12 Types of Walnut Tree: How To Grow, Locations, Seeds, Growth Rate, Care

Image Credit: Krzysztof Jaracz²⁹

Walnut Tree Facts

Walnut Trees are a great option if you are looking for a shade tree in a lawn area. They usually grow into large canopies if you plant them in open areas.

There are over 21 different types of Walnut Trees but this guide examines the 12 different types that grow in the US.

(Image: No-longer-here²⁰)

Here are some Walnut Tree facts you didn’t know:

Even though the Walnut family (Juglandaceae) has a wide variety of trees, people use the term Walnut when they are talking about two different trees; the Black Walnut and the English Walnut. The origins of the English Walnut, also called the Persian Walnut, is Iran, while the Black Walnut comes from North America.¹

Walnut Trees are deciduous, which means that when they are in dormancy, their leaves drop. They can live for more than 100 years.

These trees are widely cultivated for their high-quality timber and nutritious nuts. The timber is used indoors, in car interiors, in furniture, and in the gun industry.

The English Walnut is grown more for nuts than timber while the Black Walnut is grown mostly for timber.¹⁰ The trees mature in two to three decades after planting.

The average height of a Walnut Tree is about 80 to 120 feet (25-35 meters). You should be careful of what you plant with Walnut Trees because they make chemicals that are harmful to other plants such as Apple, Blueberry, Alfalfa, Potato, Tomato,es and many more.

The seeds of a drupe are called Walnuts and can be eaten dried or fresh. The nuts are widely used as additives in several confectioneries and also in the baking industry.

You can find Walnuts in cereal bars, ice creams, and many other snacks and sweets.

Walnuts are also used in the production of edible Walnut oil. The world leaders in Walnut production include Turkey, the United States, Iran, and China.

According to the Black Walnut Tree value calculator, cabinet and furniture makers have prized the close-grained wood of the black Walnut Tree because it has exceptional durability, is easy to work with, and has an attractive color. The logs are in high demand for veneer so much so that in the past, ‘Walnut rustlers’ stole these trees in the dead of the night.

Another interesting fact about Walnut Trees is that when surrounded by other trees (ie. In forests) they grow tall and straight with few if any, lower branches. When growing in open spaces, the trees branch out closer to the ground and develop a low canopy that makes it easier to harvest the nuts.

How To Identify Walnut Tree: What Does Walnut Tree Look Like?

If you are a resident of any central or eastern state in the US, then you’ve probably seen Walnut Trees at some point in your life. These trees are common in parks, dense wood, creeks, and in low-lying areas between rivers.

The most common Walnut Trees in the US are Butternut or White Walnut Tree, Black Walnut Tree, and the English Walnut Tree.

Because they come from the same family, they have certain similar features. However, you can differentiate among them using leaves and barks.

You can also taste the Walnuts they produce to determine which tree they come from.

What does a Walnut Tree look like? Typically, Walnut Trees are deciduous and broad-leafed and they can grow up to 4o meters or 120 feet. In most cases, they have short trunks and broad crowns.

However, they grow thin and tall when planted in woodland situations.² Their barks are olive-brown and smooth when young but they develop fissure and turn silver-gray as they mature.

Their twigs are green stout and curving.

If you want to know how to identify a Walnut Tree, the steps below will show you.

#1: Observe the Walnut Tree Leaves Color

During the summer and spring seasons, the leaves of a Walnut Tree are either green or slightly yellow. In the winter and fall, the leaves turn bright yellow or brown not orange or red like most trees.

Walnut Tree leaves appear later in the spring when leaves from other trees have already bloomed and drop ahead of other trees in the early fall or late summer. All Walnut Trees including Black Walnut, English, and Butternut have the same leaf characteristics.

Additionally, the leaves of the Walnut Tree are feather-like and pinnate.³ Each bed usually has two to nine leaflet pairs and another leaf at the tip.

If you crush the leaves of a Walnut Tree, you will get a distinct citrus spicy aroma. If you compare the three most common Walnut species, Butternuts have oblong-lanceolate leaves while Black and English Walnuts have rounded and shorter leaflets.

#2: Examine the Twigs and Leaflets of the Trees

You should look for rigid, stout twigs that hold an odd number of leaflets; a pair on each side of the twig and one at the top. The leaves will range from 5 to 25.

In most Walnuts, the edges of the leaflets are either serrated or toothed. However, the English Walnut does not have toothed leaves.

The twig center has the largest leaflets. Butternut Trees have slightly longer leaflets while the English Walnut has fewer leaflets than other Walnut Trees.

You should also check whether the leaflets are significantly staggered. Leaflets in Walnut Trees occur in an alternating fashion (staggering like a staircase).

In the English Walnut, the leaflets are more spaced out than in other Walnut Trees. As a result, the leaflets have a feather-like appearance.

The twigs should also have a small or large terminal leaflet. In Butternut Walnuts, there’s always a large end leaflet that sticks out in line with the twig.

English Walnuts also have a terminal leaflet that is smooth rather than serrated. The terminal leaflet of a Black Walnut is generally smaller than the rest and protrudes and the tip of the twig.

When you slice open the twig of a Walnut Tree length-wise, you will find that the inside is chambered. There are small chambers separated by vertical fibrous walls called pith and this is a distinguishing factor of a Walnut Tree.

#3: Examine the Walnut Tree Fruit: What Is a Walnut?

You need to examine the Walnut Tree fruits. They are usually oblong, or round green fruits that grow on thin branches.

First, you should answer the question: what is a Walnut Tree fruit? It’s definitely not the nut in the brown shell that you are used to seeing in stores.

Instead, the brown shell is enclosed inside a larger husk that is usually lime in color and the size of a small tennis ball.

(Image: Konevi²¹)

These husks grow 2 to 3 close to where the twigs with leaves shoot off from the thin branches. Bear in mind that it takes years before Walnut Trees start producing fruits.

The Black Walnut Trees start producing walnuts when they’re 4 to 7 years old. The Butternuts and the English Walnuts take 2 to 3 years and 4 to 10 years respectively.

The most bountiful Walnut harvest occurs when the tree is over a decade old.

Black and English Walnut Trees have round Walnuts while Butternuts produce fruits that are oblong and papaya-shaped. You may have to climb high in the trees to examine the fruits because the trees can grow up to 120 feet and the plumage is often found high on the trunks.

Moreover, if you want to identify a Walnut Tree, you can check for husks around the area. Birds and squirrels like to go to these trees to eat their fruits.

Therefore, next to a mature Walnut Tree, you will find scattered husks and shells around the trunk.

You may also find small mounds of dirt that have been freshly piled because squirrels have buried their nuts there. You can check for shells in the seasons when the tree is active as opposed to the winter when the tree is dormant and there are no fruits available.

#4: Look Closely at the Walnut Tree Bark

Depending on the species, the barks of Walnut Trees are either dark and ridged or light and smooth.³ English and Black Walnut Trees have deep gray barks with rounded ridges and deep furrows that run vertically up and down the trunk.

Butternut Trees on the other hand have light gray barks that are relatively smooth.

Inside the gray outer bark of an English or Black Walnut Tree, there’s a rich chocolate brown wood. Black Walnut Trees in particular, have dark gray or brown barks while Butternuts have white-gray barks.

This is a great way of identifying Walnut Trees, especially in the winter when the leaves of the trees have dropped and they are not producing Walnuts.

#5: Check for Yellowing or Dying Plants Around the Tree

Black Walnuts, and several other species of Walnut Trees are allelopathic. This means that they produce chemicals that flow to the ground and poison plants that are up to 60 feet away.

If you find a tree standing alone without neighboring bushes or other trees, chances are it’s a Walnut Tree.

English and Butternut Walnut Trees also produce this plant poison though in much smaller quantities. As a result, other nearby shrubs and trees can survive and grow next to these trees.

Additionally, a few other trees can tolerate the toxins produced by black walnuts they include but are not limited to:

• ElM
• Willow¹¹
• Black cherry
• All types of Oak: Any of the 10 types of Oak Trees can grow well with a Walnut Tree
• Sycamore
• Redbud
• Yellow Birch
• Red Maple
• Japanese Maple

Types of Walnut Trees

The most common Walnut Trees are the Butternut, English, and Black Walnut. These three species grow widely in North America.

Even so, Southeastern Europe, Asia, and South America are home to other Walnut Tree varieties. The black Walnut Trees are grown for their wood while the English Walnut Trees are grown for both wood and nuts.

The 12 common types of Walnut Trees are listed below:

Black Walnuts in North America are also called the eastern American or the American Black Walnut. Most of their populations are found in woodland and forests from northern Florida to southern Ontario.

They can live up to 130 years.

Black Walnut Trees have large pinnate leaves with rounded wide crowns. If grown in open places, the tree branches close to the ground and spreads several meters.

The branches and trees produce a pungent citrus-like odor when crushed. They also bear both sexes of flowers.

The male flowers are in the form of long catkins that dangle from the limbs of the tree while the female flowers occur in short spikes.

The fruits of a Black Walnut are usually green and globe shaped resembling green tennis balls as soon as they finish blooming. They are usually 2 inches or 5 centimeters in diameter.

When the fruits fall off the trees they are usually rough green spheres. These spheres darken to a black or deeply brown color after some time.

The hard shells usually protect the edible nuts inside them.

Black Walnut Trees secrete hazardous chemicals into the soil. This is one of their most common identifying traits.

They have black barks and deep ridges that are diamond shaped. They have pinnately compound leaves that have 15 to 23 leaflets each.

These leaves have lanceolate or ovate shape with a somewhat serrated border.

There’re a few identifying characteristics that distinguish Butternut Trees from other Walnut Trees. First, their fruits are oval rather than spherical.

They have a lesser heat tolerance than Black Walnut Trees. While Black Walnuts have an earthy flavor, Butternut Walnuts have a buttery flavor which is how they got their name.

Butternut Walnut Trees also release toxic chemicals to the soil though not as potent as Black Walnuts. These trees have a gray smooth bark when young and a rough fissured bark when they mature.⁵

Their leaves are lanceolate and oblong with varying lengths from 5 to 12 inches. These leaves also have pointed tips and are serrated along the edges.

The leaf stems also have a terminal leaf.

They are the primary source of Walnuts sold in North American markets. Other names for the English Walnut Trees are the Carpathian Walnut, Madeira Walnut and the Persian Walnut.

Their natural environment is southern Europe which is how they got their names. They are usually grown in zones 5 to 9 in full sun.

Similar to Black Walnuts, English Walnuts produce spherical drupes with really great seeds. Their fruits look like green tennis balls when they’re on the tree.

However, once they fall off, they turn nearly black. Their Walnuts have a pleasant flavor.

They can be eaten raw though in some European regions, they are pickled.

English Walnut Trees have fissured and deep bark and they range from brown to gray. They have pinnate blades with 9 leaflets and at the tip, there’s a single blade.

The leaves are 4 to 7 inches long. The English Walnut Tree has fewer leaflets than the Black Walnut and Butternut Trees.

Walnut Tree Identification: Pictures of a Walnut Tree

There are several types of Walnut Trees that have different characteristics.

However, the general rule of thumb is that they are fast-growing trees with large canopies that reach up to 18 meters in width and 30 meters in height.

They grow well in warm areas that have full sun. Below is a picture of a Walnut Tree.

When Are Walnut Tree Seeds and Walnut Tree Flower Produced?

Walnut Trees awaken their buds from winter dormancy in April to May but this depends on the cultivar. The leaves begin to fall in early November.

These large compound leaves produce a lime/lemon scent especially when they are crushed.

The flowers of Walnut Trees open either before or at the same time as the leaves. Each tree produces both male and female flowers therefore Walnut Trees are monoecious.

(Image: Lindenbluete²⁶)

The male flowers appear as catkins while the female flowers are much smaller and are usually found on the branches’ tips. The trees use the wind to carry out pollination.

The seeds of walnut trees are found inside the tree. They are usually covered by husks and they are eaten by both humans and wild animals.

How To Grow a Walnut Tree

You need to be patient when growing a Walnut Tree because they start producing good nuts after more than 10 years.^8,16 Additionally, you need to consider the consequences of growing Walnut Trees in your garden because they can take away nutrients from other plants or they can produce toxins that are harmful to other plants.

Nevertheless, if you still want to learn how to grow a Walnut Tree, you should take the following steps:

1. Collect seeds: Collect fresh Walnuts and get rid of the outer skin from the shells. You can buy the seeds either from a grocery store or harvest them from a tree growing in the wild
2. Prepare the seeds: It’s important to wear gloves when dealing with Walnuts because they produce substances that may irritate the skin. Soak the Walnuts in water for two to three days to make it easier to remove the outer shells.
   You can also choose to use a pocket knife to cut into the softened skin as long as by the end of the process, you have Walnuts that still have their brown shells
3. Cold stratify the seeds: The next step is cold stratification where you force the seeds to become dormant by stimulating winter conditions. This process jump-starts the germination of the Walnut seeds.
   You will have to place the nut shells in a container that is airtight and place it in a refrigerator for three to four months. Or place moist peat moss together with the nut shells in a sealed plastic bag
4. Check for sprouts: in about three to four months, the Walnut seeds will start producing small sprouts which will poke out on top of the shells. If you find sprouts, open the container and place the sprouts in a moist area
5. Determine a planting site: Find a place where the tree will get direct sunlight. Make sure it also has rich well-drained soil and there’s no vegetation or large rocks around it.
   You need a lot of space to grow Walnut Trees because they always have root systems that are deep and twining
6. Plant the seedlings: Once the Walnut seeds develop into seedlings, you should plant them three inches into the ground and cover them with soil. The seeds should be planted 12 feet apart
7. Water the seedlings: When it comes to growing a Walnut Tree from a seedling, once you’ve planted the seedlings, you should water them immediately and do so regularly until they are well into their maturity

Walnut Tree Growing Zone and Walnut Tree Growth Rate, Location, and Care

Depending on the species, Walnut Trees grow from zone 4 to 10.

For instance, Walnut Trees with Persian and Middle East origins grow well in Zone 5 (-23 degrees Celsius), and in contrast, those that originate from Carpathian can withstand even lower temperatures of -32 degrees Celsius or Zone 4.

You should not plant these trees in high latitudes because the climate can damage their flowers and shoots either through frost damage in the spring or early frost in the autumn.

Walnut Tree Pollination

Walnut Trees are monoecious which means they have both female and male flower parts on one tree. The trees shed pollen from male flowers that fall into the female flowers.

They produce very light and small pollen that can travel quite a distance when blown by the wind. In some cases, they can go as far as a mile away.

Fertilization occurs when the pollen produced by the male flowers settles on the female flowers at their receptive point. In some cases, the time the male sheds pollen does not coincide with the time the female flower is receptive to pollen.

This condition is known as dichogamy.¹⁷

To overcome dichogamy, a Walnut Tree grower should choose another Walnut pollinator or cultivar that has male flowers that are open at the same time as the female flowers in the main cultivar. The pollinator must be upwind from the main cultivar for the pollination to be successful.

Almost all commercial orchards have a wide variety of pollinators to ensure enough pollen is produced to create nuts in the main crop. Experts recommend planning one row of pollinators to be planted upwind for 8 rows of main crops for optimal pollination.

Propagation

Growing a Walnut Tree from a seed reproduced in the wild is easy. If you grow a tree from this seed, it will start to produce fruits well after a decade.

There’s no certainty that it will have the same features as the parent tree. Growing a Walnut Tree from a cutting is also possible.

If you graft walnut cultivars, they will start bearing fruits in the fifth year. Since almost all cultivars are 2 years old at the time of purchase, the trees will start bearing fruits in the 3rd year after planting.

Where To Plant Walnut Trees

Here are the best-growing conditions for Walnut Tree.

• Location: Walnut Trees thrive in sunny areas and open places. You should avoid frost pockets completely
• Soil: You should plant Walnut Trees in fertile, deep, and well-drained loam soil. The required pH is 6 through 7 though they can tolerate 4.3 up to 8.3
• Inhibitors: Most Walnut Trees produce growth inhibitors. They are called juglone and they are disastrous to some plant species that grow nearby.¹⁸
  Juglone affects the respiration of plants, deprives the plants of needed energy, and reduces the ability of the plant to take in water and nutrients. However, several plants are not affected by juglone and can be co-planted with Walnut Trees
• Walnut pollination: You need to consider a pollination partner when planting your Walnut to maximize yields

Irrigation, Fertility, and Care of Walnut Trees

Here’s what you need to know about irrigation, fertility, and care of Walnut Trees.

Fertility

Experts advise not to add compost to Walnut roots during planting. You may add just a little top-dressing compost after the trees are newly planted.

In the 2nd year, you should add about 10 liters of comport at the tree base in the spring when the growing plants have increased nitrogen demands. If you add too much nitrogen, then your tree will be susceptible to Walnut blight.

Irrigation

This is only necessary in areas that receive less than 600m of rainfall per year and there’s uneven distribution throughout the year. Watering needs for Walnut Tree plants are very minimal.

(Image: InnSite_2²⁷)

You should not use a sprinkler to water your plants because splashing water can facilitate the development of Walnut blight.

Weeding

When the trees are young, you should weed regularly because they are intolerant to competition, especially grass. You can also mulch them annually with straw or card but you must keep the mulch from getting on the collar to prevent it from rotting.

Walnut Tree Disease Prevention

Walnuts can encounter the following problems:

Sunburn

This occurs in excessive summer heat of above 38 degrees Celsius and the kernels usually darken and shrivel up. The problem increases if the tree is under moisture stress.

Cold Injury

Young Walnut Trees are extremely susceptible to damage by frost. Early frosts can destroy flowers.

As such, it’s important to choose cultivars that flower late if the trees are growing in areas that experience early frosts.

Pest/Insect

Common pests of the Walnut Tree include:¹⁹

• Codling moth
• Nematodes
• Mites
• Aphids
• Walnut husk fly
• Navel orange worm

Diseases

Walnut Trees are susceptible to the following diseases:

• Blight
• Crown gall
• Deep bark canker
• Crown rots
• Root rot
• Blackline

All these problems are preventable if you take proper care of your Walnut Trees.

(Image: WikimediaImages²⁸)

Bottom line, if you want to grow Walnut Trees you must choose USDA zones 4 to 10 depending on the species. You’ll need to have well-drained loamy soil, sufficient sunny days, and open space to properly grow Walnut Trees.

Once you get things going, a Walnut Tree can be a great addition to your landscape lasting more than a century.

Frequently Asked Questions About Walnut Tree