few vertical, deep-anchoring roots. A typical mature tree 30–50 m tall has a root system that extends horizontally in all directions as far as the tree is tall or more, but as much as 100% of the roots are in the top 50 cm of soil. Soil characteristics strongly influence the architecture of taproots; for example, deep and rich soils favour the development of vertical taproots in many oak species such as Quercus kelloggii, while clay soils promote the growth of multiple taproots. Horticultural considerations Many plants with taproots are difficult to transplant, or even to grow in containers, because the root tends to grow deep rapidly and in many species comparatively slight obstacles or damage to the taproot will stunt or kill the plant. Among weeds with taproots dandelions are typical; being deep-rooted, they are hard to uproot and if the taproot breaks off near the top, the part that stays in the ground often resprouts such that, for effective control, the taproot needs to be severed at least several centimetres below ground level. Gallery References External links Fullerton Arboretum on taproots Plant roots