Now that we are racing through May, I hope you’re surrounded by seedlings emerging and young plants putting down strong roots. It’s a good idea to sow about 20% more seeds than you have room to grow. I probably sow even more than that out of an abundance of caution and a sprinkling of self-doubt. Principally I do this because it’s rare that all my seeds germinate, but also so I have some extra seedlings to replace those I’ve planted out but haven’t made it through those dicey early weeks of life outside (especially as it’s so sluggy out there this season).
If all goes to plan and there’s plenty of germination, I use these bonus plants for interplanting. This is the practice of growing plants with different growth habits side by side to make the most of your space. It’s a creative and engaged way of growing crops, takes advantage of underused space, and foregoes regimented planting plans to harness the benefits of growing a diversity of plants.
The easiest approach is to sow and grow a “catch crop” – a quick-growing plant placed next to a slower-growing plant. The idea is that your quick crop (such as radishes or rocket) will grow and be harvested before your slower crops (such as leeks or parsnips) gather pace and take up the space they need to reach maturity. Lettuce, dill, coriander and spring onions are good options for this approach, particularly as they put out fairly shallow roots so can be carefully harvested without disturbing the main crop. I’m in the habit of sowing seeds into trays and planting out young plants, but you can do this by sowing seeds directly into the soil where you want your catch crop to go.
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Another method of interplanting is by growing low-growing crops around tall crops. The most notable example comes from the indigenous peoples of the Americas and is called the Three Sisters, as it involves growing sweetcorn, climbing beans and squash close together. The sweetcorn provides a structure for the beans to clamber up, the beans fix nitrogen to enrich the soil, and the squash scrambles across the earth so their leaves keep down the weeds and help retain moisture for the benefit of all of their roots.
You could try this in your own garden: grow lettuces under a cucumber, whose leaves will provide shade on warm summer days, or grow chives or basil in the spaces between your cordon tomatoes as they are modest in size and fairly shallow rooted.
My approach to interplanting tends to be somewhat chaotic. Every season I experiment with being less regimented with my planting plan, and pop crops wherever there happens to be a gap. As so often exemplified in the natural world, plants do well when grown as a polyculture.
