A plant's taproot is a straight tapering root that grows vertically down. It forms a center from which other roots sprout.
Plants with taproots are difficult to transplant.
The taproot is why dandelions are hard to uproot — the top is pulled, but the long taproot stays in the ground, and re-sprouts.
A taproot contrasts to a fibrous root, with many branched roots.
Some plants with taproots: