Ornamental plants are appreciated by humans for their colorfulness, beauty, abundant flowering and long blooming periods. Many ornamental plants can also constitute an additional foraging resource for flower-visiting insects. However, the ability of the popular ornamental plant Calibrachoa to support urban insect communities is not well documented. In this study, 20 different Calibrachoa cultivars were selected and tested in regard to their insect friendliness based on standardized observations (I) in flight tents using the large earth bumble bee Bombus terrestris as a model species and (II) in open field trials. To investigate what floral characteristics might constitute attractiveness to bumble bees, various floral traits were recorded and compared across all tested Calibrachoa cultivars. Over a two-year period, a total of 6,327 foraging bumble bees were recorded in the tent observations. In the open field observations, we counted 4,188 flower-visiting insects. Our results revealed that (I) all Calibrachoa cultivars were visited by insects for foraging, (II) the number of insect visitors varied significantly among the 20 tested cultivars and (III) the cultivars displayed different floral traits. For the morphometric floral traits and the aroma profiles of Calibrachoa, only the mean nectar quantity and a few identified compounds could be correlated with attractiveness to the model species B. terrestris. We also found that the petal color of the tested cultivars had a significant impact on the number of visitors. Therefore, B. terrestris clearly preferred red or blue Calibrachoa cultivars over those with other petal colors. However, as the cultivar preferences in the different insect groups differed, it is highly recommended to use various cultivars in urban plantings. Nevertheless, efforts must be made to explain what additional floral traits make Calibrachoa and other ornamental plants generally attractive to flower visitors. This information can then be used for breeding purposes to increase the insect friendliness of ornamental plants.

观赏植物因其色彩艳丽、美丽动人、花期丰富、花期长而受到人们的喜爱。许多观赏植物也可以成为访花昆虫的额外觅食资源。然而，流行的观赏植物Calibrachoa支持城市昆虫群落的能力并没有得到很好的记录。在这项研究中，基于使用大型地球熊蜂Bombus terrestris在飞行帐篷中的标准化观察 (I)，选择并测试了20 个不同的Calibrachoa栽培品种的昆虫友好性作为模型物种和（II）在露天试验中。为了研究哪些花卉特征可能构成对熊蜂的吸引力，记录并比较了所有测试的Calibrachoa栽培品种的各种花卉特征。在两年的时间里，帐篷观察中总共记录了 6,327 只觅食的大黄蜂。在野外观察中，我们统计了4,188只访花昆虫。我们的结果表明，（I）所有Calibrachoa品种都被昆虫访问以进行觅食，（II）昆虫访问者的数量在 20 个测试品种之间差异显着，（III）品种表现出不同的花卉特征。对于Calibrachoa的形态测量花特征和香气特征，只有平均花蜜量和一些鉴定的化合物可能与对模型物种B. terrestris 的吸引力相关。我们还发现，测试品种的花瓣颜色对参观人数有显着影响。因此，与其他花瓣颜色的品种相比，B. terrestris显然更喜欢红色或蓝色的Calibrachoa品种。但是，由于不同昆虫群的栽培品种偏好不同，强烈建议在城市种植中使用各种栽培品种。然而，必须努力解释什么额外的花卉特征使Calibrachoa和其他观赏植物通常对花卉游客有吸引力。这些信息然后可用于育种目的，以增加观赏植物的昆虫友好性。