How to Plant, Grow and Care for White Walnut

If you have like uncommon crops, why not try growing a classic tree like the fantastic butternut? They’re struggle a bit in the wild due to a particularly deadly fungus, but are often fine in the home garden.

A North American native, the butternut is a hardy deciduous, and perfect if you want a medium to large-sized tree. It readily produces tasty, creamy nuts that are hard to find in stores.

Plus, the tree could do with a helping hand to survive into the future.

Interested in delicious food and protecting heirloom species? You can’t go wrong with butternut trees.

What is a Butternut tree?

Butternut trees (Juglans cinerea) are often called white walnuts or oilnuts and are native to the eastern US and Canada. They still grow wild there, but they’re seen less and less often `due to a fungal disease that is infecting a majority of butternut trees.

Butternuts are called white walnut and they’re related to other plants in the walnut family, including black walnut. They look similar to black walnut, but the bark is smoother and the nuts are oval, instead of round.

Treat this tree right and it will provide you with a huge harvest of rich, creamy nuts. Interested? Then let’s go.

Varieties of Butternut

There aren’t any cultivars to choose from, just the main species. There is, however, a hybrid combining the native butternut and the Japanese walnut (Juglans ailantofolia). This hybrid has some resistance to canker disease, which we will talk about later.

If you live in an area where the fungal canker disease is an issue, consider planting the hybrid over the standard species.

Planting and Propagating Butternut

Talk to experts in the nurseries and gardening centers around you before planting. Find out if canker is an issue in your area and consider whether to plant butternuts or a resistant hybrid.

The best way to plant butternuts is to purchase a sapling from a local nursery. If you’re like me though, you will want to save money and propagate one yourself from a nut. There is a little bit of work involved, but it’s worth it.

Propagating a Butternut with a Nut

In the fall wait until the nuts have fallen to the ground and collect the healthiest ones you can find. They should be free of blemishes and rot, and a decent size.

Remove the husk from the nut, making sure to remove as much as possible without damaging the shell. If you find this difficult, you can soak the nut and husk in water for 12 hours.

To make sure the seed nuts you’re using are viable, submerge them in water, and discard the ones that float to the top. They are unlikely to germinate.

Wash the nuts with a bleach and water mix to prevent mold growth over the process. Use one part bleach and 10 parts water. Place the seeds in a colander and wash with the bleach mix. Then rinse the nuts in freshwater for about 20 seconds.

Place the seed nuts in a container containing moist sand, vermiculite, or sphagnum moss. This medium must remain moist throughout the whole stratification and germination period.

Store the container in a fridge or cool garage at around 40ºF. It needs to be kept there for 90 to 120 days to ensure successful stratification. Check the seed nuts regularly over this time. You don’t want mold to grow. Discard any moldy nuts or sand.

Once the stratification time is complete, you can plant the seeds directly into the soil, or as I prefer, into pots so I can watch what will take. Do this in spring when the temperature is consistently warm. Germination rates vary and can take anywhere between 14 to 80 days.

Use deep pots, sometimes called tree pots. I just used seed-raising soil, but some gardeners use a coarse mixture of coir mixed with bark, vermiculite, or peat.

Allow the growing medium to dry out in between watering, but only down to the first inch or two.

How to Care for Butternut

Butternuts grow well in USDA Growing Zones 3 to 7.

If there was ever an anti-shade plant, butternut would be it. It needs full sun and it’s even best to plant it away from other tall trees to avoid them casting their shadow over butternuts.

When they grow naturally in the wild, butternuts are always found in areas of moist soil, especially around streams.

The soil should be very rich in organic matter. The pH level you need is 6.8 to 7.2. Limestone soils that are deep are ideal.

Water butternut well. It needs at least one inch per week, so if your natural rainfall doesn’t match that, use irrigation. If you have a dry spell, make sure you water your butternut tree and don’t allow the soil to dry out for long.

You can grow butternuts in pots, but for no more than a year. This is due to the extensive root system. After a year, carefully transplant it to its permanent spot in the ground.

Keep the area around the tree free from weeds for a few years at least. When you do the wedding, make sure not to damage the bark of the butternut. It will become susceptible to canker disease.

Fertilizing and Pruning

When the butternut first germinates, I feed the soil with a good liquid fertilizer. After that, you only need to fertilize when there is a deficiency in the soil, or the tree is struggling.

When the butternut tree is young, you can prune it for shape and to allow in light and air. Remove any diseased or damaged branches.

As the tree grows the crown can start to grow downwards with branches facing the ground. Remove those or the branches will reach so low you can’t even walk under the tree.

Companion Planting for Growing Butternut

Remember butternut’s disdain for shade? It’s best to keep it away from any tree that will cause it to sit in the shade.

Also, this species of tree releases a chemical that is toxic to many other plants, especially apples. The chemical is juglone and is released by the root system of the butternut tree. It stops many species from growing well around it.

If you can, keep a clear boundary around this tree or grow juglone-resistant plants.

Problems and Solutions for Growing Butternut

No article on the butternut tree can avoid talking about the biggest problem for this tree – butternut canker disease.

This disease has decimated the butternut numbers, and many areas where this tree grew prolifically are now devoid of it. It’s a serious issue and I recommend talking to experts in your area to understand the local impact.

There may be specific rules made by local authorities on growing butternut trees, so make sure you know them and comply with them.

For instance, there may be retention rules where the tree should be maintained and supported if it has a certain amount of crown left and only a certain amount of infection.

Butternut Canker Disease

Sirococcus is a fungus that causes the canker disease that impacts butternuts at any stage of growth. It is the most serious disease facing this wonderful North American native tree.

In some areas, it’s estimated that up to 80% of butternuts have been affected, contributing to a massive loss in numbers.

Young cankers are usually found in the area of buds. They are a dark black center with a whitish margin.

The older cankers usually form on the main stem at the base, but can show up anywhere. Look at any bark fissures and you’ll see multiple callous layers of the canker.

Death is often swift, but on occasion, the affected tree can last for many years. Eventually the canker girdles and kills the butternut.

Little can be done to prevent this disease, other than maintaining healthy gardening practices. Clean garden tools well with a water and bleach solution. Remove affected trees promptly if severely affected, or in line with local regulations.

This is a disease spread by water and likely by birds and insects.

Keeping the butternut as healthy as possible and free of other pests and diseases may go some way to avoiding a weak tree succumbing to butternut canker.

Bark Beetles

Bark beetles (from the family Curculionidae) are native to the US and are a beneficial part of the natural forest ecosystem. Unfortunately, their numbers have grown in recent years, and therein lies the problem.

In large numbers they can decimate many plants and trees, butternut included.

Bark beetles release a pheromone when they find a tree to feed on. This brings in hundreds of other beetles and, in a coordinated attack, they overwhelm the tree. They bore into the wood and disrupt the flow of nutrients to the point the tree dies.

The dead tree then becomes extremely dry and poses a fire risk. Bark beetles are partially responsible for the massive wildfires that have decimated so much of the western regions of North America.

The beetles also carry fungi with them and this cancker-causing fungi, combined with the beetle damage, further harms the tree, all but assuring it will die.

Bark beetles are the size of a grain of rice and are black, red, or brown. You will likely see sap on the outside of the tree combined with sawdust, which is created as the bug bores into the wood.

The beetles are hard to control or target as they are buried deep into the tree. If reachable branches and twigs are infected, you can remove them and burn them immediately. Don’t pile the removed bits near other susceptible trees.

As with butternut canker, keeping the tree as vigorous and healthy as possible is a must to prevent serious damage from these pests.

Birds

Many birds will go for white walnuts. Woodpeckers, nuthatches, and common grackles are big feeders and like butternuts in particular. Remove the nuts from the tree or ground before birds can make a meal of them.

You can also use reflectors, decoys, wind chimes, netting, or repellants to keep birds away.

Caterpillars

Caterpillars (specifically, Lymantria dispar dispar) are also an issue for butternut. Until recently, the adult insects were called gypsy moths. The term “gypsy moth” is an outdated epithet and they have been renamed spongy moth.

Whatever you call them, they’re bad news.

During a large outbreak, which happens once a decade or so, they can completely kill a tree. Other years, they reduce vigor and harvest.

To control them, go out in the spring and scrape off any egg nests and smash or dispose of them. You can also use sticky traps and barrier bands in the spring to catch emerging larvae.

The beneficial bacteria Bacillus thuringiensis subsp. kurstaki is an effective natural pesticide. Use it whenever pests are present, following the manufacturer’s directions.

Harvesting Butternuts

In the fall, when the nuts drop from the tree, remove the husks and wash any residue off. Keep the nuts in a single layer on newspaper in a dry ventilated area. This will take several weeks and you will hear the nut rattle around inside when it’s ready.

You can also pull any nuts off the tree that have reached the mature brown-yellow color. They should come away easily.

The nuts will stay good for several months.