Sweet Peas
(Lathyrus Odoratus and hybrids)

Captain Clarke's Blue Edged

Darwin: Pollinating Sweetpeas (1866)

R.D.: Sweet Peas (1882)

Eckford: Breeding Sweet Peas (1884, etc)

Tracy: Flower Seed Growing in America (Sweet Peas) (1898)

Zvolanek: Sweet Peas under glass (1899)

Wickson: California plant breeders (1902)

Zvolanek: Winter Sweet Peas (1907)

Hayward: Winter Sweet Peas (1908)

Sim: Winter Sweet Peas (1908)

Bateson: Sweet Peas (1909)

Beal: Winter-flowering Sweet Peas (Sept 1912)

Dick: History of winter-flowering Sweet Peas (1914)

Taylor: The yellow sweet pea. Gard Chron Ser 3. 60: 146 (1916).

Barker: Sweet pea hybrids. Gard Chron Ser 3. 60: 156-157 (1916).

Beal: Sweet Pea Tests Told (July 20, 1916)

Kraus: Varying Sweetpeas (1916)

Zvolanek's Sweet Pea Lists 1910-1933

Senn: Experimental data for a revision of the genus Lathyrus (1938)
Zvolanek has traced the history of his winter-flowering sweet peas to crosses he claims to have made between L. odoratus L. and the garden pea (Pisum sativum L.) and a common vetch (Vicia sp.). The historical evidence indicates that interspecific crosses in Lathyrus have been successful only very rarely, if at all.

Senn: Experimental data for a revision of the genus Lathyrus. Amer Jour Bot 25(2): 67–78 (1938)

Beale: Genetics and Chemistry of Sweet Pea colors (1939)

Davies: Lathyrus hybrids by stylar amputation (1957)

Harborne: Lathyrus pigments (1960)

Khawaja: A new interspecific Lathyrus hybrid to introduce the yellow flower character into sweet pea (1988)

Herrick: Barriers preventing hybridisation of Lathyrus odoratus with L. chloranthus and L. chrysanthus (1993)

Hammet, Murray, Markham Hallett: Interspecific Hybridization between Lathyrus odoratus and L. belinensis (1994)
The recent introduction to cultivation of Lathyrus belinensis has enabled experimental crosses to be made with cultivars of the sweet pea L. odoratus. Lathyrus belinensis has flowers with yellow pigmentation, a color missing from cultivars of sweet pea. Chemical analyses revealed that three pigment types, carotenoid, flavonoid, and anthocyanin, are present in L. belinensis, which is easily identified as seedling leaves exhibit a diagnostic red pigment spot and pods are membranous and indehiscent. Like L. odoratus, L. belinensis is distinctly scented. A hybrid was established by means of embryo rescue. Karyotypes of the parental species are very similar, and meiotic pairing in the hybrid indicated considerable homology. The hybrid between L. belinensis and the cream-flowered L. odoratus cv Mrs. Collier showed reduced vigor and novel flower color. A chemical/biochemical rationalization for the observed color changes is presented. Light and scanning electron microscopy showed differences in petal surface features and the distribution of pigments within petals.

Markham: Spectacular colour modification in a Lathyrus hybrid (1995)
Lathyrus odoratus x L. belinensis

Markham: Yellow coloration in Lathyrus chrysantha (1998)

Poulter: Powdery mildew resistance in Sweet Pea hybrids (2003)

Sweet Peas in California: A Fragrant but Fading Memory (2007)

Dr Keith Hammett — Sweet peas and other things
Summer Flowering strains require 12 hours daylight to initiate flowering, Spring Flowering strains require 11 hours, while Winter Flowering strains require only 10 hours.