It interested me to discover that vining plants had a pivotal role in evolution. Apparently the ability of a climber to seek nutrients deep down in the soil, but to soar up through the jungle canopy in order to find light was critical. It meant that plants could at last leave the fringes of the sea and learn to thrive almost anywhere.
It’s just that will to survive anywhere that we need in the roof top potager. By introducing a whole series of trellises, wires and wigwams, I can encourage many vegetables to head for the heights. This should increase the yield from each valuable square metre of raised bed or pot.
Plants that climb include the following.
Peas - Alderman is a white flowered old fashioned cultivar which runs over two metres high. Pea stems are vulnerable to wind damage. Make sure you tie them in well and pinch out the growing tip when it gets to the top of the trellis.
Almost all varieties will climb two or three meters. Cut off the top shooting spike when it gets too tall for picking. This will encourage side shootsand more beans. It is very important to pick all the beans as soon as they are ready. Leaving runner beans on the plant, except right at the end of the season will change the structure of the plant and it will stop cropping. Like sweep peas, harvest everything once every ten days. The runners will keep fresh for two weeks in the chiller cabinet of the fridge.
Really good climbers are hard to find. I planted Courgette de Nice this year, but found even in a hot summer it didn’t make the height, though its fruits were delicious. Thompson and Morgan recommend an F1 Hybrid called Black Forest, but I haven’t tried it myself and those who have don’t rate its climbing ability. I suspect we need to learn how to train them.
Climbing French beans are a must for any garden. I can’t understand why people bother with the dwarf varieties – all that bending down to pick them. Choose a mangetout variety and then the pods can be picked at any size – they don’t go stringy.
Choose an indeterminate type and cut off all side shoots.
The choice of varieties is important. Often people recommend dainty minature cultivars for container growing. I was hesitant at first to plant notoriously vigorous varieties. I figured that only six inches of soil might exhaust them too easily. But of course I forgot about evolution. I forgot that vining plants have genes that were brought forth in response to hardship. The stress of my rooftop isn't really a hardship to them at all. I can water and feed the plants generously and the rooftop perfectly replicates the canopy level of the vegetable jungle.
Many of the vegetable climbers need a helping hand to start their climb. Plants like runner beans respond to the touch of the support by twisting their stems and embracing it. Others need to be tied in as they clamber. Plant seedlings close to the trellis and then use ties to get them going. Once the plant had reached the desired height simply pinch out the top sprout and watch your climber full out and flower.
I always plant companions around climbers. A nitrogen fixer like sweet pea seems to boost even the nitrogen fixing climbers and nasturtiums or small roses planted at the base of the trellis will attract black fly and green fly respectively. Something spindly and floriferous will also to attract bees to pollinate. This year ipomoea is scrambling all over the place, providing those heavenly single day flowers in every hue from shell pink to the deepest purple. As the year progresses climbing vegetable can look a bit dull, so the added virtue of these flowers is to extend the beauty season!