Carrot (Daucus carota subsp. sativus) is the domestic version of its wild relative. This ubiquitous vegetable is closely related to parsley, fennel, and dill. The orange root can be eaten cooked or raw. The carrot is self-fertile and is pollinated by flies and beetles, who use its flowers as a food source.
I. Appearance and Characteristics
The carrot (Daucus carota subsp. sativus) is a root vegetable, typically orange in color, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, Daucus carota, native to Europe and Southwestern Asia. The plant probably originated in Persia and was originally cultivated for its leaves and seeds. The most commonly eaten part of the plant is the taproot, although the stems and leaves are also eaten. The domestic carrot has been selectively bred for its enlarged, more palatable, less woody-textured taproot.
The word is first recorded in English around 1530 and was borrowed from the Middle French carotte, itself from the Late Latin carōta, from the ancient Greek καρωτόν (karōtón), originally from the Proto-Indo-European root *ker- (‘horn’), due to its horn-like shape. In Old English, carrots (typically white at the time) were not clearly distinguished from parsnips: the two were collectively called moru or more (from Proto-Indo-European *mork- ‘edible root’, cf. German Möhre or Russian морковь (morkov)).
Various languages still use the same word for carrot as they do for root, e.g. the Dutch wortel.
Daucus carota is a biennial plant. In the first year, its rosette of leaves produces large amounts of sugars, which are stored in the taproot to provide energy for the plant to flower in the second year.
Soon after germination, carrot seedlings show a distinct demarcation between taproot and stem: the stem is thicker and lacks lateral roots. At the upper end of the stem is the seed leaf. The first true leaf appears about 10–15 days after germination. Subsequent leaves are alternate (with a single leaf attached to a node), spirally arranged, and pinnately compound, with leaf bases sheathing the stem. As the plant grows, the bases of the seed leaves, near the taproot, are pushed apart. The stem, located just above the ground, is compressed and the internodes are not distinct. When the seed stalk elongates for flowering, the tip of the stem narrows and becomes pointed, and the stem extends upward to become a highly branched inflorescence up to 60–200 cm (20–80 in) tall.
Most of the taproot consists of a pulpy outer cortex (phloem) and an inner core (xylem). High-quality carrots have a large proportion of cortex compared to core. Although a completely xylem-free carrot is not possible, some cultivars have small and deeply pigmented cores; the taproot can appear to lack a core when the colour of the cortex and core are similar in intensity. Taproots are typically long and conical, although cylindrical and nearly spherical cultivars are available. The root diameter can range from 1 cm (3⁄8 in) to as much as 10 cm (4 in) at the widest part. The root length ranges from 5 to 50 cm (2 to 20 in), although most are between 10 and 25 cm (4 and 10 in).
Flower development begins when the flat meristem changes from producing leaves to an uplifted, conical meristem capable of producing stem elongation and a cluster of flowers. The cluster is a compound umbel, and each umbel contains several smaller umbels (umbellets). The first (primary) umbel occurs at the end of the main floral stem; smaller secondary umbels grow from the main branch, and these further branch into third, fourth, and even later-flowering umbels.
A large, primary umbel can contain up to 50 umbellets, each of which may have as many as 50 flowers; subsequent umbels have fewer flowers. Individual flowers are small and white, sometimes with a light green or yellow tint. They consist of five petals, five stamens, and an entire calyx. The stamens usually split and fall off before the stigma becomes receptive to receive pollen. The stamens of the brown, male, sterile flowers degenerate and shrivel before the flower fully opens. In the other type of male sterile flower, the stamens are replaced by petals, and these petals do not fall off. A nectar-containing disc is present on the upper surface of the carpels.
Flowers change sex in their development, so the stamens release their pollen before the stigma of the same flower is receptive. The arrangement is centripetal, meaning the oldest flowers are near the edge and the youngest flowers are in the center. Flowers usually first open at the outer edge of the primary umbel, followed about a week later on the secondary umbels, and then in subsequent weeks in higher-order umbels.
The usual flowering period of individual umbels is 7 to 10 days, so a plant can be in the process of flowering for 30–50 days. The distinctive umbels and floral nectaries attract pollinating insects. After fertilization and as seeds develop, the outer umbellets of an umbel bend inward causing the umbel shape to change from slightly convex or fairly flat to concave, and when cupped it resembles a bird’s nest.
The fruit that develops is a schizocarp consisting of two mericarps; each mericarp is a true seed. The paired mericarps are easily separated when they are dry. Premature separation (shattering) before harvest is undesirable because it can result in seed loss. Mature seeds are flattened on the commissural side that faced the septum of the ovary. The flattened side has five longitudinal ribs. The bristly hairs that protrude from some ribs are usually removed by abrasion during milling and cleaning. Seeds also contain oil ducts and canals. Seeds vary somewhat in size, ranging from less than 500 to more than 1000 seeds per gram.
The carrot is a diploid species, and has nine relatively short, uniform-length chromosomes (2n=18). The genome size is estimated to be 473 mega base pairs, which is four times larger than Arabidopsis thaliana, one-fifth the size of the maize genome, and about the same size as the rice genome.
II. How to Grow and Care
Sunlight
Carrot also needs full sun exposure for the majority of the day.
Watering
Carrot thrives in environments that mimic its origin, requiring moderate moisture levels. This species is adapted to efficiently utilize water and can withstand short periods of dryness, indicating a preference for a balanced watering regimen. Watering should occur once every 1-2 weeks, allowing the soil to dry slightly between sessions. Typically grown outdoors, carrot has a growing season that is significantly influenced by water availability, with consistent moisture being crucial during its root development phase.
Soil
Carrot requires well-drained, loose soil and consistent moisture for optimal growth. It’s crucial to avoid rocky or heavy clay soils that can lead to poor root development.
Fertilizing
For carrot, appropriate fertilization is paramount. Utilize high-phosphorus and potassium fertilizers to encourage robust root development and sweetness in harvest. Apply once at planting and again in mid-season, respecting the recommended dosage on the product label. Over-fertilization can lead to foliage growth at the expense of the root. Seasonal adjustments are noteworthy; reduce applications as temperatures drop in late fall. Gardeners should wear gloves and evenly distribute fertilizer to avoid root burn. By adhering to these guidelines, one ensures the carrot’s vitality and optimal yield.
Propagation
Carrot is typically propagated through sowing. For successful germination, the soil should be well-drained and fertile, with a pH between 6.0 and 7.0. Prior to planting, soaking the seeds can enhance germination rates. Sow the seeds directly in the ground, placing them approximately 3-4 inches apart and at a depth of half an inch. Regular watering is crucial, but care should be taken not to oversaturate the soil. Thinning the seedlings is important once they reach a few inches tall to prevent overcrowding and promote robust growth.
Transplanting
The prime seasons for transplanting carrots are spring to early summer, as warmer conditions promote growth. The plant needs a sunny location with well-drained soil. When transplanting, be cautious not to damage the fragile roots.
Pests and Diseases
There are several diseases that can reduce the yield and market value of carrots. The most devastating carrot disease is Alternaria leaf blight, which has been known to eradicate entire crops. A bacterial leaf blight caused by Xanthomonas campestris can also be destructive in warm, humid areas. Root knot nematodes (Meloidogyne species) can cause stubby or forked roots, or galls. Cavity spot, caused by the oomycetes Pythium violae and Pythium sulcatum, results in irregularly shaped, depressed lesions on the taproots.
Physical damage can also reduce the value of carrot crops. The two main forms of damage are splitting, whereby a longitudinal crack develops during growth that can be a few centimetres to the entire length of the root, and breaking, which occurs postharvest. These disorders can affect over 30% of commercial crops. Factors associated with high levels of splitting include wide plant spacing, early sowing, lengthy growth durations, and genotype.
III. Uses and Benefits
Carrots can be eaten in a variety of ways. Only 3 percent of the β-carotene in raw carrots is released during digestion: this can be improved to 39% by pulping, cooking and adding cooking oil. Alternatively they may be chopped and boiled, fried or steamed, and cooked in soups and stews, as well as baby and pet foods. A well-known dish is carrots julienne. Together with onion and celery, carrots are one of the primary vegetables used in a mirepoix to make various broths.
The greens are edible as a leaf vegetable, but are rarely eaten by humans; some sources suggest that the greens contain toxic alkaloids. When used for this purpose, they are harvested young in high-density plantings, before significant root development, and typically used stir-fried, or in salads. Some people are allergic to carrots. In a 2010 study on the prevalence of food allergies in Europe, 3.6 percent of young adults showed some degree of sensitivity to carrots. Because the major carrot allergen, the protein Dauc c 1.0104, is cross-reactive with homologues in birch pollen (Bet v 1) and mugwort pollen (Art v 1), most carrot allergy sufferers are also allergic to pollen from these plants.
In India, carrots are used in a variety of ways, as salads or as vegetables added to spicy rice or dal dishes. A popular variation in north India is the Gajar Ka Halwa carrot dessert, which has carrots grated and cooked in milk until the whole mixture is solid, after which nuts and butter are added. Carrot salads are usually made with grated carrots with a seasoning of mustard seeds and green chillies popped in hot oil. Carrots can also be cut in thin strips and added to rice, can form part of a dish of mixed roast vegetables or can be blended with tamarind to make chutney.
Since the late 1980s, baby carrots or mini-carrots (carrots that have been peeled and cut into uniform cylinders) have been a popular ready-to-eat snack food available in many supermarkets. Carrots are puréed and used as baby food, dehydrated to make chips, flakes, and powder, and thinly sliced and deep-fried, like potato chips.
The sweetness of carrots allows the vegetable to be used in some fruit-like roles. Grated carrots are used in carrot cakes, as well as carrot puddings, an English dish thought to have originated in the early 19th century. Carrots can also be used alone or blended with fruits in jams and preserves. In the European Union there is a rule specifying that only fruits can be used in making jams; to preserve the Portuguese carrot jam delicacy (or Doce de Cenoura in Portuguese), the EU council adopted a Directive that changed the legal statute of carrot from “vegetable” into “fruit”.
Carrot juice is also widely marketed, especially as a health drink, either stand-alone or blended with juices extracted from fruits and other vegetables.
Highly excessive consumption over a period of time can result in carotenemia, a yellow-orange discoloration of the skin caused by a buildup of carotenoids.