Black Walnut Trees

• Variety: Black Walnut, the big American timber and nut tree
• Latin name: Juglans nigra
• Sold as: Bareroot standard, 6/8 and 8/10cm girth
• Mature size: More than 12m tall and more than 8m wide, over more than 50 years
• Foliage: Large, fragrant leaves of 15 to 21 leaflets, butter yellow in autumn
• Nuts: Round green fruits about 5cm wide. Crops are unreliable north of about Liverpool
• Best soil and site: Any deep soil that drains well. Full sun. No frost pocket
• Pruning: Midsummer to early autumn only
• Neighbours: Releases juglone: keep it away from Apples and the vegetable plot
• Hardiness: H6, hardy through the British winter
• RHS AGM: Yes (1993)
• Delivered: Bareroot, November to April. Collection from Castle Cary also available

Black Walnut is a vigorous, broad-crowned American tree with ridged bark, large fragrant leaves that turn butter yellow, and rich-flavoured nuts in autumn. It holds the RHS Award of Garden Merit and wants full sun, deep soil and a great deal of room. Its roots hold back some neighbouring plants.

Black Walnut Trees

The Black Walnut, Juglans nigra, is a large, fast-growing deciduous tree with distinctive ridged bark and fragrant leaves that turn butter yellow in autumn.
It produces an abundance of nuts in the autumn: you will know that they're ready when you see lots of squirrels around your tree. The nuts are notoriously messy to remove from their husks, but the quality of the kernel is considered to be better than the common walnut that you normally see in the shops.
They're vigorous and can reach a height of about 30 metres in the British climate.

Standard trees are the largest size that we deliver; we also sell younger Black Walnut saplings as well as Common Walnut trees.
Browse our ranges of nut trees or fruit trees.

Delivery season: Walnut trees are delivered bareroot from late autumn to early spring, November to April.
Choosing a size: Small trees are cheaper, easier to handle and more forgiving of less than ideal aftercare, so they're best for a big planting project. If instant impact is your priority, or if you are only buying a few plants for use in a place where it's convenient to water them well in their first year, then you may as well use bigger ones. Our standard trees are measured by the girth of the trunk in centimetres, one metre above the ground, not by their height.

Growing Black Walnut Trees

Suitable for any fertile, deep, well drained soil, they do need full sun. If you want good crops, a sheltered location is ideal.

To keep your tree at a relatively manageable size, the standard practice is to prune out the leading stem and maintain them as an open centred goblet.

Please note: Walnuts do not crop reliably North of about Liverpool, especially on the cooler Eastern side of the UK.

Harvesting: The nuts are perfectly ripe when you can squeeze the outer hulls with your fingers and easily leave a dent. They'll start to fall of their own accord, but you can shake the tree with poles to encourage them.
Wear rubber gloves and work clothes, because they stain. Use a knife to slice around the hulls and then twist the halves in opposite directions to remove it.
Next, put the hulled nuts into a bucket of water and scrub them clean, or use a pressure hose. Discard any that float.
Dry them off (you can speed this up in a cool oven at 40°C) and store them in mesh bags for at least four weeks. Shake the bags every day at the start to ensure that they dry really well. They're now ready to eat and will keep for about a year in a cool, dry place.

Black Walnuts are infamous for preventing many other plants from growing underneath them. Here is a list of companion plants for Black Walnut.

History & Trivia

Black Walnuts are an American tree that was brought to Britain in the mid-1600's by John Tradescant. They are superb timber trees, and now grow wild in many parts of Southern England and Wales.

The biggest specimens in the world are around 50 metres tall, and they live for about 250 years.

Standard trees are measured by their girth in centimetres 1 metre above ground level: their trunk's waist measurement. Unlike sapling trees and hedge plants, standards aren't measured by their height, which will vary quite a bit both between and within species.
So, a 6/8cm standard tree has a trunk with a circumference of 6-8cm and an 8/10 standard has a trunk 8-10cm around. This measurement makes no difference to the tree's final height.
On average, standard trees are 2-3.5 metres tall when they arrive, but we cannot tell you precisely how tall your trees will be before we deliver them.

Planting Companions

Juglone rules the planting under a Black Walnut. Daffodils and Snowdrops are on the tolerant list, and Apples, Tomatoes and Potatoes are not. Common Walnut is markedly less potent, and Buccaneer is the self-fertile one to grow for nuts. For planting in number, buy Black Walnut saplings. Dust bareroot roots with Rootgrow as you plant.

Why Ashridge?

Ashridge has sold trees since 1949 and is a Which? Best Plant Supplier 2025. Your Black Walnut comes as a bareroot tree, lifted to order while dormant and guaranteed for 12 months. Plant it between November and April, and it will establish readily.

Frequently Asked Questions

How big does a Black Walnut grow?

The RHS gives it more than 12 metres tall and more than 8 metres wide, and more than 50 years to get there. It is a parkland tree, not one for a small garden.

What can you plant under a Black Walnut?

Its roots and leaves release juglone, which many plants cannot stand. Daffodils, Snowdrops, Hellebores, Hostas and ferns tolerate it. Our guide, linked above, lists more.

What should you keep away from it?

Apples, Tomatoes, Potatoes, Rhubarb, Asparagus, Peppers, Cabbage and Peas are all sensitive to juglone. Plant your Black Walnut well away from the orchard and the vegetable plot.

When should you prune a Walnut?

Only between midsummer and early autumn, while it is in leaf. A cut in late winter or spring runs with sap for weeks, and Walnuts do not tolerate hard pruning.

Is Black Walnut or Common Walnut better for nuts?

Black Walnut kernels have the richer flavour, but the husks are messy and the shells are hard. For an easier crop, plant a Common Walnut such as Buccaneer.

Will it crop in the North?

The tree is hardy, rated H6, but Walnuts do not crop reliably north of about Liverpool, especially on the cooler eastern side. Plant it there for the tree, not the nuts.

When are the trees delivered?

Bareroot only, from November to April, while the trees are dormant. You can order at any time of year and your tree is lifted and sent once the season opens.