SWEET peas are flowering well in gardens these days, due to the warm weather. They are grown for their beautifully coloured flowers and for their scent. But the sweet pea is an annual flower, meaning that it withers away at the end of the season.
It is not a huge effort to sow a few seeds in autumn or spring, but still, it is even easier not to have to sow each year. There are some perennial pea species that come up year after year. Unfortunately, they are not scented, but they are still worth having.
These are not just perennial for a few years but can live for many decades in gardens and in roadside hedges. Compared to the annual species, which can give up under pressure of competition or drought, they are remarkably persistent and resilient, well capable of coping with weeds and competition from other plants.
The species most widely grown is Lathyrus latifolius, which has broad leaves. Each autumn, this plant dies away completely just to the roots below soil, leaving a thatch of withered stems that mark its location. From spring it can grow to two metres or so by mid-summer, a great tangle of heavy stems and bluish green foliage.
The flowers are smaller than those of the sweet pea, more rounded, and more tightly packed on the flowering stem. The colour is usually dark pink-purple and there are pale pink forms and white kinds too. There are a few named varieties of this plant, such as 'White Pearl' and 'Pink Pearl', and 'Blushing Bride', white flushed pink.
But usually you get a packet of mixed seeds and the seedlings can show considerable variation of colour. These can be grown all together in a happy mix of pink and purple shades. This is a fine garden flower as it is easy to get going, not choosy about soil. Like most pea family plants, it thrives in well-drained soil, a little poor in nutrients.
There is another perennial pea species, Lathyrus grandiflorus, with larger flowers of distinctive dark wine purple in the centre, fading to pale purple-pink at the edge. Its foliage and stems are lighter and more airy.
It is also seen in roadside locations and old gardens, but is not so much grown in new gardens as it has a tendency to sucker.
The stems underground spread out to make a broad clump and it can smother a shrub by growing all over it. But if you have a rough bank or similar, it can be left to its own devices.