Paradise Garden

Gardening Articles written by Experts

Lathyrus Species

by Roger Parsons

Most gardeners around the world are familiar with the Sweet Pea, Lathyrus odoratus. This article considers the other species of Lathyrus in cultivation, some of which will be familiar and some not. Many will know the perennial Everlasting Pea, L.latifolius. This is sometimes called the perennial sweet pea but, as it has no scent, it lacks the essential sweetness that makes a sweet pea. In fact most other Lathyrus species have no scent but they have a range of other qualities that make many of them worthy of a place in the garden.

Lathyrus is a rare example of a genus with flowers in the three primary colours of red, blue and yellow. The Sweet Pea has a remarkable range of colours but this is nothing compared with these other species. The species are evenly divided between those which are perennial and those which are annual. Hybridisation between the species is very rare so it is possible to maintain a collection of annual species true to type. The decorative value of the different groups is considered below.

Lathyrus belinensis

Self-supporting Perennials

These are perhaps the easiest to grow since they are low perennials that require no support and can be accommodated in any garden. The Spring Pea, L.vernus, provides welcome blooms in early Spring, followed by a decorative mound of green foliage to about 40cm high. It comes in various colour forms of which the pink and white bicolour is delightful among the yellows and blues of other plants so commonly found at that time of year. This is followed by L.aureus, with brownish yellow flowers, and then L.venetus with attractive purple blooms. The later species flower, the taller they become until the climbing perennials are Summer flowering. These three are of woodland origin but L.laxiflorus is perhaps better suited to the rock garden where it is smothered in mauve and lavender bicoloured flowers. If cut back after flowering, it should produce a second flush in early to mid Summer.

Lathyrus nervosus
Climbing Perennials

Equally easy, but requiring support or room to sprawl, are the climbing perennials such as L.latifolius. This comes in various colour shades from deep magenta through to pink and white but does not always come true from seed. The group has dense bushy foliage on vigorous growth and are useful for screening but the foliage dies back in Winter. There are several related species that all provide blooms for cutting. Most choice is perhaps the Persian Everlasting Pea, L.rotundifolius, found in red and pink forms with foliage a little less coarse than the others.
Two very exotic climbing perennials proving hardy in sheltered southern gardens during most Winters, are L.pubescens and Lord Anson's Pea, L.nervosus. Both are from South America and have large racemes of violet blue flowers but differ in their foliage. On hot still days they are very strongly scented.

Climbing Annuals

I find this group most rewarding and much of my work has been to re-select and maintain superior forms of these for cut flowers. Although the flowers are never larger than an old fashioned Sweet Pea, they are useful for petite and miniature flower arrangements and have a very wide range of useful clean colours. They can be allowed to sprawl but do better of given support. In choosing which to grow, the number of blooms per flower spike, size of the individual flower and length of flower spike, should all be taken into account. They are hardy annuals and easy to grow. A good choice for beginners is:

Lathyrus sativus var. azureusTrue BlueL.sativus  var. azureusapprox. 1m high
WhiteL.sativus  var. albusapprox. 1m high
Bright PinkL.tingitanus  var. roseusapprox. 2m high
Royal PurpleL.tingitanusapprox. 2m high
RedL.annuus  Hotham Redapprox. 1m high
YellowL.annuus  var. annuusapprox. 1m high
OrangeL.annuus  Mrs. R. Penneyapprox. 1m high
Red and YellowL.belinensisapprox. 1m high

Meadow Flowers

The increasing popularity of wild flower borders and meadow gardening provides an opportunity for climbing annuals to be naturalised in the garden and also provides an opportunity for many of the other true meadow annuals to be seen at their best, for example cream and yellow forms of the Yellow Vetchling, L.aphaca. There is hardly any Lathyrus which cannot be adapted to this style of gardening but for some, such as the Grass Pea, L.nissolia, and the perennial Meadow Vetchling, L.pratensis, this is their natural environment.

How to Grow

As with all plants, a good guide is to understand their natural habitat and try to reproduce it. Annuals are produced from seed and are normally sown in Spring in the UK. Most are quick to germinate and flower so respond to successional sowing to achieve flowering at different times. An Autumn sowing will provide blooms in May. Two species which I normally sow in Autumn because they are slower to germinate and produce flowers are L.chloranthus and L.paranensis.
They required the removal of dead flower heads and watering during dry spells to prolong flowering. Most species do best in full sun but some of the more delicate annuals and the South American climbers seem to benefit from light shade during the mid-day sun.
Perennials may be bought as young plants (L.grandiflorus is only available this way) or grown from seed. The more popular species, such as L.latifolius and L.vernus, germinate quickly but others may take several months. Perennials seem to prefer a well-drained soil, even if they are moisture lovers. They do not like cold wet soils. Garden compost, or some other form of humus, should be added to the soil when planting, unless the soil type makes this unnecessary. Many perennials spread by stolons and can be increased by division in the Spring.
The fun with any gardening is to try something different and see how it works for you. The genus Lathyrus provides a wide range of forms and can be very rewarding.

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© 2006 Roger Parsons

Roger Parsons is joint holder the National Collection of Lathyrus species, holds the national collection of Lathyrus odoratus cultivars, and is a member of the Executive Committee of the National Sweet Pea Society.

Seed of the Lathyrus species mentioned in the article, and many others, is available from Roger Parsons Sweet Peas

More information on Lathyrus species can be found on the website.