Wild collection of seeds

Although more labor-intensive than purchasing materials, materials collected in the field can be more effective for achieving restoration goals than commercially available materials [1]. There are laws in place to protect wild and rare native plants in Arizona. Do not collect materials without landowner permission or proper permits, and know the rules pertaining to seed collection and transfer (additional information).

Seed collection by hand

Seed collections should be conducted as close to the proposed planting location as possible (i.e. within 150m) [2] to ensure overlap between seeding conditions and germination requirements [3]. Seed collection can occur directly from the plant or from the ground (often the case for trees). Although seed collection should typically be conducted once the plant is dry, some studies have shown that seeds can be removed from green plants and stored until cured [4]. Planning can enhance seed capture. For example, using a nylon sock to cover a section of ocotillo is very effective for seed collection [5]. Although these proactive strategies are time consuming, data has shown that plant collected seed can demonstrate much higher viability than ground collected seed [6]. Seed processing (cleaning, storage, testing) can also take substantial amounts of time and energy. Lippitt et al. 1994 is an excellent overview of strategies for effective seed collection. Important points from the paper include: collection from at least 50 individual healthy plants (ideally, from different stands with approximately 200 yards distance between individuals if collecting from grasses) should be attempted to ensure sufficient coverage of a site. Be sure to leave at least 50% of the target plants within a population alone to ensure adequate recruitment for the following year.

Although this can be an issue with purchased seed as well, collected seed can often require exposure to environmental factors that overcome seed dormancy. These factors can be dissimilar across species living in the same region [7] and can include periods of heat, cold, moisture and physical scarification. Some species have also been shown to germinate and survive at higher rates when exposed to chemicals such as Salicylic acid [9]. After seeds are collected care should be employed for transportation and storage to avoid destroying the seeds by overheating. Seeds should be kept in material that allows air in and should be stored in a cool and dry environment. Best management practices for post seed collection suggests storing seed at -20 degrees C at low moisture conditions [8].

Seed collection with machines

Hand collecting seed is more time consuming than bulk harvesting with machines. However, in addition to increased cost, the use of machines such as a combine or seed stripper, can result in harvests of materials associated with seed, such as leaves and stems. This reduces the amount of pure live seed per pound, subsequently requiring additional labor for cleaning the seed or increased pounds required for seeding. Moreover, weeds and other undesirable material is much more likely to contaminate collections when conducting bulk harvests.