Achillea

EUSTOMA GRANDIFLORUM 279
Many thanks to Ginny Kristl and Jeff Hartenfeld for reviewing this section.
Eustoma grandiflorum lisianthus, prairie gentian Gentianaceae
annual Nebraska, Colorado, Texas many colors 1
2–3'/2' (60–90 cm/60 cm)
This great cut flower has come a long way from its humble origins on the western
plains, and growers, sellers, and consumers are wild about it. Perhaps Dave
Lines of Dave Lines’ Cut Flowers says it best: “Many of us feel passionately that
its customer acceptance and popularity will continue to soar. Lisianthus is without
doubt the best cut flower that has come along in years. Customers love them
and particularly appreciate their beauty and long vase life.”
Now among the most important greenhouse cut flowers, this North American
species continues to be crossed by American, Dutch, Japanese, and Israeli
breeders and shows no sign of losing popularity in world markets. The blue
flower color of the species has been complemented by cultivars with flowers of
white, pink, yellow, red, and purple, and various combinations thereof. Though
plants are biennials in their native habitat, they may be treated as annuals in the
field; however, some growers find that overwintered plants produce the best crop
the following spring. Flower production is challenging, particularly in warm
climates, and the environment plays a major role in plant development and
flower initiation.
Propagation
Seed: Plants are raised almost exclusively from seed by specialist propagators;
terminal cuttings are only occasionally used because they tend to flower irregularly.
For the small- to medium-sized operation, mature plugs should be purchased;
however, if seed propagation is attempted, sow seed on top of medium
(do not cover) at 70–75F (21–24C). Germination usually occurs in 10–15 days.
Chilling seed at around 35F (2C) for 11–15 days dramatically increases germination
(Ecker et al. 1994), but for most commercial seed, germination is not
seen as a problem. Seed is small, with approximately 600,000 seeds/oz (22,000
seeds/g), 20,000 pelleted seeds/oz (715/g). For 1000 plants, only about 1/256
oz (110 mg) is needed (Nau 1999). Pelleted seed is available for most cultivars.
Cuttings: Not recommended unless stock plants are available. Terminal cuttings
root under mist in approximately 2 weeks at 75F (24C). Stock plants
should be maintained under LD (>12 hours) for maximum cutting production.
Some plants, once established from cuttings, are shorter and weaker and have
fewer flowers than those propagated from seed (Roh et al. 1989).
Growing-on
Two distinct growing phases occur, according to the plant’s response to temperature.
In the first phase, growth occurs slowly; seedlings require up to 3