Balled-and-burlapped plants are usually planted in the fall or spring. When started from seed, it is best to plant an acorn between mid-fall and early spring; the acorn will germinate in four to six weeks. Rather slow-growing, an English oak may live for hundreds of years. English oak contains gallotannin, quercitrin, and quercetin compounds, which can cause various digestive ailments when young leaves or acorns are eaten. This is most often a problem in areas where horses and other grazing animals feed on the leaves and nuts. The mature size for most trees will be 40–60 feet tall, though in the wild, centuries-old trees can sometimes grow to over 100 feet tall. In its early years, an English oak has a pyramidal shape, but over time it will form an irregular rounded crown. The leaves may turn brown in the autumn and may not fall off until winter.
Light
The English oak grows best in full sunlight, though it can tolerate some shade. In humid climates, full sun is more necessary to prevent fungal problems.
Soil
Quercus robur is able to tolerate a range of soil pH from acidic to slightly alkaline (pH 4.9 to 8.0). For optimal growth, find a location with soil that stays moist but still provides good drainage.
Water
English oak trees prefer regular irrigation, especially when young. A good 1-inch soaking each week, through a combination of rainfall and irrigation, will keep young trees happy for the first two or three years. An English oak can, however, tolerate relatively mild drought once it becomes established. Mature trees can get by nicely on a monthly deep watering.
Temperature and Humidity
This tree is best suited for zones 5 to 8. The tree can grow in sheltered spots in zone 4, though freezes can be damaging or even deadly. This tree does not like humid conditions, and if planted in such a region make sure to give it good air circulation and full sun to prevent fungal diseases.
Fertilizing
Fertilizing oak trees is usually not necessary if the tree is growing in good soil. If planted in barren soil, an oak tree will benefit from feeding with a product with a relatively high nitrogen content, such as a 12-6-6 formulation. For the amount to use, follow the product label instructions. Twice yearly feedings—in fall well before the ground freezes and in the spring just before new growth begins—are recommended for trees clearly in need of help. Where necessary, this feeding should be done each year for young trees, but mature trees can usually do well on a feeding every three or four years.
Types of English Oak
There are many named cultivars of English oak to choose from, including:
‘Fastigiata’ and ‘Skyrocket’ are columnar varieties that spread up to 15 feet wide, making it possible for more people to plant Quercus robur in their landscapes. ‘Pendula’ has branches that create a weeping form. ‘Filicifolia’ and ‘Dissecta’ bear leaves with a lacy look as the lobes are deeply divided into many narrow sections. As the name suggests, ‘Variegata’ features leaves variegated with a cream color. The ‘Atropurpurea’ and ‘Purpurea’ varieties boast stunning purple leaves. ‘Concordia’ offers golden-hued foliage. ‘Attention’ has a columnar shape and good resistance to powdery mildew.
Pruning
English oaks are best pruned during the dormant winter season to avoid the possibility of oak wilt infection. Up to three years old, oaks should be pruned only to remove dead or diseased branches, not to control the shape or size. After three years of age, the tree can be pruned to shape, but it is best to trim only inner branches that rub or hinder sunlight from reaching into the tree’s interior. Use of wound coatings is normally discouraged—except when trimming is necessary due to damage during the tree’s vulnerable spring and early summer period. Make the pruning cuts down close to the branch’s collar, but not so close as to damage the main branch or trunk.
Propagating English Oak
English oak does not transplant well, thanks to the long taproot, so vegetative propagation is not common. In addition, most named varieties are created by grafting, which means that rooting a stem cutting is not likely to produce an identical tree. Propagation is most often done by planting the ripened seeds (acorns), which are usually not produced until the tree is at least 20 years old.
How to Grow English Oak From Seed
As a member of the white oak group, English oaks do not require a cold stratification period before the acorns are planted. Be aware, however, that most named cultivars are grafted trees, so the acorns likely produce trees with differing characteristics. But if you want to try propagation of a pure species tree by seed, it is easy to do: Simply gather three or four acorns that have fallen from an English oak tree (fallen acorns will be fully ripe). Fall is a standard planting time, but the acorns can be stored in the refrigerator over the winter and planted in the spring. Plant the group of acorns in the location where you want the new tree to grow, at a depth about three times the diameter of the acorn. Orient the acorns lengthwise in the planting hole. Water weekly until the seeds germinate and sprout. This can take as little as one week. If more than one seedling sprouts, clip off the weaker stems, giving preference to the seedling that is healthiest. Water the seedling weekly for the first two years, until it is well established.
Overwintering
If planted within its established hardiness range, English oaks require little in the way of winter protection once they are mature. Rake up leaves as winter sets in to prevent fungi from overwintering. Young trees may benefit from protecting the trunks with tree wrap or plastic tree guards for the first two winters in zone 4 landscapes. It is best to water the tree well going into winter, but then reduce watering during the winter months.
Common Pests and Plant Diseases
This oak tree species is noted to be resistant to sudden oak death, a disease that plagues some other oak species. The biggest problem English oak faces is the unattractive presence of powdery mildew. Anthracnose can also be an issue in wet conditions, causing leaf drop. Regular fertilization will help to combat canker diseases if they prove to be a problem. Some possible diseases that do not need to be treated include shoestring root rot, leaf blister, and leaf spots.
Common Problems With English Oak
Other than powdery mildew, a non-life-threatening fungal disease that frequently occurs in humid climates, English oak is largely free of cultural issues and is less susceptible to the common diseases that can be problems with other oak species. The most common complaint is that the tree is just too massive and low-hanging for most residential landscapes. When it overwhelms a yard—which may well occur with older trees—it can be sharply pruned to raise and thin out the canopy to allow sunlight down into space.
