Planting floral margins in agricultural landscapes has been shown to increase the abundance of pollinators in agro-ecosystems. However, to create efficient margins, it is necessary to use attractive, not weedy native plants with different blooming periods to prolong the availability of floral resources. Six native perennial plants of the Lamiaceae with different blooming periods were studied in a randomized block design, with the final aim to select the most efficient plants in floral mixtures by studying relationships between their floral phenology, floral density, and attractiveness to pollinators in Central Spain. In addition, their spatial expansion, i.e., potential weediness, was estimated under the field conditions, as the final purpose of the plants is to be implemented within the agro-ecosystems. The results showed that plant species with higher floral density (Nepeta tuberosa L. and Hyssopus officinalis L.) showed significantly higher attractiveness to pollinators and enhanced the attractiveness of floral mixtures. Species that bloomed in early spring (Salvia verbenaca L.) and in summer (Melissa officinalis L. and Thymbra capitata L.) did not efficiently contribute to the attractiveness of the mixtures to pollinators. In addition, besides high floral density of Salvia officinalis L. and N. tuberosa in the spring, warm and dry weather in spring 2012 enhanced the activity of bees, while cold and rainy weather in spring 2013 enhanced the activity of hoverflies. None of the plants showed weedy growth and so posed no danger of invading adjacent crops.