “and ‘Primrose’ was essentially a field name or descriptor. It is one that I take out of the deep freeze every now and again to use as a bench mark to see whether we’re making any advance towards true yellow.

“I guess that as my field name was ‘Primrose’ rather than yellow, it suggests that I did not consider it to be yellow enough. I have later selections, all of which are in the same ball park, but I guess someone might claim it to be the closest to pure yellow yet disseminated. “I could not possibly comment” he said.

‘Primrose’ is shorter than most sweet peas, reaching about 1-1.2m in height, but is also very bushy and very prolific. The lime-green buds open to rich cream flowers that develop stronger yellow tints as they mature.
 

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