Lobelia erinus, the beautiful blue-eyed annual beauties that grace spring beds and baskets, are a gardener's delight. Known commonly as lobelia, various cultivars provide traditional shades of vivid blue, purple, and white to complement hanging baskets. One of the nicest features of lobelia is the habit of trailing or gently spilling over the edge of baskets with its dainty little flowers and lacy foliage.
If you see a racy red shade of lobelia listed as a perennial at your local garden center, you are looking at Lobelia cardinalis or the cardinal flower. For hanging baskets, Lobelia erinus is the most widely used species. Cultivars include Blue Moon and Crystal Palace, both dark blue but more upright versions of lobelia. Blue Cascade is the perfect blue trailing form of this hanging basket favorite. Sapphire and Rosamunde are purple and bright purple-pink shades respectively, each with a white center that resembles an eye. Choose Snowball or White Lady to enjoy pure white blooms.
Cool temperatures and part shade are friends of the lobelia. Hanging baskets should be placed where plants receive soft or filtered light and plenty of cover from mid-day heat. Soil with good drainage is a must, and organic matter will aid in this as well as provide nutrients.
Choose a container that will allow lobelia to trail over the sides while highlighting the flowers in the center of the basket. Fill with a potting mix composed of one part perlite, one part sand and two parts peat moss. Purdue University Cooperative Extension experts suggest that in a 10- to 14-inch basket, three small lobelia plants equally spaced around the container edge should fill out the pot nicely.
Keep the soil evenly moist at all times for best blooming results, but avoid overwatering, which can encourage root disease. Since lobelia do not like excessive heat, expect a temporary cessation of blooming during the most stressful days of the summer swelter. Come the cooler temperatures of early fall, however, your lobelia should rebloom with ease. To further assist in bloom production, cut the plant back after the first full bloom has died back to encourage more flowers. Also deadhead spent blooms as noticed.
If you choose to compose an eclectic basket in which lobelia will complement other flowers, choose a few specimens with upright height to add structure. Cyclamen and geranium are two upright flowering beauties with detailed features that will contrast nicely against the romantic splash of lobelia. Another option is to combine the small-featured plant with another rambler that has larger flower faces, such as petunia or monkey flower. All of these can tolerate the shade that lobelia requires, although some may bloom slightly less frequently.