Walnut trees are more than just their delicious nuts. They also sport an amazing tree profile especially for their shade spread and their ornamental value. It is the cousin of hickory and pecans. It also comes with a lot of cultivars which you would find interesting if you are thinking of planting your own walnut tree in your yard.
In getting to know this tree more, here is some information that you may find handy later. So, if you are interested in everything about walnut trees, you have come to the right post because we will rundown everything for you.
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Facts about walnut tree
Before we roundup the types of walnut trees, here are some interesting facts about the tree that you should know about.
- Walnuts grow in a height that is the same as their spread.
- All walnut trees contain a toxic substance called juglones. As such, no vegetation should be grown underneath or beside it. Some walnut types are not that harsh. Of the types, black walnuts have the most juglones.
- In ancient Greece, the walnut was called ‘karyon’ or skull because its seeds are brain-shaped.
- Walnut seeds are high in oil maintaining its buttery or earthy taste for long.
- Walnuts are vitamin rich (A, B, E, and K) and mineral rich (iron, magnesium, and phosphate).
- The leaves of the walnut tree are harvested and processed because they are beneficial in decreasing glucose levels.
- The green pigment of the husk is used for textile dyeing.
- Walnut shells are used in adhesive and plastic production.
- Walnuts could live to up to 250 years.
- Walnuts are extracted for their oil (used as salad dressing) and to produce nocino liqueur.
How to identify walnut trees
There are three key characteristics that you should look out for to identify a walnut tree. The trick lies on the leaves, bark, and nuts of the walnut and here are the features that you should know about.
Walnut tree leaves
All walnuts share pinnate, feather-like leaves. Some types like the English walnut have rounder and shorter leaves while the butternut have oblong, lancing leaves. The leaves are arranged in 2-9 pairs in a branch and some types have a single leaflet brimming at the tip. They have a distinct citrus aroma when sliced.
Walnut tree bark
Walnut barks are in between dark gray to brown. When the bark is peeled, you would find chocolate brown wood. They have rough, deep fissures all over with ridges vertically running along the trunk. Some species like the butternut have smooth, whitish gray barks, though.
Walnut tree nuts
The nuts of this truth are actually called a drupe. It is not the walnut’s fruit but its seed. This fruit is covered with a fleshy, green colored husk, enclosing a shell containing the seed that we consume as walnuts. Walnuts take the shape of the brain and strikingly, are also known as brain food because they help in memory, and cognition. The taste is earth and sweet.
Walnut tree symbolism
The walnut is also a well-referenced tree in a lot of literature including the bible. It is one of the oldest trees out there and is well-archived in literary texts. Here are other tree symbolisms that you should know about.
- Its botanical name Jupiter regia literally translates to Jupiter’s nuts. With Jupiter as the highest deity in Roman mythology, walnuts are associated with abundance, good fortune, and prosperity.
- In ancient Greece, walnuts are associated with fertility and are eaten by maidens who want to get married and be pregnant immediately and of women who cannot conceive. This is reaffirmed in one verse in the Bible found in the Song of Songs.
- In Roman literature, walnut trees are associated with grief and sorrow because all plants that are planted near it die.
- For Native American tribes, walnut trees are associated with clarity, discernment, focus, and wisdom because of its brain-shaped seeds.
- In Bulgarian folklore, the walnut is a symbol of new life.
What do walnut trees look like?
The walnut is a large deciduous tree, with broad leaves. It has a single base, dark brown bark, smooth at youth and rough, deep fissured, and dented when mature. When broken, it reveals chocolate brown wood that is prized for timber.
Its leaves are feather-like and finely serrated at the edges. It produces a broad canopy and is known for its fruits with green husks and brain-shaped, edible seeds. I
How many types of walnut trees are there?
There are at least 21 types of walnut trees. The most popular ones would be English walnut, the California black walnut, butternut, little walnut, Andean walnut, and Japanese walnut. Walnut tree types are native across Asia (especially in China), as well as in North America and Europe.
What is the difference between black walnut and English walnut trees?
Being the two most popular walnut types out there, it is important that these two be differentiated. If you are wondering how they are different, this is a table of comparison of the black walnut and the English walnut.
|Black walnut||English walnut|
|Taste||Earthy||Buttery and mildly earthy|
|Shell||Harder||Easier to crack|
|Wood||High-grade lumber||Grown for its nut and not for timber|
|Bark||Rough and grooved bark||Smoother and softer bark|
Types of Walnut Trees
There are almost two dozen walnut types out there but listed here would be the most popular and are considered high-value walnuts. If you are looking for the best walnut for your landscape or just curious about the best walnut types out there, here is a roundup of some of the most popular walnut trees.
1. Andean Walnut (Juglans neotropica)
As the name implies, this slow-growing walnut is native to the Andes, specifically in Columbia, Ecuador, and Peru. It is also called as the cedro negro and the Columbian walnut. They are distinct for their red-colored inner wood which is a high-prized timber in the lumber industry.
The bark is dark-gray with deep fissures and vertical furrows. It could reach a height of 130ft and is now listed as endangered in its native range. It is rarely found in the US.
2. Arizona Black Walnut (Juglans major)
This one is relatively small compared to the other walnuts with a max height of 40-50ft and a spread of up to 65ft. It is distinct for its tiny, earthy-tasting nuts. Its bark is deeply fissured, with gray-brown color, horizontal furrows, and flat ridges. Its leaves are pinnate, oblong, and lancing.
Each branch has 9-15 leaflets. Its native habitat would be riverbeds and ravines. As such, it is also called the river walnut. It is native to Mexico and the southwest US.
3. Black Walnut (Juglans nigra)
As the name suggests, the black walnut has a deep, fissured bark that is darker than the other types. It also sports diamond-shaped ridges. It grows in moderately cool to subtropical climates at around 75-130ft. It has the same spread length. It is also called the American walnut and can live for up to 130 years.
It produces catkins in the summer and both the stems and leaves smell citrusy. The downside among black walnuts is that they ooze out a toxic chemical which contaminates the soil.
4. Brazilian Walnut (Ocotea porosa)
This one grows in hardiness zones of 10-11 and is native to Argentina and Bolivia. It grows to up to 80ft, known for its straight trunk, and is known for its prized lumber which is used in hardwood flooring.
As a matter of fact, it is considered as the hardest walnut (even harder than white oak and ironwood). While it grows rarely in the northern hemisphere, it is cultivated ornamentally in more tropical climates in the US and Europe.
5. Butternut or White Walnut (Juglans cinerea)
This one is notable for its whitish-gray and smooth bark that turns rough and more deeply fissured at maturity. They are smaller in height compared to the black nut as they only reach a max of 66ft and grow in cooler and more temperate climates.
It is also distinguishable for its oval nuts (compared to the round nuts of most walnuts), and their foliage is composed of fewer leaflets.
While they thrive in full sun, butternut cannot tolerate too much heat. The seed of the butternut is more buttery than earthy, hence the name. Unlike the black walnut, butternut is gentle on the soil.
6. California Black Walnut (Juglans californica)
This one is the shrub version of the black walnut that grows either in a single stem or multiple stems. It thrives in warm climates into heights of 20-60ft. It is distinguishable for its dark gray, and very thick bark with distinct, deep furrows running vertically down the trunk.
Its leaves are smooth, olive green, and glossy. It has 10-20 pairs of leaflets per branch. It is native to Southern California with nuts that are bland and earthy.
7. English Walnut (Juglans regia)
The English walnut has an olive-colored, smooth bark at youth and turns dark gray, rough, and deeply fissured at maturity. It grows at 65ft max and it is an important walnut because it is where commercially sold walnuts come from. It is also called the Madeira walnut or Persian walnut because this tree’s native habitat is southern Europe.
It produces round drupes that turn dark brown or black when they fall to the ground. In Europe, its drupes are pickled and are considered as a native delicacy. It has pinnate leaves with a solitary leaflet at the tip. Compared to butternut and black nuts, the English walnut has fewer leaves.
8. Japanese Walnut (Juglans ailantifolia)
This one is often confused with butternut because they have the same oval shaped leaves and butter-flavored nuts. The bark is also deeply fissured but with a lighter gray bark, and distinct grooves that look like webs. It reaches a height of 66ft and it has a unique heart-shaped, edible nuts instead of the usual round nuts.
The leaves are composed of 11-17 leaflets per branch, with a coarser texture and lighter green color than other walnuts. Its flowers are salmon pink and bloom during spring. It is also called the heartnut.
9. Little Walnut (Juglans microcarpa)
It is also called the Texas black walnut and is more of a large shrub than a tree. It grows at a max height of 30ft and thrives in warm climates. Its fruit might be edible but is insignificant because it is more prized for its timber. Its bark is light gray to dark brown, with deep fissures, and furrows that run in random patterns.
The leaves are slightly serrated, deep green in color, glossy, with 7-25 pairs in each branch. It has drooping branches and forms a rounded crown on top. Its native habitats would be riverbeds and ravines.
10. Manchurian Walnut (Juglans mandshurica)
This is the most cold hardy walnut, thriving in temperatures of up to -45C. It is native to Eastern Asia and is grown more as an ornamental shrub because its fruits are too small to be harvested and eaten. Its bark is grayish-brown, and the leaves are pale green in color.
Each branch is composed of 3-9 pairs of leaves with a terminal leaf at the tip. It is fast-growing, reaching up to 60ft (sometimes even at 100ft). It is also called the Chinese walnut and unlike other walnuts, it does not contain any toxic compound.
11. Northern California Black Walnut (Juglans hindsii)
This one grows from a single trunk at a height of 60ft. It has a short and bulky look with a crown that is wider than the tree. Its foliage is composed of 13-21 pairs of leaflets per branch and are unique for their coarse texture and serrated margins.
This one is popular in the lumber industry because of its high-grade inner wood. However, this is also the reason why it has been listed as endangered in California. It is also called the Claro walnut or the Hinds’ black walnut.
Where do walnut trees grow best?
Walnut trees grow in a range of climates but specifically in well drained, deep, and fertile soils. It also tolerates alkaline, loam soils. It does not thrive in windy and frosty areas (but they could only tolerate up to -2C). They generally grow in warm temperatures where they could get full sun but some walnut types could also thrive in harsh winters.
How to grow and care black walnut trees
Black walnuts have a growth rate of 2ft annually and reach 75ft in height. To grow black walnuts, here are its care requirements.
- Sun: Walnuts need at least six hours of direct sunlight every day. It can tolerate partial shade and dappled sunlight in the afternoon. Avoid planting in areas where frost accumulates or where it gets too windy.
- Soil: It requires deep, well-draining and fertile soil. It loves acidic soils but could also thrive in slightly alkaline ones. It is, however, sensitive in soils with too much sodium and chlorine. It would not survive in hilly terrains.
- Water: It does not fare well in dry conditions, so you have to know these two walnut watering guides. One, it needs one inch of water every week and two, it requires 2 inches of water during the summer months.
- Fertilizer: Black walnuts benefit from two types of fertilizers. Apply ammonium sulfate during early spring to give it its needed nitrogen supply and then apply a 15-15-15 fertilizer during summer. Make sure that you water the tree every after fertilizer application for the nutrients to run deep down to the roots.
Walnut trees pests and diseases
Walnuts are not perfect and not generally disease resistant. Here are the most common walnut tree pests and diseases that you should be on the lookout of if you have a walnut orchard at home.
- Walnut bunch
- Caterpillar infestation
- Aphids (gall aphids)
- Codling moth
- Cigar case bearer
- Bark beetle
- Walnut blight
- Leaf rollers
- Husk flies
The silver lining to this is that some are quite hardy like the black walnut and English walnut. And given proper care and maintenance, these would not even be a problem.
When do walnut trees bloom?
Depending on the walnut type, the walnuts’ catkins bloom in late spring, particularly between mid-April to late May. The leaves of walnuts fall by November and enter dormancy all winter.
When to prune walnut trees?
The best time to prune walnuts would be during the last weeks of winter while it is at its last phase of dormancy and preparing for budding in spring. Through this, you can easily maintain the shape of the tree and would not disturb new growths for spring.
Harvesting walnut trees
Again, depending on the type, it takes 3-7 years before walnut seeds could be harvested. The best time to do the harvesting when it is time would be late August to mid-September. To harvest walnuts, you must shake the tree for the hulls to fall. Gather them up before they turn black.
English walnut trees growth rate
The English walnut is a fast-growing walnut. It has a steady growth rate of 2-3ft per year. This walnut type self-pollinates. They are prized for the commercially sold walnuts they produce and are relatively resistant to common walnut diseases.
How fast do black walnut trees grow?
Black walnuts grow in the zones of Ontario, South Dakota, Georgia, Texas, and Florida. They grow at a rate of 3-4ft per year. This fast growth habit allows the black walnut to reach a height of 100ft and a shade of 40ft.
Can you eat walnuts from a walnut tree?
Most walnut trees have edible seeds. As a matter of fact, you can crack the shell and eat the seeds right away. The best tasting walnut seeds would come from the English walnut trees. They have a rich buttery and earthy taste compared to the more bland and more earthy tastes of other common walnut types.
How much are black walnut trees worth?
As have been mentioned previously, black walnuts are not prized for their seeds but for their high-grade wood. Having been significant in the lumber industry since the 1700s, one black walnut can cost to up to $20,000. In timber value alone, an acre of black walnuts can have a minimum price of $100,000.
How long do walnut trees live?
Walnuts are also known for their longevity aside from their prized nuts and high-grade wood. At an average, walnuts live for 40 years. Some types get to live for 100-150 years and some notable ones like the black walnut lives to up to 250 years.
How far apart to plant black walnut trees
Regardless if it is for timber production or ornamental landscaping, the rule of thumb is for black walnut trees to be planted at 30ft apart. Remember that they have a deep root system and a branching root growth habit. With this spacing, you can plant 48 walnut seedlings per acre of land.
Plants that grow under walnut trees
There are only a handful of plants that could thrive being beside the walnut tree. This is because of the toxic component of the tree called juglone. As such, plants that also love acidic soils are most likely to be planted under walnut trees like the following:
|Eastern Red Cedar||Hazelnut||Hosta||Beets|
|Black Cherry||Juniper||Morning Glory||Corn|
|American Elm||American Holly||Lobelia||Onion|
You can find a full list of plants that you can grow with walnut trees here.
Where to buy black walnut trees?
With everything that we have covered here, you might have been convinced of buying one. If you ever want to give it a go, you can always check local nurseries (as well as university nurseries) for black walnut seedlings. For online stores, here is a list of stores that you can check:
- Nature Hills
- Arbor Day
- Ty Ty Nursery
- Fast Growing Trees
- Willis Orchards
- Greenwood Nursery
- Tree Plantation
- Burnt Ridge Nursery
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