Like many gardeners I’ve decided to grow a little more this year – just in case. I don’t want to create more beds (yet), but I do want to produce more food, so a little planning is required to tweak my planting plan and maximise how much food I can eke out from the space available.
Intercropping (also known as interplanting or double cropping) is key to making the most of limited space. While I do use intercropping techniques every year it’s not something I usually plan to any great extent. Fast-growing, undemanding intercropping stars like lettuce and radishes are so quick and easy I just pop them in wherever I have gaps, without any real forethought. They’ll happily canoodle with most vegetables for at least a little while before the growth of the other crop threatens to swamp them, or until one or both crops are harvested.
But to get maximum benefit from intercropping it pays to think more deeply about how plants might interact with potential partners.
Slow Crop, Fast Crop
Mixing slow-growing crops with speedier ones makes excellent use of space. Crops that take time to mature leave a lot of bare soil around them for a long while. Haven’t we all been horrified by the space required by some plants, and been tempted into planting much closer than recommended? While that dalliance can end in disaster, planting at slightly wider than the recommended spacings and filling in the gaps between with something smaller and faster (or planting it closely alongside) can make for far more productive use of the space.
I’ve found that sowing radishes or rocket in the gaps in rows or blocks of bigger brassicas like cauliflower and Brussels sprouts works well, while lettuce can be snuggled in between young leeks. The fast-growing crop helps to shade out weeds and is harvested by the time the slower one decides it needs its own space. Or start off lettuces and spinach in your greenhouse or cold frame in early spring, then when you plant potatoes transplant the sturdy young greens into the gap between the rows. They should be ready to harvest before the potato foliage shades them out.
Another option is to sow fast-germinating crops as ‘marker’ vegetables along with others that take their own sweet time. Eager little radishes for instance will pop up fast so you know where to look for your parsnips, which can take weeks to show green shoots.
Relay cropping is like succession planting, but with a little overlap between successive crops. It works well for plants that are harvested around midsummer, particularly in areas with shorter growing seasons. The idea is to sow or plant the replacement crop where you want it to grow a few weeks before the first crop is harvested. Seeds germinate fast in the warm soil, and the almost-ready crop doesn’t get the chance to feel jealous of their new bedfellows. Once the first crop is harvested (carefully, so as not to disturb the new seedlings), the second sowings are free to spread out into the vacated space.
As an example, sowing carrots and beetroot between onions and garlic a few weeks before they’ll be harvested works well.
Try growing plants that have different growth habits in the same space. A classic combination is sweetcorn and squashes – two-thirds of the popular three sisters growing technique. This works well because the tall sweetcorn doesn’t cast a lot of shade over the ground-hugging squashes, while the squashes’ large leaves help keep weeds under control. Dwarf French beans will do a similar job. You could also grow climbing beans (the third sister) with squashes between their feet. Or go for the whole menage a trois!
Tall crops can be used to provide shade to those vegetables that benefit from it. While most vegetables crave as much light as they can get, some prefer a little respite from the heat of the day, especially in warmer climates. Hot weather and dry soil trigger crops like beetroot, lettuce, rocket and radishes to bolt, or go to seed, which prompts edible roots to turn woody while leaves become bitter. Undercrop lanky sun-lovers like tomatoes with compact cool-season crops such as salad leaves, winter radish and spinach to make it easier to keep the soil moist for these heat-averse plants.