When thinking of celery, does California come to mind? Although the state is the largest grower of celery, it isn’t the only place where celery cultivation can thrive. Historically, Michigan and Florida also have been large celery production states, though neither can compare with California’s large-scale production.
Today, according to the National Agricultural Statistics Service (NASS), California produces close to 30,000 acres of celery and 90 percent of the crop in the United States. Michigan is the only other state whose celery production is enumerated, with not quite 2,000 acres planted. Florida celery production, which occurs from December to May, is no longer included in NASS statistics, although some commercial production occurs in the Everglades region. In 2007, about 3,000 acres were harvested, according to University of Florida Extension data.
“Our soils are infested with celery pests, and demand is much greater than Michigan can provide,” said Bernard Zandstra, professor, Department of Horticulture at Michigan State University. “Western states are more suited for large-scale production and have the infrastructure to produce, pack, cool, store and ship the product.”
A cool-season crop, the biennial celery is a member of the parsley family. The plant naturally produces its vegetative stalks – what we think of as celery – the first year, and the seed stalk in the second year. But celery is not the easiest vegetable to grow, requiring high nutrient levels, good drainage and dry and sunny weather with optimal growth achieved when temperatures are in the mid-60s to upper 70s degrees Fahrenheit.
“Generally, Michigan is able to put celery in the marketplace from July through October, whereas the California growers are able to supply the marketplace nearly year-round now, by growing in various locations from south to north,” said Darryl Warncke, professor emeritus, Soil Fertility and Plant Nutrition, Michigan State University.
Celery production requires extensive management to provide the amount of moisture and nutrient levels the plant requires, to control bolting and to combat pest and disease pressures. Celery is seeded in the greenhouse environment and planted out as transplants.
“No one direct-seeds in the fields,” Zandstra said. “In prior years, transplants could be grown in the field, but I doubt that anyone does that now.”
Seeds are sown in the greenhouse and must be protected from high temperatures before germination. Temperatures over 75 degrees Fahrenheit will inhibit germination due to the celery seeds’ need for thermodormancy. After emergence, growing temperatures should be maintained between 60 and 80 degrees Fahrenheit.
California growers don’t direct seed, either. It can be done, but is difficult. Celery seeds are very tiny and slow to develop. The seeds require a high moisture content for germination, which promotes weed growth. Weeds are a main concern, even when planting transplants at high densities, as seedlings and young plants aren’t able to shade them out. Even at field transplant densities of 40,000 plants per acre, weeds remain a concern.
“Celery production requires a high level of overall management starting with the growing of the transplants, which requires seven to eight weeks in a greenhouse. It will take celery 10 to 12 weeks or more, depending on the season, to grow from a transplant to a harvestable product,” Warncke said. “Early spring planted celery will take longer than main season celery growing during the summer months.”
That’s because celery grows best with six or more hours of sunlight and mild summer temperatures. Early plantings can be exposed to cold weather, and too much cold exposure causes the celery to bolt. Temperatures below 50 degrees Fahrenheit for 10 days or more can cause these young plants to bolt. The cold temperatures force the plant into a reproductive stage, so it produces seed rather than vegetative stalks.
“Lots of sunlight, continuous moisture, continuous nutrients and no frost” are the general growing conditions required by the celery crop, Zandstra said.
To combat the tendency to bolt in cold weather, growers can select early varieties bred to resist bolting. Some growers cover early plantings to keep them warm. Bolting doesn’t mean a total crop loss, however. The plant can still be harvested for market before the resulting seed stalks grow from the center, Zandstra said.
Soils and nutrients
Soil moisture, drainage and nutrient levels are critical aspects of celery cultivation.
“Since celery requires a good moisture supply, it is important that the soils have moisture-holding capacities,” Warncke said. “In Michigan, nearly all of the celery is currently grown in muck soils that have good drainage systems. Muck soils have good moisture-holding capacity and usually a good subsoil water table for the celery. Some irrigation is also needed during dry periods and when the celery is rapidly growing.”
Soils don’t have to be muck, however, as long as nutrient and water management is precise. Sandy loams and loam soils are all good for celery production, as long as they are well drained and fertile. With limited moisture, celery tends to develop calcium or boron deficiencies. Steady moisture is also needed for regular growth. Periods of high growth typically require irrigation, or the stalks can develop a stringy, dry taste.
Muck soils provide “good water-holding capacity and potential for good macro and micronutrient management,” Zandstra said. “Any friable, manageable soil can be used for celery production.”
Nutrient management of this high-requirement crop typically requires added nitrogen, with amounts depending on soil type. As a rough estimate, 190 pounds of nitrogen per acre, split between a preplant application and two top-dressed applications, will be needed depending on soil type, Warncke said. Added potassium, phosphorus and boron are typically needed as well.
“A good nutrient management program based on soil test information is essential for good yields of high-quality celery,” Warncke said.
Michigan’s production yield was 58,000 pounds per acre in 2015, while California’s was 62,000 pounds per acre, according to NASS statistics.
Diseases and pests
Black streak is one disease of concern in Michigan. The disease occurs when 90 F temperatures occur in conjunction with rapid celery growth. This period normally occurs between Memorial Day and mid-June. Growers change cultivars, the only management used against the disease. They switch from planting susceptible early-season celery cultivars to ones better able to resist the disease. The timing – having the proper resistant transplants available to plant out into the fields during this window – is critical.
Early and late blight, black rot and root knot nematode are some other celery diseases of importance, all of which require moist soil conditions and humidity. Bacterial blight, foliar leaf blight and Fusarium yellows are also significant concerns for Michigan growers.
“Michigan’s humid climate is conducive to a variety of diseases and insects compared to the drier climate of California,” Warncke said.
In Michigan, growers are also combating a relatively new fungal disease, celery anthracnose, which entered the picture about eight years ago. Plants become stunted and unmarketable in severe cases. Warm temperatures and high humidity favor disease development.
Celery leaf tier moth, cutworms and the tarnished plant bug are some significant insect pests in Michigan. Rotation crops are onion and potatoes, as these plants share few pest concerns with celery. Winter cover crops of rye or barley are common.
Celery mosaic virus (CeMV) is aphid-vectored and the primary disease of California celery crops. Wild weeds in the parsley family are disease hosts. A host-free period of three months is recommended to prevent infection in crop fields, requiring good weed control in and around fields, according to the University of California’s Pest Management Guidelines. Aster yellows phytoplasma also impacts celery production. It is hosted by a wide range of weeds and vectored by leafhoppers, making it difficult to control.
Read about additional pest pressures on page 30.
Harvest and market
Pascal, or green celery varieties, are commercially grown in the U.S., while other nations prefer to cultivate self-blanching types of celery. Cultivars that have “long petioles below the node, consistent dark-green colors and a tight heart,” according to Zandstra, are favored by commercial growers here.
Resistance to prevalent diseases, as well as varieties that grow best during the desired season of production, are other factors. Whether destined for processing or the fresh market, similar varieties are grown.
Some might remember when celery was blanched, producing white petioles. According to Zandstra, fall harvested celery was stored and stripped of its outer green petioles before shipping. Thus, white celery was sold in the winter, and consumers developed a preference for this white celery, leading to the blanching of fresh stalks.
It was also believed that blanching created more tender stalks, so green celery was, at one time, blanched, This fell out of practice during the 1970s, and commercial growers no longer blanch celery.
“Customer preference changed as the quality of green celery was improved,” Warncke said.
Depending on the season, celery crops mature in 90 to 110 days. The first harvest of celery is for celery hearts and typically begins July 1 in Michigan. These plants are harvested small, about one week prior to the main crop. When celery growth is rapid, the harvest window is about one week long, after which the plants become pithy. Harvest continues as succession plantings mature, terminating in October with the frost.
Commercial growers typically harvest mechanically. The harvest machine cuts off the stalks and cuts the roots below soil level. Stalks are collected in wagons and transported to the packing shed, where loose petioles and stalks are removed, leaving tight bunches. Celery stalks are not stems of the plant. They are petioles, which are actually parts of the leaf.
Celery seed, celery root and the green leafy parts of the plant are also valuable products, consumed as flavoring or for medicinal purposes. These are not normally commercially produced in the U.S.
Storage requires rapid cooling to 45 degrees Fahrenheit or shelf life is reduced. Hydrocooling or vacuum cooling after packing is advised. With good air circulation, storage temperatures of 32 degrees Fahrenheit and relative humidity maintained at about 97 percent, celery can be kept fresh for two to three months.
Celery is a labor-intensive vegetable crop. From seeding to storage, the crop requires intensive management to produce the precise growing conditions, which it favors, and avoid common issues due to nutrient deficiency, soil moisture levels, temperature fluctuations, or disease and pest issues. The harvest window is short.
“Celery is a very high-value crop,” Warncke said. “But the costs of production are also very high. Investment before any return is very high.”
California – with its conducive climate, ability to produce year-round and large-scale growers – has taken over commercial celery production in the U.S. Entering the commercial market may not be feasible for most growers. But celery can be grown throughout most of the nation to serve local markets and is, perhaps, under-represented due to its demanding reputation.
Resource on Michigan celery production:
“Celery: Commercial Vegetable Recommendations,” by Bernard Zandstra and others is available.