Run for Cover! What’s Covering Your Greenhouse and How Is It Affecting Seedling Growth?

Analysis of seedling growth characteristics between two greenhouse cover types, old fiberglass and new polycarbonate, shows significant differences in height and sturdiness coefficients in ponderosa pine (Pinus ponderosa) seedlings. Three rates of nitrogen (N) application (20, 40, and 60 mg) indicate that seedling growth will increase under both cover types, but may cause a reduction in seedling quality attributes including shoot-to-root ratio and seedling sturdiness. Under the new polycarbonate cover type, the mid and high rates of N fertilizer application showed no significant gains in seedling growth. Significant differences in germination were also detected between the two cover types favoring the old fiberglass material. When considering replacing a greenhouse cover with a new material, it is important to consider alterations in the seedling growth environment and make the appropriate cultural adjustments to ensure high seedling