Planting Trees for Pollinators

A summer afternoon doesn’t feel like Summer without a round little bumble bee buzzing by, butterflies flittering around, and birds signing above. Between climate change and habitat loss, many pollinator species are struggling to survive, which threatens crops and other plant species. What can you do to help? Plant trees! Many tree species not only provide shade and interest, but trees can be crucial sources of pollen and nectar to pollinators.

Honey bees have gotten a lot of attention, but important pollinators include native bee and wasp species, butterflies, moths, beetles, and flies. Most bee species native to North America are solitary bee species that nest either in the ground or in wood tunnels. Bumblebees are particularly effective pollinators due to their size and fuzziness. Our native bees are just as important to consider as honey bees. There are several species of wasps, beetles, and flies that provide multiple benefits. In addition to pollination, they also hunt pest insects such as aphids, thrips, and Japanese beetle grubs. Butterflies and moths, beyond being pretty to look at, also provide multiple ecosystem benefits. They are great pollinators for many plants native to our area and their larvae are the primary food source for young songbirds. Planting a diverse array of trees, shrubs, grasses, and perennials is the best way to provide for a wide number of pollinators, but this article is going to focus on trees.

We’ve all heard about no Mow May and other efforts to help early Spring pollinators, but did you know that trees are a huge part of providing for pollinators? Pollinators do best when they have a diversity of species to choose from year-round, with overlapping bloom times, in close range to their nests. Many of the pollinator plants we are more familiar with don’t start blooming until late Spring or Summer. Trees can help to fill the need for early blooms for pollinators. Because of their size, the amount of pollen or nectar a mature tree can provide can rival a whole field of wildflowers. When you stick to native tree species, they bloom times are often synchronized to the life cycles of native pollinator species, since they have been evolving together for millennia.

Early Spring (March – early April)

They may not be as showy or fragrant as the blooming tree’s you’re familiar with, but some of the earliest flowers available to pollinators come from species like Elms, Maples, Filberts, and Willows.

While not known widely for their flowers, native Maples are a vital source of early pollen for native bees. They are typically some of the earliest sources of pollen available on our landscape. Silver Maple blooms are easy to miss with how tall the trees are and how tiny the flowers are. They are some of the earliest flowers on our landscape in early March, long before leaves emerge. Another native, Red Maple, produces tiny, dangling bright red flowers in March that bees go crazy for. They don’t last very long before turning into samaras, but they are beautiful against the light gray bark, and provide for a lot of native bee species.

Willows are also a vital early source for pollinators with some blooming as early as the first week of March. The green and yellow blooms of Black Willow are primarily pollinated by wind, but still provide pollen and nectar to native bees. While Black Willow tends to be too large for most yards, American Pussy Willow is another great early source of pollen. While not native, the iconic Weeping Willow is also regularly visited by numerous bee species. Other species of Filbert, Hazelnut, and Witchhazel also bloom as early as the beginning of March, helping out bee species when they first emerge.

Mid Spring (April – early May)

Mid-Spring is when we start to see our showiest blooming trees.

Cherry species are a great early-mid Spring source of early pollen and nectar for a variety of pollinators. Chokecherry starts blooming in April, and continues into July. Its blooms are visited by several species of flies and bees. A close relative, Black cherry, blooms later in May. Fruiting Cherries and ornamental Cherries also bloom in April, and while not native, can still be a good source of pollen and nectar for bees.

April is also when we see most magnolia species bloom. Magnolias are a more ancient genus of tree, evolving before many bees and butterflies. They are pollinated primarily by beetles, which is why many of their flowers are so large. Ornamental Pear trees, most commonly Bradford Pears, also reach their peak bloom in late April. You may know these trees for their somewhat rotten smell. That odor resembles rotting flesh because this species is pollinated by flies. Neither Magnolias nor Bradford Pears are native to Wisconsin, but we do have pollinator species that visit them.

Eastern Redbud’s bright fuchsia blooms noticeably stand out against its dark purple-ish bark.  Redbud attracts a large number of bee species, early butterflies and moths, and is known to attract hummingbirds. The flowers are also edible for us humans. Adding them to salads brings a colorful, sweet and spicy interest. We also tend to see native Serviceberry trees bloom in late April and Early May. Serviceberries provide pollen and nectar to a wide number of bees, butterflies, wasps, and moths. Once the flowers bloom, they turn to berries that feed birds, mammals, and people. Both Serviceberry and Redbud are important native trees that serve as fabulous ornamentals in the landscape.

Native Birch species also see their catkins mature and release pollen in mid-Spring. Like Willows, Birches are primarily pollinated by wind, but get extra help form bees, butterflies, moths, and even hummingbirds.

Late Spring (May to early June)

Crabapples may be the most widely planted showy blooming trees in our landscapes. They bloom in various shades of pink and white, bright and aromatic at the peak of Spring. Heavy with blooms, provide a ton of nectar to bees right when they are growing their bee nurseries. Wasps, flied, and butterflied also love Crabapple flowers. Early cultivars start blooming in late April and late Crabapples bloom into late May. As Crabapple blooms wrap up, their close relatives, Hawthorns, begin their bloom in mid-to-late-May. Beyond the ornamental, fruiting Apples and Pears begin blooming in May as well. Fruit tree blooms are another great source of nectar to numerous pollinator species.

American Basswood and its European Linden relative can be found completely covered with bees at peak bloom in Late May and early June. Basswood nectar may be the most preferred nectar of any other flower at this time of year, earning its nickname “the bee tree”. They may be small and not very showy, but the Basswood blooms are unmistakably sweetly fragrant and provide huge amounts of nectar to many pollinator insects.

Native Dogwood species such as Pagoda Dogwood also open up white blooms in late Spring. Pagoda Dogwood is loved by bees, wasps, butterflies, moths, and fly species. Pagoda Dogwood and its close relatives, Gray Dogwood and Rough Leaf Dogwood serve a large number of insects and pollinators, while providing great landscape interest.

Summer (June – August)

As we move into Summer, most trees are finished blooming, and pollinators turn more to perennials for nectar. But, there are still some summer-blooming trees you can plant to provide more options.

Tulip Poplars (while not real Poplars) are a fabulous, showy source of nectar for bees and beetles. They produce large, cup-shaped flowers in late spring that provide a lot of nectar per flower. A 20-ft tall tree can provide 8 pounds of nectar, and Tulip Poplars can reach 100 feet in height. In warmer years, you may see Tulip Poplars blooming in late May, but cold years can push nectar production into early Summer.

Catalpa trees are large shade trees that bloom in June and July. Their large, trumpet-like flowers provide large amounts of nectar to bumblebees during the day, and moths at night. In fact, both their nectar production and fragrance increases at night to specifically attract moths to increase their pollination odds.

If you are looking to help out your local pollinators, consider planting the trees above. Reach out to Tree Health Management today for a tree planting consultation with one our ISA Certified Arborists. We can help you decide on what species is best for your yard and your pollinators.