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Brent K. Harbaugh

Rosetting response was determined for four lisianthus [Eustoma grandiflorum (Raf.) Shinn.] cultivars exposed to photoperiod and temperature treatments during stage 1(14 to 43 days after sowing) and stage 2 (43 to 79 days after sowing) seedling development. Stage 1 seedlings were exposed to short days (12 h photoperiod) or long days (18 h photoperiod) in combination with high (26C) or low temperatures (12C). After stage 1 treatments, stage 2 seedlings were divided and exposed to the same treatment combinations resulting in 16 treatments. Seedlings were then grown at 22C for 120 days to determine rosetting response. Cultivars responded differently to temperature and photoperiod. Short day-high temperature exposure during either stage 1 or stage 2 resulted in the greatest number of rosetted plants (50 to 100%) for `Yodel White', `HeidiPink', and `BlueLisa'. `GCREC-Blue' did not rosette with short day-high temperature. Low temperature during stage 1 did not prevent rosetting when stage 2 seedlings were subsequently exposed to high temperature, but low temperature during stage 2 decreased rosetting of seedlings exposed to high temperature in stage 1. Less rosetting occurred with long day-high temperature than with short day-low temperature, especially for `Blue Lisa'.

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Brent K. Harbaugh

Caladium × hortulanum Birdsey `Candidum' tubers were forced in pots until at least one-half the visible sprouts were 2 cm above the soil surface. These prefinished plants were subjected to simulated transit durations of 2, 4, or 6 days in the dark at 12.5, 15.5, 18.5, 21.0 or 24C. Plants were then grown for 4 weeks in a greenhouse and were either fertilized weekly with 100 ml of a solution containing 500 N-218P-415K (mg·liter-1) or were not fertilized. Interactive effects between transit duration and temperature were significant for all measured growth responses. Transit temperature maintained for 2 days had little effect on subsequent growth and only moderate effects after 4 days. With transit duration of 6 days, an increase in temperature resulted in increased plant height, fresh weight, number of leaves, white coloration of leaves, and percent of plants judged marketable (finished) in 4 weeks. Holding at ≈ 18.5C was most favorable for transit durations of 4 or 6 days. Use of fertilizer during finishing improved plant growth regardless of transit conditions, but did not totally negate deleterious effects from transit conditions.

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Brent K. Harbaugh

Symptoms of foliar chlorosis or bleaching, interveinal chlorosis of lower leaves, leaf edge and tip necrosis, stunted growth and delayed flowering of Eustoma increased as pH decreased below 6.5 in various peat-vermiculite based media for all cultivars tested. Symptoms were evident with or without microelement amendments in the media or fertilizer. A 5×5 factorial with pH of media and fertilizer solutions ranging from 5.1 to 7.5 indicated fertilizer pH did not negate plant response to low media pH. Leaf tissue levels of Zn were elevated at low media pH and negatively correlated to plant growth and flowering characteristics, while imbalances in tissue levels of N, P, K, Ca, Mg, Fe, Mn, Cu and B appeared to be less important. Symptomatic plants grown in media with a pH from 5.0 to 5.8 had tissue levels of Zn ranging from 200 to 1200 ppm, and plants without symptoms in media with a higher pH had leaf tissue levels from 40 to 100 ppm Zn.

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Brent K. Harbaugh

Seedling growth and flowering responses were examined for four Eustoma cultivars exposed to photoperiod × temperature treatments during two seedling ages. Seedlings were grown under short days (SD, 12-hour photoperiod) or long days (LD, 18-hour photoperiod) in soil at 12 or 28C from 14 to 43 days after sowing. Seedlings from each treatment were then subdivided into four lots and subjected to the same photoperiod × temperature treatments from 43 to 79 days after sowing, for a total of 16 treatments. To determine flowering response, seedlings were grown subsequently for 120 days at 22C under the same photoperiod that they received from day 43 to 79. For all cultivars and both seedling ages, seedlings were larger and had more leaves when grown at 28C rather than at 12C, but the tallest plants at flowering were from seedlings exposed to 12C. Seedlings from some treatments bolted but did not initiate visible flower buds, and some seedlings developed visible buds that later aborted, resulting in plants that did not flower by the termination of the experiment (199 days). Cultivar and interactive effects of photoperiod and temperature influenced the percentage of flowering plants. Vegetative growth and flowering responses were similar for `Yodel White', `Heidi Pink', and `Blue Lisa'. They flowered as LD plants when seedlings were grown at 12C from day 14 to 43 or day 43 to 79. Seedlings of these cultivars that were grown under SD at 28C from day 43 to 79 did not flower, regardless of photoperiod or temperature treatments from day 14 to 43. However, SD photoperiod or 28C did not decrease flowering for `GCREC-Blue'.

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Brent K. Harbaugh

Interveinal chlorosis of lower (oldest) leaves followed by development of interveinal necrotic spots, marginal necrosis, downward cupping of leaves, and leaf abscission were symptoms of a disorder commonly observed during production of potted pentas. The disorder was determined to be an Fe toxicity problem associated with accumulation of extremely high levels of foliar Fe (649 to 1124 ppm). Cultivars varied in their response to soil-applied Fe-DTPA chelate solutions: `Starburst', `Mauve' and `Ruby Red' were very susceptible, `Pink Profusion' was intermediate, and `White', `Lavender Delight', and `Pink Rose' were resistant. Potted plant production in a root medium with an initial pH of 6.7 ± 0.1 and a end pH of 6.4 ± 0.2 reduced the accumulation of foliar Fe to levels ranging from 59 to 196 ppm and prevented development of significant visual symptoms for all Cultivars.

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Zhanao Deng and Brent K. Harbaugh

Cultivated caladiums (Caladium ×hortulanum Birdsey) are valued for their bright colorful leaves (Evans et al., 1992). They can be broadly classified into three groups based on leaf shape: fancy, lance, and strap (Deng and Harbaugh, 2006; Wilfret, 1986). Fancy-leaved caladiums have heart-shaped leaves with three main veins, petiole attachment peltate, and they have two large basal lobes. Strap-leaved caladiums have narrow, linear leaves with one main vein and no obvious basal lobes. Lance leaves are intermediate between fancy and strap types with leaf blades that are broad sagittate to cordate–lanceolate.

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Zhanao Deng and Brent K. Harbaugh

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RongNa Liang and Brent K. Harbaugh

Trachelium caeruleum has been grown in the United States as a cut flower for about a decade. Only two cultivars, `White Umbrella' and `Purple Umbrella', were readily available for commercial use before 1997, but nine new cultivars became available in the last few years. Comparative performance trials have been lacking for these cultivars in the United States. This trial evaluated 11 cultivars of trachelium for cut flower production performance (vegetative and flowering characteristics) and postharvest longevity. The evaluation was in the spring of 1999 at Bradenton, Fla. (27.4 N, 82.5 W; AHS Heat Zone 10; USDA Cold Hardiness Zone 9b). Plant height for all cultivars except `White Umbrella' was above 30 inches (76 cm), a height required for acceptance as a high quality cut flower. `Summer Lake' had the smallest inflorescence diameter of 3.9 inches (10.0 cm) and `Lake Powell' the largest at 6.1 inches (15.4 cm). `White Umbrella' (160 days from seed to flower) was the earliest to flower and `Lake Powell' (169 days) the last to flower. Vase life was as short as 7 days for `Summer Lake' to as long as 11 days for `White Umbrella'. `Lake Powell' (white color group), `Summer Blue Wonder' (blue color group), and `Lake Superior' (purple color group) had the highest overall rankings.

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Zhanao Deng and Brent K. Harbaugh

Caladiums (Caladium ×hortulanum Birdsey, Araceae Juss.) are tropical ornamental aroids. They are often forced as potted plants and grown in the landscape to provide color (Evans et al., 1992). A great majority of caladium plants in the floriculture trade are propagated from tubers. More than 95% of the caladium tubers used in the world comes from central Florida (Bell et al., 1998; Deng et al., 2008). Many existing commercial caladium cultivars show attractive coloration patterns but have poor pot or landscape performance and/or poor tuber yield. ‘Marie Moir’ is an