It has been proposed that pollen nutritional content is the most important factor in the selection of flowers by bees. We hypothesized that pollen and nectar quality affect bee visitation among co-flowering plant species. We also hypothesized that increased soil fertility increases pollen nutritional content and subsequently floral visitation. We conducted two field studies to test these hypotheses. In the first experiment, we recorded the following taxa groups of bees: 1) Apis mellifera (L.), 2) Bombus ternarius Say, 3) Bombus spp., and 4) Other Bees (solitary bees); visiting the following plants: Helianthus annuus L., Gaillardia aristata Pursh, Borago officinalis L., and Phacelia tanacetifolia Bentham. We measured the number of open flowers, corolla depth, flower diameter and nutritional content of pollen and nectar to determine which characteristics were correlated with bee visitation to flowers. We found that bees in different taxa foraged preferentially on one or several of the four plant species, and that pollen amino acid profile was associated with the amount of visitation for honey bees, B. ternarius, and Other Bees; and plants with higher percent nectar sugar content was positively related to visitation for honey bees and Bombus spp. In the second experiment, we varied soil fertility for Impatiens capensis Meerb. (Jewelweed, Family: Balsaminaceae) by adding fertilizer to potted plants and measured subsequent floral production, flower morphological characteristics, pollen amino acids, and bumble bee, Bombus impatiens, visitation from an adjacent commercial bumble bee hive. We found that fertilizer application had a positive effect on plant growth, flower production, and amino acid content, which positively influenced bumble bee visitation rate.

Abstract In a common garden study in Maine from 2012 to 2015, we used two bee species (Apis mellifera L. and Bombus ternarius Say (1837)) and three field-recognizable bee categories (‘Most Bombus', ‘Halictidae’, and ‘Other Bees') plus an ‘All Bees' data aggregation to compare 17 native and 68 introduced plant taxa. Data were from three 1-min timed periods per flowering plant taxon on a given day at a site. We observed 17,792 bees and found that their response varied by bee species or group. Using mixed models to analyze our data, we found that native bees had higher visitation rates on native plants, while A. mellifera visited both native and introduced plants. Most groups visited native late-flowering and native mid-late-flowering plants at higher rates. ‘All Bees’ were attracted to native perennials (vs annuals and shrubs) and to tall plants, both native and introduced; A. mellifera was attracted to introduced perennials, to introduced tall plants, and to lower-growing native plants. Asclepias tuberosa L. elicited a strong response from B. ternarius. In only two of six pairs of wild types and cultivars, bees visited wild types more. Plants with long bloom periods and with small, densely arranged white flowers attracted higher bee visitation than did other configurations (e.g., Origanum vulgare L., one of our most attractive taxa). A general linear model showed that linear combinations of flower density, floral resource height, flower corolla depth, and flowering duration explained significant variation in visitation rates for each of the different bee taxa groups.

Bee reservoirs can be effective in agricultural and habitat restoration projects, but the relative attractiveness of plants is not fully understood. To improve plant selection with better knowledge of spatial, temporal, and competition aspects, we tested up to 90 plant subjects from 2012 to 2015 at four sites in Maine. We recognized Apis mellifera L., Bombus ternarius Say, 1837, 'Most Bombus' (except B. ternarius), 'Halictidae' and 'Other Bees' (collectively the socalled 'bee groups') on open flowers in three 1-min periods per site and day, with numerous repeated observations per plant taxon. In 14,311 observations, we recorded 17,792 bees in 61 species. Most-visited plants included Asclepias tuberosa, Borago officinalis, Clethra alnifolia cv. Hummingbird (especially by A. mellifera), Melilotus officinalis, Origanum vulgare, Rosa palustris (especially before 1400 hours), Spiraea alba var. latifolia, and taxa in the family Asteraceae. Early-flowering shrubs were visited, especially by 'Other Bees'. Bee groups each ranked plants uniquely, with some overlap, and differed in most-visited of six plant taxa that we had included in all 4 yr and sites. For 'All Bees' among 84 plant taxa, the most-visited plants were M. officinalis (June), A. tuberosa (July), and C. alnifolia (August). Indicator Species Analysis revealed low bee fidelity to host plants for all but a few plant taxa. Apis mellifera differed from native bees in plants it visited intensively, with some overlap (e.g., A tuberosa), and was associated with increased visitation on seven plant taxa by 'Most Bombus' and B. ternarius.

Twinflower ( Linnaea borealis ) is an understory subshrub native to northern regions of North America, Europe, and Asia. Some growers report that this native plant is difficult to propagate. Although twinflower prefers partial shade and grows in areas with naturally variable moisture, there has been no greenhouse propagation work testing the impact of light or soil moisture conditions on root development of this plant or whether fertilizer impacts root development or root:shoot ratios during propagation. The goal of the first experiment was to propagate twinflower under a variety of daily light integrals (DLI)—27.6, 14.4, or 5.8 mol·m −2 ·d −1 —and soil volumetric water content values (θ = volume of water ÷ volume of soil) 0.30, 0.35, 0.40, and 0.45 L·L −1 , both parameters aimed at reproducing a range of natural conditions. The largest roots were grown at DLIs of 5.8 and 14.4 mol·m −2 ·d −1 and θ values of 0.30 and 0.35 L·L −1 . In the second experiment, twinflower plants were grown in substrates with 0, 2.1, or 5.0 g·L −1 of incorporated controlled-release fertilizer (14N–6.1P–11.6K). Root and shoot dry weight increased at both treatment rates. The relative percentages of nitrogen, phosphorus, and potassium, and the total concentrations of manganese in parts per million, increased in foliage, as well. In both experiments, the source of cuttings impacted results. In the first experiment, cuttings taken from the source that was in the most light were least likely to survive (26% survival rate) compared with cuttings taken from stock plants growing in partial shade (65% or 82% survival rates, by site). In the second experiment, cuttings taken from source plants that were most intensively managed for removal of weeds and competing plants had the highest survival rate and the greatest shoot and root dry weight. We recommend propagating twinflower with moderate rates of fertility (i.e., 2.1 g·L −1 of incorporated controlled-release fertilizer) under some shade (5.8–14.4 DLI) and a moderate θ (0.30–0.35 L·L −1 ).

Pollinator-dependent agriculture heavily relies upon a single pollinator-the honey bee. To diversify pollination strategies, growers are turning to alternatives. Densely planted reservoirs of pollen-and nectar-rich flowers (pollination reservoirs, hereafter "PRs") may improve pollination services provided by wild bees. Our focal agroecosystem, lowbush blueberry (Vaccinium angustifolium Aiton), exists in a simple landscape uniquely positioned to benefit from PRs. First, we contrast bee visitation rates and use of three types of PR. We consider the effects of PRs on wild bee diversity and the composition of bumble bee pollen loads. We contrast field-level crop pollination services between PRs and controls four years postestablishment. Last, we calculate the time to pay for PR investment. Social bees preferentially used clover plantings; solitary bees preferentially used wild-flower plantings. On average, bumble bee pollen loads in treatment fields contained 37% PR pollen. PRs significantly increased visitation rates to the crop in year 4, and exerted a marginally significant positive influence on fruit set. The annualized costs of PRs were covered by the fourth year using the measured increase in pollination services. Our findings provide evidence of the positive impact of PRs on crop pollination services.Agricultura que depende de los polinizadores depende fuertemente de una especie-la abeja melifera. Para diversificar las estrategias de la polinizacion, los productores buscan alternativas. Una reserva de flores muy densa con una gran cantidad de polen y nectar (una reserva de polinizacion, en lo sucesivo la 'PR') puede que mejore los servicios de polinizacion por parte de las abejas silvestres. El agroecosistema focal, el arandano bajo, (Vaccinium angustifolium Aiton), crece en un campo sencillo que se beneficiaria de las PRs. En primer lugar, contrastamos la tasa de visita de las abejas a lo largo de tres clases de PR. Tenemos en cuenta los efectos de las PRs sobre la diversidad de las abejas silvestres y la composicion de la carga de polen de los abejorros. Cuatro anos despues de establecimiento, contrastamos los servicios de polinizacion al nivel del campo entre las PRs y los grupos de control. Finalmente, calculamos el tiempo para realizar ganancias. Las abejas sociales prefirieron los cultivos del trebol; las abejas solitarias prefirieron los cultivos de flores silvestres. En promedio, en los campos de tratamiento, las cargas de polen de los abejorros contuvo 37% de polen de la PR. Las PRs aumentaron significativamente las tasas de visita al cultivo en el ano 4, y ejercieron una influencia positiva y marginalmente significativa sobre el cuajado del fruto. Utilizando el aumento medido en los servicios de polinizacion, los costos anualizados de las PRs habian sido cubierto del ano 4. Nuestros hallazgos implican que hay un efecto positivo de las PRs sobre los servicios de polinizacion.

Ethephon was sprayed on Euphorbia pulcherrima Willd. ex Klotzsch (poinsettia) ‘Sonora Jingle’ and ‘Sonora White’ to control their height and produce more compact potted plants. The results showed that Ethephon could effectively control the growth of ‘Sonora Jingle’ and ‘Sonora White’ poinsettia. Height was reduced by was 33.4 ± 0.8% for ‘Sonora Jingle’ and 30.8 ± 1.3% for ‘Sonora White’ poinsettia, when 700 mg L−1 Ethephon was sprayed three times on 29 August, 20 September, and 13 October 2005, respectively. Similar to other plant growth retardants, side effects including phytotoxicity and delays to first bract color were also observed on Ethephon treated poinsettia. However, all plants produced were still of a marketable quality.

A survey of the Maine landscape and nursery industry was conducted to identify industry views on invasive plant issues, attitudes towards potential regulation, and to estimate the potential economic costs of banning the sale of specific invasive plant species in Maine. Analysis of the 190 surveys returned (19% of 980 mailed) revealed that 76% of industry member respondents were genuinely concerned about invasive plant issues, and the same percentage felt the horticulture industry is responsible for educating customers about invasive plants. Industry members (68%) did not feel compelled to sell invasive plants merely on the basis of customer attraction to the plant, or due to competition with a neighboring business that sells the invasive plant. Self-reporting of sales indicated that Norway maple ($96K), burningbush ($68K), and Japanese barberry ($44K) constituted the largest portion of annual industry revenue (maximum values reported for 2006 to 2008) derived from the sale of seven identified invasive plants. Industry self-regulation was the most favored form of regulation, although the industry likely would not be significantly affected by legislated state-wide bans of at least purple loosestrife and oriental bittersweet. Bans on other popular invasive plants, including burningbush, Japanese barberry, and Norway maple likely would have a relatively small, short-term impact on the horticulture industry until alternative plants with similar properties were identified. The results of this survey demonstrated a need for identifying which plants are truly invasive or potentially invasive in Maine, as well as a need for open discussion of invasive plant issues among all interested parties in Maine.

Using Sonora Red and Sonora White Glitter as materials,the effects of five different combinations of plant growth regulators on the growth and ornamental characters of poinsettia were studied. The results indicated that compared with water treatmnent,each of the five plant grow regulator treatments decreased:growth rate and height;canopy diameter and bract area,as well as dry weight and fresh weight,but variation existed between cultivars. In short,treatment B(sprayed florel 5.0×10-4 twice) and treatment E(sprayed florel 5.0×10-4 and cycocel 5.0×10-4+ B9 1.0×10-3 once individually) were better,in controlling the heights of poinsettia and maintaining their ornamental characters.

Organic and conventional greenhouse growers in Maine were surveyed to determine the research needs of growers who may produce organic ornamental bedding plants. Organic growers were also asked to identify their greatest motivator to determine whether they feel that there is a greater market for organically grown ornamental plants. The greatest percentage (75%) of organic growers indicated that they choose to grow plants organically because “it's the right thing to do.” The second greatest percentage (36%) of organic growers choose organic production techniques for ornamental plants because they grow food crops organically and consider it convenient to use only one production technique. A relatively small number of organic growers (7%) considered the market for organic ornamental plants to be a strong motivator for growing organically. Organic growers were asked to select production issues that pose the greatest challenge for them from a list of common production problems. They considered insect and disease management and organic fertility, substrate, and pH management to be their greatest problems. Conventional growers primarily avoid organic production techniques because they consider organic fertilization or organic insect management to be too big of a challenge. Because organic and conventional growers consider insect and fertility or substrate management to be challenges facing organic growers, these topics should be top priorities for future research on organic greenhouse production.

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.

The application of supplemental blue light in greenhouse chrysanthemum production is part of a biological control strategy to enhance reproduction of Orius insidiosus Say, a natural predator of the western flower thrips, Frankliniella occidentalis Pergande. Two greenhouse experiments were conducted to determine the influence of a blue light—supplemented long day on flowering and vegetative growth in three cultivars of the short-day plant Dendranthema ×grandiflora (Ramat.) Kitamura. In Expt. 1, two cut chrysanthemum cultivars (`Manatee Iceberg' and `Naples') were exposed to: a) 9-hour ambient light and 15-hour artificial blue-biased (400-500 nm) light at two blue light intensities (3.6 or 7.0 μmol·m-2·s-1); b) 9-hour ambient light and 15-hour artificial broad spectrum light at a broad spectrum intensity of 3.6 μmol·m-2·s-1; c) 9-hour ambient light maintained with black cloth; or d) an ambient short day. Under a continuous photoperiod, flower initiation in both cultivars in the lower intensity blue light was not significantly different from that in short-day regimes. However, in both blue light intensities, flower size and dry mass were significantly less than in the short-day regimes. Increasing the dose of blue light decreased flower dry mass in `Naples' by 60% and in `Manatee Iceberg' by 72%. Plants were shorter with less vegetative mass in the short-day regimes. In Expt. 2, `Naples' and the pot chrysanthemum `Boaldi' were exposed to a) 9-hour ambient light and 6-hour artificial blue-biased (400-500 nm) light at four blue light intensities (0.4, 0.7, 1.6, or 3.5 μmol·m-2·s-1); b) 9-h ambient light maintained with black cloth; or c) an ambient long day. For both cultivars, in all blue light regimes, neither flower dry mass nor vegetative dry mass differed significantly from those in the short-day regime. The results indicate that exposing D. grandiflora to a blue light—supplemented long day at blue light intensities <3.5 μmol·m-2·s-1 does not adversely affect flower initiation and development.

Five of the ten training sessions for Maine Master Gardeners (MGs) were taught using interactive television (ITV) in 1993. Trainees at one location participated in the sessions live; trainees at seven locations participated in the sessions from distant locations but in real time; and trainees at two locations viewed videotapes of the ITV sessions at later dates. Trainees (n = 215) were quizzed weekly to assess their level of learning and surveyed about their learning experience 6 months after completing their training. ITV distance learners' quiz scores and hours of volunteerism were equal to those of local learners. More than 90% of all respondents would enroll in a MG program again if it were conducted and taught locally, while 83.9% would enroll in a program taught half locally and half using ITV.

A mail survey of greenhouse growers was conducted in 1994 and 1995 to determine the presence and importance of western flower thrips (WFT), Frankliniella occidentalis Pergande, in Maine greenhouses in growing years 1993 and 1994. Respondents were licensed growers with at least 1000 ft 2 (93 m 2 ) of greenhouse growing area. The survey objectives were to develop a grower demographic profile; determine the incidence of WFT and two WFT-vectored plant viruses, tomato spotted wilt (TSWV) and impatiens necrotic spot (INSV); and identify current WFT management strategies. The survey shows that Maine greenhouse growers are seasonal, experienced and retail oriented. Their growing area averages less than 10,000 ft 2 (929 m 2 ) and they produce a diverse crop mix and choose to import production stock as much as propagate it themselves. Both WFT and TSWV/INSV have increased in severity in Maine greenhouses over the past 10 years. Larger, year-round greenhouses are more likely to experience infestations of WFT and higher virus incidence. An integrated pest management (IPM) strategy is employed by the majority of growers surveyed. Insecticide application is the primary tactic used to control WFT. Fewer than 4% of the growers use natural enemies to control thrips. However, 63% responded that future research in pest management should focus on biological control.

Penobscot Co. (ME) Master Gardeners initiated a highly successful demonstration garden in 1994, on the university's sustainable agriculture farm. Five factors for the garden's success are suggested for consideration by groups planning similar projects: 1) The garden has a permanent site with excellent road visibility, on a public farm that supports public service; 2) The farm manager tills the plot and manages cover crops; 3) 10 to 12 Master Gardeners and two extension educators commit significant ongoing labor to the project; 4) Local businesses supply plants and other materials; 5) A vital statewide Master Gardener Program assures an ongoing supply of volunteers, ideas and enthusiasm.

A 2-year field study was initiated in May 1994 to show the effects of alternative weed control methods on weed suppression and cut flower yield. Cultural and economic analyses evaluate the feasibility of various management decisions. Gomphrena globosa cv. Woodcreek Pink seedlings were transplanted at 12-inch spacings with the following treatments: 10 mm chopped straw mulch, 10 mm shredded paper mulch, 1.25 mm black plastic mulch, bare soil with postemergent herbicide (Glyphosate) and bare soil with hand weed control. First-year results of the study show weed control was statistically equal between plastic, herbicide, and hand control. These methods provided significantly better barriers to weed growth than shredded paper and oat straw. Economic analyses show variation in the cost efficiency of these methods, however. It is expected that the results of the first year will be corroborated in 1995 for the herbicide, hand control, and plastic treatments, but will reflect change in the chopped straw and shredded paper treatments due to improved focus on experimental design and material selection.