When Bees Ignore Blossoms

Keeping Gardens Fruitful

This spring, I was invited to a farm that included a small (20 tree) cherry orchard where the bees were ignoring trees in full bloom. The owner wanted to know what if anything he could do to get some bee action for his blooms. As a rule, bees will snub flowers that are low in nectar and pollen. Even favored blossoms like cherries can be lacking and the bees are evidently able to detect (nobody quite knows how) blossoms with low levels of these important substances. Sometimes this is because other bees have already been there and done that. There is some evidence that foraging bees leave behind a scent marker that other bees can sense. A study done at Humboldt State University in Arcata, California found that when bees approached flowers, then flew away without foraging, the rejected blossoms had about half the nectar of an average bloom.

Foraging is a lot of work. Honeybees boost efficiency by tending to ignore empty flowers in favor of loaded blossoms. The most common reason for low nectar and pollen levels in flowers that normally have high levels is nutrition; poor soil or soil that has been chemically fed or treated can low in nutrients. In this case, some of the orchard trees are mulched with shredded paper or chopped field hay, while other are surrounded with bare soil. Hmm. In an orchard setting where trees are expected to be fruitful, low-nutrient mulches are not adequately helpful. The owner wanted to keep weeds down, and the paper did that, as did frequent scuffle-hoeing of the bare earth areas. However, mulches can also be valuable soil amendments. A nutrient-rich mulch like shredded leaves mixed with grass clippings, coarse compost mixed with fine shredded bark, or chopped hay mixed with shredded leaves could make those trees more attractive to pollinators.

Investments That Pay Off

For one thing, improved soil will boost blossom fragrance, which is one of the factors that can draw in pollinators. Fragrance is costly for plants to produce, and when soil nutrients are low, it’s one of the qualities that can diminish (along with color and flavor). Instead of using paper mulch, or none, I suggested that the owner surround each fruit tree with a generous circle of compost. Fruit trees benefit the most when compost is concentrated in a 3-4 foot wide band around the dripline of the tree. That’s where the active feeder roots are so that’s where compost will be of most use. Pile it on generously, heaping 3-5 inches of compost or aged dairy manure around each tree.

To keep that inner circle weed free, I suggested surrounding each tree with a ruffle of big, easy going plants such as Six Hills Giant catmint (Nepeta), which quickly makes a 2-3 foot mound. That has the advantage of keeping mowers and weed whackers away from tree trunks (important since mechanical injury is a leading cause of death). Catmints are also deer resistant, drought resistant, healthy ad vigorous, besides being highly attractive to bees and other pollinators. To pull in early bird pollinators, plant native annuals such as Clarkia, bleeding heart (Dicentra), poached egg plant (Limnanthese douglasii), and California poppies, as well as calendulas, sweet alyssum, and annual forget-me-nots. One of the prettiest orchards I ever saw was an Oregon hazelnut plantation that was carpeted in blue scilla in early spring. The bulbs had been spreading for decades and the result was a haze of happy bees.

Healing Ground Covers And Mulches

Small home orchards can profitably be sown with an annual soil improver such as crimson clover (Trifolium incarnatum), (NOT red clover, Trifolium pratense, which can be a trouble maker). A splendid nitrogen fixer, it will reduce the chore load for you by forming a summer cover crop in empty beds and around established trees and shrubs. Crimson clover is often called a “green manure” since it acts much like compost. Don’t skimp the true compost, though, because flowering and fruiting plants grown in compost-enriched soil have more fragrance, more nectar, and better flavor than fruit given only chemical fertilizer. That’s because the combination of plant- and soil-feeding nutrients in compost increase beneficial biological life in the soil. Healthier soil makes for healthier plants. In addition, compost helps plants take in and store a higher percentage of natural sugars. A sugar meter (called a brix meter) tells organic growers how well their crops have been nourished. The higher the brix, the better the flavor and nutrient quality.

My orchard owning pal recently told me that tiny cherries were forming, so his fruit had been visited by somebody. Who might have been busy in those cherry blossoms? Most native bees are a lot smaller than honeybees and are not as obvious in the garden. Other less visible insects do their share of pollinating as well, from hover flies to little wasps, so it is possible to get some fruit set without seeing the usual big bees bustling about. He had also done some hand pollinating, transferring pollen from blossom to blossom with a small brush. This is manageable for those growing miniature fruit trees in half barrels on the back deck, but a daunting task for a farmer with 20 trees to service.

Enlisting Help From Friendly Natives

To encourage visiting bees, he decided to plant more flowering native shrubs around his farm. This will most certainly help to bring in bees and other pollinators. Some good choices for those with fruit trees are early bloomers like native mahonias (Oregon grapes), Indian plum (Oemleria cerasifolia), and flowering currant (Ribes sanguineum). Later blooming fruit crops may be boosted by adding summer bloomers like native roses and ocean spray (Holodiscus discolor), which drapes the wood verges with frothy plumes of ecru lace right about now. It’s one of my favorite natives, since besides being a bee magnet, nectar rich ocean spray is a great favorite with butterflies, including Spring azures, pale swallowtails, Lorquin’s admirals and Gray hairstreaks.

Onward!