Green Man Publishing

Celery

Apium graveolens

Introduction: This cool weather biennial is native to Europe and has been used as food at least since the time of the Romans (though this was probably leaf celery). There are three distinct types of celery commonly grown as crops. Here I am talking about the stalk celery that is familiar to all of us (in fact it is the only one most of us would even recognize. There is also root celery, usually known as celeriac, which is popular in Eastern Europe. Lastly there is leaf celery (sometimes knows as Chinese celery), which is the type most commonly used in Asia.

Ease of growing: Celery is notorious among home gardeners as being one of the hardest crops to grow well and it definitely isn’t for the beginner. It is very particular about its requirements and must have all the nutrients it needs for fast, uninterrupted growth. It also needs a constant supply of moisture and a long period of cool weather. Celery is said to be even harder to grow organically and to be a true test of the organic gardeners skill.

Nutritional content: Celery mostly consists of water and fiber and has barely any nutritional value (64 calories per pound). I guess that’s why it is associated with people who are trying to lose weight. It does contain some useful phytochemicals though, including apigenin, which has anti-cancer properties.

A few people are allergic to celery and can have a severe reaction to it

Crop value: Celery isn’t a very important crop from a nutritional or productive standpoint. It does provide an interesting flavoring though.

Climate: Celery needs 120 days of cool (60 – 75˚F) moist weather for optimal growth. It doesn’t like extreme

heat or hard frost, though it can tolerate mild frost.

About Celery  

Seed facts
Germ temp: 40 (60 – 70) 80˚F
Germ time: 14 – 21 days
41 days / 41˚F
16 days / 50˚F
12 days / 59˚F
7 days / 68˚F * Optimum
8 days / 77˚F
Viability: 5 years
Germination percentage: 55%+
Weeks to grow transplants: 8 – 12  

Planning facts
Hardiness: Half hardy
Growing temp: 45 (60 – 65) 75˚F
Plants per person: 6
Plants per sq ft: 1 – 1½
Days to harvest:
85 – 200 days
75 – 120 days from transplant  

Planting
Transplants:
Start 8 – 10 wks before last frost
Plant out 2 weeks after last frost
Direct sow: 2 wks before last frost
Fall crop: Start 3 – 4 months before first fall frost  

Harvest facts
Yield per plant: 1 – 2 lb
Yield per sq ft: 2 – 4 lb sq ft  

Soil

pH 6.0 ‑ 7.0

Wild celery naturally grows near water and this is reflected in its preference for a rich, deep, moist (but well-drained), fairly acid soil, with lots of organic matter. It is a hungry crop, requiring a lot of nitrogen, potassium and phosphorus. The roots are fairly shallow and can tolerate wet soil better than most crops (it was originally a marsh plant).

Soil preparation: Incorporate a source of organic matter to supply nitrogen and to increase its water holding capacity (use 2˝ of compost or aged manure). Add a source of phosphorus (colloidal phosphate), potassium (wood ashes or greensand) and micronutrients (kelp). If the soil is heavy, or compacted, you might also think about double digging. Add lime if the soil is very acidic.

Planning

Celery must be planned carefully, because it takes a long time to grow to maturity from seed and you often end up with a lot at one time. It is possible to sow it in succession, but this is even more complicated.

Where: Celery is an upright, compact plant and doesn’t take up a lot of space (which is good, as it is in the ground for quite a long time). It prefers full sun, but will tolerate light shade for part of the day (in warm climates this may even be beneficial). However too much shade will make for tall, leggy plants that fall over easily.  It needs quite a lot of attention, so should be sited where it can be watched closely and tended frequently.

When: Celery needs a long period (3 months) of cool temperatures (60 – 70˚F) for optimal quality and in warm summer areas it does best as a fall crop. It will grow in warmer temperatures, but above 75˚F growth slows down and the stalks may be more fibrous and strongly flavored.

Spring: In areas with long cool spring weather, it can be started inside 8 – 12 weeks before the last frost. It is planted out 2 weeks after the last frost.

Fall: Celery generally does better as a fall crop, planted in mid to late summer. It then gets to mature in the cool weather of fall.

Winter: In areas with mild winters, celery does well as a winter crop, planted in early fall.

Planting

Sowing: Celery seed has a reputation of being difficult to germinate, but I have never found it to be particularly problematic. I have read one piece that said fresh seed germinates best and another that said 2 or 3 year old seed is actually better because germination inhibitors have broken down. It is fairly slow to germinate (up to 3 weeks) and get going though, so you need to give it plenty of time.

Some people pre-soak the seed in hot (120˚F) water for a half hour before planting, or in compost tea overnight.

Some authorities say the seed must be scattered on the surface and left uncovered, as it needs light to germinate. Others say a light ⅛ – ¼˝ covering of soil is best. I can’t say I have noticed much difference either way,

Seed sitting on the surface must be kept moist at all times, as it can dry out easily which can be fatal. Germination may take as little as a week, or as long as three weeks. Some books say it is important that the temperature fluctuates below 60˚F at night during germination. Temperatures above 80˚F may inhibit germination.

Transplants

Starting inside: Celery is usually started indoors, because it is so slow growing initially. It doesn’t mind transplanting when young, so is commonly started in flats, leaving 1˝ between plants.

Though celery germinates best at 78˚F, the seedlings prefer a fairly cool 60˚F temperature for growth. Prick out the seedlings to 2˝ apart when they have their first true leaves, as they seem to benefit from transplanting at this stage. As always, take care to keep them moist. They should take 8 – 12 weeks to reach 5˝ in height and grow 5 – 6 leaves, which is the ideal transplant size.

Hardening off: If transplants are to go outside while it is still cold, the seedlings should be hardened off. They will then tolerate temperatures as low as 25˚F. Start by putting the plants outside for 2 hours on the first day, then 4 hours on the second day. Adding 2 hours every day for a week.

Vernalization: If the recently planted seedlings are exposed to extended cold temperatures (10 days below 45˚F) after a warm period they could be vernalized. They would then react to warmer weather by bolting. If cold weather unexpectedly returns after planting out, you should protect the plants with cloches.

Transplanting: When planting celery make sure you keep the root ball of each plant as intact as possible. Some people run and knife between the plants in the flat, a few days before planting to separate them.

Trench planting: An old method of growing celery was to plant in a trench. This was dug 12 – 18˝ deep by 12 – 18˝ wide and was half filled with compost, aged manure or other organic matter (if necessary add lime to raise the pH). This was left for a couple of weeks to settle before the transplants were planted in to it. The trench is filled in later for blanching.

Direct sowing: Celery can be direct sown if you have a suitably long and mild growing season.

Direct sowing celery is so slow it is only practical (barely) in areas with very long, cool growing seasons, such as in coastal California. There it can be planted in spring to mature in late summer or fall. Of course you still run into the usual problem with direct sowing; the small plants take up a lot of bed space that might be used more profitably for other crops (See Outdoor nursery bed below).

Spring celery needs to be sown as early as possible, though the soil must be at least 50˚F (much lower and it will take a month to germinate). If necessary use cloches to warm the soil and protect the young seedlings during early growth. Usually the seed is sown quite thickly and the growing plants are harvest thinned several times until they reach they required spacing (the thinnings can be used in the kitchen).

Outdoor nursery bed: In summer you can start transplants in an outdoor nursery bed. This is a much more efficient use of space than direct sowing, as the plants don’t take up bed space for the first 8 – 12 weeks of their lives.

Sow the seed about 1˝ apart and when they have all emerged and are growing vigorously, thin them to stand 3˝ apart.

Spacing: Celery is spaced fairly closely as this helps to keep down weeds and reduces the need for blanching (the soil has to be very fertile and must be kept moist for this to work).

The plants are normally arranged in offset rows across the bed. The spacing varies from 9 – 12˝, depending upon the fertility of the soil. Plants have been spaced as close as 6 – get a greater quantity of smaller plants.

Care

Weed: Celery needs to be kept free of weeds at all times, but especially when the plants are small (which is quite a while in this case).

Water: Consistent watering is the single most important factor in growing good celery; the soil should never be allowed to dry out. This may mean watering daily in dry weather, though every other day is more usual.

Water is particularly critical as harvest time approaches, because this is the time of fastest growth (plants may double in size in their last month). Lack of water at this time can result in bitter, pungent, stringy plants with hollow stems and may also encourage bolting.

The best way to water celery is with a drip system or soaker hose as this keeps the leaves dry and reduces the chance of fungus disease developing.

Fertilization: Celery needs lots of nitrogen to produce succulent growth, so if your soil isn’t very fertile you should feed your plants every 2 – 3 weeks with compost tea or liquid kelp. You can also put a side dressing of fertilizer mix on the soil between the plants. If plants don’t get enough nutrients they may be stringy and tough. 

Mulch: This is useful to conserve moisture, keep down weeds and keep the soil cooler.

Blanching: Celery was traditionally blanched (covered to deprive the stems of light) to improve its flavor and make it less fibrous. Most modern varieties don’t need blanching, but a few are improved by it (it makes them milder and nuttier). When celery is planted in close blocks, it tends to self-blanch to some extent.

Blanching should only be done a couple of weeks before harvest, as too long a blanching can cause it to deteriorate or rot.

The traditional way to blanch celery is to remove the outer leaves to expose the tall stems and then surround it with a 12˝ wide sheet of brown paper (newspaper isn’t used as it may adversely affect the flavor). The paper is held in place by piling soil around the plant. This was one reason they were planted in trenches, as the soil could easily be pulled down to hold the paper.

A simpler way to blanch is to wrap the stem with a paper grocery bag and tie it in place (and forget about the soil).

Another method is to tie the stalks together and gradually earth them up over 3 – 4 weeks by piling soil against them (up to the base of the leaves). The disadvantage of this is that soil tends to get down between the stalks, making them gritty and hard to clean.

In cold climates celery is sometimes blanched and protected from frost at the same time, by placing a board on each side of a row and filling it with dried leaves or straw.

Problems: The month before harvest is the most critical time when growing celery. The plants are growing very rapidly at this time and need a steady supply of water and nutrients.

Pests: Celery is a relative of the carrot and is afflicted by many of the same pests. Carrot fly, celery fly, celery worms, aphids, leaf miners, slugs and snails can all be a problem at times.

Disease: Celery leaf spot, pink rot and black heart.

Harvesting

When: The first harvest you get from celery is the leaves. These can be harvested at any time for use as flavoring for salads, soups, etc.

You can harvest individual stalks of celery as soon as they are big enough to be worthwhile. This might affect the final size of the plant, but is worthwhile because it extends the harvest period.

You can start harvesting whole plants when their base is 2˝ in diameter (though 3˝ is better).

Spring celery should be harvested before hot weather arrives as this will cause its quality to deteriorate.

How: Harvest whole plants when the stems are 8 – 10˝ tall, by cutting them down at ground level.

Storage: Celery will keep for a couple of weeks in a plastic bag in the fridge. If you want to store it for longer than this, pull it up with the root attached and re-plant it in moist sand in a root cellar. It likes to be kept at 32 – 40˚F and 90% humidity.

Seed Saving: Celery is a biennial and doesn’t produce flowers until its second spring (it sometimes produces flowers prematurely in its first year, but you don’t want to save seed from those plants).

The biggest problem with saving celery seed is just getting the plants to survive the winter. In mild areas they will usually do this in the ground, perhaps under a mulch to protect them from frost. In colder areas they may have to be dug up and stored in a root cellar until spring (See Storage).

Celery flowers are cross-pollinated by insects, which makes it hard to save more than one variety at a time (unless you isolate by 1000 feet or more). One plant will produce quite a lot of seed, though you should still ideally save seed from at least 6 plants to ensure genetic variability. When most of the seed is ripe on the plant, cut the entire head and dry it in a paper bag. Be aware that some fungus diseases can be seed borne.

Celery seed is also commonly used as a flavoring for cooking.

An excess of seed could be sprouted to make delicious celery flavored sprouts or micro-greens.

Unusual growing ideas

Multi-planting: It is possible to plant celery in multi-plant blocks. Plant 6 seeds per cell and thin to the best 3 plants, when they have all emerged.

Containers: Celery can be grown in a container, though it has to be a fairly big one. The resulting plant is probably best used as a source of leaves for flavoring. Growing good stems is a lot more difficult.

Varieties:

Celery isn’t a very popular garden crop, so the number of varieties available is fairly limited. There are some interesting old varieties with pink, yellow or red coloration.

Heirlooms: These have the best flavor, but generally need blanching to really bring this out.

Golden Self-Blanching – Juicy, tasty and tender (and it doesn’t need blanching!)

Giant Pascal – Hardy, not fibrous.

Giant Red: Has red stalks and strong flavor.

Modern varieties: Most of these are self-blanching (and more disease resistant), which makes them easier to grow, but their flavor isn’t as good.

Utah 52 – 70R Improved – A standard commercial variety.

Tango – Somewhat heat and drought tolerant.

Conquistador – Adaptable and somewhat heat and drought tolerant.

Kitchen use

Celery is most often used raw in salads, but it is also an important flavoring for soups and sauces.

In France celery is used for mirepoix, (a mix of chopped celery, carrot and onions) which is used as a base for soups, sauces and other dishes.

Celery and potato soup

3 tbsp olive oil
3 cups celery
1½ cups green onions
½ potatoes
½ tsp salt
½ cup soy milk
1 tsp salt
⅛ tsp black pepper
½ tsp thyme  

Chop the celery stalks and tops finely (peel the stalks if they are stringy), then saute them with the green onions for 2 minutes. Add the potatoes, thyme, salt, pepper and 3 cups of water. Cook for 15 minutes in a covered pot until the vegetables are tender. Allow the soup to cool slightly, add the soy milk and puree it until smooth in a blender. Reheat and serve.  

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