Tanoak reproduces prolifically by  vigorous sprouts that appear at practically any time under a wide  variety of conditions (3). Sprouts may start to grow after a  relatively minor basal injury, after bark has been stripped from  the trees for tannin extraction, or when the aerial parts of the  tree are destroyed by fire or logging (22). Even healthy trees  sometimes sprout.

   

Sprouts develop from conical woody buds that lie under the bark at  the base of the tree. Most of these buds are found on burls below  the groundline. Because the number of buds varies from few to  thousands, the number of sprouts also varies. As many as 1,400  have been counted on one large stump. The only mechanical damage  that prevents sprouting is stripping the bark below the ground  level to expose the buds.

   

Sprouts from burls grow rapidly in a wide range of environments.  In clearcuts, they have reached 1.7 m (5.6 ft) the first year and  4.1 m (13.6 ft) after 5 years. The microclimate within sprout  clumps is quite different from the microclimate immediately  adjoining them (21). Sprout growth is reduced somewhat by a  conifer overstory (13). The size of parent trees between 3 and 43  cm (1.3 and 16.8 in) in d.b.h. determined the height and diameter  growth of sprout clumps, and the number of sprouts in a clump.  The larger parent trees produced greater sprout development.  Sprouts are reduced drastically in numbers early in their life  and growth is concentrated on the dominant stems. In the first 15  or 20 years, sprouts grow an average of about 0.6 m (2 ft) in  height a year. Often, a circle of four to eight slender  30-year-old poles grows around the stump of a parent tree. These  poles may average 30 to 38 cm (12 to 15 in) in d.b.h. (24).  Thinning all but 2 to 4 sprouts per clump of 3 to 10-year-old  sprout clumps did not increase height or diameter growth of the  remaining sprouts, largely because rapidly growing new sprouts  quickly replaced those that had been cut (14).

   

Leaf area, total above-ground biomass, height, clump width and  area, and number of stems 1 to 6 years after cutting were  statistically correlated with parent tree diameter at 1.4 in (4.5  ft) before cutting or burning (9). Thus, sprout clump size and  total stand cover can be predicted from stand stocking tables  before harvesting or burning either conifer stands with a tanoak  understory or pure tanoak stands (30).

   

Although not growing as fast as sprouts of some associated  hardwoods, such as bigleaf maple and madrone, tanoak sprouts are  significant competitors because they are usually abundant,  especially in conifer stands. Tanoak sprouts often quickly  dominate the vegetational cover after logging or fire. Although  this ability helps reduce soil erosion, tanoak sprouts often  provide severe competition to conifer reproduction and may  suppress it. The thick, stiff, flat, leathery leaves often cover  young conifer seedlings or cover the ground so thoroughly that  conifer seedlings cannot emerge above them (20).

   

Propagation of tanoak by grafts or cuttings has not been reported.

   

Tanoak sprouts can be controlled by herbicides applied to frills  on the stems, to stumps of freshly cut stems, or to foliage of  young sprout clumps (32).