Alternative Crops to Sustain Native Alfalfa Pollinators

OBJECTIVES

In the southwest area of Washington State, the native alkali bee is the prominent pollinator of alfalfa. The main objective of this project was to explore and evaluate marketable native seed crops that will be a cost-effective alternate food source for the bees when alfalfa acreage must be withdrawn from production. The plants must bloom simultaneously with adult bee flight, and the seed crop cannot compromise later certification of alfalfa seed fields.

RESULTS

The first year of the project we planted four different plant species: purple prairie clover (Dalea purpurea), purple cone flower (Echinacea), northern sweet vetch (Hedysarum boreale) and rocky mountain bee plant (Cleome serrulata). They were seeded in early March, in a plot 90 feet by 250 feet, next to the alkali bee bed. They were hand seeded because the seeds would not fit through the tubes on the seeder.

Water is limited in the summer, so the plants were given no supplemental water, which is the practice with alfalfa seed. The sweet vetch and the purple cone flower grew, but did not bloom. The rocky mountain bee plant grew, bloomed and went to seed.

The plot was plowed up because leftover alfalfa and weeds had taken over. The second year, the same seeds were planted, except the purple prairie clover. It was a dry spring and few of the plants germinated so the plot was abandoned. Another challenge was the bloom cycle. The Gaillardia released seed and bloomed constantly regardless of the season and temperature changes; however, it was very difficult to harvest commercially.

The most promising plant was rocky mountain bee plant. It germinated and grew well the first year, flourishing with very little water and producing seed at specific times. The alkali bees were attracted to it as well as many other species. When they died, the stems were brittle and moved through a harvester easily.

In conversations with other people about the project, the project coordinator noted that there seemed to be considerable interest in the subject of encouraging native plants for seed production, and added that there seems to be a need for sources of seed for the native species. He noted that there is no problem with pollination, but considerable hand labor would be required to harvest the seed.

NOTE: This project encountered several problems, including a lack of labor to manage the native plots, so the project coordinator filed this final report with some of the early findings and declined the final payment for the funded grant.