UMass Extension Greenhouse Crops and Floriculture Program

Garden Asters

In Denmark and Holland asters are grown as a potted plant and as cut flowers. With their small daisy-like flowers in shades of purple, blue, white and pink, asters have become a popular crop in the European market.

In the early '90s, Yoder Brothers Inc. introduced a line of vegetatively propagated aster cultivars. Some cultivars are for indoor potted culture, some for outdoor garden pots, while others are for use as cut flowers. Asters are easy to incorporate into New England production. They can be grown as a companion crop to the garden mum and offered to the market in September and October.

The culture of asters is very similar to chrysanthemums. They require long days for vegetative growth and short days for flower bud initiation. For indoor greenhouse production between September and April or May a mum lighting system must be utilized to produce strong vegetative growth. For outdoor garden pot production the crop is grown under natural daylength conditions just as is done with garden mums.

Aster Cultivars

Table 1 lists the aster cultivars currently being offered by Yoder Brothers Inc. Many have been developed by Sahin, a well known seed and propagation company in Holland. Other companies are also actively involved in developing this crop including Ball and Yoder themselves. All of the cultivars originated or are currently being used in perennial production. Therefore they should overwinter outdoors in New England. The color selection is limited to blue, white, pink, and red. Blue is the most popular color as it is not found in many other commercial flowering plants. Blue is the color of the largest number cultivars. Most cultivars are early to mid-season translating to early to late September in New England.

Table 1. Aster cultivars and some of their characteristics
Cultivar Color Season Source
Butterfly Blue Med. clear blue Early-mid Sahin
Purple Monarch Dk. blue Early-mid Sahin
Lilac Blue Admiral Lilac blue Early-mid Sahin
RasBlue Light blue Early-mid Rusbach
Elta Dk. lavender Early-mid Sahin
Schone VonDietlikon Med. blue Early-mid Ball
Ideal Med. blue Mid-late Ball
Butterfly White Snow white Early-mid Sahin
Butterfly Pink Light pink Early-mid Sahin
Butterfly Rose Med. rose pink Early-mid Sahin
Patricia Ballard Lavender pink Early-mid Ball
Skipper Rose pink Early-mid Ball
Painted Lady Med. pink Early-late Ball
Winston Churchill Dk. red Early-mid Ball
Bold-faced cultivars are outstanding cultivars suggested by Yoder Brothers Inc.

Trying several cultivars will enable you to determine the cultivar with the best growth habit for production and color for your market.

Scheduling Asters

As with garden mums, asters can be produced in pots ranging from 4 to 8" using either plastic or fiber. They can be grown using from 1 to 3 cuttings per pot depending on when they are started, pot size, and market time.

To obtain a full large plant in a 6 to 8" pot, the rooted cuttings must be planted in late May to early June. Asters are very vigorous growers and branch easily. If they are potted at this time only one cutting per pot is needed. Pinching is required every 14 to 18 days after potting to produce a full plant. After recent experimentation at least three pinches are required to produce a marketable plant, but more may be necessary. The first pinch should be as low as possible leaving 3 to 5 internodes. This will help to prevent a chimney-looking appearance to the plant. The pinching can be done with scissors or shears. Hand-held electric trimming shears are excellent for this job. Hand-pinching is difficult and too labor intensive. Table 2 shows a typical schedule for a 6 to 8" container.

Schedule for a 6 to 8" aster crop

Plant: Mid-May to mid-June, 1 rooted cutting/pot.

Pinch: Begin 7 to 14 days after potting.
Continue every 14 to 18 days as needed.

Last pinch: Mid to late July.

Flower:Early to mid-September.

If plants are potted in mid-June, then three cuttings per 6 to 8" pot is suggested. Cuttings are placed toward the center of the pot but separated from each other by 2".

A rooted aster cutting will cost between $0.23 and $0.25. So purchasing them early will accommodate using one cutting per pot. Therefore the initial cost per pot will be $0.25, versus three cuttings per pot in later production making an initial cost of $0.75 per pot.

Cultural Requirements

Potting medium.Use a well-drained soil or soilless medium with a pH of 5.5 to 6.5. Generally the same potting medium used for garden mum production can be used for asters.

Fertilizer requirements. Use 150 to 200 ppm N constant feed program with a well- balanced fertilizer such as 15-16-17. Slow-release fertilizer can be used as top-dressing, but liquid fertilization may be needed as a supplement in case the fertility level drops, Asters are sensitive to high soluble salt levels. Injury is exhibited as root damage, leaf yellowing, and leaf drop.

Watering. Maintain an even moisture content in the container; excessive drying will cause leaf browning and drop. Overhead watering or drip irrigation is adequate.

Growth retardants. B-Nine will control the height of cultivars which exhibit excessive growth. Use 1500 to 2000 ppm as needed. Experimentation is required based on cultivar.

Early flowering. Early flowering can be accomplished by mum shading beginning July 8 (if potted June 1). Plants treated in this manner will flower in mid-August.

Marketing Asters

Market the crop along with garden mums. The blue colors will attract a lot of attention. Promote it as a new crop that it will survive frosts and flower into November. Stress that asters are perennials which will flower the next year in the garden. Asters, as mentioned, can be grown in 4" pots throughout the year. Scheduling and cropping times can be determined with the help of your cutting salesperson or extension specialist. More information can be obtained by writing Yoder Brothers Inc., P.O. Box 230, Barberton, OH 44203.

Prepared by Robert Luczai