Known as The Everlasting Pea, this is the perennial form of the annual sweet pea which, as you can see from the images, looks very similar to the annual climbing pea. Its Latin name is Lathyrus latifolius whereas the annual sweet pea is called Lathyrus odoratus, and the Latin name, "odoratus" highlights the essential difference between the two peas. Most annual sweet peas are scented, hardly any everlasting peas have scent.
Generally, the Everlasting Pea plants offered for sale are nonscented varieties. There are about 20 varieties of everlasting Peas seed available to buy. There is one variety available to grow from seed called Lathyrus nervosus, Lord Anson's Blue Pea, which has a discernable sweet pea scent. It is a vigorous climbing plant, with blue/lavender coloured scented flowers.
The Everlasting Pea is an attractive shrubby climber, easy to grow from seed with many delicate flowers, usually in soft pastel shades, blues and purples. There is also a pure white variety called "White Pearl". Many climbing plants are more difficult/time consuming to grow think, Clematis, Wisteria and the annual sweetpea whereas the Everlasting Pea is refreshingly easy to grow.
Annual Sweet Peas are lovely, but they are time consuming to seed and grow. The Everlasting Pea needs attention in the summer to ensure it does not dry out and to check the tendrils so it does not become too tangled, but it is not as time consuming as the annual variety, and will return reliably each year.
The Everlasting Pea will flower best grown in full sun, although tolerant of some shade. It grows similarly to the annual sweet pea clinging on with tendrils and it will climb or scramble over an obelisk, trellis or adjacent shrubs. It is very hardy, H7 which means it will survive the most severe of winters. It is not particular about the soil type, acidic or alkaline, clay, etc, although it will grow best in fertile soil with plenty of moisture. Ensuring it has plenty of moisture will help to fend off powdery mildew.
Except for cutting back the Pea in the autumn, the growing conditions for the annual and Everlasting Pea are really the same. The tendrils can be a problem as it will grab adjacent plants, so it's best to check it is constraining those plants growing nearby.
It is deciduous and should be cut back to ground level in the autumn.
There is also a variety called Lathyrus grandiflorus, which you may want to give a miss as it is vigorous, bordering on invasive, whereas L. latifolius is well behaved and makes a great easy to grow garden climbing plant.