Indigo, coreopsis, marigolds: blue, orange, yellow; three plants to produce three colors (and then some.)
Japanese indigo/Polygonum tinctorium - a tender annual that produces shades of blue. Generally easy to grow, but requires moist, fertile soil, and plenty of sun. Seeds should be started indoors in colder areas; plant out after the last frost and when temperatures have warmed a bit. I usually plant them out with my tomatoes - on Cape Cod where we have colder springs, this is generally around Memorial Day. Harvest once plants are about 15" tall and leaves turn navy blue when bruised. Cut stems a few nodes up from the ground to yield multiple harvests. In addition, this indigo variety can be propagated very easily, offering up more plants to grow. Cut a stem and place in water. Roots will grow from the leaf nodes, and the cutting will be ready for transplanting in a week or so. You can also pop cuttings directly into soil, just be sure to water often until it roots become established. Learn more about growing and working with indigo in my Growing Color workshop series at The Provincetown Art Association & Museum.
Dyer’s Coreopsis/Coreopsis tinctoria - an easy annual to grow that is prolific with flowers until the first frost of fall. The entire plant - stems, leaves, and flowers - will yield shades of orange. Dyer’s coreopsis can be sown directly outdoors in spring and will grow in any soil type. Maintain steady soil moisture until the seedlings are about 6” tall; beyond that, they are drought tolerant. Plant this in the back of your garden, as it can grow quite tall through the season. Pinch flowers daily and dry blooms in a well ventilated area. At the end of the season, cut the whole plant down and chop into smaller pieces to be dried for later use.
African Marigold/Tagetes erecta - another easy annual to grow that yields lots of large flowers all season long. (French marigolds have smaller blooms, but still pack a punch of color.) Requires full sun and prefers moist soil, but can deal with drier conditions. An excellent pollinator, bees will flock to the large blooms; I’ve often found them asleep inside the folds of petals. All parts of this plant will produce shades of golden yellow to ochre. Great for container gardening if you’re running out of space, and it also makes a good companion plant for vegetables like tomatoes. Start seeds indoors about 4-6 weeks before your average last frost date.
In general, you’ll need the same weight of flowers as material to be dyed, so consider growing more of the same plant as opposed to growing multiple varieties.
Depending on the plant variety and your growing zone, seeds can either be directly sown outdoors, or started from seed inside with the help of heat and light. Once these seedlings have grown up a bit and the weather is warm enough, they are transplanted outside.
What you’ll need for indoor seed starting:
Seed-starter or soil
Seed containers, pots, recycled yogurt or salad containers, etc.
Watering can + bucket
1. Begin by wetting out your soil in a large bowl or bucket. Add water until it holds together, but isn’t too muddy.
2. Fill seed containers with damp soil. Tamp down. Fill again.
3. Plant 2-3 seeds in each container, 2x their size deep; meaning a larger seed gets planted deeper than a smaller seed. Refer to seed packet or grower website for specific instructions. Label containers with plant variety.
4. Ensure your seedlings get plenty of moisture, light and warmth during their time indoors. A sunny south-facing window will work, but grow lights and heat mats will offer seedlings a better start than a sunny window. Without enough sunlight, seedlings will get ‘leggy’ - growing too tall as they search for more sun.
5. Meanwhile, prep your area for transplanting by working compost into the soil. Refer to seed packet for spacing between plants as well as soil and sun preferences. Mark out where your plants will go and prepare labels for seedlings.
6. Refer to seed packet for the planting out date. Generally, it’s after the threat of frost has passed. A few days prior, begin to harden off your seedlings by exposing them to the elements. Place them outside in a protected area, out of direct sun for a few hours each day; this will acclimate them and help prevent transplant shock once they go in the ground. When ready to transplant, check the weather: transplant on a cloudy day, preferably after a good soaking rain.
7. Continue to offer plenty of moisture throughout the growing season, especially for indigo; some plants, like coreopsis, are drought tolerant once established, while indigo prefers moist soil. Daily garden check-ins are helpful to the plants (as well as the grower).