Oregon grape, Mahonia aquifolium – care and pruning

Mahonia can be planted in spring and autumn. Before planting, you should water the root ball well. Meanwhile, a planting hole can be dug, which should be a little deeper and wider than the root ball of the plant in question. Then the plant is placed in the planting hole, so deep that the upper end of the ball sits just below the surface of the earth.

Now it is filled with excavated earth, the earth is pressed down well and the whole thing is watered thoroughly. In the case of loamy soils, it is advisable to mix the excavated earth with horn shavings, compost or mulch material. This loosens the soil and optimizes the growing conditions. The Oregon grape is very often planted as a hedge. Here, planting distances of around 50 cm between the individual plants should be maintained.

Location and soil

• The Oregon grape grows very well in both sunny and partially shaded locations.
• This makes them a particularly easy-care wood.
• It also makes no special demands on the floor.
• This can be sandy to humus but also rather dry to moist.
• Heavier soils are also suitable.
• Loamy soils can be improved with horn shavings, compost or mulch, for example.

Watering and fertilizing

The first time after planting or from spring to autumn should be watered regularly, especially on warmer days. However, the Oregon grape copes well with drought. It should be poured in the morning if possible. This allows the excess water to evaporate throughout the day. When watering, care should be taken not to wet the leaves with water. Otherwise, stains may form on the leaves. Too much moisture and waterlogging should be avoided at all costs, both of which could lead to rot.

Fertilization is not absolutely necessary for the Oregon grape. However, if the stinging nettle manure is particularly poor, you can give it yourself. Potted or container plants should only be fertilized one year after repotting, from April to September about every 4-8 weeks with a liquid fertilizer.

To cut

The Oregon grape is easy to cut. As a rule, a cut is not absolutely necessary, but it is recommended. March, for example, is the right time to cut out dead or frozen wood. In June, after flowering, a so-called rejuvenation cut can be made on this wood.

The bush or twigs are cut back about a third to a height of about 40-50 cm. It is best to always cut just above an outward-facing bud. In the following year, the remaining older branches are cut.

A cut is seldom necessary for a dense hedge, as the oregon grape is one of the slow-growing trees. However, if no wild growth is desired, hedge plants must be cut back regularly. A cut into the old wood is also very well tolerated. A pruning should also be done here at the beginning of June. This allows the plant to form new leaves before winter so that the cut leaves can no longer be seen.

These plants can even tolerate radical pruning down to a few centimeters or a total pruning. Thanks to their branched root system, they keep sprouting.

Overwinter

• As a rule, the Oregon grape aquifolium is well hardy.
• It can withstand temperatures of up to – 30 degrees.
• However, you should protect them from the morning winter sun.
• In particularly cold and dry winters, the Oregon grape sheds its leaves.
• This protects the plant from drying out.
• Because in the frozen earth it is not able to absorb water from the ground.
• A layer of peat or leaves on the root area can protect against particularly severe frosts.

Propagation by sowing

The Oregon grape mainly reproduces itself, either through subterranean runners or through seeds that are spread by birds. However, they can also be sowed by hand and thus propagated. However, in contrast to division or cuttings, this does not result in single-variety plants. These differ in vigor and shape as well as in the shape of the leaves from the mother plant.

Propagation by sowing is somewhat more complex than, for example, straight-link propagation, because the seeds must first be stratified, ie subjected to a cold treatment, in order to remove the inhibition of germination and to stimulate germination.

To do this, the seeds are first placed in a moist substrate and the whole thing is placed in the refrigerator for 2-4 weeks, covering the seed tray to prevent the substrate from drying out. After this time, the whole thing is put in a warm place in a bright place.

To avoid mold, the substrate should be briefly ventilated regularly. In order to keep the substrate moist despite everything, it should be sprayed from time to time. It can then take about 12 weeks for germination. Before the seedlings are finally planted in the garden, they should be hardened slowly.

Propagation by cuttings

The corresponding cuttings are cut from the plant in late summer or early autumn. They should be half lignified and about 20 cm long and are put in a partially shaded place in the earth where they take root. Then they are lightly watered. Too much moisture should be avoided, otherwise the cuttings could rot. Once the cuttings are rooted, they can be planted in their final location in the garden.

Propagation by runners

The Oregon grape forms subterranean runners through which the plant reproduces itself. But there is also the possibility of separating these runners and replanting them elsewhere and thus propagating the Oregon grape.

Multiplication by division

Another form of reproduction is division. To do this, the plant is carefully dug up and divided with a spade, for example. The new plants obtained in this way are then planted separately.

Diseases

Powdery mildew
As a rule, Oregon grape aquifolium is very robust and relatively resistant to diseases and pests, but if the location or care conditions are unfavorable, it can become infested with powdery mildew or downy mildew. Powdery mildew can be recognized by a white, flour-like coating on the upper side of the leaves as well as on the stems, flowers and buds.

A number of beneficial insects, such as some species of ladybirds, are helpful in controlling powdery mildew. If the infestation has not progressed that far, it can help to remove and dispose of the infected parts of the plant. In addition, this fungus can be treated with silicic acid and non-containing sprays.

Downy mildew
Downy mildew is also a fungus that, in contrast to powdery mildew, which only occurs superficially, penetrates the plant tissue. Signs of downy mildew are a whitish coating on the underside of the leaves and yellow, brown or purple spots on the upper side of the leaves.

The control is similar to that of powdery mildew. In addition, you can support the fight by spraying with homemade brews made from onions or garlic.

Rust diseases
The Oregon grape aquifolium can also be susceptible to rust diseases in dry locations. If this is the case, pustules of different colors form on the leaves and stems. These can go from creamy white to yellow, orange and red to brown or black.

In the event of an infestation, the affected plant should be severely cut back and the clippings removed completely and disposed of, as well as fallen leaves. To prevent infection, the plants should be watered well.

Nice varieties

• Mahonia aquifolium ‘Apollo’ – This variety is an evergreen, broad and low-growing dwarf shrub that reaches heights of 60-80 cm. The dark green leaves are up to 30 cm long and are brownish both when budding and in autumn and winter. The flowers are deep yellow and appear in very large panicle-shaped racemes from April to May. This variety is suitable for container planting but also as a ground cover and for low hedges.
• Mahonia aquifolium ‘Atropurpurea’ – The particularly frost-hardy variety ‘Atropurpurea’ grows as a dwarf shrub about 60 cm high and 1 m wide. The deep yellow flowers appear from April to May. The foliage of this Oregon grape turns reddish brown in autumn. It is suitable as a ground cover, for planters and low hedges.
• Mahonia aquifolium ‘Smaragd’ – This variety is also a dwarf shrub that grows around 80 cm high and 1.50 m wide. The 25 cm long leaves are emerald green all year round. The flowers are deep yellow and appear in large, dense racemes from April to May. This variety is also suitable for planters, low hedges and as a ground cover.

Special features
Apart from the berries, almost all parts of the plant are poisonous. They contain up to 1.5 percent berbin and other alkaloids, whereby the proportion in the berries is only 0.05 percent. The highest proportion is found in the root and trunk bark. Because of their high acid content, the berries of the Oregon grape taste very sour.

While the berries are edible when cooked, for example in the form of jam, they are slightly poisonous when raw. They are unsuitable for children from 1 to 3 years of age. In their case, consumption could lead to slight symptoms of intoxication. This wood is also said to be poisonous for rodents such as guinea pigs, hamsters and dwarf rabbits.

Conclusion
The Oregon grape aquifolium is an evergreen plant that impresses with its large, yellow flower clusters in spring. It is very easy to care for and is suitable both as a stand-alone position in a planter and for hedge planting and as a ground cover. It also comes into its own between other flowering shrubs. It reproduces itself through seeds and root runners, but can also be propagated through division or cuttings. In optimal conditions, it is relatively resistant to diseases and pests.