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15 15 greg฀houseal Overview Postharvest processes include drying, precleaning, cleaning, and storing seed properly. If the seed is collected in bulk and immediately spread on a restoration site, little processing is necessary. If the seed is to be stored for any length of time, the next step is to properly care for the harvest. Drying, cleaning, and storage requirements for prairie seed after collecting will depend on how and which species are collected, the length of time stored, and the intended seeding method. Keeping seed of individual species separate will aid cleaning and assessing of seed quality and amount. Provisions should be made to begin drying any material stored more than a day. Knowledge, skill, and access to specialized equipment are necessary for some of the cleaning steps described, and these factors will determine the quality of the finished product. Most commercial producers of native seed use all these methods to clean seed to a very high degree of purity and germination. Drying฀Seed Drying bulk material immediately after harvest is critical for preventing mold and mildew. Drying allows some immature seed to ripen; it aids threshing of the seed out of seed heads or pods and thus helps maximize seed yield. One drying method is to spread the seed out on screening or newspaper in a cool, dry place with good air circulation. Seed can also be dried in breathable cloth collection bags if good air circulation is provided and the bags are checked for dampness and turned frequently. If using paper bags for drying seed, leave bag tops open and turn the contents once or twice daily. Take care not to pack collected bulk material into bags too tightly; keep it loose so air can circulate. Plastic bags or airtight containers can be used for storage only after the seed is properly dried and cleaned. Larger quantities of material will require special Drying,฀Cleaning,฀and Storing฀Prairie฀Seed 226฀ native฀seed฀production bins with screened bottoms and a source of airflow up through the material for it to dry properly (fig. 15-1). Smaller quantities can be collected in large, 100 percent cotton bags made to fit inside a 30-gallon plastic bin. Fill the bags loosely with seed heads, tie them closed, label them, and place them in the drying bins. If the material associated with the seed is very green, as is the case with spiderwort , or is damp from a recent shower, it’s best to spread the material out on tarps and position several box fans overhead, turning the seed frequently with pitchforks or shovels if dealing with larger quantities. Drying may take several days to a few weeks, depending on quantity and drying conditions (fig. 15-2). Precleaning฀Seed฀ Much of the bulk material in collected native seed is nonseed, inert floral parts, leaves, and stems. Harvested material will require some degree of precleaning to reduce bulk and improve flow for later cleaning processes. The extent of precleaning required will depend on the method of seed harvest, intended storage period, and method of planting. Threshing, debearding and deawning, and brushing are considered precleaning methods, because they are designed to prepare the seed for later cleaning processes by removing unnecessary appendages and improving seed flow. If the material was machine-combined, threshing has already been accomplished. Otherwise, you can use several low-tech hand-threshing techniques, including stomping, shaking, and screening. threshing฀seed Threshing removes the seed from seed heads. Species with large, coarse seed heads that tend to hold the seed tightly can be threshed by stomping on the seed heads. This method is very effective on species of wild indigo, rattlesnake master, compass plant and rosinweed, sunflowers, black-eyed Susan and fragrant coneflower, and golden alexanders. Place about 2 inches of bulk material in the bottom of a large plastic tub, and stomp on it with waffle-sole boots. Toe kicks to the corners of the tub help break up any stubborn seed heads. Screen the stomped material through a coarse, half-inch or quarter-inch screen into a second tub. Continue in batches, returning any intact seed heads to the stomping tub. Pale purple coneflower tends to be stubborn and may require machine threshing, unless it’s collected late in the season after seed heads naturally begin to break apart. Many species have seed that shakes free of a capsule or open pod. The shake method can be effective for dried seed heads of Culver’s root, cardinal flower and...

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