The cultivated blueberry encompasses a wide variety of cultivars developed through plant breeding from plant species of the subgenus or section Cyanococcus within the genus Vaccinium. Blueberries belong to the plant family Ericaceae. Contrary to common assumption, cultivated blueberries do not descend from the European bilberry, blueberry, or whortleberry (Vaccinium myrtillus), whose fruits stain the mouth and lips blue when eaten, but originate from North America. The coloring anthocyanins are located in the skin of the nearly spherical, blue berries; their flesh is light-colored.
Since the beginning of the 20th century, over 100 new cultivars have been developed. Cultivated blueberries are of global importance as market fruits. Before their cultivation as a fruit supplier, the cultivated blueberry had already been introduced in European landscape architecture as an ornamental plant due to its decorative autumn coloration.
Botanical description
Cultivated blueberries are perennial, upright-growing, highly branched, deciduous subshrubs (chamaephytes). They can reach heights of several meters or grow as ground covers with only a few centimeters in height. Characteristic are urn-shaped flowers and blue, bloomy berries.
Growth forms and root system The habit of cultivated blueberries varies from cultivar to cultivar. While some selections grow strictly upright, others spread wider and form an expansive shape. The group of highbush forms (Northern and Southern Highbush Blueberries) form 2 to 5 meter tall, rounded, dense, and compact bushes. The upright cultivars of rabbiteye blueberries (Rabbiteye Blueberries) reach about 4 meters, half-high forms (Half-Highbush Blueberries) between 1 and 2 meters. The lowbush cultivars (Lowbush Blueberries) grow between 0.2 and 0.7 meters tall and form runners. They grow more loosely than the highbush and half-highbush forms. The main plant mass in these consists of rhizomes, from which the upright shoots grow.
The root system runs highly branched and shallowly spread out. It has a high proportion of partly matted fine roots.Hans-Dieter Warda: Das große Buch der Garten- und Landschaftsgehölze. Prull-Druck Oldenburg, 2001, ISBN 3-9803833-3-4. They are fibrous and very thin and, unlike other plants, not equipped with root hairs, which are important for the uptake of water and nutrients.
Leaves and shoots The wood of the shoots is hard and brittle, the bark gray and cracked. Depending on the cultivar, they branch more or less strongly. Young shoots are usually hairless, green to yellowish green, and partly flushed red (two-year-old shoots) with a warty surface.
The leaves are arranged alternately on the shoot. They are fresh to dark green and hairless on the upper side. On the underside, they are lighter colored and, at least on the venation, usually slightly hairy. Around mid-June, the bushes have developed their largest leaf area in the annual cycle. Before leaf fall in autumn, the leaves turn yellow to bright red due to the formation of anthocyanins. This gives cultivated blueberries a high ornamental value. The leaves of high to half-high cultivars are ovate to elongated oval, pointed with smooth leaf margins. Leaf size varies greatly on the bush. The leaves of lateral shoots usually do not exceed 5 to 6 cm, while those of vigorous basal shoots reach 10 cm and more. The foliage leaves of lowbush selections are smaller than those mentioned and usually more or less toothed at the margin.
Flowers, fruits, and seeds The yellowish white to delicate pink flowers are urn-shaped. These up to 20 mm long and somewhat inflated flower tubes consist of five fused petals. Each flower has eight to ten stamens at the base of the calyx, which in turn surround a distinctly longer stigma.S.E. McGregor: Insect Pollination Of Cultivated Crop Plants. USDA, originally published 1976, Virtual Beekeeping Book, Updated Continuously. Additions listed by crop and date. URL (Archived from the original on February 28, 2008), accessed on March 7, 2008. At the base of the calyx are the nectar-producing nectaries. The flower bud produces a raceme of up to twelve individual flowers. The lower flowers are longer stalked than the upper ones. Some cultivars develop several racemes from one flower bud. The flower buds appear mostly at the shoot tips, less at the shoot base. They are distinctly rounder and stronger than the small and pointed leaf buds. Cultivated blueberries flower predominantly on first-order lateral shoots. The inferior ovary is surrounded by five green sepals, which are visible on the ripe fruit as fleshy humps.
All cultivated blueberry cultivars share light blue, bright blue to black-blue fruit skins of the berries. The flesh is whitish. The berries bear a white bloom on the surface; this coating is caused by microscopically small wax particles formed in the fruit skin, transported outward with the respiratory water, and deposited there. Berry size varies widely depending on the cultivar, averaging between 5 and 12 mm in width, sometimes up to 30 mm.
The fruits contain 30 to 80 very small, light brown seeds. About 4000 seeds weigh 1 gram. They are already germination-capable at fruit maturity and do not require a prolonged cold period (vernalization). The radicle appears after about 14 to 35 days, the cotyledons after about 3 to 8 weeks.
Growth and development
Vegetative growth, flowering, and fruit development extend in Central Europe over a period from about early April to mid-October. Harvesting occurs from early July to mid-August. Due to the large spatial extent of North American blueberry cultivation across various climate zones, harvesting there begins as early as April in Florida and ends late September in Newfoundland.
Vegetative growth The main growth period of shoots is between mid-May and early October. The annual increment of the bushes and thus the yield performance decreases with increasing age, as flowers are mainly formed at the tips of one-year-old shoots. Flower and fruit set occur at the expense of shoot growth, so they become weaker and thinner with age; the bushes "senesce". The shoots have a cultivar-specific production period. In highbush forms, they form flowers and fruits for four years with good yield performance. Rabbiteye blueberry selections bear for seven years; in lowbush forms, the new shoots growing from the rootstock flower and fruit only in the second year. Although older shoots still produce fruits, these are usually smaller and the harvest remains low. Regular pruning is therefore one of the most important maintenance measures in blueberry cultivation. This promotes vegetative growth and stimulates new shoot formation from the bush base. Fruit size and quality are increased, and fruit ripening is accelerated. Removed are bearing wood, excess shoots, and inward-growing branches.
Root growth is strongest at soil temperatures between 14 and 18 °C, apparently significantly restricted below 8 °C. In cultivated blueberries, two phases of intense root growth occur. Under Central European climatic conditions, these are around mid-May to early June and from mid-August to mid-September. Since the root system is not particularly effective for water uptake, the bush stops growth when soil drying begins.
Flowering and fruit development The flowers are initiated in Central Europe in the previous year after fruit ripening in a period between July and September (flower induction). In autumn, the flower buds grow and differentiate, so they are almost fully developed in winter. The main flowering of cultivated blueberries under Central European conditions is usually in the first two weeks of May and thus later than in North American growing areas. The flowering period extends over about four weeks, depending on weather. The flowers at the shoot tips open first, and within a flower cluster, always the upper ones first and then those closer to the ground.
Most blueberries are self-fertile. Through targeted cross-pollination, a larger fruit set with larger fruits and shorter ripening times can be achieved in cultivated forms. Southern highbush blueberries are only partially self-fertile and thus additionally dependent on cross-pollination. The rabbiteye blueberry group and lowbush cultivars are predominantly self-incompatible. Pollination in them occurs exclusively via insects. Bumblebees (Bombus) and wild bees play a decisive role. Pollination by honey bees (Apis mellifera) seems little effective, as they tend to open the flowers from the side and do not pick up pollen. Promoting certain native plants on the cultivation areas plays an important role in the settlement and establishment of flower-visiting insects.A. Fiedler, J. Tuell, R. Isaacs & D. Landis: Attracting Beneficial Insects with Native Flowering Plants. Department of Entomology, Michigan State University, 2008 PDF, accessed October 29, 2025.
Fruit growth and ripening extend, depending on cultivar and weather, over eight to 16 weeks. The fruits go through three development phases. After fertilization, the young fruits rapidly increase in size through cell divisions in the fruit tissue for about four weeks. This phase is replaced by an apparent rest phase in which the fruits do not grow further, but the seeds or embryos inside store reserve substances. Then the fruit increases noticeably in size again, although the number of cells no longer increases, but they strongly take up water and elongate. At the end of this phase, the fruit skin color changes from green through pale green and purple to the cultivar-typical blue, the fruit ripens and becomes soft. At the same time, the contents change: sugars are built up (or stored) and acids broken down. The characteristic aroma compounds and the typical bloom on the surface form only at the end of fruit ripening. The latter fulfills several functions for the fruit: It protects the berry from excessive heating by reflecting sunlight; it prevents the penetration of microbial pathogens, and finally rainwater beads off completely, so the berries dry quickly and harmful fungi have no good development conditions. The fruits of a bush do not all ripen simultaneously, even within a fruit cluster. The ripening stages are divided according to an American scheme into six phases, derived from the external color impression:
{| class="wikitable" ! style="background-color:#CCCCFF" | Ripening stage (English) ! style="background-color:#CCCCFF" | German ! style="background-color:#CCCCFF" | Fruit condition |- bgcolor="#EEEEEE" | IG = Immature Green || Unreif Grün || Completely green and hard |- bgcolor="#EEEEEE" | MG = Mature Green || Reif Grün || Light green to whitish, softer |- bgcolor="#EEEEEE" | GP = Green Pink || Grün Rosa || Pink coloration of the calyx region |- bgcolor="#EEEEEE" | BP = Blue Pink || Blau Rosa || Beginning blue coloration, stem region pink |- bgcolor="#EEEEEE" | B = Blue || Blau || Blue, except for pink ring in the stem region |- bgcolor="#EEEEEE" | R = Ripe || Reif || Completely blue and bloomy, soft
The seeds, already germination-capable at fruit ripening, germinate at 50 to 80%. About six to ten weeks pass until the unfolding of the first foliage leaf. Already after the appearance of the tenth to fifteenth leaf, the first lateral shoots form, which quickly overgrow the main shoot and ensure early branching.
Dormancy phase