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Summer Gardening: The Right Plants in the Right Location
Adapted from the Bountiful Gardens Archive

As empty spots appear in the garden, they fill up with weeds: more work for you, and less return for your effort. Garden books suggest sprinkling some lettuce seed in the gaps, as a "catch crop." Great concept—except that lettuce hates to sprout in hot weather. Books also suggest having flats of seedlings ready to plant when a gap appears, which is not realistic for most of us. We like to use a real-world combination of the right plants and the right location: the key is creating microclimates by layering sun-lovers above and shade-lovers underneath, just as nature does.

Say you have a bed of broccoli or lettuce. As you cut the veggies, bare spots appear. If you scratch in a few seeds for heat-adapted crops like orach, purslane, amaranth, or squash, they’ll cover the ground quickly and you’ll have a healthy, juicy crop to harvest. Learning how to use a bumper crop of an unfamiliar heat-lover is better than watching weeds choke out a few bitter, stressed, cool-weather crops like lettuces, or radishes. Using the right crops makes it easy, if you're willing to try something new.

Creating the right location is mostly a matter of pairing tall sun-lovers with short shade-lovers. Carpet the ground under and between your taller plants with varieties that need protection from direct summer sun. Any plant that tends to have problems with bolting, tip burn, scorching, sun-scald, or bitterness when grown in hot sun is a great candidate for the understory layer. Beets, lettuce, cucumbers and arugula do well under tomatoes; cilantro and greens thrive under corn. Less room for weeds, more food for you! Smaller plants that love sun are best placed to the south of your tall sun-lovers. That is where the hot sun will slant in. Plant basil on the sunny side of your pepper plants to protect the peppers from sunscald.

The Three Sisters

The three sisters: corn, beans, and squash - plus a fourth sister, sunflower

This "high-low" planting theme isn't new: home gardeners are rediscovering the "three sisters" garden that fed North America for hundreds and probably thousands of years, which follows the same model. 

Indigenous peoples in several regions grew all their own staple foods using hand tools and traditional methods, using plants native to the Americas and adapted to grow well here, particularly corn, beans, and squash. Like sisters, these three did not grow in isolation, but together. Each gave something to create the best conditions for all to thrive. Because the sister crops were the staff of life, they are the focus of legends, songs, and ceremony. In some regions, a fourth sister might be included: in fertile areas like the midwestern US, it would be the sunflower; in drier areas, local basketry or pollinator crops like sunflowers might be planted; while zinnias might be grown among the squash to attract pollinators. 

The three sisters work in home gardens now for the same reasons they worked then: they produce big yields without mechanized equipment; they provide a well-balanced diet; they are easy to grow, harvest, and store. They are delicious both fresh and as dry staples. And the way they are grown as companions, forms a little ecosystem within the garden: 

  • The corn makes a trellis for the beans to grow on, its deep roots break up the soil for the weaker bean roots, and the sugars in the sap of the corn plant leak out into the soil a little bit, giving other plants—as well as beneficial soil microorganisms— energy for growing.
  • The nitrogen-fixing microorganisms that inhabit the bean roots use that corn-sugar energy to pull nitrogen out of the air and fertilize the soil, feeding the nitrogen-loving corn and squash.
  • The big, sprawling squash leaves provide a living mulch that keeps the ground moist, and the low-growing blanket of vegetation makes a sunny clearing that smothers weeds while allowing the higher-growing corn and beans to get the sun they need. 

The corn is planted in a circle, fairly well spaced. Pole beans grow up the corn. Squash carpets the ground outside the circle. Since all of these are sun-lovers, they need to be spaced fairly widely for the sun to get in. 

Three sisters plantings traditionally focus on flour corn, drying beans, and winter squash—crops that can be stored over the winter, and do well with a long growing season and hot weather. However, in short-season areas, or places with cool summers, a faster-growing, fresher alternative is to use sweet corn, green/string beans, and summer squash. 

The three sisters model can be adapted to use other plants as well: sunflowers and amaranth can replace the corn. They still provide a tall trellis for beans, produce plant sugars during the hot days, shade the beans just a little, and benefit from the nitrogen from the beans and the moist soil under the squash. Corn, amaranth, and sunflowers are what scientists call “C-4 photosynthesizers” which means they have a metabolism that can use sun that is too strong for other plants to produce sugars through photosynthesis on hot days when other plants shut down.  

You can also use the shade among the squash plants to shelter brassicas like kale and collards from the heat when they are young transplants. The strong smell of the brassicas confuses pests who might be looking for squash, and they go on to make a winter crop once the squash has finished.

The key to creating a “sisterhood” in your garden is to use plants that prefer the conditions created by the other plants in the group, and give some benefit to the others as well. 

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