Mediterranean Hackberry: Planting, Growing, and Care

Description and botany

The Celtis, commonly known as Hackberry, is a majestic tree belonging to the Cannabaceae family like hemp (Cannabis sativa) or hops (Humulus lupulus). The genus includes 60 to 70 species of deciduous-leaved trees distributed in warm temperate regions of the northern hemisphere. Among them, the most widespread are the European hackberry or Mediterranean hackberry (Celtis australis), the Common hackberry (Celtis occidentalis), the Chinese hackberry (Celtis sinensis) and the Sugarberry (Celtis laevigata). In southern France and Corsica, one encounters Celtis australis, hence its other names “Mediterranean hackberry” or “Southern hackberry”, which is native to Southern Europe and Western Asia. It is very common in Mediterranean regions. It often grows in hedgerows and on hillsides, up to 900 metres above sea level, where it benefits from an environment favourable to its development.

This light-loving species, from southern regions, needs good sunlight to develop fully. In France, it is found mainly in lowland and low mountain areas, where it can enjoy optimal climatic and geological conditions. It stands out for its great longevity: the Mediterranean hackberry can live up to 500 years.

In southern regions, the Mediterranean hackberry, encouraged by abundant sunshine and mild temperatures throughout the year, is a fast-growing tree. It can reach a height of 25 metres and a spread of 15 metres, making it an imposing tree. In cooler regions, when there is a lack of warmth, it grows more slowly and moderately but will nevertheless form a robust and resistant tree, capable of adapting.

This tree with a short bole, dense and spreading to rounded habit, has beautiful dark green deciduous foliage. The leaves are alternate, ovate and finely dentate, with a length between 10 and 15 cm. They are rough to the touch and have a shiny dark green colour on the upper side, while their underside is greyish. They resemble those of nettles, hence its other nickname “nettle tree”. In autumn, the leaves turn a pale yellow before falling. The bark is greyish and smooth, marked with fine longitudinal cracks.

The flowering is discreet, in the form of greenish flowers that appear during the bud burst period. These flowers give way, in June, to small fleshy round fruits. These hackberries are green then reddish-black at ripeness, in early autumn. The drupes of the Mediterranean hackberry are edible, they have a sweet flavour. They persist all winter on the branches and are also very popular with birds, who feast on these sweet and juicy fruits.

In the past, the fruits of the Mediterranean hackberry, although small and not very fleshy, were appreciated for their sweet flavour and used to flavour liqueurs or to be eaten raw. Its flexible and resistant wood was used to make tool handles, furniture and other wooden objects. Today, the Mediterranean hackberry is mainly planted as a shade or avenue tree, particularly in cities where it provides dense and refreshing shade. Very tolerant of pollution, it thrives in urban heat islands where air quality may be poor.

Main species

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Planting the Hackberry Tree

Where to plant it?

The Southern Nettle Tree is an easy-to-grow plant. Although native to Mediterranean regions, it has shown great adaptability to different climates and soils across France. Indeed, it has begun migrating to northern regions, where it can withstand winter temperatures as low as -20°C. This is a highly resilient tree, capable of adapting to varied growing conditions. It requires a sunny position sheltered from cold winds. While it can tolerate cold, it dislikes prolonged frost periods. Let’s not forget this is a sun-loving tree that particularly needs hot summers. That’s why it’s recommended to plant it in a sunny spot protected from cold winds, especially in regions north of the Loire.

It thrives in deep, cool, well-drained soil. It can tolerate poor or slightly alkaline soils, making it an easy subject to grow in many soil types. The Southern Nettle Tree needs sufficiently deep soil to allow its roots to develop properly and withstand long summer drought periods.

Magnificent as a specimen tree, it’s ideal for planting in the middle of a park or large garden. It’s also commonly used as a street tree to line grand avenues, providing generous shade and pleasant aesthetics.

When to plant a Southern Nettle Tree?

Plant it in spring, when all risk of frost has passed, or in autumn, from September to November to ensure deep rooting before winter.

How to plant it?

• Choose a sunny position sheltered from cold winds, with deep, cool, well-drained soil.
• Dig a planting hole two to three times wider than the root ball
• Place a drainage layer at the bottom of the hole (gravel, clay pebbles) if your soil is heavy and poorly drained.
• Position the root ball in the hole ensuring the collar (base of the trunk) is level with the soil.
• Install a stake
• Backfill with the excavated garden soil mixed with compost
• Water thoroughly, then regularly to encourage establishment
• Mulch around the trunk to retain moisture and suppress weeds.

Maintenance, pruning and care

The Celtis australis requires little maintenance. It is recommended to keep the soil moist during the first two summers after planting to promote healthy growth. Thereafter, it will make do with rainwater and will not require watering. Using mulch can also help maintain good soil moisture. Once established, this tree is relatively drought-resistant.

Pruning the European Nettle Tree is not strictly necessary. However, formative pruning can be carried out on young plants to shape the framework and clear the trunk. Subsequently, pruning every three years, to be done between October and December, is recommended to maintain its harmonious shape and remove dead or damaged branches. This tree tolerates pruning well. Remove the numerous suckers that appear at the base of the trunk.

The Mediterranean Hackberry is not very susceptible to diseases and parasitic pests.

Propagation

The Hackberry can be propagated by sowing, a simple method to obtain new young plants.

If you have a specimen in your garden, harvest the seeds present in autumn. The seeds should be sown after cold stratification.

• Sow the seeds in autumn or spring under a cold frame or in a nursery and cover them with about 1 cm of compost
• Keep moist until germination, which may take over a year
• Transplant into open ground in spring when the seedlings are at least 50 cm tall

Garden Companions

The Hackberry is a majestic tree which, if left to grow freely, has a beautiful stature. It is therefore best suited to parks and very large gardens where it can be planted as a standalone specimen as a remarkable feature or in an alignment to frame a grand avenue. The ultimate shade tree, it is ideal for creating a sheltered area to rest or dine away from the sun’s intensity. You can pair it with a backdrop of evergreen bushes or conifers such as cypresses, yews or junipers, and combine it with Mediterranean perennials, bushes and southern trees (Lychnis, Salvia, Rockroses, Ceanothus, Teucrium, Phlomis and Arbustus unedo).

Acer monspessulanum, Celtis australis (photo: Claudio Gioseffi), Ceanothus thyrsiflorus ‘Repens’ (photo: A. Barra), Phlomis fruticosa, Cistus albidus and Arbutus andrachne

In the shade of this grand tree, place a Photinia serratifolia with ornamental evergreen foliage year-round. Nearby, in a large park, other trees of character can join without overshadowing it: holm oak, sycamore maple, Montpellier maple.