| General Description | The Valley Oak is a long lived, fire-retardant, deciduous tree that is native to California and is endemic (limited) to the state. It is a very large and very fast growing tree. The Valley Oak is one of the largest oak trees in all of North America, and can be found throughout valleys and slopes of California below 610m in elevation. This large growing tree can reach ages up to 800+ years old. It has bright green leaves that turn to a yellow-orange colour in autumn, along with yellow blooms of flowers hanging from the tree. |
| ID Characteristic | The leaves are covered in hairs called cilia, which gives them a fuzzy feeling that resembles a peach. The fruit is also much larger than other oak trees, which gives off easy to identify characteristics. |
| Shape | The tree has a rounded, spreading and irregular shape to it. It has a high branch growth habit, which is the reason the crown of this tree is so wide spread and large. As the tree matures with age, the branches start to slightly droop, giving off a slight weeping shape. |
| Landscape | The Valley Oak doesn't have too many landscape uses other than the main use of being a general landscape tree. The tree is very large with a very large crown size, so typically it will be too large for residential use. It can be used as a backdrop landscape tree in parks, as an ornamental landscape tree and also as large shade trees. This tree is also commonly used in bird and butterfly gardens as it attracts certain birds and insects. |
| Propagation | The main way of propagating this plant is through seeding. Seeds should be directly sown into the ground during autumn. This plant requires hypogeal germination which is the method of germinating seeds below the surface of the soil. Caring for this plant is very easy, as it can withstand both dry and moist soil conditions, and doesn't require much watering due to the tap root system. It does not need anything done prior to germination. Seedlings and saplings may also sprout from the crown root when the aboveground portion is damaged. |
| Cultivation | This tree will show the most growth and be in the best health in full sun conditions, but can also be grown in moderate sun conditions. The tree produces the most acorns possible in full sun, which helps re-establish propagation, an area in which it lacks. It is an easy to care for plant and is commercially available for the average person to grow on their own. It is best to plant somewhere close to a water source, although you cannot provide irrigation from within approximately 9 metres away, as they can absorb too much water, causing branches to break. Ideally these trees also grow best when water tables are 10 metres below the surface. Can be grown in slightly acidic soil to high alkaline soil pH ranging from 6.0-8.0. |
| Pests | Most Valley Oaks are or will be infected with Armillaria mellea (Heart rot fungus), but the disorder is typically only fatal in mature trees. Another disorder that is commonly found in Valley Oak trees is the infestation of acorns by filbert worms and filbert weevil. This disorder puts a strain on the germination rate of infected acorns, as roughly 58% of insect-infected acorns will still germinate and grow without problems. Leah Hoppers are an insect that is a pest of the Valley Oak tree, as they feed on the bottoms of leaves which essentially sucks out juices from the plant. The insect causes leaves to yellow, curl, stunt, and distort plant growth, and can also create white spots on foliage due to the toxicity of their saliva. Pests that don't physically damage the tree itself, but still do have a role in the decline of these trees, are squirrels that eat their acorns. Due to their large size of fruit, squirrels typically choose to go for this acorn over others. The amount of squirrels that are contributing to this is far too great for the amount of fruit that is actually produced, which is why there has been a decrease in the plant's numbers directly related to a drop in germination. |
| Habitat | The Valley Oak grows the best in a Mediterranean climate, which consists of dry summers with wet and mild winters. The tree is found growing throughout the Inland valley (Southern California
region) and floodplains as it contains deep, rich soil that the plant thrives in. It is commonly found growing on slightly angled slopes throughout the region.
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| Bark/Stem Description | The bark is a thick, dull-brown to a slight grey colour with a slight rippled-fissured texture that almost resembles alligator hide. The stems sometimes resemble a slightly yellow colour but are mainly grey in colour. |
| Flower/Leaf Bud Description | The flower/leaf buds found on the stems of this tree are light brown and ovoid in shape. They are in an alternate arrangement on each side of the stem located at the base of each flower or leaf. |
| Leaf Description | Leaves are a vibrant matte green that are slightly pale green on the underside, which turn a yellow-orange colour in autumn. Leaves are simple, round, deeply lobed and covered in fuzz. Leaves grow roughly 5 to 10 centimetres in length and roughly 2.5 to 5cm in width. The base of the leaf is a wedge shape and the tip of the leaf is obtuse. Leaves also produce a nice odour that resembles a forest scent if they’re rubbed or broken. |
| Flower Description | This is a monoecious flowering tree with male and female flowers on the same tree. The flowers and leaves on this tree start to grow at the same time. It blooms from March to early May, and produces nice, bright yellow-green coloured catkin flowers that hang down from the tree. |
| Fruit Description | The Valley Oak produces a nut type fruit called acorns, which are roughly 3 to 7.5cm long and 1 to 2cm wide in a pointed ovate shape. The fruit has a cap at the top where it connects to the stem. The acorns of this specimen are larger than most other acorns found on trees in the same genus, giving it an easier ID characteristic. The acorns will normally fall from the tree or ripen in October. |
| Colour Description | This tree has a very nice colour both in summer and autumn. The leaves are a bright, rich, almost matte-green colour during summer time, changing to a vibrant, golden-yellow to a bright orange colour in autumn. |
| Texture Description | Smooth leaves, with coarse/rough textured bark. |