Oak

Read the oaks in two groups before reading any cultivar, because the split decides what the tree is for.

The white oak group matures its acorns in a single season, and those acorns germinate in autumn at or shortly after they fall. They carry markedly less tannin than the other group, which is what makes them the food oaks. The red oak group takes two years to mature an acorn, drops it in autumn, and germinates the following spring, and its acorns are considerably more bitter. A planting made for people or livestock is a white-group planting. Bur oak, swamp white oak, white oak and chinkapin oak are where that search starts.

Neither group is an annual crop. Oaks mast: years of light to moderate production hold the populations of acorn-eating animals down, so that a heavy year produces more acorns than anything present can eat. That is a reproductive strategy, and it is also a yield forecast. Designing around oak means designing around a crop that is genuinely absent some years.

The reason this file is shaped the way it is comes down to propagation. Oaks are hard to graft — reported success in the literature runs around half to two-thirds on species like northern red, white and chestnut oak, well under what an orchardist expects from a fruit tree, and European nurseries respond by growing the species from seed and offering only a handful of grafted forms. Where a plant cannot be cloned cheaply, cultivars do not accumulate. Chestnut has hundreds of named selections; oak, after two thousand years of cultivation, has a shelf of columnar street trees.

So the named oaks in commerce are overwhelmingly urban and ornamental: selected for narrow form, for mildew-resistant foliage, and — read this one twice if you came for the crop — for smaller acorns, marketed as less litter on the pavement. Most of them are patented, and most are sold under a trademark rather than under the cultivar name. The handful of selections actually made for edible acorns are barely a list, and the best known of them is propagated as a seed strain rather than as a clone. Both kinds are recorded below, because a grower reading a nursery tag needs to know which kind they are holding.