Celery and its rooty cousin celeriac are slow growing, but easy to care for once established. Celery can provide harvests all summer and fall, while celeriac is an eye-catching winter storage root vegetable. Celeriac is sometimes called “turnip-rooted celery.” Its flavor is starchier and sweeter than celery, with hints of parsley, and a nutty taste.

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Commercial celery is one of the most sprayed crops, so the market for sustainably grown celery is increasing, as people become more aware of the perils of pesticide use, and more appreciative of the flavor of really fresh produce. Less well-known members of this family include Leaf Celery (Cutting Celery). This plant is grown for the leaves only, to add celery flavor to salads and soups. Another is Root Parsley. There is also French celery, Dinant, which produces many small, flavorful stems for soups and stews, rather than raw eating. Lovage and parsley are also related, more distantly.

Varieties
Relatively little commercial attention has been paid to varieties of these two vegetables for small-scale organic growers, which does at least make the choices easier. We like ‘Ventura’ (80 days to maturity from transplant), a very widely adapted variety, for our central Virginia climate. We tried ‘Conquistador’, but it had less hardiness in both hot and cold conditions. ‘Ventura’ has some tolerance to Fusarium, a disease that causes hollow pithy stems. In England, I used to grow ‘Golden Self Blanching’ (85 days from transplant), as I couldn’t be bothered with the wrapping and earthing up of traditional celery that was then considered essential. These days I find that people are very accepting of green celery, and there’s no real need to trench, wrap or hill, which is how white celery happens.

There are also red varieties of celery, although the trade-off for the attractive color can be stringier stalks. Frank Morton at Wild Garden Seeds is working to improve red varieties. Fans of red celery describe the flavor as more spicy than green. ‘Redventure’ is a cross between ‘Giant Red’ and ‘Ventura’.
As for celeriac, we compared two commonly available varieties, ‘Diamante’ and ‘Large Smooth Prague’ (both 110 days from transplanting), and are strongly in favor of ‘Diamante’, as it seems to us to be more tolerant of warm weather, less prone to rot, and easier to clean. Several growers on the Market Farming list-serve  HYPERLINK http://lists.ibiblio.org/mailman/listinfo/market-farming http://lists.ibiblio.org/mailman/listinfo/market-farming say that ‘Diamante’ and ‘Brilliant ‘are virtually indistinguishable.

Crop requirements
These crops like rich soil with lots of organic matter, some shade from mid-day and afternoon sun, and ample water without sitting in waterlogged soil. We make sure to choose beds on the shadier side of the garden, near one of the buildings. For celery, we roll mulch hay over the bed before planting. This helps keep the soil cool and damp. Celeriac, however, can rot if too damp, so we don’t mulch it, and we try extra hard to keep it weeded and we remove some of the lower leaves to improve airflow. If you also live in a warm climate, consider planting celery behind other tall plants, or between rows of something else. Challenges with this approach include the need for plentiful irrigation, and that the celery is likely to be around longer than most other crops.

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Celeriac requires long steady growth, so the task of the grower is to prevent checks to growth. The Virginia climate is actually on the warm side for these crops, as they prefer cooler areas, but we have good success if we pay attention at a few critical times. Celeriac can tolerate frost quite well, so there is no hurry to harvest in the fall. Both crops can benefit from side-dressing with compost during the growing season, or a foliar spray of seaweed. A pH 5.8-6.7 is ideal.

Sowing
There are 70,000-75,000 seeds per ounce, 2500 seeds per gram. They’re tiny. Rodale suggests soaking the seed overnight, then freezing it for a week before sowing. Some people suggest pouring 120°F/48.5°C water on the seeds and soaking overnight. This can cut the germination time from 3 weeks to 1 week. Because celery seed is very small, the easiest way to do this is to pour the seeds and the water together on the surface of the potting soil in the flat. The seed should be then barely covered with fine soil. Simply soaking overnight helps. Some say that older seed has a better germination rate than new seed, because the germination inhibitor that induces dormancy has reduced in strength. My experience is that the freshly self-sown seeds in our hoophouse come up very freely, right next to their mother plant, so I’d suggest experimenting with, but not relying on, the old seed theory. If it works, it could have the advantage that seed-borne diseases have died before the seed does.  

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Germination is slow, typically 14 to 21 days, and these two crops take 10-12 weeks to grow to transplant size, so start in plenty of time. We sow in open flats, then spot out (prick out) into deeper flats. We sow February 10, which is about10 weeks before our last frost date. Celeriac can be sown from 56-67 days before the last frost date to 184-205 days before the first fall frost date, according to Tanya Denckla in The Gardener’s A-Z Guide to Growing Organic Food (2004). If your climate includes long chilly springs, I’d suggest starting 12 weeks before the frost date.

Sow seeds 1/8”/3mm deep, and keep the soil surface moist. The minimum germination temperature is 40°F/5°C, and the optimal range 59–70°F/15-21°C. Emergence takes at least 12 days at 59°F/15°C and 7 days at 68°F/20°C. The ideal temperature is 68°F/20°C day, and 59°F/15°C at night. The fluctuating temperatures, with nights cooler than days by 9°F/5°C, help speed germination. Another factor when choosing germination temperature to aim for, is that at 59°F/15°C, only 40% of the seeds produce seedlings, compared to 97% at 68°F/20°C. This information comes from Nancy Bubel’s Seed Starters’ Handbook and Knott’s Handbook for Vegetable Growers.

We’ve tried a couple of methods to achieve this temperature fluctuation, given that we don’t have thermostatically controlled germination chambers. One way is to pull the seed flats out of the germination chamber at night, and set them in the greenhouse. Another method is to have one chamber just for celery and celeriac, and to turn off the heating (lightbulbs in our case) at night. A max/min thermometer would be a good tool to use when trying this – the insulation of the germination chamber may prevent the temperature dropping enough!

Once the seedlings have germinated, you’ve succeeded with the most difficult part of celery growing! Bring the seedlings into full sunlight in the greenhouse (or windowsill) and grow at 70-75°F/21-25°C to the two leaf stage. At this size, the seedlings can be spotted out (pricked out) to individual cells, or a 2”/5cm spacing in 3”/7.5cm deep open flats. These crops do not develop deep roots, and so deep containers are not needed.
If you have a long growing season, you could direct sow celeriac in the summer, for a late fall harvest. Perhaps put a board over the seed row to keep the soil damp and cool until the seedlings emerge.

Transplanting
Celery and celeriac should not be hardened off by reducing temperatures, as that can cause them to bolt. More than about nine nights below 55°F/12°C will cause bolting. Plants can have their watering reduced to help them get ready for the big outdoors. Use row covers if a cold spell arrives after you have planted them out, or if you know cold weather is likely to return. Falling apple blossom is said to be a phenology sign that conditions are suitable.

Transplant when plants are 2.5-3”/6-7.5cm tall, once the weather seems settled and warm, after your last frost date. If the weather is cold, just wait. We transplant celery around May 1 and celeriac around May 7 (our last frost is expected April 30).

Celery plants need to be 6-12”/15-30cm apart. We plant two rows in a bed, and position the plants 12”/30cm apart in all directions, along the crown of the bed. Celery does fine when “crowded” like this.
Celeriac also gets 12”/30 cm here, with 4 rows to a 4’/120cm bed- that’s about 10”/25cm between rows. We have tried 8”/20cm, intending to remove some of the roots earlier at a younger size than full maturity. We found close spacing doesn’t work in our humid climate, as poor air-flow encourages rot.

Rotations
Celery and celeriac are umbelliferous vegetables, like carrots and parsnips. Ours follow the previous year’s brassicas, peas, or onions. We follow early carrots with late tomatoes, and our fall carrots follow garlic. Celery and celeriac occupy the space all season, and often are not cleared in time for a winter cover crop. Hence the space is easy to prepare in early spring, for March planted crops, often cabbage or kale.

Pests and diseases
Celery and celeriac are susceptible to the same troubles as carrots and parsnips. Additionally, celery is a “canary in the coal-mine” indicator crop for boron deficiency. The Connecticut Agricultural Experiment Station has good information on plant health problems of celery and celeriac:  http://www.ct.gov/caes/cwp/view.asp?a=2823&q=377614

The most common pests are aphids, whiteflies, cutworms, tarnished plant bug, and spider mites. Ours have sometimes been visited by the parsley worm, but not in high numbers. Carrot weevils and carrot rust flies are other possibilities.

The most common diseases include the fungal diseases Fusarium Yellows, Rhizoctonia root and crown rot, and leaf blights (Cercospora and Septoria types. Additionally there is the virus disease Celery mosaic.
Black heart/heart rot  is a calcium deficiency caused by fluctuations in soil moisture. This first shows up as brown leaf tips, and quickly spreads to the heart of the plant, where soft bacterial rots enter. Maintain adequate calcium levels and irrigate regularly to avoid this problem.

Cultivation
As mentioned, these crops need a good supply of water regularly. The only other care that healthy plants need is to remove weeds. If you have mulched the celery, just hand-pull weeds on sunny days and lay them on the mulch to die. Because the roots are shallow, any hoeing of celeriac or (unmulched) celery should be done carefully. Some people like to remove lower leaves of celeriac to improve airflow, and some people hill them slightly to improve the quality of the roots. We don’t hill ours at all, so I can’t vouch for that.

Harvest
Celery can be harvested one stalk at a time as soon as the stems look big enough, which could be  six weeks after transplanting. This can be useful for making up “stir-fry packs” of mixed vegetables. To harvest individual stalks, bend the stalk out and down, and twist it off, or cut with a sharp knife, being careful not to damage adjacent stalks. Once the plants get big, they will start to grow side shoots, which can become full-size bunches in their own right. We harvest by cutting out the central bunch with a knife, just above ground level, leaving the side shoots undisturbed for later harvesting. We find it best to aim to cut all the main bunches from each of the celery plants by mid-July. This helps the side shoots to grow big and produce tender bunches for August, September and October. I picture that the large root mass helps the small side shoots grow quickly once the main bunch is removed. We trim off the leaves, although if they are in good condition, they make a tasty addition to soups, or even hearty salads.

Celeriac could be harvested individually as they reach 2-4”/5-10cm in diameter, or up to grapefruit size, but we tend to wait and do a single harvest in the fall. Celeriac gets harvested here before the kohlrabi and turnips, which I expect to be hardy to 20F/-6.5C. A light frost can improve the flavor. To harvest celeriac, loosen the roots with a digging fork, pull the plants out of the ground and trim off the small roots with a sharp knife. Then cut off the leaves and collect the roots in buckets or tubs for washing.

Post-harvest/ storage
After harvesting celery, we stand the bunches in 5 gallon/20 liter buckets and add an inch of water before storing the buckets in a walk-in cooler. It’s important to keep celery stalks well hydrated.
We store celeriac, after washing and draining, in perforated plastic bags, tied at the neck. In a walk-in cooler, they will keep well for several months, even till the spring. The keys are temperatures of 35-40F/2-5C and high humidity.
   
Season extension
We keep our outdoor celery going as long as possible, and cover it with large wire hoops and thick row cover at the beginning of winter. Although celery is cold sensitive in the spring, it is fairly tolerant in the fall. It is hardy down to 25°F/-4.5°C,  and thick row cover gives you about 5°F/3°C degrees of protection. Piling up straw or tree leaves around the plants is another option. We also dig up 12 mature celery plants in November and move them into the hoophouse, where we replant them. They provide us with stalks and leaves right through the winter. They do not seem to suffer at all from being moved when already such big plants, and they can be planted very close together, so that 12 plants only need a 3’/90cm length of a 4’/120cm wide bed. Celeriac will not take a hard freeze.

Seed saving
Celery and celeriac are biennials, and so anyone growing seed needs to wait for the second season after sowing to get seed. This gives the opportunity to select good plants to save seed from. Once the seeds have set, tie a big paper bag over the heads until they seem ripe. The bagged seed heads can be hung from a beam or rafter until you get around to cleaning them. Celery seed is very easy to clean. A common kitchen sieve has the right size holes to keep the big chaff and let the seed and small dust pass through. Then a smaller sieve (tea strainer) is just right for screening out the dust and keeping the seed. Celery plants are very productive, so you’ll probably find yourself with enough seed for everyone you know, or to keep your kitchen stocked with the seed as condiment for the whole year.

The isolation distance for celery is 600’/183 m for home use, up to 0.5 mile/ 0.8 km depending on barriers, for commercial growing. An important question with seed saving is to determine what is the minimum number of plants to grow to ensure genetic diversity. For these two crops, the minimum population size is 60 plants. Remember celery and celeriac will cross with each other.

Pam Dawling is the garden manager at Twin Oaks Community in central Virginia. The gardens supply the 100 residents with nearly all their fresh and preserved  vegetables. Pam writes about vegetables every month. She can be reached at pam@twinoaks.org

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