Scaevola aemula R.Br. (fanflower), an ornamental plant native to Australia, produces stunted growth when fertilized with high concentrations of P. To determine optimum P concentration, rooted cuttings were transplanted into 15 cm standard pots and grown with a water soluble fertilizer, where P concentrations were 0, 14.5, 29.0, 43.5, 58.0, 72.5, 87.0 mg·L-1 and all plants received 200 mg·L-1 N and 166 mg·L-1 K. Shoot growth and flowering data were taken every 21 days until the experiment was terminated after 84 days. Shoot length, number and dry weight, and leaf size were reduced significantly at P concentrations higher than 14.5 mg·L-1 with severe reduction at P levels higher than 43.5 mg·L-1. Number of flowers per plant was not affected by P concentrations in the range of 0 to 43.5 mg·L-1, but decreased significantly at P levels higher than 43.5 mg·L-1. Medium pH decreased with increase in P rate due to the acidic nature of the P fertilizer. When P was applied in every irrigation, the optimum concentration was 14.5 mg·L-1 or less. P greater than 43.5 mg·L-1 was detrimental to vegetative growth and flowering, possibly due to above optimum P or to medium acidification.
Donglin Zhang, Renae E. Moran and Lois B. Stack
Stephanie E. Burnett, Donglin Zhang, Lois B. Stack and Zhongqi He
In commercial greenhouses, fan flower ‘Whirlwind Blue’ (Scaevola aemula R. Br.) plants are sensitive to phosphorus applications in the range typically applied to other floricultural crops. To quantify this response, fan flower plants were grown in Hoagland solutions containing 0, 20, 40, 60, or 80 mg·L−1 P. Plants fertilized with either the highest (80 mg·L−1) or lowest (0 mg·L−1) P concentrations had significantly shorter stems and smaller shoot dry weights and leaf areas than plants fertilized with 20 to 60 mg·L−1 P. Low or high P concentrations negatively impacted flower number; fan flower fertilized with 0, 60, or 80 mg·L−1 P had fewer flowering branches and flowers compared with plants fertilized with 20 to 40 mg·L−1 P. Plants receiving no P had longer roots than those receiving any P and had greater root dry weights than plants receiving all other P concentrations except 20 mg·L−1. Foliar nutrient analysis indicated that although P treatments significantly impacted foliar concentrations of at least some essential macro- and micronutrients, all essential elements were within or near recommended ranges except P. Foliar P concentrations exceeded 1 mg·g−1 in fan flower that received even the lowest concentration of supplemental P, but leaf chlorosis was only observed in plants grown in 60 to 80 mg·L−1 P. As a result of rapid accumulation of P in fan flower foliage and subsequent reductions in flower number and shoot elongation, fan flower should be fertilized with no more than 20 mg·L−1 P.
Gwendolyn Hawkins, Stephanie E. Burnett and Lois B. Stack
In 2008, we administered a survey to participants at four venues in Maine to determine: 1) the degree of interest in organically, sustainably, and locally grown plants; 2) whether respondents would pay more for these plants compared with conventional plants; and 3) which demographic groups expressed the greatest interest in organically, sustainably, or locally grown plants. Respondents were highly interested in organic and sustainable vegetable/herb and ornamental plants; median interest was 9 on a scale of 1 to 10 where 1 indicated low interest and 10 indicated high interest. They were less interested in locally grown plants; respondents’ median interest in local plants was 6 on the same scale. Survey respondents stated that they would pay 15% more (vegetable/herbs) or 10% more (ornamentals) for organic, sustainable, or local plants than they would for conventionally grown plants. Several demographic factors indicated that respondents were either willing to spend more money on nonconventional plants, or were at least more interested in these kinds of plants. Income and education were positively correlated with the amount of money respondents stated they would spend on nonconventional plants. Younger participants were more interested than older participants in sustainable and organic plants, but they were not willing to pay more for these plants than older participants. Similarly, women were more interested than men in nonconventional plants, but were not likely to spend more on them than men. This survey indicated that there is a strong market for organic and sustainable vegetable, herb, and ornamental plants. Growers could potentially charge 10% to 15% more for these plants than for conventionally grown plants. They would likely receive the highest premium for organic and sustainable plants from individuals with higher incomes and education levels.
Katherine F. Garland, Stephanie E. Burnett, Lois B. Stack and Donglin Zhang
Coleus (Solenostemon scutellarioides) traditionally has been recommended as a shade plant, but many cultivars are also suitable for full sun. In regions of the country where light limits growth and photosynthesis, supplemental lights are used to increase daily light integral (DLI). Understanding the minimum DLI necessary to produce coleus would minimize supplemental lighting use, reducing costs and improving production sustainability. ‘Kong Red’ and ‘Wizard Coral Sunrise’ coleus were grown in a greenhouse under a 12-hour photoperiod and a mean DLI of 2.9, 3.8, 5.8, or 10.0 mol·m−2·d−1 to determine the lowest light level needed to produce high-quality plants. After 8 weeks, both cultivars had a 4.2-fold increase in shoot dry weight as DLI increased from 2.9 to 10.0 mol·m−2·d−1. Plants grown under 10.0 mol·m−2·d−1 were 22% to 25% taller and 18% to 21% wider compared with those grown under 2.9 mol·m−2·d−1. ‘Kong Red’ had 3.6 times as many branches and ‘Wizard Coral Sunrise’ had over twice as many branches when grown under 10.0 mol·m−2·d−1 compared with those grown under the lowest DLI. Leaf counts for both cultivars were 64% greater when grown under the highest DLI compared with those produced under the lowest DLI; leaf area for both cultivars was also positively correlated with DLI. Leaves of both cultivars had significantly more green area (i.e., less variegation) when grown under lower DLIs. Overall, both cultivars exhibited a more dense growth habit and greater degree of variegation when grown under the highest DLI. Therefore, we recommend growing ‘Kong Red’ and ‘Wizard Coral Sunrise’ coleus under a minimum DLI of 10.0 mol·m−2·d−1.