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  • Author or Editor: Ken Altman x
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One cactus and 17 succulent species/cultivars were grown at 10, 16, 22, or 28 °C (plant temperature) for 10 or 15 weeks. The change in leaf/tubercle number at each temperature (after 10 or 15 weeks) was determined, and leaf/tubercle-unfolding rate was calculated. ‘Jade Necklace’ kebab bush (Crassula rupestris ssp. marnieriana), ‘Lola’ echeveria (Echeveria), ‘Green Ice’ gasteraloe (Gasteraloe), and lithops (Lithops species) leaf-unfolding rate per day was unaffected by temperature. Leaf-unfolding rate per day increased as temperature increased from 10 to 16 °C on ‘Firebird’ aloe (Aloe), ‘Key Lime Pie’ adromischus (Adromischus cristatus), prostate rainbow bush (Portulacaria afra variegata), burro’s tail (Sedum burrito), and ‘Sir William Lawrence’ houseleek (Sempervivum calcareum). Leaf-unfolding rate per day increased as temperature increased from 10 to 22 °C on mescal agave (Agave parryi truncata), ‘Firebird’ aloe, Sunrise anacampseros (Anacampseros telephiastrum variegata), ponytail palm (Beaucarnea recurvata), subsessilis echeveria (Echeveria subsessilis), zebra plant (Haworthia fasciata), prostrate rainbow bush, burro’s tail and ‘Sir William Lawrence’ houseleek. Increasing temperature from 22 to 28 °C decreased ‘Kiwi’ tree houseleek (Aeonium percarneum) leaf-unfolding rate per day, increased ‘Firebird’ aloe and tiger tooth aloe (Aloe juvenna) leaf-unfolding rate, and resulted in shoot tip death on burro’s tail, and plant death of ‘Sir William Lawrence’ houseleek and ‘Silver Dollar’ jade (Crassula arborescens). The cactus, ‘Arizona Snowcap’ mammillaria (Mammillaria gracilis fragilis), tubercle-unfolding rate per day increased as temperature increased from 16 to 28 °C. Taken together, temperature (10 to 28 °C) effects on development rate were species specific and related to the indigenous environment of a species.

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Photoperiod, irradiance, cool temperature (5 °C), and benzyladenine (BA) application effects on Echinopsis ‘Rose Quartz’ flowering were examined. Plants were placed in a 5 °C greenhouse under natural daylight (DL) for 0, 4, 8, or 12 weeks, then moved to a 22/18 °C (day/night temperature) greenhouse under short days (SD, 8-hour DL) plus 0, 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–1600 hr; 8-hour photoperiod), long days (LD) delivered with DL plus night-interruption lighting (NI) (2200–0200 hr), or DL plus 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–0200 hr) for 6 weeks. Plants were then grown under DL only. Percent flowering plants increased as irradiance increased from 0–25 to +75 μmol·m−2·s−1 on uncooled plants, from 0% to 100% as 5 °C exposure increased from 0 to 8 weeks under subsequent SD and from 25% to 100% as 5 °C exposure increased from 0 to 4 weeks under subsequent LD. As 5 °C exposure duration increased from 0 to 12 weeks (SD-grown) and from 0 to 8 weeks (LD-grown), flower number increased from 0 to 11 and from 5 to 21 flowers per plant across irradiance treatments, respectively. Total production time ranged from 123 to 147 days on plants cooled from 8 to 12 weeks (SD-grown) and from 52 to 94 days on plants cooled for 0–4 weeks to 119–153 days on plants cooled for 8–12 weeks (LD-grown). Flower life varied from 1 to 3 days. BA spray application (10–40 mg·L−1) once or twice after a 12-week 5 °C exposure reduced flower number. Flower development was not photoperiodic. High flower number (17–21 flowers/plant) and short production time (including cooling time, 120–122 days) occurred when plants were grown at 5 °C for 8 weeks, then grown under LD + 45–75 μmol·m−2·s−1 for 6 weeks (16 hours; 10.9–12.8 mol·m−2·d−1) at a 22/18 °C day/night temperature. Taken together, Echinopsis ‘Rose Quartz’ exhibited a facultative cool temperature and facultative LD requirement for flowering.

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