Celery and Celeriac

Introduction

Celery (Apium graveolens var. dulce) is a long-season crop that grows best under cool, consistent conditions (60-75°F). Deep, loamy, fertile soils with ample and uniform soil moisture is ideal for celery.  Muck soils are also used for celery production.  Even though most of the celery root system is within the top 6" of soil, many roots penetrate as deep as 2 feet; thus, heavy clay soils are unsuitable for celery culture.  Hardpans should be avoided or disrupted before planting to allow for adequate drainage.

Celeriac (Apium graveolens var. rapaceum), also called celery root, is a smaller plant that looks like celery, but that is grown for its swollen tuberous base, which has a celery-like flavor. The petioles, or stalks, are less vigorous than those of celery and are not palatable. Celeriac can be used much like any root vegetable: roasted, in stews and soups, or eaten fresh in salads when grated or thinly sliced. The plant is ready for harvest about 100-110 days from seed or 80-90 days from transplanting. Celeriac may be blanched by covering with soil a few weeks prior to harvest, although plants with crowns sitting higher on the ground will have fewer roots to trim. Cultural requirements are similar to celery. 

Types and Varieties  

Celery and Celeriac Varieties
Celery Celeriac
Balada (F) Tall Utah 52/70R Improved (F) Balena (F)
Command (F) Tango Brilliant (F)
Hudson (F) TZ 6200 (F) Cisko RZ
Kelvin Victoria Diamant (F)
Merengo (F)   Mars
    Rowena
Resistant or tolerant to: F - Fusarium Yellows

Soil Fertility

Celery and celeriac are heavy feeders and require adequate fertility to produce a quality crop. Apply lime according to soil test to maintain soil pH at 6.0-6.8. Use a liquid starter fertilizer at transplanting, especially with cool soil conditions. Use a high phosphorus starter fertilizer mixed at a rate of 3 lb/50 gals of water. Apply 8 fl oz (1 cup) per transplant. Sidedress 40 lb N/ac 3-4 weeks after transplanting. On light soils, a second sidedressing may be necessary. The second sidedressing application of nitrogen can be reduced or eliminated if legume biomass was incorporated ahead of planting, or if manure was applied  (see Table 1 and Table 7). 

Celery is very susceptible to magnesium and calcium deficiencies.  Interveinal yellowing of older leaves is a good indication of magnesium deficiency. Magnesium requirements can be partially met by using dolomitic (high magnesium) limestone. Any further need of magnesium can be met by spraying or fertigating the plants with Epsom salts (magnesium sulfate) at 8 lb/ac per week until green color is restored. Calcium deficiency can result in a physiological disorder known as blackheart (equivalent to tipburn in other crops), where the growing tips of the heart die and turn black. However, this is typically a result of inconsistent water supply rather than inadequate soil calcium. Provide a steady water supply to maintain even plant growth and calcium uptake, and provide foliar applications of calcium nitrate or calcium chloride during prolonged dry periods. High soil potassium can result in decreased magnesium and calcium uptake; maintain high levels of these nutrients relative to potassium to facilitate their uptake.

Boron, manganese, and copper are also critical in the growth and development of celery. Plants grown on organic soils with low levels of boron and high levels of potassium often have brown, cross-checked cracks and russeting on the inside of the petiole (“brown checking”). Add boron to fertilizer at planting and provide foliar applications during dry periods. Tissue analysis is the best method of determining the sufficiency of these elements.

PLANT NUTRIENT RECOMMENDATION ACCORDING TO SOIL TEST RESULTS FOR CELERY and Celeriac
CELERY and celeriac NITROGEN (N)* LBS PER ACRE PHOSPHORUS (P) LBS P2O5 PER ACRE    POTASSIUM (K) LBS K2O PER ACRE
SOIL TEST RESULTS   VERY LOW LOW OPTIMUM ABOVE OPTIMUM VERY LOW LOW OPTIMUM ABOVE OPTIMUM
Broadcast and Incorporate 100 180 120 30-60 0 240 180 45-90 0
Sidedress 3-4 weeks after setting 40 0 0 0 0 0 0 0 0
Sidedress 7-8 weeks after setting 40 0 0 0 0 0 0 0 0
TOTAL RECOMMENDED 180 180 120 30-60 0 240 180 45-90 0

Planting

Celery should be seeded 10-12 weeks before transplanting into the field. This is often done in open flats in order to maximize heating mat space. Seedlings are transplanted into cell trays once they have 2-3 true leaves. Keep greenhouse temperatures above 55ºF to prevent bolting and ensure continuous development. Ideal temperatures for germinating celery are 70-75ºF, and temperatures can be lowered to 65-70ºF thereafter. Heating mats can be used to augment soil temperature if necessary. Seeds may become dormant if temperatures exceed 80ºF. Do not lower temperature to harden off plants. Pelletized seed is generally used because of the small size of raw seed. Mature seed and ample moisture are critical for germination. Use two- or three-year old seed that has all matured and maintain planting media near field capacity. Priming seed improves germination. One ounce of seed produces about 15,000 plants.  Use 2-4 oz to produce enough plants for one acre (20,000-58,000 plants). 

Transplant to the field in June when the risk of frost is past. Although this crop will withstand light frosts, bolting (premature flowering) will occur if plants are exposed to temperatures below 55ºF for more than 7 days, depending on variety.  Plants that have begun to bolt will often have petiole splits at harvest, necessitating more trimming. Space rows 18-36" apart and 6-12" between plants in rows (100-200 plants per 100 feet of row).  Double rows on plastic-lined beds are common.  Flat culture is used on muck soils.  

Celeriac seedling production and transplanting is similar to that of celery. Celeriac, however, tends to be more sensitive to the warm temperatures under plastic mulch so bare ground or white plastic mulch may improve the crop compared to black plastic mulch.

Field Culture

Celery and celeriac are long-season crops that grow best under cool conditions (60-75°F) with an ample and uniform supply of water. It may be necessary to irrigate when transplanting and once or twice each week thereafter. Drip irrigation is recommended to mitigate the spread of pathogens. Avoid working fields when plants are wet.

Harvest and Storage

To harvest, cut the whole celery plant at the soil level. Older, stringy, or cracked outer petioles may need to be removed to provide a fresh tender crop. Celery is commonly topped at 14" for retail and wholesale markets but healthy tops may be appealing to some direct market customers. If marketing without plastic sleeves, rubber-banding petioles at three-quarters height can improve appearance. Freshly harvested celery may have a bitter flavor, which can be improved by storing at 32-34°F for a few days. Chilling injury can result if the storage temperature falls below 32°F. If storing for longer than 1-2 weeks, keep plants upright so they maintain straight petioles. Celery typically holds in the field only 1-2 weeks depending on variety and environmental conditions. Plants left in the field beyond their peak will continue to mature and deteriorate in quality, becoming pithy, cracked, and developing an off-flavor. In storage, celery imparts its flavor to other crops.

Celeriac holds fairly well in the field, although timely harvest may prevent development of internal hollowing and rot in wet conditions. Frost will improve flavor of celeriac. It is harvested and trimmed of roots and stalks when tubers reach 3-4" in diameter. Celeriac may be stored for 3-6 months if kept at 32-34°F and 95% relative humidity, but internal quality over long storage periods is affected by both variety and exposure to disease before harvest.