The cordon system of growing sweet peas was developed by Tom Jones of Ruabon in North Wales. He discovered that by restricting a sweet pea plant to a single stem and removing all the side shoots, he could obtain extremely high quality flowers. This technique is now used universally by exhibition growers as well as by many commercial cut flower growers. Far fewer flower stems are produced by each sweet pea plant, but this is to some extent compensated for by the fact that the plants take up much less space and can be planted much closer together.
Seedlings have their growing tips pinched out when they have produced 3 true leaves, forcing them to produce basal side shoots. One of these, usually the strongest, is chosen to form the main stem of the plant, and the rest of the growth is cut away. Sweet pea haulm is quite flexible, so this stem will require supporting as it grows, by tying it to a cane or similar support. In glasshouses strings are often used for support in much the same way as for tomato or cucumber crops.
All side shoots must be removes as they develop, and young leaves should have their tendrils pinched off before they harden. The presence of tendrils has no effect on the vigor of the plant, but they do grab onto neighbouring plants causing bent flower stems and tangled growth that is difficult to manage.
Sweet pea flower stems are self supporting and will normally grow straight, but if the plant is re-positioned or there is some obstruction which impedes the elongation of the flower stem, then bent or twisted flower stems will result. This will reduce the vaue of the affected stems, or even render them unsaleable.
© 2006 Mark Rowland