Black Walnut Juglans Nigra
JUGLANS NIGRA – Black Walnut
Black Walnut can be extremely fast growing in warm area with rich damp soils, it can however be difficult to establish.
It has large pinnate leaves and a pyramidal habit it can reach 25m (80ft) in the UK. The nuts are also edible with a stronger earthier taste than Juglans regia, however it can be difficult to open the shell without breaking the nut.
Where to grow
Walnuts grow best on fertile soils that are deep and well drained. As the leaves are killed by frost avoid valley bottoms and any area prone to water-logging. They will not grow well in compacted soils.
Did you know?
Native to the Eastern United States and introduced in the early 17th century it makes a fine large ornamental tree in parkland.
Its timber is highly valued as it is heavy and strong but easily splits without splintering. The dark heartwood has historically been used for furniture, coffins and in the manufacture of guns. Indeed, during the American Civil War, the phrase 'to shoulder walnut' meant to enlist as a soldier
- Mature height
- Very Large - 20 metres+
- Broad headed
- Growth rate
- Soil type
- All soil types
- Sun levels
- Full sun
- Difficulty/hard to grow
- Season of interest
- Autumn colour
- Large Leaves
- Parkland Tree
- City/Urban Sites
Pruning Juglans nigra
Juglans nigra should be trained with a clear stem as this will accommodate for the slightly weeping branches. It should have a natural central leader, however dual leaders might develop. Remove competing leaders as soon as possible, either as a bud or young shoot.
Juglans do not respond well to hard pruning, and pruning of established trees should be kept to a minimum. If you do need to remove established branches, the branch collar needs to be kept.
What time of year should I prune? Late summer through to early winter. The sap rises early so pruning in late winter will result in bleeding.
For the continued healthy growth of your trees, shrubs or hedging it is vital that you follow the advice below.
The main reason that plants die within 12 months of having been planted is lack of water. It is essential throughout the spring and summer, to give a heavy enough watering to enable the water to penetrate right down to the deepest root level of the tree. In hot dry spells give the equivalent of 2 bucketfuls every three days.
One of the most common causes of lack of water is competition from grass. When trees are first establishing, the grass roots would be at the same level as the tree roots and are far more efficient at taking up water and thus choke the tree. It is vital for 3 years after planting that your tree or hedge has a circle or strip one metre wide completely free of grass. The way to eliminate grass in order of effectiveness is:
- Spray off the grass with a glyphosate based weed killer such as Roundup. Apply each year for the first 3 years. It is best applied when the tree is dormant as it is absorbed through green leaves and kills the plant off at the roots.
- Firmly fit a mulch mat around the base of the tree by tucking the edges into the soil and put a thick layer of bark mulch on top of this. This can be done after the initial spraying with glyphosate and should avoid the need for further spraying.
Mowing or strimming is NOT an answer to the problem. Each time you mow, the grass will grow back more vigorously and strimming invariably leads to lacerated trunks.
If trees are not correctly secured they will rock in the planting pit. Roots not firmly in contact with the soil are unable to take up moisture and nutrients, resulting in die back or death of the tree. Check, particularly after windy weather, that stakes are still solidly in the ground keeping the base of the trunk firm. The purpose of the stakes is to anchor the roots. Flexing in the wind, higher up the trunk, is not necessarily a problem if the roots are firm.
Bellow is list of the correct system to use to secure your trees.
- 40/60, 60/80, 80/100 whips - Unless rabbit/deer problem no need to stake.
- 100/125, 125/150 1.2m Cane and Easi tie.
- 150/175 1.2m square stake and a buckle tie and spacer.
- 175/250, 6/8, 8/10 15L 1.65 Tree stake and a buckle tie and spacer.
- All larger trees. 2 x 1.65 Tree stake and cross rail with 38mm cushion spacer and 1m of 38mm strapping.
Always use our recommended tree ties or strapping. These are designed and manufactured with the correct amount of give to hold the tree firm without strangling it. They should be checked at the end of each growing season for adjustment as the trunk thickens. Non proprietary materials such as baler twine will cut into the bark and should not be used.
Protection from Animal Damage
Rabbits, deer, sheep, cattle and horses can all potentially damage trees. Ask us for advice on the most appropriate guards for your trees or hedge. Squirrels are also a terrible pest when trees get to about 20ft tall but there is no protection available.