Were it not for the bur oak, pioneers in the Midwest would have been greeted by nothing but waving prairie grass. Instead, they also were welcomed by invitingly open groves of wide-spaced trees. Beneath the trees' dropping boughs grew a soft green carpet. What a relief from the East's tangled forest! Yet, little did the pioneers know of the great battleground they had entered.
Botanists now understand that the bur oak -- called that because of the fuzzy cap on its acorn -- was in constant combat with the tall prairie grass. In periods of dryness, the grass advanced. When it was wet, the forest gained, led by the bur oak.
Prairie fires, too, kept the oaks at bay. Then, with settlement, came cattle to pack down the soil so acorns had trouble sprouting. Livestock also ate the young seedlings' leaves. Yet, the bur oak survived due to its remarkable roots.
If you were to somehow peer beneath the ground under a bur oak, you'd discover a vast system. A relatively short taproot soon turns to a spreading maze of thick, horizontal roots. Each of the horizontals sends capillary roots down and up until the size of the entire growth below ground equals that of the tree above! Such a root system rises to penetrate even the deep-rooted prairie grasses to catch the slightest rainfall and remain in competition. In fact, the bur oak's prime competitor is another bur oak. That's why they always grow some distance apart -- the diameter of each tree's roots determining their closeness.
Illurstration: Jim Stevenson