Date of Award:

8-2025

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Melanie Stock

Committee

Melanie Stock

Committee

Claudia Nischwitz

Committee

Brent Black

Committee

Sheriden Hansen

Abstract

Cut flowers have become an increasingly important specialty crop for small farms nationwide, and particularly in Utah, where decreasing agricultural land has heightened the need for profitable cropping options. However, production is challenged by Utah’s high-elevation climate, which presents unique constraints not addressed by current recommendations. Cool-season crops, like delphinium (Delphinium spp.) and larkspur (Consolida ajacis L.), are underproduced yet highly marketable, generating strong interest among growers throughout the state. Developing region-specific production guidelines is essential to help optimize yields, extend harvest windows, and meet local demand. This research evaluated spring planting dates in high tunnel and field systems, assessed the performance of series and colors for regional adaptation, and examined the effects of 30% shade cloth in field production on harvest timing, yield, and stem quality of delphinium and larkspur. Trials were conducted at a research farm in North Logan, Utah, during the 2023 and 2024 growing seasons. Delphinium series were transplanted into the high tunnel in late March and early April, and into the field in early and mid-May, with second-year growth also evaluated in the high tunnel. Larkspur was direct-sown in the high tunnel in mid- and late March, and in the field in late April and early May. For first-year delphinium, late March transplanting in the high tunnel resulted in the earliest harvest (mid-June) and up to 37 marketable stems per m2, while second-year plants yielded up to 70 stems per m2 with an earlier first harvest in late May. For larkspur, mid-March sowing in the high tunnel produced the earliest harvest in late July and up to 5.5 stems per plant. Staggering planting dates between high tunnel and field systems enabled an extended harvest duration and improved crop availability to meet local market demand. This work also contributed to broader impacts through Cooperative Extension programming focused on cut flower production and pest management.

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