Watering black walnut

• Black walnut origin
• Black walnut care and location
• Cutting black walnut
• Fertilizing black walnuts
• Watering black walnut

Black walnut origin

The black walnut (juglans nigra) is a species of walnut native to North America and belongs to the walnut family (Juglandaceae). Its natural habitat extends from the Great Lakes in the north down to the southern Appalachians and the middle Mississippi River basin. It grows primarily in floodplain forests, along riverbanks, and on deep, moist soils with good drainage.

The first written records of the black walnut come from Native Americans, who used the nuts as a valuable food source and valued the durable, dark brown wood for making tools, arrows, and boats. The black walnut also played an important role in early American settlement history—as a source of shade, tasty nuts, and high-quality timber.

In the 17th century, the black walnut tree was brought to Europe by European settlers. Initially, it was cultivated in botanical gardens, later also in parks and larger gardens. Because of its straight growth, deep taproot, and extremely valuable wood, it was also deliberately cultivated in forests. Its wood is among the most expensive domestic precious woods; it is hard, has a decorative grain, is easy to work, and is particularly durable.

Botanically, the black walnut differs significantly from the native walnut (Juglans regal). Its leaves are longer, more finely pinnate, and darker green. The fruits – round, green nuts with a very hard shell – are smaller than walnuts but extremely aromatic. They are difficult to crack, but contain an intense, oil-rich kernel with a deep, nutty flavor.

A remarkable aspect of the black walnut is its ability to exhibit allelopathy. It secretes a substance called juglone through its roots and foliage. This inhibits the growth of many neighboring plant species—particularly nightshade plants such as tomatoes and potatoes. This makes it a demanding tree for mixed plantings, but also very assertive in solitary positions.

Today, the black walnut is found in Europe primarily in parks, on agricultural land used for timber production, or occasionally in large gardens. Its imposing appearance, expansive canopy, and exotic character make it a fascinating solitary tree with a rich history.

Black walnut care and location

The black walnut is a heat-loving, deep-rooted tree that requires plenty of space. It prefers sunny to slightly partially shaded locations with deep, nutrient-rich, and moist soils. Ideally, sandy loam soils with good drainage that can retain moisture evenly without waterlogging are ideal.

When young, the black walnut grows relatively slowly, but with age it develops a strong root system and impressive height growth – it can reach up to 30 meters tall. Its broad, rounded crown is particularly beautiful when grown alone. However, it is out of place in small gardens.

A layer of mulch around the trunk helps retain soil moisture and protect the root zone. Due to their allelopathy, sensitive companion plants should not be planted too close together. Perennials or grasses adapted to dry, juglone-rich soils are a better choice.

Cutting black walnut

The black walnut tolerates pruning but requires little shaping. Regular pruning is usually not necessary. Remove dead, damaged, or troublesome branches ideally in late fall or winter, when the tree is dormant and producing less sap.

Training pruning in the first few years after planting can be beneficial to promote a stable and evenly developed crown. Attention should be paid to good light penetration and a balanced distribution of the main branches. Excessive pruning in summer can impair development.

Important: Always use clean and sharp tools to keep the cuts smooth and prevent infection. Since the wood is very dense and hard, pruning older trees can be strenuous—so consider early on what shape you want the tree to develop in the long term.

Fertilizing black walnut

A regular fertilization is not absolutely necessary for black walnut in good soils. The tree prefers nutrient-rich, humus-rich soils with a slightly acidic to neutral pH. In poor locations, you can incorporate compost, horn shavings, or farmyard manure in the spring to increase soil fertility.

Avoid over-fertilizing with nitrogen-rich fertilizers—these promote excessive, soft shoot growth, which is more susceptible to disease and frost. Soil compaction from heavy machinery should also be avoided, as black walnut grows deep but is sensitive to disturbed soil structure.

An annual Mulching From leaves or bark humus can help bind nutrients in the soil over the long term, promote soil fauna, and improve water retention. This keeps the tree vital and vigorous even without intensive fertilization.

Watering black walnut

When young, the black walnut is regular watering This is especially important during the first two to three years after planting. Keep the soil consistently moist, but not wet. Waterlogging can damage the delicate roots, and drought stress can severely retard growth.

Mature trees are much more tolerant of drought periods thanks to their deep taproots. However, occasional, thorough watering is recommended during long dry periods to maintain soil life and prevent cracks in the soil.

The water supply is particularly efficient with the baumbad watering bagThis is placed around the trunk, zipped shut, and filled with 75 to 100 liters of water. The water is slowly released into the soil over several hours – exactly where it should reach the roots.

The system reduces water loss through evaporation, ensures a deep water supply, and saves time and effort. Especially for newly planted young trees or during hot summers, the baumbad watering bag is a worthwhile investment to promote the growth and vitality of black walnut trees.