I found myself doing the strangest thing in the yard the other day: planting flowers. A few years ago, I could not have predicted this day would come. Flowers were for girls. Or maybe for old men who like to prune roses. But no — I’ve since become enlightened: Flowers are for bees.

Flowers are food for bees

One day a few Marches ago, my broccoli plants were bolting, going to flower as the spring weather warmed. This was when I customarily cut them down, to make space for new vegetables.

Flowering broccoli.

I considered myself a very practical gardener. I only grew edible plants, and within my garden I only gave space to plants that were providing for me, so the flowering broccoli had to go.

But as I thought to cut the broccoli down, I saw how many bees had arrived and were buzzing all over the stalks of yellow blooms. And I thought again. I thought about what flowers meant to bees; they are providers of nectar (carbohydrates) and pollen (proteins and fats). Flowers are food for bees.

Bees make food for me

It so happened that these flowering broccoli plants were twenty feet from a pair of avocado trees I’d recently planted, and in March these trees were also blooming. But whereas the broccoli flowers had bees bumping into one another in a feeding frenzy, there was only a lone bee visiting the nearby avocado flowers every once in a while. Avocado flowers aren’t particularly tasty to bees.

But I needed those bees to be working the avocado flowers because without them I would have no avocados. For avocado flowers to be pollinated and grow into fruit, they need pollen to be transfered onto the stigma, the little stick in the center of the flower.

For avocados, the wind can’t do this, nor can ants. Only flying insects like bees can move avocado pollen onto the stigma. At least that’s what I’d always read. (For example, here: “Avocado Flower Pollination and Fruit Set” by Peter Peterson, UC Riverside.)

So I cut a few stalks of broccoli flowers off and laid them on the ground beneath the avocado trees, trying to lure the bees that direction. It kind of worked. A few bees visited the migrant broccoli flowers before they dried out. I continued to cut and move a few broccoli flower stalks each morning until the broccoli blooms were all done, having turned into seed pods.

But in the end the lesson was clear: I needed bees, bees needed flowers, so I needed flowers.

Honey bees aren’t the only bees

Gordon Frankie likes to ask, “Who did all the pollinating before the honey bees came from Europe in 1853?” Honey bees were brought to America back then, but they are only one kind of bee, Apis mellifera. Yet there are approximately 20,000 bee species across the globe, and we have 1,600 different species of bees native to California alone.

Attending a lecture by Frankie last summer opened up my eyes to the world of bees beyond honey bees. The very day after the lecture, I spotted an Ultra Green Sweat Bee in my garden for the first time. This is one of the most common native bees in California, only I had never noticed it before. And if I’d ever seen it, I’d probably ignored it thinking it was a funny green fly.

Ultra Green Sweat Bee, Agapostemon texanus, on cosmos flower.

What is a bee, anyway? Early in Frankie’s talk, I raised my hand to ask that very question. I was embarrassed to realize that I didn’t know the difference between a bee and a fly, or a wasp for that matter. Frankie explained that bees are flying insects that have a close relationship with flowers. That’s the main way in which they’re different from flies. He also noted that bees are vegetarians whereas wasps are carnivores.

Gordon Frankie is a professor at UC Berkeley where he also directs the Urban Bee Lab. See the Bee Lab’s website here. He’s been studying the habits of native bees for many years. He mentioned innumerable fascinating things about native bees — 70% nest in the ground, so don’t mulch thickly everywhere; they get all of their water from nectar —  but one thing really caught my attention. He’d noticed that small carpenter bees of the genus Ceratina visit avocado flowers often and may be important pollinators of avocados.

I approached him after the talk. I told him I wanted to know more about his observations of native bees and avocado flowers. Since then I’ve emailed with him and read the paper that he and his colleagues have published on this topic, “Native Bees in the Avocado Orchards.” 

Frankie mentioned to me that he has seen species of two other groups of native bees, Halictus and Andrenid, also visiting avocado flowers often, and in fact just today I saw a kind of Halictus bee on the flowers of my Pinkerton avocado tree. They’re so small and fast that they’re easy to miss, unlike the big and loud European honey bees.

I still appreciate honey bees. But since learning of the hundreds of other bees that are around, I’ve become much more interested in identifying and attracting them to my garden.

And it’s not just for my avocado trees. My apricots need bees for pollination, my butternut squash do, as do my watermelon, and nectarines, and passion fruit, and on and on. Moreover, native bees vary in their size and shape, and many have the ability to pollinate crops better than honey bees. For example, Frankie mentioned that we might think honey bees pollinate squash because we see them in squash flowers, but actually squash bees wake up earlier and usually pollinate squash flowers before the honey bees even arrive. (Also see this article about native bees pollinating watermelon.)

Honey bee digging into one of my Blenheim apricot flowers last March.

Providing flowers for bees

So I find myself planting flowers these days. Which flowers am I planting? I do remain a practical gardener, and a frugal one at that. So I prefer native flowering plants, which don’t require irrigation, such as this Ceanothus or California Lilac, a plant which grows wild in my neighborhood.

Honey bee on flower of Ceanothus

But the other day I was planting a mix of native and non-natives — sunflowers and cosmos and poppies — because I’ve noticed in years past that bees love those flowers. Yes, I’ve actually been growing more and more flowering plants in my yard for the past few years now.

I let cilantro self-sow near some avocado trees and I’ve seen different types of bees and other insects enjoy their white flowers (on left). On the right are poppies that also self-sow. They come up every year and take care of themselves. Both cilantro and poppies get no irrigation.

I have also increased the number of flowers in my yard by simply allowing more of my vegetables to live out their lives and bloom just as I did with the broccoli. As much as my space and harvest needs allow, I now always let the following vegetables or herbs flower because I’ve noticed that bees (not just honey bees) love them: lettuce, basil, oregano, cilantro, carrots, onions.

Here’s a short video tour of some flowers within my vegetable garden and near a couple of avocado trees:

Frankie’s Urban Bee Lab has put together a nice list of Best Bee Plants for California here. And it is talking about European and Californian bees both.

Frankie wrote a book with a few colleagues titled, “California Bees and Blooms,” which I highly recommend. (My review of the book is here.) It also describes plants that bees love, plus profiles a number of the most common native bees we might see in our gardens.

Will my plants be more fruitful in years to come as I provide for the bees and they provide for me?

You might also like to read my post:

Growing a Bee Garden