Help pollinators with these bee-friendly plants

I had the opportunity to evaluate a university campus recently for bee-friendly landscape plants. Most of the campus was composed of large trees and sweeping lawns, a soft and inviting carpet of greensward that swept like draped velvet around massive buildings and trees. It created a place of soft repose for, I’m happy to say, students and many families using or walking through the campus with small children.

The trees were so numerous they formed an almost closed canopy, and the campus felt like it was a land of trees where they had allowed buildings to be put among themselves for our benefit.

Oaks, American elm, ash, mimosa, catalpa, mulberry, willow, golden chain tree, linden, flowering crab apple, hawthorn, cedar, fir, pine, horse chestnut, honey locust, eastern redbud grew in unison and profusion on the university grounds. A number of the trees and large shrubs were pollinator friendly.

The earliest spring blooming bee-friendly trees were willows followed in bloom by red buds (both eastern and western), flowering crab apples, hawthorn and horse chestnut.

Honey locust, linden, catalpa, mimosa and golden chain tree brought continuous tree bloom up to the end of July.

Each tree holds a huge amount of floral resources during bloom time and is of real benefit to pollinators, provided there are other pollinator friendly plants blooming before and after them; bees need sustained floral resources during the growing season.

Trees like oak, ash, elm and conifers are wind pollinated and for the most part are not bee-friendly.

Hydrangeas were widely planted on the campus and it was very interesting to see which ones were pollinator friendly and which were not. We don’t think of them as bee-friendly plants but there are some that are very attractive to bees while others are not.

On the east side of a large building there was a very long planting of lacecap hydrangeas. The more common mop-head hydrangea macrophylla hortensis is not bee-?friendly as the flowers are all sterile - showy to our eyes but with no floral resources of pollen or nectar to bees.

The fertile flowers of hydrangeas are small and insignificant and not as showy to our eyes but are heavily frequented by bees. Lacecap hydrangeas have a broad central cluster of fertile flowers surrounded by showy infertile flowers.

They are the best of both worlds - combining delicacy and grace with pollinator friendly flowers. These elegant flowers come in a number of colors from white to blue and purple.

A too rarely planted lacecap type is Hydrangea aspera, or rough-leaf hydrangea. It is best used in zone 9 areas with coastal influence, adequate water and yearly compost. Requiring filtered shade, this gorgeous large shrub grows to 8 feet and blooms in late summer.

The highly fragrant fertile flowers are a florescent purple and are surrounded by a ring of pale purple sterile flowers. Bees love its flowers and so do we.

The hydrangea paniculata types vary in their attractiveness to bees. The white flower heads are elongated and are usually a mix of both sterile flowers and fertile flowers.

Some cultivars are highly fragrant and very bee friendly, and others have non-scented mostly infertile flowers. All ?are showy.

It is best to visit a nursery and look for those that have a lot of bees visiting and are fragrant, and those that do not. The size of the plants can vary from 3-feet to about 6-8-feet. There are many cultivars.

Hydrangea arborescens is native to the eastern United States and is often planted on the coast or in areas with coastal influence. The cultivar ‘Annabelle’ is widely grown.

It has very large umbels of white mophead-type flowers except each individual flower is much smaller than the mophead types, and together gives the flowering plant a softer and more refined appearance.

Leaves are much smaller, not waxy and are a lighter green. Flower heads are large and the stems not strong so that sometimes they fall over.

This cultivar has all sterile flowers, but cultivars like ‘Haas Halo’ have lacecap flowers composed of both fertile and sterile flowers and is very showy and bee-friendly. The wild type of H. arborescens has all-fertile flowers. In hydrangeas, fragrance is a good indicator of bee-friendliness.

Pollinator-friendly perennials growing on campus were plants like dusty miller, lavender, Salvia nemerosa ‘Caradonna,’ sea holly (Eryngium), Russian sage, coreopsis, echinacea, monarda (beebalm), plumbago, penstemons, goldenrod, asters and sedum.

As the scale of landscape was large, the perennials were often planted in large swaths, giving the bees a large area to gather pollen and nectar. They greatly helped extend the season of bee-friendly plants.

The monarda had many bumblebees on it. The groundcover sedum flowers had many tiny native bees visiting. Overall, the eryngium had the most number and variety of bees on it.

The flowers engage us and increase our enjoyment and perception of the beauty of a place, while providing an uplifting and happy environment to spend time in. Wherever we go there ?is much to observe and learn about the life around us.

Kate Frey’s column appears every other week in Sonoma Home.

Contact Kate at: katebfrey@gmail.com, freygardens.com, Twitter @katebfrey, Instagram @americangardenschool