By Dr. Lynette Morgan
Chives are one of the most popular herb plants grown in hydroponic systems. The small size and perennial nature of chive plants, means they take up little space and can provide a continual supply of fresh leaves for cutting in both indoor and outdoor systems. Chive plants thrive under hydroponic cultivation and can withstand a wide range of growing conditions, performing well in indoor grow rooms and windowsill planters as well as commercial greenhouse systems.
Demand for pre-packaged fresh, hydroponically grown chives is growing rapidly as many consumers have come to realize the dried product just does not stack up against the freshly harvested foliage for flavour, aroma and appearance.
Introduction to the Chive family
Chives and garlic chives are both members of the onion or Allium family which also includes leeks and garlic. Chives are found wild in the mountains of Europe from England and Ireland eastwards to Siberia and Japan. Garlic chives (allium tuberosum), also known as Chinese chives, are a native of China and the Eastern Himalayas and possibly also of Japan.
Chives have been grown in herb gardens for centuries, and are produced on an extensive scale mostly for production of dried product used by many manufacturers. Both the leaf and flower of the chive plant is edible, with the chive flowers also being cropped for dried and fresh use. World-wide, 24,000 hectares of chives are in production outdoors for the fresh and process markets, but there exists good potential for greenhouse and hydroponic producers to fill the market for fresh chives out of season and to also supply grocery stores, restaurants and caters with a higher quality packaged product on a year round basis. Many smaller growers also realize the value of having one or two chive plants in their hydroponic system, ready to snip and use when required.
Common Chives (Allium schoenoprasium L.)
Fresh chives have a mild onion flavour and are widely used as a garnish. These are perennial plants which are relatively easy to grow provided the correct conditions are provided. Chives are a temperate or cool season crop, which prefer good light levels combined with average temperatures, although they will grow well in partial shade. Warm temperatures (above 27°C), promote the formation of flower stalks which restricts foliage development. If both foliage and flowers are required for harvest then a compromise needs to be reached in terms of flower or foliage production. Often groups of chive plants are set aside for flower harvest only so that total removal of the tough, fibrous flower stalks can be carried out on those plants used for foliage production.
Chive crops have a high water requirement and any form of water, salinity or EC stress will result in plant die back, wilted leaves and discoloration of the foliage. Plant stress from overly warm temperatures, insects, diseases, root pathogens, nutrient deficiencies and over crowding will result in a yellowing of the older foliage, making grading after harvesting necessary.
Chive seed germinates easily and rapidly, usually within eight to ten days, but a constant moisture level must be maintained and a media with a high water holding capacity is recommended. Optimal temperatures for germination are between 16° – 22° C, with germination being most rapid at 21°C. After four to six weeks the young plants, often grown in cells, rockwool cubes or small pots in groups of seedlings, can be transplanted into the hydroponic system. Chives can also be direct seeded into hydroponics media beds, but there will be a significant time lapse between sowing and the first harvest of foliage. Few leaves will be able to be harvested in the first few months as the plants must build up reserves in the root system to support future cuttings. For a more rapid, but time consuming method of propagation chives can be divided from established clumps. A large clump will produce many smaller plants each consisting of about five bulbs each. In hydroponics, and in NFT gullies in particular, large clumps should be divided and cut back every few months to keep a check on root development and prevent nutrient ponding.
There is not a great selection of chive cultivars to choose from, however the best variety for cut foliage production is ‘Fine Leaf’ which produces a rather delicate, fancy leaf, although it can be light in weight. The finer leaves are usually preferred by consumers when used as a garnish. There is also ‘Staro’ which is suitable for fresh market sales, but has a thicker, heavier leaf. Commercial growers should consider mixed plantings of the two types so that fine garnish leaf or thicker leaves for flavouring could be selected by potential customers.
Chives will grow year round, provided they receive a sufficiently long day length. In areas with low winter light levels, supplementary lighting may be used to prevent dormancy and maintain good rates of production. Dormancy in chives is induced, even in warm temperatures, by days less than 14 hours long (the critical day length) with a critical minimum light intensity of about 50 lux. By extending the day length with artificial lighting when it begins to fall below 14 hours in every 24, you will prevent chive plants from going into dormancy. However, leaf quality will not be as good from plants which are cropped continually as those which are permitted to go through the natural rest period. Plants growing under artificial lighting, can be kept growing and producing new foliage for many months, so long as the light period is at least 14 hours in length. Eventually the plants, after many harvests, can become less productive, so replacing plants every two years with new seedlings or divisions is a good idea.
Relative growth rates of chive crops is highest at an air temperature of around 19°C. Above 27°C growth of foliage is inhibited and flower production promoted. Below 10°C, growth is slow and under short day conditions, dormancy is induced at a more rapid rate.
Nutrient solutions for chives in hydroponics are similar to those recommended for other members of the Allium family, requiring good levels of sulphur for the production of essential oils and aromatics in the foliage. Care must also be taken with the balance of nitrogen so that lush, overly weak growth does not develop at the expense of foliage quality and shelf life. A Nitrogen deficiency will usually be characterized by reduced growth and nitrogen and calcium deficiencies, and reduced leaf quality and will speed up senescence of the older leave and harvested product. pH levels are best maintained at a level of 6 to 6.5, with an EC of 1.8 – 2.0 mS cm-1.
Forcing of chives
Dormant clumps of chives can be forced into production once the rest period has been broken by cold or hot temperature treatments. Growers have used a heat temperature treatment consisting of hot air at 33° – 36° C at an air humidity of 80% for two to three days to break dormancy and force the plants into active growth.
The first foliage cut should not occur until the plants are at least 15 cm tall, and only a limited amount should be taken at the first harvest. It is vital that sharp scissors or knives are used when harvesting chives as this limits the amount of cell damage caused during this process. Restricting the amount of cell damage will help prevent the browning and die back of cut foliage which chives is particularly prone to. The leaves should be cut 5 cms above the base of the plant, leaving sufficient foliage to help the plant to regenerate and carry out some photosynthesis. All of the leaves should not be cut at any one time – 1/3 to 2/3 of the plant can be cut, leaving some foliage for the next harvest and to provide assimilate production for the plant. In large commercial operations, this selective harvesting may not be carried out due to the extra time, care and labour involved – however when entire clumps are cut, the regeneration time is several weeks before harvesting can be carried out again.
Garlic Chives (Allium tuberosum)
Garlic, or Chinese chives, has larger, flatter leaves than common chives with a mild onion-garlic flavour. These are widely used in Chinese and Asian dishes and are becoming more popular with growers and consumers. Garlic chives can be used in a number of ways: as green leaves, as blanched leaves, as fresh flower buds and their bulbs can also be harvested in much the same way as garlic. Most consumers, however, purchase garlic chives to use in much the same way as common chives – as a garnish or mild flavouring for savoury dishes, and packaging options are much the same for both chive species.
Garlic chives are a perennial plant 30 – 45 cm tall that grows in clumps of four to ten bulbs each producing four to five thin flattish leaves. As with common chives, garlic chives are a cool season herb which flowers in the warmer months of the year and tends to go dormant through winter. The plants can however live for a number of years and spread rapidly, allowing for division of larger clumps. Commercial crops of garlic chives are normally produced outdoors in beds as a semi-permanent crop for up to four years, the same growth can be obtained in hydroponic media systems, although the root system can rapidly block even large NFT channels if not controlled.
Garlic chives produce a heavy leaf and are higher yielding than common chives. They also multiply faster and produce well under winter conditions, provided heating is maintained to correct levels (above 10°C) and supplementary lighting to prevent dormancy being induced. Garlic chives are stimulated by 17 hours of day length and temperatures varying from 13° to 18°C.
A well grown crop of garlic chives, produced in hydroponics should achieve eight to ten Kg harvested foliage per year at a planting space of 10cm by 10cm. Garlic chives also regenerate faster than common chives after harvesting and are better able to withstand multiple harvests and hard cut backs. These plants should be harvested every three to eight weeks depending on the time of year. Unlike regular chives, garlic chives does not tend to suffer from tip die back after harvesting, making grading and trimming less labour intensive. Just as with common chives, garlic chives will require the flower stalks to be removed as they form if flowers are not being harvested for sale. These stalks are fibrous and should not be included in cut bunches or packages of chives. However, producing these edible flowers can provide another addition to the herb product range as they make attractive garnishes for many dishes.
Garlic chive plants produce well in temperate climates and within heated greenhouses during the winter months, but once temperatures drop below 5° C, the plants will go dormant and die back. New growth will resume when temperatures begin to increase again. Year round cropping is possible under greenhouse or grow room conditions, provided the plants are not over harvested, are given day lengths in excess of 16 hours, and can produce sufficient reserves for storage in the root system to support new foliage growth after cutting. Garlic chives should only be lightly cut in their first year of growth so that reserves can build up in the root system for later growth and development. Over harvesting in the first year will weaken the plants to the point where they become highly susceptible to disease and may die back completely.
Pests and diseases
Thrips can be a significant problem on both species of chives in hydroponics, with the onion thrips resulting in large losses in yield and quality when present. No insecticides appear to be cleared for thrips on fresh chives so thrips screening and excellent sanitation must be used to manage these insects. Use of oil sprays and botanical/organic insecticides may give some degree of control is applied correctly using the best spraying technology such as foggers, misters or electrostatic sprayers. There is also a thrips predator which can give good control if introduced early in the infestation process.
Aphids are also a common problem on chives, and are easily controlled with low toxicity oil/soap sprays as smothering agents or many of the allowable botanical agents such as pyrethrum and neem based products.
Where chive clumps become dense and matted, fungal diseases can take hold. Selective foliage removal helps assist air flow through plantings of chives. Sprays of bicarbonate based products such as sodium or potassium bicarbonate or soluble silica can assist in the control and prevention of fungal diseases which may affect chive plants under humid conditions.
Chives and garlic chives are relatively easy and hardy herbs to grow in all types of hydroponic systems. Use of artificial lighting, warm conditions and a good nutrient formation will ensure these plants can be cropped year round without the need for the dormancy period which outdoor chive plants often go through. Whether it’s a continual supply of succulent fresh green chives picked direct from your indoor hydroponic system or a profitable commercial crop, chives are a rewarding plant to grow.