Winter’s a-comin’ on — time to pot those amaryllis bulbs, germinate those paperwhites, and do whatever you can to chase away the dark of winter. One activity that I enjoy is sprouting acorns on my kitchen windowsill. I place an acorn, flat end up, on top of a narrow-necked vase or flask, filled with water. If I keep the end of the acorn in water it should germinate within a couple of weeks.
Along with the acorns this year came surprise tag-alongs: half-inch weevil larvae (Curculio spp) that had hatched from tiny eggs deposited in the acorns by their moms earlier in the growing season. In fact, a larva emerged from every one of the acorns that I had brought in. In each case, the larva hadn’t eaten the developing embryo, so the acorns have sprouted and are producing roots and shoots, the latter topped with developing leaves. I’ll soon have a lilliputian oak forest on my windowsill. Although the little plants don’t have much of a life expectancy there, they do a great job of bringing the sunshine in on these short winter days.
Several years ago, herbarium director Jon Evans and students produced an interesting study on the ecological relationships between chestnut oak, deer, rodents, and weevils, as related to chestnut oak germination and recruitment. Rodents apparently don’t like weevil-infested acorns — imagine that! Also, oak trees grown from acorns that had hosted larvae, even if they germinated, often had truncated lifespans.
If you’re interested in sprouting acorns on your windowsill this winter, you can start now, even with nuts that have already put out roots. And if you get larvae too, so much the better! For more on studying acorn insects from a naturalist’s perspective, see these entomology notes from the University of Michigan.