One of the things that gardeners often forget is that the vast majority of the plants that we grow hail from far distant shores. That’s why we need a greenhouse! To lull these hot house flowers and sun loving plants into thinking that they are growing in their native environment. Of course some plants hail from places with a colder climate than the UK and others from places with a similar type of weather and these will fare well in our gardens, but can also be ‘forced’ into growth, flower and action weeks earlier using the greenhouse conditions in our glass houses. Solar panels are nothing new a greenhouse already uses the energy from solar radiation to nurture plants. And don’t blame the greenhouse for greenhouse gases, if there is ever a misnomer it is that, our greenhouses do more for the environment and enable gardeners to be ever more self-sufficient than many other things. Anyway I digress (again). What I wanted to share this month was a system of growing employed by the native American Indians, an ingenious way of using land to its full potential, utilising the habit of plants and getting more crops both in quantity and diversity from a small area. It’s a system called the three sisters and refers to three very different groups of plants that can be grown harmoniously in the same plot, namely corn (Sweetcorn or maize), beans (climbing ones) and squash. The idea is that the corn provides support for the climbing beans and the squash creates a ground cover to protect the soil from the heat of the sun and to harness the sun’s energy to ripen the fruit. You can choose to grow courgettes, marrows or any other squash like pumpkins or even melons, if it’s hot enough and if you have a greenhouse you can start them all off in pots and modules in the greenhouse now. You can even grow them in a greenhouse bed or a polytunnel if you pay close attention to their pollination needs. The corn is wind pollinated, so you may need to assist spreading the pollen by shaking the plants when the pollen is ripe. By planting corn in clumps or squares rather than lines you enhance the pollination, as the pollen will blow in all directions. The beans need bumblebees to pollinate them and the squash can be hand pollinated or insect pollinated depending on your circumstances.
By sowing the seed in April you get a head start and you can even plant them into large planters ready to move outside into the garden when the last frost has passed. But don’t forget to keep some seed back and sow some more in May and in June, that way if you lose any plants or we have a spell of bad weather you have a succession of plants and a succession of harvest that should keep cropping into autumn. You can even sow in July and if we have an Indian summer (and these are south American plants don’t forget) you’ll get the benefit of a real harvest festival at just the right time of year.
Sowing
All of these plants have large seeds that are easy to handle, easy to grow and pretty fast to germinate. Fill small (7-8cm diameter) flowerpots with fresh seed sowing compost. Make a hole in the middle of each with a dibber about twice the depth of the seed and sow one seed in each. Sow the squash seeds on their sides with the thinnest edge uppermost to reduce the risk of rotting. Cover over the seed with more compost and cover the pots with a propagator lid until they germinate. Protect from frost.
Plant Out
When all danger of frost has passed harden off in a cold frame and then plant them out into the garden, arrange the corn plants in a block in the centre, plant the beans near the base of the corn and then plant the squash plants around the outside about 60cm away from the others. Keep well watered until the plants have established a good root system.