Raspberry 'Polka'

Raspberry Polka (Rubus idaeus Polka) – an remontant (everbearing) cultivar of the common raspberry from the genus Rubus. Bred at the Institute of Horticulture and Floriculture in Brzezni (Poland) by Janek Danek in 1998 by crossing the line R89141 and seedlings Otm Bliss. License holder: Hargreaves Plants. In 2003 it became a major cultivar exported to the United Kingdom and the main commercial remontant raspberry variety in Belgium. It is almost a benchmark cultivar in Eastern Europe and one of the earliest remontant varieties suitable for commercial production, the fresh market, and amateur gardening.

It is a medium-sized shrub 1.5–1.8 m in height. Thorns are present, not overly stiff. The ability to produce new shoots depends on cultivation practices; on average one plant will produce up to 10 replacement shoots. The root system is vigorous and produces a large number of root suckers.

The fruit is striking, large, somewhat elongated in the shape of a regular thimble; drupelets are well formed, neat, and attractive. Each cluster contains 7–10 berries. Fruit weight 3–3.5 g, maximum 8 g. First (crop) — length 3 cm, second 2.5–2 cm. Fruiting occurs about two weeks earlier than 'Heritage'. Color at full ripeness – dark red. The sweet-and-sour flavor of the berry consistently receives positive reviews and there is a pronounced fruity aroma. Seeds are small and unobtrusive. Fruits are fairly firm and tolerate storage and transport well. In addition, a low percentage of loss during freezing is noted; only about 5% of berries significantly lose marketable quality. Polka raspberry is fairly productive, yielding on average 9 tonnes per hectare. It usually begins to ripen at the end of July and fruits until October, up to the first frosts. Berries exposed to the first frosts at around 0 to -2 °C will still ripen.

Winter hardiness: -28°C

Location: prefers open, well-warmed sites sheltered from cold winds. Grows well on fertile, neutral soils (pH 5.5–6). Preferably planted on moisture-retentive but well-drained (groundwater should be at least 1.5 m deep) light loam soils. On sandy and sandy-loam soils annual application of organic fertilizer and regular moderate irrigation are required.

Planting: plant raspberries in spring before bud break (with spring planting raspberries require regular watering for 2 weeks). In autumn seedlings are planted from mid-September to mid-October. Planting scheme 2 x 0.5 m. Planting holes are dug 0.4 x 0.4 x 0.5 m. Seedlings should not be planted deep; after planting prune shoots to 30 cm above ground.

Diseases: resistant to most fungal diseases.

Pests: raspberry clearwing, stem fly, shoot gall midge, raspberry-strawberry weevil, raspberry beetle, Prodoxididae and bud moths, leaf and raspberry aphids, nut weevil, stem fly, spider mite. Resistant to raspberry mite.

Care: requires regular weeding and soil mulching. Responds well to potassium and nitrogen fertilizers. In the second year after planting apply organic fertilizer – 1 bucket of compost or humus per 1 cubic meter, 25 g of double superphosphate, 20 g of potassium sulfate. In early June, if growth is weak, apply a feed of manure infusion (5:1) or poultry manure (12:1) at a rate of 1 bucket per 5 plants. In autumn it requires a deep (moisture-charging) watering. Support is necessary; a trellis is best used.

Raspberry pruning is carried out in spring when one-year shoots that survived the winter can be identified. Pruning shoots by 10–15 cm stimulates the formation of new fruiting branches. Per linear meter of row, leave 10–15 strong shoots 1.5 m high, spaced 15–20 cm apart. Thinning is done in early spring, but if done in summer when stems have reached only 20–25 cm, the remaining stems develop better. To speed ripening of a young shoot it is recommended to pinch the tip in mid-August. Winter covering is necessary – stems are bent and tied down in the last days of autumn before frosts. Do not do this on frosty days, as stems can freeze and break.

Propagation: propagated by root cuttings, rooted tip cuttings, and green and lignified root suckers. Many shoots grow from the rhizomes each year and can be used for propagation the following year. For this they are dug up while they have not reached 15–20 cm in height and transplanted to a new location. Root cuttings can be an effective propagation method: roots at least 0.5 cm thick are cut into 20 cm pieces and planted in specially prepared trenches.

Uses: raspberry fruits are used fresh, preserved and frozen; for making jam, liqueurs, jellies, marmalade, juices, wine and tinctures. Widely used in medicine. Leaves are used as a tea substitute. Suitable as a pioneer planting, for spoil heaps and slopes, and for planting under other plants.