There is some confusion, particularly among gardening writers, about the role and nature of sweet pea tendrils and why some commercial growers find it necessary to remove them. It must be stressed that tendrils are in no way detrimental to plant growth, and that removing them will have no effect on plant vigour.
The nature of tendrils
Tendrils are nothing more than modified leaflets, adapted for clasping and gripping nearby objects, thus helping to support the plant. Usually a sweet pea leaf has one pair of leaflets and several pairs of tendrils, but if the plant is growing vigorously there may be two pairs of leaflets and fewer tendrils. Indeed, not all sweet peas have tendrils; the 'acacia leaf' varieties have pinnate leaves with several pairs of leaflets and no tendrils. At the other end of the spectrum, garden peas are bred which have only tendrils and no leaves. This makes for faster and cleaner mechanical harvesting, essential in the production of frozen peas where the field-to-factory time has to be kept to an absolute minimum.
Removal of tendrils
Cordon grown sweet peas, whether for exhibition or cutflower, need to have their tendrils removed to prevent the plants becoming entangled with each other. This would make it impossible to layer the crop when the plants got too tall, besides causing bent flower stems. It is worth stressing that many Dutch cut flower growers prefer to produce their sweet peas on multi-stemmed plants supported on a netting. These crops are not layered in the same way as cordon sweet peas, and do not have their tendrils removed.
In conclusion, cordon grown sweet peas need to have their tendrils removed to facilitate layering and avoid bent flower stems, but this is not generally necessary for bush grown sweet peas. In neither case will removing tendrils increase the vigour of the plant.