In California, most farmers grow medium-grain varieties. The commercially available medium Calrose rice varieties have been selected to meet the high quality and yield standards for California.
Varietal selection is one of the first and most important decisions a rice grower will need to make each year. In doing so, consider the maturity class that fits into your farming operations and climatic zone.
There are three maturity classes: Very early (M-104, M-105), early (M-202, M-205, M-206, M-208, M-209) and late maturing (M-401, M-402 — both premium medium grains). Broadly adapted varieties include M-105 and M-206 and can be grown across all regions due to their cold tolerance. In cooler areas south of Highway 20 and the Sacramento Delta region (perhaps the coolest area where rice is grown), these are good varieties to consider.
M-205 and M-209 are not suitable for the cooler regions and should be grown north of Highway 20. In 2017, which was an unusual year due to late planting and warm growing season temperatures, M-209 performed well relative to other varieties.
In the University of California Cooperative Extension Rice Yield Contest, the 2017 winners were all M-209. On average, M-105 heads a couple of days earlier than M-206, and M-209 and M-205 head five to six days later than M-206. Importantly, many of these newer varieties can be safely harvested at lower grain moisture content than the last generation of varieties, such as M-202, which ensures higher grain quality, may reduce drying costs and allow for greater flexibility in harvest operations.
Due to weedy rice concerns, the California Cooperative Rice Research Foundation Board of Directors in 2016 passed a policy that only classes of certified seed (foundation, registered and certified) of CCRRF rice varieties may be planted. Beginning 2019, growers will be required to plant only certified seed classes or seed from an approved seed production system of any rice variety in California.
While this policy will take effect in 2019, we strongly urge growers to plant certified seed in 2018 to limit spread of weedy rice.