How Do Holly Bushes Reproduce?
Holly (Ilex) bushes are sprawling shrubs that often reach heights of 9 feet, depending on the variety. Many are hardy to USDA zones 8 and 9, such as winterberry (I. verticillata), inkberry (I. glabra) and American holly (I. opaca). Evergreen hollies are known for their prickly leaves and red fruits, which sometimes adorn holiday wreaths. Deciduous varieties have softer leaves. The berries are preceded by flowers, which open in late spring and early summer. But when it comes to reproducing, these lush plants require careful planning if you want to see a healthy berry production in your garden.
Each holly bush tends to produce only male or female flowers, making hollies dioecious. Female plants rely on male plants for pollination, so you'll need both male and female holly bushes in your garden. Occasionally a holly shrub can set fruit without a male plant acting as a pollinator, but the berries that develop will be sterile.
Female flowers have obvious pistils, each with a showy green ovary, while male flowers have four stems with anthers that release yellow pollen. Bees and other pollinating creatures transfer the pollen from the male plants' anthers to the female plants, where it slips down the pollen tubes to the embryos. This results in fertilization, the precursor to germination.
Many creatures help holly bushes cross-pollinate. Besides bees and flies that transfer pollen, animals such as raccoons, rabbits and birds eat the berries and flush out the seeds in their feces. This can contribute to the spread of holly bushes in wild landscapes. If you worry about a lack of pollinators around your holly bushes, you can purchase bees for your garden.
Having male and female hollies of the same species encourages healthy cross-pollination and berry production. Choosing the same variety also means they will bloom at the same time -- a key factor if bees are to transfer pollen in a single trip. Typically, one male holly shrub can pollinate five to 10 female plants, though sometimes it can pollinate up to 20. If weather is typically wet during the blooming period, it's smart to include many male plants in the garden, as the weather may interfere with insects' traveling and pollinating.