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Plantwise Technical Factsheet

cranberry (Vaccinium macrocarpon)

Description

The cranberry plant is a long-lived, woody, perennial, trailing, evergreen vine. The vines spread by sending out horizontal shoots (stolons) called runners. The fruit are borne on short vertical shoots from the axillary buds, called uprights. Uprights typically grow from 5 to 8 cm annually. Terminal buds on uprights may be either vegetative or mixed. The fruit are found on the basal portions of the current season's growth. The leaves are 3-4 mm wide, 7-10 mm long, persistent and narrowly elliptical with a thick, waxy cuticle. The stomata are abaxial, sunken and marginally functional. The flowers are borne singly, and are small with four recurved white to pink petals. There are eight stamens and the pollen is borne as tetrads. The fruit have four locules. At maturity the fruit are dark red, waxy, 9-14 mm diameter and 12-18 mm long. Cranberry is diploid, 2n=24 (Kloet, 1983).

Bud initiation occurs in the immediate post-bloom period. Individual uprights tend to be biennial bearing. Uprights that produce fruit one year are less likely to flower and set fruit than uprights that did not produce fruit the previous year, although there is variability in this trait between cultivars.

The nomenclature for bud growth stages has recently been standardized. When the plants are fully dormant the buds are small and the bud scales are tight. This stage is called 'tight bud'. In the early spring (May) as the plants come out of dormancy, the buds swell pushing the bud scales apart. This stage is called 'bud swell'. As the bud continues to grow the bud scales are pushed farther apart. This stage is called 'cabbage head' because the bud looks like a small cabbage. Finally, the bud grows so the bud scales are open and the structures of the developing bud are visible. This stage is called 'bud break'. As the bud grows and develops it begins to elongate. When the elongation is less than 1.5 cm, this stage is called 'bud elongation'. As the bud, and now the upright, continues to grow the bracts covering the individual flowers are clearly visible and also the new leaves. This stage is called 'roughneck'. When the upright reaches its full length and the flowers emerge from their protective bracts, before the petals open and recurve, this is called 'hook stage'. Within a few days of the hook stage, the flowers are in full bloom (Workmaster et al., 1997). Individual flowers on an upright open from the base to the top of the upright. The typical flower number is five per upright, but may vary from 1 to 11.

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