Spring Pollinator Flowers Are Most Often Woody

Metallic green bee and a hawthorn (Crataegus spp.) flower

Two-winged silverbell (Halesia diptera)

A pollinator garden is not a wildflower garden if done correctly. It simply can't be. Many who have recently embraced the connection between pollinators and flowering plants seriously fail to grasp the very real importance of woody plants in a pollinator landscape. To many, a pollinator garden is a plot of native wildflowers and very little else. The truth is that a carefully thought out pollinator garden is everything in your landscape - including the trees and shrubs. Not because some of the woody plants serve as larval hosts for butterflies and moths, but because so many are critical at providing pollen and nectar during the early spring when very few wildflowers are in bloom.

Honey bee and flowering red maple (Acer rubrum)

Here in Florida, where I've lived for 33 years, I can garden 12 months out of the year, but although it is warm enough to putter around outside, there are very few native plants in bloom and even fewer native pollinators. That's the way it's supposed to be, but beginning now, in February, things begin to change. For the past few days I've seen the return of the southeastern blueberry bees that were here last year at this time. They are a harbinger of more bees yet to come. Butterflies, also, have started to become more common. I've had gulf fritillaries throughout the winter, but others, like the giant swallowtail are making themselves obvious once again. To keep them, I have to provide food and the best way to do that is with flowering trees and shrubs.
I've carefully chosen the woody plants I've added to my new landscape and it includes a great many spring-flowering species. Most are also important bird plants, but all produce flowers that are significant sources of pollen and nectar. These will sustain my developing pollinator base much more reliably than the patches of Spanish needle (Bidens alba) that I have left in a couple of the out-of-the-way corners.
Not all spring-blooming trees and shrubs are equally important to pollinators, but nearly every species relies on them to produce their fruit. It is a rare flowering woody plant that relies on wind like a pine or a red cedar does. I am not a fan of red maples as a significant wildlife plant, but it cannot be argued it is alive with bees at a time of year when virtually nothing else is blooming. The tiny flowers of oaks (Quercus spp.) attract the attention of a great many tiny pollinating insects and these form a significant food base for migratory birds such as warblers, tanagers, gnatcatchers, and even hummingbirds.
I don't have a lot of room to create a woods of very large canopy trees and the maples and oaks are present close-by. I've chosen to anchor my deciduous woods with a native basswood (Tilia americana) as this tree is also a pollinator magnet and is not represented elsewhere in my neighborhood. Beneath this canopy and along the edges of my new yard, I have added a great many members of the Rosaceae - apples and hawthorns for example. I believe I have 10 species of haws (Crataegus spp.) scattered here and there and I'm hoping most are mature enough to flower, at least a little, in about a month. I've planted a southern crabapple (Malus angustifolia), a flatwoods and scrub plum (Prunus umbellata and P. geniculata), and a pair of common serviceberries (Amelanchier arborea) - all members of the rose family. 
I am not aware of any good publication for my region of the world that rates the various woody trees and shrubs for their pollinator value, but I have 33 years of observations to fall back on. There are few better genera than the buckthorns - Sideroxylon spp.; plants that were recently taken out of the Bumelia genus. I have added 4 different species in my new landscape. Hollies are often exceptional as are shrubs in the Florida privet genus - Forestiera spp. and not to be confused with the invasive "privets" that are in completely different genera. Most exceptional among the Ericaeous species (blueberries, azaleas, lyonias, etc.) is sparleberry (Vaccinium arboreum) - literally, the "tree blueberry." I love viburnums (Viburnum spp.) as bird plants, but I never see the level of activity on them as I do on the ones I've mentioned above.
If I had my wish, there wouldn't be "pollinator people", "bird people" and all the other groups of folks who seem fixated on a subset of the living world with their approach to landscaping. Truth be told, all of us need to broaden our designs to create a living landscape that welcomes everything to the extent possible. No more "10 Best Trees" lists or lists of the "10 Easiest Wildflowers."  I have striven for diversity above everything else and time will determine if I'm right in doing so, but as I sit here waiting for another Florida spring I know that the woody plants I've added here are the real heart of my spring pollinator garden.

Sparkleberry (Vaccinium arboreum) is an amazing pollinator magnet