The Beekeeper’s Companion Since 1861
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The Other Side of Beekeeping

Some More Members of the Salicaceae

- July 1, 2015 - - (excerpt)

Poplar, Aspen, Cottonwood in general

Scientific name:
 Populus sp. From the beekeeper’s perspective members of this group of plants seems much the same and here are treated as a group.

Synonyms: In my view, taxonomically the genus Populus is a bit messy. My interpretation of the USDA Plants website[21] is that it currently lists a mix of 25 different species and 11 hybrids suggesting that at least in some cases we are dealing with interspecies breeding, which to me, trained as an animal biologist, is almost an oxymoron. At the least it’s messy. In addition, frequently under those headings, there are quite long lists of what the website apparently considers to be synonyms of a particular species or hybrid.

Origin: Probably mainly the Northern Hemisphere (see distribution below).

Plant description: The Genus Populus is dioecious.1 The trees generally have furrowed pale bark, the buds are sticky and the branches almost always possess terminal buds. The leaves are alternately placed and generally ovate to ovate-lanceolate2 with longish stems. They can be entire or dentate3 and while still in the bud the edges roll inward toward their upper surface. The flowers are displayed in pendulous scaly bracted4 spikes before the leaves appear. Each flower possesses a cup-shaped disc at its base. There are 4 to many stamens; the style5 is short terminating in 2-4 stigmas. The fruits are 2-4 valved6 and ripen before the leaves are fully formed. The seeds are numerous.[18]

In this writing I use Populus deltoides as a representative example. The distribution map provided indicates that it is fairly widely spread across North America.

Distribution: The genus seems to be distributed mainly in North America, Europe and Asia, and to some extent, Northern Africa.[18]

Blooming period: Early in the spring, before the leaves emerge (Genus in general).

Importance as a honey plant: Probably none7, but they produce copious amounts of early pollen. Oertel­[14], from his questionnaires, found Populus deltoides to be at least of some importance in NE and TX, Populus tremuloides to be of at least some importance in NE, and Populus trichocarpa hastate8 to be of some importance in NE, and just the Genus Populus to be of at least some importance in: ND, WY, AZ, CA, CO, IL, KS, KY, MT, NM, OK, SD, TN, UT, WA, TN, IA, ID, and ME. Ayers and Harman[1] from their questionnaires were unable to distinguish between species, but found the genus to be of at least some importance in: AL, AR, AZ, CA, CO, CT, ID, IL, IN, KS, KS, LA, MA, ME, MI, MN, MO, MT, NB, ND, NE, NH, NM, OK, SC, TN, TX, VT, WA, WI, and WY. They also found it to be of some importance in Canada in: AB, PE and NS.9

Honey potential: Probably none from nectar but honeydew is sometimes collected.[16]
From their extensive review of the literature Crane et al.[3] report that the aphid Chaitophorus populeti feeding on Populus alba, P. nigra and P. tremula produce heavy flows (that I interpret as flows of honey dew) being collected by bees. From the same aphid in conjunction with the aphid Pterocomma salicis they report intense flows from late May to mid June with colonies gaining 10-20 kg (~20.2-44lbs) /colony in 10 days of which they attributed 60% to be from poplar honeydew. They also, from their literature survey, provide estimated honey potentials for P. alba of 20 kg/ha and from P. nigra, 20 kg/ha (~17.8 lbs/A). They also report that a crystallized honeydew sample from an unspecified poplar and insect contained 40% melezitose. Melezitose is a trisaccharide made up of two molecules of glucose and one of fructose that is thought to cause honey to crystallize quickly, sometimes while still in the comb. For more about this, see this column March 2015.

Pollen: The beekeeping industry seems to be in nearly unanimous agreement that from their flowers, members of the genus Populus provide only pollen to the bees[2, 4, 12, 13 & 17] Nye[13] even claims that bees continue to collect pollen after the catkins have fallen to the ground. Table 1 provides an estimate of the nutritional value of pollens10 from different sources from Stanley and Linskens.[20] I have provided the information found in this reference in its entirety because it will be of interest to many readers who will have difficulty obtaining this reference.

Additional information: John Lovell[11] indicates that Populus angustifolia and Populus balsamifera produce materials that the bees collect in …