Heat Stress Threatens California's Romaine Crop

Successive heat waves in California could squeeze romaine supplies and push prices higher through mid to late July. Salinas in Monterey County and Watsonville in Santa Cruz County, which produce nearly all US romaine during California's April to November lettuce growing season, are currently contending with their third heat wave since late May, and a fourth heatwave is forecast for the coming weeks. 

Despite this increased potential for heat stress, romaine prices are currently tracking a normal price pattern. Prices for a case of whole head romaine, a product primarily used in the foodservice industry, have risen 10% to $15/case during the last two weeks. Meanwhile, packages of romaine hearts, which are usually more expensive because outer leaves are trimmed off at harvest, have increased about 15% to $22.75/case. 

Ideal growing conditions for romaine include temperatures in the 65-75°F range and gradual temperature increases, but so far this summer California’s key romaine-growing centers have experienced much higher temperatures, as well as volatile temperature swings.  

In Monterey County, daily maximum temperatures have either come in above - or are forecasted to come in above - 100°F for about a third of the days during the May 24th and July 8 period. During the same period, Salinas and Watsonville will have experienced two sudden temperature jumps, including a two-day period when temperatures shot up 20°F. 

In 2019, the most volatile California summer growing season in the last 10 years, a 27°F temperature spike in early June led to a 10 million pound drop in romaine volumes through early July and a tripling of prices that took romaine prices to more than $30/case. At that time, prices stayed elevated for about 7 weeks because farmers discarded their damaged crops. 

Similar, but less extreme, temperature spikes also occurred during the 2015, 2020, and 2021 growing seasons, with the 2020 season bearing the closest resemblance to this year. 

In mid-June 2020, two separate events saw temperatures shoot up 20°F over a one-to-two day span twice within a week of each other. This was followed by a third, smaller heat event that occurred in late June, by which time the first set of heat events had pushed up romaine prices. Elevated prices held through the end of July, and above trend romaine prices persisted for the remainder of the California growing season. 

When temperatures pop above their normal range and during extended periods of high temperatures, romaine crops often face heat-induced quality issues, including tip burn, where a plant's outer leaves begin to dry and burn out, and bolting, when a plant begins to prepare for flowering and seed development. Both of these quality issues can cause yield and harvesting reductions that impact available volume and ultimately price.

To see how temperature and other market conditions are impacting romaine lettuce volumes and pricing this growing season, Gro clients can use the 2022 Salinas romaine monitor, or they can access the data through Gro’s Excel add-in, which helps clients monitor the prices of romaine - and other products - so that they can directly compare their purchases against the market price in real time.

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