Providing Habitat for Native Bees

The newly rebuilt Pollinator Palace at the Williamsburg Botanical Garden

Did you know the majority of bees that pollinate our food crops and wildflowers do not live in hives and do not produce honey? 

Hive-dwelling honey-producing bees did not even exist in North America until they were brought here by European immigrants in the early 1600’s.  That means the honeybee, which has become important to commercial agriculture and has captured press attention due to hive collapse, is not a native insect species.   

There are roughly 4,000 species of native bees and they are all in grave peril because all of them are in population decline. 

Informed  gardeners know and love native bumble bees, carpenter bees, mason bees, leaf cutter bees and sweat bees, to name only a few.  This branch of entomology is still expanding as scientists are now beginning to understand just how important native bee are to healthy ecosystems.  Many native bee species haven’t yet been thoroughly studied.

There are things that gardeners and enthusiasts can easily do to support our native bees.  A gardener’s  most important role in protecting and supporting bees (and other pollinators) is to grow plenty of flowers to provide them with nectar and pollen.  Bees come out earlier in the springtime now than in previous years, and so it is helpful to provide early blooms to feed them.

Mahonia aquifolium, native in the Pacific Northwest, has naturalized in coastal Virginia. It blooms in late winter to feed bees as they emerge in early spring.

Flowers vary in the quality and nutritional value of their pollen.  Native plants provide the highest quality food for native bees.

Any gardener who supports wildlife simply must not use pesticides or other chemicals in the garden that will poison them.  Pesticides and herbicides get into the ecosystem of the garden and have a profound impact on pollinators, birds and small mammals, in addition to the problem insects they target.

A bumblebee feeds on Lantana camara, a favorite of many pollinators, at the WBG

Bumble bees are probably the most recognizable of our native bees because they are large and easily observed.  They are ‘generalists’ and will visit almost any blooming flower.  While other bee species will only forage from one type of plant at a time and may prefer certain flower species or flower forms, bumblebees will freely visit most flowers in bloom.   Bumblebees often live in communities underground with a queen and her daughters managing the hive and caring for the young.

Bees frequent garlic chives in late summer

While some native bees prefer to live in the ground, many other species are solitary, and make nests to lay their eggs in wood or the dried stems of plants.  When we thoroughly clean up our gardens each fall, cutting the drying, dying stems of perennials, picking up all the sticks and raking all the leaves, we also dispose of many larval bees and other important insects.

Gardeners who understand the importance of native pollinators in their gardens are finding ways to provide habitat for them, as well as appropriate forage to support an increasing population of insects.  Native bees don’t live long as adults and will die after laying eggs.  Individuals don’t overwinter as adults. That is why providing safe habitat is crucial to support the population of native bees.

The simplest thing is to delay cleanup of last year’s perennials and downfall.  When you do tidy up, keep in mind that much of this material may harbor larvae and pile it in an out of the way place until the young ones have a chance to emerge.  If you are tempted to run these materials through a chipper-shredder, realize that some of next summer’s bees may be living in these stems in larval form.

January finds perennials still standing at the Williamsburg Botanical Garden

It requires very little effort to provide intentional, protected habitat for native carpenter and mason bees.  They like holes in logs or blocks of wood, crevasses in woody plant stems, or even tubes of rolled up butcher paper.  Straw, hollow bamboo stems, even wooden pallets, bricks, bottles, and a range of other materials may be used in creating a native bee habitat.

The first Pollinator Palace was built at the Williamsburg Botanical Garden in March 2014, long enough ago that it required renovation this spring.  Built from wooden pallets, bricks, glass bottles, clay pots, bamboo, drilled logs, and planting trays of succulents, a team of garden volunteers decided to rebuild it this year, cleaning it up and providing fresh materials as needed.

The original Williamsburg Botanical Garden Pollinator Palace in the spring of 2018. It was originally installed in March of 2014 and was the only structure of its kind in the Williamsburg area at the time.

As with honeybees, a number of parasites and other microorganisms can attack native bee larvae, so it is important to keep the environment clean and dry.  This is one reason that a roof is necessary on a ‘bee house’ or ‘Pollinator Palace.’  Woodpeckers and other insect loving birds will also explore the habitat for tasty larvae.  It is important to provide long enough stems and deep enough holes in any drilled wood so a bee can lay her eggs deeply enough that they will be safe from hungry birds.

A variety of materials can be used to fill the spaces between the pallets.  Building a Pollinator Palace would be a great activity for a group of families, a class, or a youth club to work on together.  Different individuals can make contributions depending on their interests, age, and level of skill.  While elementary aged children may stack paper straws into bundles (avoid using plastic, please) or roll brown paper around a pencil to create these tubes, teens may be able to drill deep holes into the end of a log with a 5/16” drill. 

These nesting materials are freshly placed in our renovated Pollinator Palace

Our original Pollinator Palace’s green, living roof was the first casualty of age.  The flats that once held thriving succulents died back as surrounding trees filled in.   There was no longer enough sunlight for those original succulent plants.  The heavy flats holding growing medium were removed and stacked on the ground when the wooden slats holding them safely on the roof gave way.

In early March, the old Pollinator Palace was carefully disassembled by a team of volunteers.  They salvaged and cleaned up what they could, hauling away the old wooden pallets and other plant material to another spot in the park where any remaining larvae can emerge.

New wooden pallets were brought to build a new structure on the old foundation of concrete blocks and flagstone.  New bamboo was cut into 12” lengths, and the entire structure was rebuilt.  Master Naturalist volunteers provided dried stems, drilled logs, and other materials.  A team effort, many hands worked together to prepare the Pollinator Palace for a new generation of bees this summer.

I decided to replant the green roof with mixed vegetation (mostly native) for dry shade.  Using the original flats, which were filled with an aggregate mix of gravel and soil, the first step was to loosen the packed soil, pull out old roots, and enrich the mix with Espoma Bio-tone.

The first of six planting trays is ready to clean and replant. Plastic tubs hold bare root ferns and vines, re-hydrated, and ready to transplant into the tray. Succulents in the tray to the left will be torn into smaller pieces to use in the green roof trays.

Bio-tone is an organic fertilizer blend designed to help transplants get off to a quick start by reducing transplant shock and supporting early development of root mass.  Since the plants will grow in an extremely lean, mostly gravel medium, starting them off with good nutrition is crucial.  I will fertilize the new green roof plants with liquid Neptune’s Harvest every two weeks during the growing season, at least through the first year as the plants establish.

The green roof is an important part of this bee habitat.  Some species of native bees, and other insects, burrow into the soil for shelter and to nest.  The roof will keep the entire structure cool and protect it from the weather.

The newly replanted green roof

As I loosened the gravel-soil mix and prepared for planting, I was able to remove some of the medium from each of the original six trays to re-use in two new trays to cover the front of the peak of the roof.  I will mix up additional medium from granite chips and compost for two more trays to cover the peak of the roof on the backside of our Pollinator Palace.

Our Pollinator Palace roof gets partial sun during the winter and early spring.  By early summer, as surrounding trees unfold their leaves, most of the roof will be in partial to deep shade.  The trays are very shallow, and so this selection of plants needs to tolerate short periods of drought, between rain and occasional waterings from our volunteer crew.

Walking ferns, Asplenium rhizophyllum, have re-hydrated in moist potting soil for two days and are ready to plant. Walking ferns can root from the tip of each frond, spreading by ‘walking’ across a planting area.

I’ve used a variety of evergreen and deciduous ferns in this planting, evergreen Partridgeberry, native violets, site native mosses, spring blooming Saxifraga stolonifera and a mixed selection of Sedums already planted into a shallow tray for use on a green roof or other planting.

The mixed Sedums were provided by our local Homestead Garden Center.  The mosses and native blue Viola cucullate were sourced on site. 

Friends at Homestead Garden Center donated this flat of Sedums left over from last year’s stock. It is perfect to divide and replant into our green roof. I also re-filled the tray with fresh medium and replanted to cover the peak of the roof of the PP.

We ordered the Partridgeberry, Mitchella repens; Walking fern, Asplenium rhizophyllum, Ebony Spleenwort, Asplenium platyneuron; all native evergreen plants. 

The Partridgeberry provides nectar and pollen for bees early in the season and red berries for birds later in the season.  This is also a site native, like the Ebony Spleenwort, growing in wooded areas of the garden.  Rather than disturb established plants in the woods, we ordered fresh starts from Tennessee.

Ebony Spleenwort, Asplenium platyneuron, is another evergreen native fern. These rhizomes and roots will soon send up new fronds.

All these native plants will grow well in the thin, gravely soil in the planting trays.  They will provide year-round color and interest, support wildlife, and should grow into a self-sustaining community of plants.

While the Saxifraga, sometimes known as Strawberry Begonia, is native in Europe, it is much like native North American Saxifraga species.  It grows well in deep shade and spreads quickly through runners.  It is evergreen and produces delicate white flowers for pollinators in mid-spring. 

Saxifraga stolonifera spreads when new plants form at the tips of runners. It will eventually form a thick, evergreen mat of delicate leaves.

This is one of the more ornamental plants in the mix.   This plant is easy to grow and easy to propagate by division.  I used a few divisions I had overwintering at home.

The final two trays, for the back of the peak of the roof, will grow in the deepest shade.  I expect to plant these almost entirely in moss and ferns.  They will be installed once some additional ferns arrive from the Tennessee Wholesale Nursery.

Native ferns are usually hard to source in local garden centers.  When ordering ferns online, most are shipped bare root, in a slightly moist growing medium and sealed into plastic bags.  Once the ferns arrive one should inspect them right away and allow the ferns to re-hydrate for several hours while soaking in water.

In this case, I was able to add some water to each bag of plants and let them rest, out of the shipping box, overnight.  Later, I unpacked the vines and ferns, gently pulled the plants apart, and heeled them into moist potting soil in shallow plastic tubs.  They will keep for several days in this way, recovering from their trip through the mail, until you are ready to pot them up or plant them into the spots where they will grow.

Once bare root plants re-hydrate and begin to grow again, they usually take off.  You may not notice a great deal of growth for the first few weeks as their roots grow first.  But new fronds will soon unfold on the ferns, and new stems extend on the vines.  I was thrilled to find the rare Walking Fern, and other hard to find native ferns with Tennessee Wholesale Nursery.

The Pollinator Palace is a cooperative effort among many volunteers, each with their own interests and skills, and it is a work in progress.  We hope it will prove interesting and educational for visitors to the Williamsburg Botanical Garden.  But even more, we hope it will support and protect the native bees that pollinate our garden.

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