Growing and Propagation


This week I’ve been constructing the frame for my sweet peas to grow up in the polytunnel. I use the cordon method which involves pinching out all the side shoots and tendrils and training just one stem up a support.

The sweet peas are sown in root trainers, one per cell and allowed to grow on until their roots fill the compost. When they have developed three sets of leaves, I pinch the tips out.

Before planting, I dig out a trench and back-fill it with well rotted manure. Sweet peas are hungry and thirsty plants. I know some growers who line the trench with wet newspaper first to help retain water in the soil. I plant the seedlings 20cm apart through holes burned in landscape fabric.

After planting, a 10 foot bamboo cane is pushed into the holes next to the young plants, one per plant.

After the initial pinching, each plant usually throws up at least one, sometimes more new shoots from the base. In this picture, you can see the darker green shoot is the original seedling which had it’s tip pinched out and it has now sent up two sideshoots, one stronger than the other.

I select the strongest of these and remove everything else.

To build the frame, I attach galvanised wire between the crop bars in the tunnel and cable tie the tops of the canes to the wire. This is a simple but sturdy framework that works well because there isn’t much weight on each vine. I attach the stems of each plant to the canes using little loops of thin gauge wire. The wire goes round the cane and the stem, just above a leaf joint.

As the plants grows I move the rings further up the stem.

It’s really important to keep pinching out sideshoots and tendrils as they form. The vines will produce huge thick stems – think ‘Jack and the Beanstalk’ and are almost unrecognisable as sweet pea plants.

When the plants start flowering, I give them a weekly dose of tomato food. I also like to spray the foliage with Vitax 2-in-1 plant invigorator. This contains emulsions and seaweed that give the plants a boost of micronutrients and also coat the leaves making it harder for insect pests to get a purchase on them and lay their eggs.

When the plants reach the top of the canes, they are removed, laid along the floor and brought back up a cane 5 along from where they are planted. This allows the plant to keep growing taller and taller. It’s best to do this because the main leader stem produces the best quality blooms with the longest stems so you don’t want to pinch the tip out and allow sideshoots to develop in it’s place.

Cordon growing is labour intensive but I love it! Harvesting is so much easier because there is less foliage and no tendrils to get in the way. It’s also much easier to make sure you’ve cut all the flowers and stopped the plants setting seed, which puts an end to flowering. But for me, the main reason for doing this is the quality and size of the flowers produced. Because the plant is putting all its energy into growing one stem and no tendrils, the flower stems grow to enormous lengths as in this picture and the flower heads are really full.

Cordon growing isn’t anywhere near as productive as growing sweet peas as bushes in terms of quantity of flowers but the quality is in another league. These long, strong stems are idea for bouquets and arrangements that need longer stems. I’m hoping to improve my record keeping this year but to give you some idea of productivity, last year I grew 180 plants using this method. They started flowering in mid may and only started to flag in mid July when the heat wave regularly sent temperatures in the polytunnel over 40 degrees. We layered them once in that time. I would harvest every couple of days and usually get 1 or 2 stems off every other vine each time.

As with all sweet peas, the stems get shorted as the season progresses but because they start out so long, you always have lovely usable length stems, even once the plants are mature.

I do miss not having lovely tendril covered side shoots to use in arrangements with this method which is why I’ll be growing a separate patch of sweet peas that I’ll allow to bush up for this purpose.

At the moment, the plants are only just being tied into their supports but soon they’ll start racing away as the days lengthen and I can’t wait to smell than unmistakable fragrance again.

Two of my absoluute favourites are Juliet and Mollie Rillstone.

Cordon growing isn’t for everyone but it really suits me. I hope this has inspired you to give it a go, even just if it’s to see if the process works for you. It is actually pretty addictive. I learned from a exhibition showbench medal winner several years ago and have been hooked ever since.

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