The tree hazel from Asia Minor and Southeastern Europe is a robust tree that has been used in central Europe in extensive parks and to fortify slopes since the 16th century. The fruits, which are not unlike the local hazelnut, stand out particularly striking. As a pioneer plant, Corylus colurna requires little maintenance. If you want to cultivate the shade provider in the garden, little need to be considered. The tree with its upright growth can easily cope with domestic winters and delights the gardener in autumn with its golden yellow foliage.
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- The leaves are ovate to heart-shaped and can reach a length of up to 20 cm.
- Flowering time is between February and March.
- Female flowers are inconspicuous red; the male catkins are yellowish and up to 12 cm long.
- The shells of the hazelnut-like fruit are slashed and covered with sticky glandular hairs.
- Has a flat, furrowed, gray-brown bark.
- The leaves turn golden yellow in autumn.
- The fruits, known as “witch nuts”, are popular in domestic kitchens and in the aquarium hobby.
Location and substrate
The deciduous tree from the birch family likes it sunny. Its natural habitat ranges from the Himalayas through Asia Minor to Southeast Europe. There the plant prefers to grow on stony slopes, but can also be found in sparse mixed forests. Corylus colurna is now widespread in Central Europe and is planted in parks or occasionally on roadsides in many places. The sturdy tree can cope with the urban climate without any problems, even a high volume of traffic at its planting site does not harm it. The tree, also known as “Turkish Hazelnut” or “Byzantine Hazelnut”, has considerable problems with shady and moist locations. The growth and development of the tree hazel visibly suffer from the lack of light.
The tree hazel is not very picky about the substrate. With the right soil, however, growth can be optimally promoted:
- Tolerates weakly acidic to strongly alkaline soil.
- The substrate must be permeable and rich in humus.
- A sandy to loamy soil is ideal.
When choosing the right location, space plays a not insignificant role. Corylus colurna can reach a height of up to 20 m. As a heart root, the root network of the tree extends a few meters below the ground and can damage pipe work or other large, deep-rooted plants. The stable roots make the upright tree interesting for fastening steep slopes and sloping properties.
Fertilizing and watering
Older trees are able to draw nutrients and water from the deeper layers of the earth with their extensive network of roots. The younger specimens of the tree hazel cannot do this yet. The young plants are particularly hard hit by hot summer days. Up to the age of about 5 years, the plant with the pyramid-shaped tree crown must be watered regularly during the hot spell. Regular watering makes more sense than a weekly supply of large amounts of the valuable fluid. As a result, the soil cannot dry out completely and the tree hazel has sufficient water available. If you pour into the blazing midday sun, there is a risk that the moisture will evaporate too quickly. For this reason, apply the water in the early morning or evening hours.
- Avoid waterlogging.
- Mulch the soil regularly.
- Cover with horn shavings and / or brushwood if necessary to minimize evaporation.
- There is no need to water in winter.
The robust tree hazel has no objection to a supply of nutrients. Liquid fertilizer is rather unsuitable for deciduous trees. Organic material, such as bone meal, compost or lawn clippings, has proven its worth. It is fertilized in spring and late summer, but no later than mid-August. Then Corylus colurna prepares for the approaching winter and stops growing. An excessive amount of nutrients is putting a strain on the plant. It makes more sense at this time to cover the ground with brushwood or, if available, withered leaves. The material decomposes only slowly, warms the soil and slowly releases nutrients and minerals to the substrate.
Tip: Trees can rarely cope with compacted soil. For this reason, regularly loosen the soil around the tree hazel.
Corylus colurna is an impressive pioneer plant. With a height of several meters, it dominates its location. The tree hazel has a slender habit for a tree. For this reason, if you want to cultivate the plant with the hazelnut-like fruits in the garden, you should keep a certain minimum distance to buildings, above-ground power lines and underground pipe systems. With increasing growth, later moving the tree is hardly possible or associated with considerable effort and costs. Plan a minimum space of around 4 m – 6 m. This is especially true when several of the plants are to be cultivated next to each other. This is easily possible in larger gardens.
The tree hazel is extremely fast-growing in the first years of its life. An increase of up to 65 cm is not uncommon. The deciduous Corylus colurna is an ornament in the home garden with its heart-shaped to egg-shaped foliage. If you own a hillside property, you can stabilize the soil through the trees with the failed fruits through the root network of the tree hazel. Whether for ornament or utility: In both cases, the site must be adequately prepared for planting. The best time to do this is in February / March or between September and October. Outside the main growing season, the tree can put its strength into developing the roots. Planting is only done in the frost-free time, a thick layer of compost or sackcloth protects and warms the freshly planted plants.
Trees need a sufficiently large planting hole. It is advantageous if this is twice the circumference of the root ball. This measure benefits the roots. The weave, which is still sensitive at the beginning, can develop and take root better in the loose soil. To plant the hazel tree, do the following:
- Dig the planting hole.
- Mix the excavated earth with humus, clay and small amounts of sand.
- Soak the bare-root tree in lukewarm water for a few hours before planting.
- Insert into the planting hole up to the upper root neck and fill back the substrate.
- Regularly press the soil into place, thereby eliminating voids.
If the soil tends to be very compact, you should mix some pebbles with the substrate. Rainwater and irrigation water can drain into the ground more easily, and the risk of waterlogging is minimized. The soil must not dry out for the first 14 days after planting. Due to the high proportion of humus in the substrate, the hazel tree does not have to be fertilized in the first few months. The first nutrient supply is made after three months at the earliest.
A pouring rim around the trunk has proven itself. This consists of earth, which is piled up in a conical shape around the lower end of the tree and pressed flat at the top. The diameter should be at least 50 cm. Over this area, the irrigation water and rainwater can more easily get to where it is urgently needed. The pouring edge must not be planted in order not to restrict its function.
The propagation of Corylus colurna is unproblematic and takes place via cuttings or seeds. In addition to some materials, such as poor substrate, patience and time play an important role in the cultivation of the tree hazel.
Cuttings: One of the three ways to propagate the pioneer plant. Propagation by cuttings is tricky. Strong roots develop in only about 70% of the removed shoots. For this reason, you should always root several cuttings at the same time to increase the chances.
- Cut slightly woody shoots over a length of 30 cm.
- Completely remove the lower pairs of leaves and buds.
- Cover 2/3 of the shoot with poor substrate or potting soil.
- Keep evenly moist.
You can cut cuttings in spring and autumn. In the cold season, the sensitive shoots must be protected from frost. Rooting directly in the bed is most likely; a large planter has also proven its worth. Whether and when the development of the roots is complete can be easily recognized by the formation of new leaves and buds.
Seeds: Immediately after ripening in autumn, the hard fruits can be used to grow a new generation of tree hazel. The sowing takes place in the field.
Tip: To protect them from garden animals such as squirrels and birds, you can protect the seeds in a tall planter with a close-meshed wire screen.
- Cover the nuts minimally with conventional garden soil.
- Do not let the substrate dry out.
- Cover minimally with withered leaves in severe frost.
In the warm spring, the first green shoot tips of the germinating nuts usually appear. To increase the chances of success here too, several nuts can be sown at once.
In the first few weeks, the “Turkish nut” must be protected from other, fast-growing plants. When the young plants have reached a height of 15 to 20 cm, they should be separated.
The question of how and whether the tree can be brought safely through the cold season does not usually arise in the case of Corylus colurna. The tree hazel is insensitive to frost and cold. Even double-digit minus temperatures or freezing temperatures cannot harm older plants.
Young trees or trees newly planted in autumn gratefully accept a warming layer of organic material. Brushwood has proven itself here as well as compost and bark mulch. Alternatively, burlap can be used. This will generously cover the lower part of the trunk and part of the substrate.
Corylus colurna is sensitive to strong back and thinning cuts. For this reason, the sturdy tree cannot be used as a hedge. You don’t have to do without pruning shears and saws here.
- Remove branches that are growing transversely – the water shoots.
- Cut out sick and dead wood.
- Do not remove branches close to the trunk, about 10 cm can remain.
- Seal the edges of the wound with a special herbicide in damp weather.
Functioning and well-cleaned tools are one of the most important work utensils of the passionate gardener. The devices come into contact with many plants. For this reason, it is important to thoroughly clean and disinfect the tool at regular intervals. This reduces the risk that diseases and pests can spread unhindered in the garden.
Tip: Cut young shoots can be used immediately as cuttings.
Diseases and pests
Pests such as spider mites or aphids play a rather subordinate role in large deciduous trees. If the hazel tree is healthy, the cell sap-sucking pests cannot cause any significant damage to the plant. The control is also difficult and dangerous due to the height of growth. The measure to promote the habitat for the natural predators of the insects, such as ladybirds and predatory bugs, is more beneficial.
However, a fungal disease can affect the tree hazel. The Verticillium wilt attacks the root system of the tree and penetrates from there into the interior of the plant. The deciduous tree takes care of the toxic secretions of the fungal pathogens and dies completely within a few years. There are no effective cures for Verticillium wilt. To protect the fungal spores from spreading, the entire tree, its roots and the substrate should be completely removed.
The tree with the golden yellow leaves in autumn and the distinctive fruits is an undemanding garden companion. Only the location and the space required have to be right so that the birch plant, which grows up to 20 m high, feels comfortable. A robust shade provider whose hazelnut-like fruits can enrich the home kitchen.