Ephemeral Crops for Time-based Polycultures

Polyculture, growing multiple plants together, rather than only one, is all about minimizing competition and maximizing the opportunities for cooperation between your plants. 

One way of doing this, is by gardening in the 4th-dimension, time. At Lillie House, we take advantage of plants that thrive throughout different times of the growing season, so that we start get harvests as soon as the snow melts in late winter, right up through the first snows of Winter. Ephemeral crops like garden cresses, avoid competition since many of them will be grown and off to college in April or May, well before the next set, like tomatoes, are going into the ground in June. 

They also help our crops cooperate, since over-wintering ephemerals keep nitrogen circulating in the garden that would otherwise be lost to winter rains, and provide habitat for soil organisms when we'd otherwise have bare soil. 

Many of these are also light feeders, making them ideal to grow as part of a polyculture ground cover, prior to a "main crop" of heavy feeders. 

Remember that when you design polycultures to get constant successions out of the same beds, you can rapidly deplete soils, so we think it's important to use lots of mulches, nitrogen fixers and dynamic accumulators, and a rotation that allows our self-sowing polyculture to grow as a "green manure" cover crop every few years. 

I hope you'll help me improve this list by adding your own suggestions in the comments. 

Over-wintering crops for cold-temperate climates

Walking onions

Garlic

Sweet rocket (Perennial)

Onion grass (Wild Garlic)

Yarrow

Wild cresses

Miner's lettuce

Biennial Crops that Overwinter, then Set Seed

Carrots

Parsnips

Kole Crops (Possibly overwinter, depending on variety.)

Lettuce (depending on time of sowing)

Parsley

Fennel

Very Early Spring Crops

Ramps (perennial)

Claytonia Virginica (perennial)

Sweet rocket (Perennial)

Pea tips

Salad Cress

Wild Cresses

Mustards

Spring Crops (that likely finish before Summer planting)

Mustards

Peas

Salad Cress

Arugula

Lettuces

Baby Carrots

Radishes

Quick "Catch Crops" for Cool Weather

Radishes

Beets

Chard

Salad Cress

Those are my recommendations based on our experience, ease of germination, and suitability to polyculture plantings. If you want to experiment with other options, here are a few lists that can help you design polycultures: 

List of Cool and Warm season crops: https://www.northeastnursery.com/blogs/the-complete-list-of-cool-season-warm-season-crops

List of cool season crops from Sunset: http://www.sunset.com/garden/garden-basics/cool-season-crops-0