Planting Multiple Varieties Increases Plant Establishment

ABSTRACT Establishing desirable plants is challenging because low survival often results in low plant densities. Identifying varieties with greater survival is difficult, partly because which varieties best survive depends on environmental conditions that are unknown at the time of planting. Rather than identifying the best variety for a given site, planting multiple varieties might better ensure establishment. Dividing a species’ planting rate among multiple varieties reduces chances it develops relatively low densities, especially when survival probabilities vary widely among varieties. To determine how much survival probabilities vary, we relied on data from three grassland seeding studies. Survival probabilities varied widely among varieties, so dividing seeding rates among multiple varieties meaningfully guarded against low densities. For example, when one randomly chosen Elymus trachycaulus variety was seeded, there was a 50% chance density was 0.3 (0.5) plants m −2 [mean (standard error)], whereas dividing the seeding rate among two varieties provided 4.2 (1.6) plants m −2 . Also, if one randomly chosen Poa secunda . Variety was seeded, there was a 75% chance density was <1.0 plants m −2 , whereas dividing the seeding rate among four varieties provided 3.9 (0.5) plants m −2 . In addition to increasing densities, seeding multiple varieties reduced establishment failures. With 13 of 48 combinations of site and seeding year, dividing the seeding rate among multiple varieties eliminated the possibility that species failed to establish. We recommend dividing seeding rates evenly among as many varieties as possible. One downside to this is needing to handle seed from multiple suppliers, but an additional benefit is increased genetic diversity. In addition to different varieties, our findings apply to different seed lots, different wild populations harvested for seeding, and other propagules (e.g., seedlings). As well as grasslands, our findings apply to pasturelands, forests, cropland set-aside areas, and other areas where establishing vegetation is challenging.