#The aforementioned photographs and following observations and measurements describe plants grown during the late summer in 12-cm containers in a glass-covered greenhouse in Maasdijk, The Netherlands and grown under environmental conditions and cultural practices which approximate those generally used in commercial container Aster production. During the production of the plants, day and night temperatures ranged from 18° C. to 19° C. Plants were pinched 24 days after planting and were twelve weeks old when the photographs and the description were taken. In the following description, color references are made to The Royal Horticultural Society Colour Chart, Fifth Edition, except where general terms of ordinary dictionary significance are used. Botanical classification: Aster novi-belgii ‘BKATRWT’. Parentage: Female, or seed, parent.—Proprietary selection of Aster novi-belgii identified as code number 1000051, not patented. Male, or pollen, parent.—Unknown selection of Aster novi-belgii, not patented. Propagation: Type.—Terminal vegetative cuttings. Time to initiate roots, summer.—About 10 to 14 days at temperatures of about 19° to 20° C. Time to initiate roots, winter.—About 14 to 16 days at temperatures of about 19° to 20° C. Time to produce a rooted young plant, summer.—About three weeks at temperatures of about 19° C. to 20° C. Time to produce a rooted young plant, winter.—About three to four weeks at temperatures of about 19° C. to 20° C. Root description.—Medium in thickness, fibrous; white in color. Rooting habit.—Moderately freely branching; medium density. Plant description: Plant shape and habit.—Herbaceous daisy-type potted Aster; broadly upright with lateral branches somewhat outwardly spreading; inverted triangle with uniformly mounded crown. Branching habit.—Strong and freely branching growth habit with about four lateral branches per plant; pinching enhances lateral branch development. Plant height.—About 16 cm. Plant width.—About 18.7 cm. Lateral branches.—Length: About 11.2 cm. Diameter: About 2.5 mm. Internode length: About 6 mm. Strength: Strong. Angle: Upright to about 55° from vertical. Texture: Slightly pubescent. Color: Close to 137C. Foliage description: Arrangement.—Alternate, simple; sessile. Length.—About 4.4 cm. Width.—About 9 mm. Shape.—Lanceolate. Apex.—Narrowly acuminate. Base.—Cordate, amplexicaul. Margin.—Finely serrate. Venation.—Pinnate. Texture, upper and lower surfaces.—Glabrous; slightly rugose. Color.—Developing leaves, upper surface: Close to N137B. Developing leaves, lower surface: Between 138A and 147B. Fully expanded leaves, upper surface: Close to N137C; venation, close to 147B. Fully expanded leaves, lower surface: Close to 137C; venation, close to 138A. Inflorescence description: Appearance.—Daisy-type inflorescence form with narrowly oblanceolate-shaped ray floret; inflorescences borne uniformly on terminals above and beyond the foliar plane; disk and ray florets arranged acropetally on a capitulum. Fragrance.—None detected. Natural flowering season.—Under natural conditions, plants flower from midsummer into the autumn in The Netherlands; plants begin to flower about 40 days after planting. Inflorescence longevity of the plant.—Inflorescences maintain good substance and color for about two weeks; inflorescences persistent. Quantity of inflorescences.—Freely flowering habit with about 75 inflorescences developing per plant. Inflorescence bud.—Height: About 9 mm. Diameter: About 7 mm. Shape: Broadly ovate. Color: Between 155C and 157D; towards the base, between 143B and 144B. Inflorescence size.—Diameter: About 3.5 cm. Depth (height): About 1.3 cm. Diameter of disc: About 1.5 cm. Receptacle height: About 1 mm. Receptacle diameter: About 3 mm. Receptacle color: Close to 144C. Ray florets.—Length: About 1.8 cm. Width: About 2.5 mm. Shape: Narrowly oblanceolate. Apex: Retuse. Base: Cuneate. Margin: Entire. Texture, upper and lower surfaces: Smooth, glabrous; longitudinally ribbed. Orientation: Initially upright, then about 75° from vertical. Number of ray florets per inflorescence: About 36 arranged in about two whorls. Color: When opening, upper and lower surfaces: Close to NN155D. Fully opened, upper and lower surfaces: Close to NN155D. Disc florets.—Quantity per inflorescence: About 40. Length: About 6 mm. Diameter: About 2 mm. Shape: Tubular, elongated; apices, acute. Texture, inner and outer surfaces: Smooth, glabrous. Color, when opening and fully opened, inner and outer surfaces: Close to 145C. Phyllaries.—Number of phyllaries per inflorescence: About 40 arranged in about four whorls. Length: About 5 mm. Width: About 1 mm. Shape: Lanceolate. Apex: Narrowly acute. Base: Cuneate. Margin: Entire. Texture, upper and lower surfaces: Smooth, glabrous. Color, upper and lower surfaces: Close to 143A; towards the margins, close to 143C. Peduncles.—Length, terminal peduncle: About 2.8 mm. Length, fourth peduncle: About 1.8 cm. Diameter: About 1 mm. Angle: Upright to about 40° from vertical. Strength: Strong, flexible. Texture: Smooth, glabrous. Color: Close to 137D. Reproductive organs.—Androecium: Present on disc florets only. Quantity of stamens per floret: Five. Filament length: About 5 mm. Filament color: Close to 145C. Anther shape: Obovate. Anther length: About 1 mm. Anther color: Close to 9A to 9B. Pollen amount: Scarce. Pollen color: Close to 9B. Gynoecium: Present on ray and disc florets. Quantity of pistils per floret: One. Pistil length: About 8 mm. Stigma shape: Bi-parted. Stigma color: Close to 145D. Style length: About 6 mm. Style color: Close to 145D. Ovary color: Close to 157A to 157B. Seeds and fruits.—Seed and fruit production have not been observed on plants of the new Aster. Disease & pest resistance: Resistance to pathogens and pests common to Asters has not been observed on plants of the new Aster. Garden performance: Plants of the new Aster have been observed to have good garden performance and to tolerate temperatures ranging from 5° C. to about 30° C.