When we think about supporting pollinators, we often picture flowers — bright blooms buzzing with bees and butterflies in the warmth of summer.

In Wisconsin, some of the most important food sources for pollinators appear much earlier and much higher.

They’re in the trees.

Before most flowers bloom, trees provide critical pollen and nectar that help pollinators survive the transition from winter to spring. Without them, many early-season insects would struggle to find the resources they need.

A Critical Moment in Early Spring

As temperatures begin to warm, pollinators emerge from winter dormancy. Native bees, flies, and other beneficial insects become active at a time when food is still limited.

This early window (often in April) is one of the most vulnerable times of the year.

Few garden flowers are blooming yet. Perennials are just beginning to emerge. But overhead, trees are already at work.

Trees as Early Food Sources

Many trees produce large amounts of pollen in early spring… sometimes we see this evidence as a yellow film on our cars when they’ve been parked outdoors! For pollinators, this pollen is essential.

It provides:

• Protein needed for growth and reproduction
• Nutrients for developing larvae
• Energy to sustain early activity

Some trees also provide nectar, though pollen is often the primary resource.

Common Wisconsin trees that support pollinators include:

• Maples, which are among the earliest to flower
• Willows, known for their soft catkins rich in pollen
• Birches and aspens, which release pollen as they leaf out

These trees may not look like traditional flowers, but for pollinators, they are one of the most important food sources of the season.

Native Trees & Native Pollinators

In Wisconsin ecosystems, plants and pollinators have developed relationships over thousands of years. Many native bees are active specifically when certain trees bloom. Their life cycles are timed to match these seasonal resources.

This means that native trees don’t just offer food, they offer the right food at the right time.

When native trees are present, pollinators are more likely to find what they need to survive and reproduce in spring.

Supporting the Whole Food Web

The impact of spring trees extends beyond pollinators.

Trees also support:

• Caterpillars, which rely on leaves as host plants
• Birds, which depend on insects to feed their young
• Soil systems, through leaf litter and organic matter

In fact, many songbirds rely on caterpillars as a primary food source during nesting season. Without trees supporting insect populations, that connection breaks down.

What begins in the canopy ripples throughout the entire ecosystem.

What to Look

Spring tree activity can be easy to miss, but once you know what to look for, it becomes more visible.

Look for:

• Catkins on willows and aspens
• Subtle blooms on maple branches
• A light dusting of pollen on surfaces
• Increased insect activity on warm days

These signs often appear before leaves fully emerge, making early spring a unique time to observe the connections between trees and pollinators.

Why This Matters More Than Ever

As landscapes change and habitats are lost, early-season food sources become even more important.

Planting and protecting native trees helps:

• Support pollinators at a critical time
• Strengthen biodiversity
• Build more resilient ecosystems

Even a single tree can provide a meaningful resource within a larger network of habitat.

Experience It Through Woodland Wonders

At the Garden, these relationships are part of the story unfolding this spring.

Woodland Wonders presented by Selner Tree & Shrub Care invites you to look more closely at how trees support life — from the earliest pollen sources to the layers of plants and wildlife that depend on them. It’s an opportunity to see beyond the blooms and understand the role trees play in shaping the entire ecosystem.

As you explore, take a moment to look up. The activity happening in the branches is just as important as what’s happening at ground level.

A Quiet but Essential Beginning

Before the color of summer arrives, before gardens are in full bloom, trees are already doing the work.

They feed pollinators. Support wildlife. And quietly set the season in motion.

It’s easy to overlook, but it’s one of the most important parts of spring.

Sources & References

• Xerces Society — Pollinator dependence on early-season pollen sources
• University of Wisconsin–Madison Arboretum — Native trees and pollinator relationships
• Wisconsin Department of Natural Resources — Native tree species and habitat support
• University of Wisconsin Extension — Pollinator-friendly landscaping practices
• USDA Forest Service — Tree ecology and ecosystem services