By: Dan Wyns and Anne Marie Fauvel of The Bee Informed Partnership
This article originally appeared in the Winter 2020 issue of BEEKeeping Your First Three Years
The vast majority of commercially managed honey bee colonies in the United States spend February and a portion of March pollinating almonds in the California central valley. Almond pollen is very nutritious to bees, and colonies build up well on it when good weather conditions prevail during bloom. The weather during the 2020 almond pollination season was very favorable and colonies made significant increases in both population size and food reserves during the bloom period.
While warm and dry conditions led to a good nut set this year, it also meant the almond bloom progressed quickly, and once it was finished there were few other flowers supplying significant sources of honey bee forage. Working in various almond locations from Kern county in the south to Chico near the northern end of the valley, the BIP Tech Transfer Team Field Specialists were able to cover a lot of ground and observe the plants that bees were visiting. Aside from almond flowers, bees were also seen on a few other plant varieties, from unintentionally established invasive exotic weeds, such as mustard, wild radish and filaree, to beneficial cover crops intentionally planted by almond growers and other producers in the region.

This forager is collecting pollen from filaree (Erodium cicutarium) flowers on an orchard floor near Orland, California. Photo credit: Dan Wyns
Growing Wild
A welcome sight in a sea of declining almond blooms is Filaree (Erodium cicutarium), a common occupant of orchard floors and surrounding areas where it is able to utilize irrigation water intended for almond trees. Also called redstem filaree, E. cicutarium, a member of the Geranium family, is native to Europe and Asia. Its ability to tolerate a wide variety of light, moisture, and temperature conditions has led to its widespread distribution in Mediterranean climates, particularly in the western United States. The small, pink, upright facing flowers appear in clusters on the end of hair-covered stalks. It can bloom for several months and peaks in the central valley during February and March. The fruits of the plant mature into a long-beaked capsule whose shape has led to one of its common names: “stork’s bill” (also regionally termed “heron’s bill”).
Once the almond flowers are gone, filaree becomes an attractive option for bees as they shift their attention to orchard floor flowers if the ground cover has a significant amount of filaree. While filaree does produce some nectar, it does not do so in sufficient quantities to yield a honey crop. However, when most beekeepers have exited almonds as soon as they are released from pollination contracts, the locals that stay recognize that filaree can be an important component of Spring forage.

The seed containing fruits provide inspiration for the alternative common names of filaree which include storksbill or heron’s bill. Photo Credit: Dan Wyns
Deliberate Plantings
Honey bees need an abundance and diversity of floral resources to grow and thrive throughout the season. In areas of intensive agriculture, like the almond orchards of California, forage can be scarce before and after the primary cultivated crop blooms. The sole reliance on wild species to supply additional nutrition for honey bees is simply not enough. One of the pollinator friendly plants that is more and more commonly seen in and around orchards and agricultural fields is mustard. Its common appearance is due to both deliberate planting as a cover crop and through self-sowing.
The most common mustard variety, white mustard (Sinapis alba), originated in the Mediterranean and has spread to its current global distribution. It is cultivated as a cover crop and is also harvested for human consumption, including prepared mustards (from seeds) and young greens. White mustard also grows in a wide variety of environmental conditions including roadsides and disturbed soils leading many locations to classify it as an invasive species. In a cultivated context the crop will bloom 6-8 weeks after planting, while wild plants typically bloom in the Spring into the early Summer with bloom lasting about a month. When it is sown in agricultural fields it is typically done so as a Fall crop to be incorporated into As the far soil as a as a resource green for manure.

Almond orchards in the central valley of California sown with PAm Mustard Mix between rows to provide supplemental bee forage. Photo Credit: Project Apis m.
As far as a resource for honey bees, mustard is always a very welcome sight to beekeepers and its attractive and easily accessible nectar can provide significant resources to honey bees when soil pollen is moisture abundant is and adequate.
White mustard pollen is abundant and foraging bees often have much of their heads and bodies covered by the golden dust. The nutritional content of the pollen is moderate, but it is of great value to colonies when the availability of other blooms is limited. As a natural bloom it can be an important nutritional component for Spring buildup, and when cultivated, it is often among the last available pollen sources available to honey bees prior to Winter.
Both Dr. Sagili from Oregon State University and Dr. Nino from UC Davis have reported interesting preliminary results regarding the benefits of mustard plantings in and around almond orchards. Dr. Sagili’s group has observed significantly higher hypopharyngeal gland protein content in bees – a nutritional health indicator – from colonies placed in orchards with rapini mustard compared to colonies in orchards with no supplemental forage. The brood area was also significantly greater in colonies placed in orchards with rapini mustard. More specifically, Dr. Nino’s group at UC Davis observed an average increase of 3 full frames of bees in colonies near mustard plots.

A forager has her head covered in pollen while seeking nectar from deep within a mustard flower. Photo credit: Dan Wyns
There is a great deal of research aimed at developing cover crop seed mixes to supplement honey bee forage before and after almond bloom. Many of these seed mixes contain a high proportion of mustard, including the mustard mix from Project Apis m. In addition to providing forage and habitat for pollinators and other beneficial insects, cover crops can increase soil organic matter, breakup compacted soil, improve water retention, limit erosion, all without increasing frost damage. It is not just almond growers that are adding cover crops between their rows; mustard blooming throughout California central valley vineyards and walnut groves has become an increasingly common sight in early Spring. While some growers may express concern about the potential for these additional plant species to compete for pollination services and reduce almond pollination success, growers’ observations and study results on this topic reveal increased nut yield per acre in orchards with supplemental forage floors and compared higher to those Nitrogen with bare content orchard and floors and higher Nitrogen content and soil surface temperature during bloom.

A forager shows that the pollen color for mustard is a slightly darker yellow than the petals. Photo Credit: Dan Wyns
Given the many benefits that supplemental plantings provide to both beekeepers and almond growers during an almond pollination, one would expect to see the practice more widely adopted. In fact, BIP’s Tech Transfer Team Field Specialists do increasingly see mustard mix plantings in almond orchards each year, it still only represents approximately 5% of the total almond acreage. Although Project Apis m. reports to planting 40,000 the California Central Valley since 2013 wider through adoption their of Seeds for supplemental Bees program, planting a would not only make sense for almond growers in terms of increased yields, but the improvements in colony health provide benefit to the entire beekeeping industry and many agricultural sectors.