Obviously there’s no fooling Naturally Curious readers! The trick part of yesterday’s Mystery Photo question was that the pictured fruit were not, botanically speaking, “cones” — true cones are found only on conifers, which Speckled Alder (Alnus incana) is not. The resemblance of Speckled Alder fruit to cones is marked (which is why they are referred to as “cones”) and there are many similarities between the two. They are both woody, contain seeds and develop from catkins (flowering spikes). However, the nature of their respective seeds is quite different. Angiosperms, or flowering plants such as Speckled Alder, produce seeds that are enclosed within a covering (the ovary), whereas gymnosperms (conifers) have un-enclosed or “naked” seeds. Alder “cones” open to release seeds in a manner similar to many conifer cones and, like most cones, do not disintegrate immediately after maturity. (Photo: female flowers/catkins of Speckled Alder which, if fertilized, will develop into “cones.”)
Once leaves start to fall, one often observes white, fuzzy patches along the branches of Speckled Alder (Alnus incana). These fuzzy patches consist of colonies of aphids feeding on the sap of the shrub. In order to get enough nitrogen, they must drink volumes of sap, much of which is exuded from their abdomens as a sweet liquid called honeydew. The honeydew accumulates and hardens onto the branches as well as the ground beneath the shrub. Yesterday’s Mystery Photo was the honeydew of Woolly Alder Aphids (Paraprociphilus tessellates) which has been colonized by a fungus known as black sooty mold, a fairly common phenomenon.
Woolly Alder Aphids produce white wax, or “wool,” filaments from their abdominal glands. Clustered together, these aphids look like a white mold. If disturbed, the individual aphids pulse their abdomens in unison – apparently an effective defense mechanism.
Woolly Alder Aphids, also known as Maple Blight Aphids, have two host plants at two different stages of their lives. In the fall they lay their eggs on Silver Maple trees. The eggs hatch in the spring and the aphids feed on the maple leaves. During the summer a winged generation flies from maple leaves to alder shrubs and establishes colonies. In the fall, some of these aphids fly to Silver Maples and lay eggs, while some overwinter in the leaf litter beneath alders.
Speckled Alder is a shrub in the Birch family that is found growing in wetlands. It is named after the “speckles” on its bark — horizontal lines or lenticels (spongy openings for the transfer of gases). In winter, Speckled Alder branches are distinctive because they carry two kinds of buds as well as last year’s fruit. The male flower buds are in the form of inch-long catkins which appear reddish in winter. They begin to turn yellow in March just before they extend into long, yellow pollen-bearing flowers. The female flower buds are small and drooping just ahead of the catkins on the branch. They look like miniature unopened versions of the seed-bearing fruit they’ll become. Last year’s woody fruit, or “cones” are also present, having opened and had their seeds, or winged nutlets, dispersed by the wind last fall.