Overwintering Improves Ranunculus Cut Flower Production in the US Intermountain West

Ranunculus (Ranunculus asiaticus L.) cut flower production in the US Intermountain West is limited by a narrow window of optimal temperature ranges in the spring. With the increasing number of Intermountain West cut flower growers, regional management recommendations are needed to improve ranunculus harvest timing and yield. The objectives of this research were to evaluate planting dates, winter insulation, tuberous root (TR) preparation, and cultivar selection for flower timing, yield, quality, and profitability in high tunnel and field production systems. Trials were conducted in a North Logan, UT (41.7665° N, −111.811° W, 1405 m elevation, USDA hardiness zone 5) high tunnel and field from fall 2019 to spring 2022. TRs were either pre-sprouted or directly planted into a high tunnel (left bare or covered with low tunnels) or field (left bare or covered with mulch, a low tunnel, or mulch and a low tunnel) from November to April. High tunnels advanced production by four weeks, nearly doubled total yield, and increased the proportion of quality (longer than 25 cm) stems by 50% compared to the field. Planting pre-sprouted TRs in the high tunnel in November delivered the earliest harvest (6 Apr.), highest marketable yield (286 stems per m2 ± 36 SE), and highest net returns ($54 per m2), with 39% greater marketable yield for ‘LaBelle’ than ‘Amandine.’ Insulation nearly doubled emergence and improved marketable yield by 49 stems per m2 ± 8 SE for November field plantings. Ranunculus production was optimized as a fall-planted high tunnel crop in the Intermountain West but may be fall-planted in the field with insulation, allowing growers to maximize production during more optimal, early-season temperatures.