Article written for the Wildflower Association of Michigan Newsletter (Fall 1998)
The Michigan Wildflower Farm produces over 50 native Michigan forbs and grasses for seed and now through Thanksgiving, we are harvesting the last of the wildflower and grass seed for the season. The New England aster and Smooth aster (Aster spp.) still await our picking as do Blue-stemmed, Gray and Stiff goldenrods (Solidago spp.) and Rattlesnake Master, Joe pye weed, Boneset and Snakeroot (Eupatorium spp.) Due to the early warm temperatures and droughty conditions, this year’s harvesting began about four weeks earlier than usual with Round leaved ragwort (Senecio obovatus) in the third week of May. The speed at which a plant completes its cycle varies according to the climate conditions, and so monitoring for seed ripeness is a critical part of our business and it is extremely helpful to refer to monitoring records of previous years. For the most part native wildflower seed does not ripen uniformly and therefore we return over a period of 2 weeks to collect ripe seed of a given species.
Once the seed is ripe, there is competition with nature in the form of birds eating the seed and the wind and rain transporting the seed. In fact, there are several wildflowers that we have covered with netting to prevent the seed becoming bird food before we can collect, including Rough blazing star (Liatris aspera), Sand tickseed Coreopsis lanceolata), Flowering spurge (Euphorbia corollata) and Prairie dock (Silphium terebinthinaceum). There are a few species of wildflowers which are a challenge to harvest, but produce seed that requires minimal cleaning after harvesting. For example, as Columbine (Aquilegia canadensis) hanging blooms dry the seed head tilts up and opens, appearing like an elegant vase full of irredescent shiny black seeds, which if not harvested are poured from the vase by the wind and rain. Wild lupine (Lupinus perennis) is another species which is labor intensive in the harvesting of seed. The Lupine field is monitored frequently as the blooms diminish, for once the ripe seeds are popped from their pods we have sacrificed them to the soil. Elin Doehne, previous owner of the Michigan Wildflower Farm, measured dispersal of up to 24 ft. away from the mother plant. The stems of dried pods are harvested, laid on black plastic and covered with netting. When the sun’s warmth hits the plastic it sounds as though a popcorn popper is working on the driveway. Other species that we monitor closely before the seed is dispersed in this fashion are Flowering spurge (Euphorbia corolata) and New Jersey tea (Ceanothus americanus). Many wildflower species produce seeds with fluff, floss, hairs, or beards. In harvesting these wildflowers we are typically clipping the top portion of the plant and allowing the seed to fall onto sheets as they dry further or if harvesting on a smaller scale placing that portion upside down in a paper bag would be adequate. Have you peaked inside a ripened Butterly weed (Asclepias spp.) pod? If you haven’t, I’d encourage you to do so. At ripening the seam of the pod will split and the rich multi-toned brown seeds that are layered in perfection are visible. As the pod dries further, the tuft of hairs (floss) attached to the seed expand and are pulled out of the pod by air movement carrying the seed to its final destination. We are harvesting the Asclepias pods as they dry and open.
Seeds vary tremendously in their morphology and therefore for each seed type there is a different cleaning process or recipe that is followed in preparing the seed for sale. For example, with Columbine (Aquilegia canadensis) and Wild lupine (Lupinus perennis) mentioned earlier, the only cleaning required is separation of the seed from the seed heads in the case of Columbine, and seed pods in the case of Lupine. We are using a fanning mill with screens for this process. The “bearded” seeds such as the Asters, Solidago, Eupatorium, Asclepias, Senecio and Liatris must be debearded in the cleaning process. Burning, vacuum and tumbling are different methods to achieve this. More compact seed heads such as that of coneflowers (Rudbeckia, Ratibida, and Echinacea) and Rattlesnake Master (Eryngium) require a shaking or breaking up of the seed head to collect the ripened seed. Whereas, the Bergamot (Monarda spp.) call for a shaking out of the seed.
The size and weight of the seed varies tremendiously as well. For example, Prairie dock (Silphium perfoliatum) produces one of the larger seeds and may have approximately 800 seeds per ounce. While Culver’s root (Veronicastrum virginicum) is almost dust fine and produces about 800,000 seeds per ounce (Packard, Stephen & Cornelia F. Mutel, The Tallgrass Restoration Handbook, Island Press, 1997). Wild lupine (Lupinus perennis) although not the largest in seed size, is the heaviest seed that we produce at about 1000 seeds/oz. When one considers the seed/oz. ratio it is easier to comprehend a seeding rate of 3 oz./1000 sq. ft. or 8 lbs./acre.
There is a tremendous amount of labor involved in the business of native species seed and plant production. However, for myself and other growers that I have a pleasure to associate with, this a truly a labor of love in that as these seeds are sown across our landscapes our precious natural plant heritage is being restored.