Bur oak

Profile

Family

Fagaceae

Habit

Tree

Height

15 m

Spread

8 m

Growth

very slow

Lifespan

400 years

First yield

after 35 years

Hardiness

zone 3–8

Shade tolerance

partial shade

Soil

Silt, Loam, Clay

Soil moisture

very dry – very moist

pH

5 – 8

Synonyms

Großfruchtige Eiche, Bur-Eiche

Flowering & harvest

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Uses

Edible: The seed of this species is notably large, with dimensions of around 5 cm x 4 cm, although its size and shape can vary. It can be crushed into a fine powder and utilized in baking bread, making dumplings, and as a soup thickener. Regarded as one of the most flavorful among oak trees, many trees bear sweet seeds low in tannin, suitable for raw or cooked consumption. Bitterness in the seed is attributed to the presence of tannins, which can be removed by washing the dried and ground seed thoroughly in water, albeit resulting in some mineral loss. Traditionally, the seed was prepared by burying it in damp soil during winter, with the germinated seed unearthed in spring, having shed most of its astringency. When roasted, the seed serves as a coffee alternative.

Medicinal: All galls produced on the tree have astringent properties and can be used to treat bleeding, chronic diarrhea, dysentery, and other conditions.

Other uses: A layer of oak leaves can deter slugs and maggots, but avoid using fresh leaves to prevent hindering plant growth. Oak galls, formed by insect larvae, provide nutrients and can be utilized for tannin and dye once the insect matures. Oak bark was historically employed as a mordant in dyeing processes. Known for its hardness, weight, strength, toughness, and durability, oak wood finds applications in construction, basket making, flooring, carpentry, shipbuilding, and as a fuel source.

Propagation

Seed viability decreases rapidly when it dries out. It is recommended to sow the seeds right after they mature in an outdoor seedbed, ensuring protection from rodents. Alternatively, seeds can be stored in a cool, moist place over winter. For small seed quantities, deep pots in a cold environment can be used. The plants form a strong taproot and should be relocated to their final position promptly. Ideally, trees should be directly sown in their permanent spot for optimal growth. It is advised not to keep trees in a nursery bed for more than two growing seasons to avoid difficulties during transplantation.

Notable

Special features: drought, pollutant, fire, wind, and pest resistant; heat-loving; freely hybridizes with other oak species: great cross-breeding potential! Cuttings bear fruit after just a few years; no precise, differentiated data can be found regarding the yield and calories of this acorn species; probably the same as for common oak: 1500 kWh/m³; 4.1 kWh/kg

Origin & habitat

Eastern North America - Nova Scotia to Manitoba, Wyoming, Massachusetts, Georgia, Kansas, and Texas.

Forests and shrubs in arid, rocky areas.

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