The delightful and hardy hazel tree (or bush) is a familiar sight in forests and along rural hedgerows. But it’s also grown commercially for its delicious hazelnuts (also known as filberts, cobs or cobnuts), used in many foods and flavorings. It’s an appealing tree to own, especially as you can get your very own crop of this popular nut. But it doesn’t always work out – many things can get in the way of a good yield. Why does a hazelnut tree sometimes not produce a decent crop of nuts?
On average, hazelnuts are not produced until a tree grows for 7 or 8 years from seed. Trees grown from other propagation methods can produce nuts in 2 or 3 years. However, self-incompatibility, temperature changes, biennial bearing, pests, disease and animal consumption can greatly affect yield.
I’ll be happy to unpack this, and present you with a hands-on guide to ensuring an excellent crop of those delicious hazelnuts.
Hazelnut tree species and nut production
First of all, I just want to clear up some terminology issues, so this article makes sense! The terms filbert and hazelnut are often used interchangeably. The filbert is technically the nut of Corylus maxima, a hazel species native to southeast Europe – they’re the largest type of hazelnut, up to 1 inch diameter. But in the big commercial spots of hazelnut growth in the USA (looking at you Oregon) they’re commonly called filberts, even though they’re growing Corylus avellana, the European hazelnut. The European nuts are about 3/4 inch diameter, and also grow natively throughout Europe and western Asia. These nuts are felt to be the tastiest, and hence are big business.
Wherever you see the word ‘hazelnut’ in this article, you can go ahead and replace it with ‘filbert‘ if you like.
If you’re in the USA, the native tree is Corylus americana. It’s similar, but the nuts are smaller again (1/2 inch diameter) and said to be less tasty. However, it’s hardier – surviving colder winters, and still a treat to collect and enjoy.
When do hazelnut trees produce nuts?
As a general rule, hazelnuts growing in the northern hemisphere are visible on trees in early summer and are ripe in September or October.
How old are hazel trees before they bear nuts?
As mentioned above, hazel trees don’t produce straight away. If a tree is grown from a nut, you probably won’t see any nuts for the first 7 or even 8 years! If you bought a tree from a nursery, there’s a good chance it was propagated in some other way. This might have been by layering (where a branch has essentially been bent into the ground and encouraged to take root and make a new tree- quite easy with hazelnuts). Alternatively, it may be grown from a cutting, or it may be grafted, meaning the upper part (scion) was attached on to the rootstock of another, and the more mature part gives it a headstart. You usually won’t have to wait nearly as long for these hazelnuts to appear – just a couple of years.
The heaviest yields of hazelnuts should start after the tree has been bearing nuts for 5 years or so.
Hazelnut trees and biennial bearing
In common with many fruit trees, many hazelnuts have a tendency to be biennial bearing – meaning they will concentrate on producing lots of flowers one year, and lots of nuts the next – only giving a reliable nut yield every other year. This is more common in certain cultivars and in Corylus americana.
If you didn’t get hazelnuts this year, consider if the tree seemed to produce more flowers than usual in the late winter/early spring. You may be in for a better crop next year – it’s just the tree’s natural cycle.
Biennial-bearing tendencies can be reduced by pruning the tree – more on that later.
Hazelnut production and pollination
Hazelnut trees are monoecious, which means they have both male and female flowers on each tree. They appear in the late winter or early spring. The male ones are long, showy yellow catkins – dangling, like a lamb’s tail – while the female flowers are much smaller, looking almost like little buds with strikingly red tufts.
Having male and female flowers on the same tree is usually a plus when it comes to nut production. However… hazelnuts, through a glitch in their genetics, are self-incompatible – meaning pollen from male flowers can’t fertilize female flowers on the same tree.
What this means is that nuts will not appear unless you have a compatible fertilizing tree within about 150 feet (since the pollen has to travel from one tree to the other by wind).
If your tree has reached the appropriate age (as above) and there’s no sign of nuts, you may need to plant another hazelnut on your property. It doesn’t need to be right next to it – on some commercial farms where the trees are planted in lines, they’ll plant one pollinating tree every three trees down and three across. It will help if you plant it upwind from your main tree. If you’re not sure what the prevailing wind direction where you live is, there’s a handy wind map available for the USA here.
It gets complicated when deciding which hazelnut tree to plant as your number two, so I would consider consulting a specialist nursery to make sure you get a genetically compatible variety. Since hazelnut varieties don’t all pollinate at exactly the same time in the season, if you know when the flowers appear on your first hazelnut, you may be able to acquire a variety that will flower at the ideal time to match.
Planting at least three varieties increases the probability of a really good yield.
What causes blank or empty hazelnuts?
Another common issue is the production of hazelnuts that, when split open, are hollow, or ‘blank’, having no kernel. Pretty disappointing when this happens! These are hardly going to satisfy anyone looking for a harvest of delicious nuts.
Blank hazelnuts are more common in certain hazel cultivars, such as Corylus Avellana ‘Barcelona’, which is grown commercially. They seem to occur as a result of a failure of development after fertilization.
There are also some pests that can burrow into the nut and devour the inside! It’s possible to tell if this has happened – scroll down.
Could temperature changes affect hazelnut production?
If you want nuts, you need pollination. Wind pollination (carrying pollen from male flowers of one hazel tree to female flowers of another) occurs in early spring before the leaves emerge.
Here’s where temperature comes into play. An unusually warm winter can cause the leaves to appear too early, interrupting the process and preventing fertilization, and therefore hazelnut production.
It’s likely that the situation will self-correct next year unless the same weather pattern re-occurs. This is a concern with unusually warm winter temperatures in many parts of the world in recent years. However, hazelnuts are less susceptible to the harms of warm winters than many other tree species that produce fruit.
Sun, soil, and water requirements for hazelnut production
It’s important to give your hazelnut tree the very best growing conditions – an unhealthy tree is unlikely to produce much in the way of nuts. Conversely, optimizing its sun exposure, irrigation and soil requirements will help increase the nut yield significantly. Commercial hazelnut producers get all these factors down to an art.
If you’re planting hazelnut trees, it’s felt that deep, well-drained loam soils that have been cleared of rocks will afford it the best chances. Hazelnuts are quite tolerant to a range of pH levels, but slightly on the acidic side (6.5-7) is probably best.
Like many other nut-producing trees, they’ll do best in full sun. Most will tolerate some light shade, although the American hazelnut usually fares better in this regard than the European hazelnut.
Think about where your hazelnut is situated – does it have adequate sun exposure? A recently planted tree may fare better in the long room if transplanted to a sunnier spot.
When it comes to water, hazel trees don’t grow well in boggy areas. They’re quite tolerant of drought though. You may need to give it some special watering attention in the first 2 or 3 years of its growth however when the shoots are young and the deeper roots have not yet developed. During dry spells, water it approximately weekly – a 20 to 30-minute soak using a sprinkler should do it – avoid blasting at the base of the tree with a hose.
Alternatively, just check the water weekly to see if it’s dry – you can do this by digging your finger about an inch down into the ground, and checking if the soil feels damp or if it will stick to your finger. If not – irrigation time.
When your tree’s more mature it likely won’t need such regular watering, but if you’d like to get a good number of hazelnuts, keep a close eye on the soil.
Do hazelnut trees require fertilizer?
Commercial nut producers do use complicated fertilizer regimes. It’s important to realize that applying fertilizer at the wrong time can actually be harmful, causing leaves to grow in the wrong part of the season and interfering with the normal cyclical development of the nuts. Others think that fertilizer will be more likely to stimulate leaf production rather than nut production. You might get around this by using a technique called ‘brutting’ though – scroll down for the pruning section.
If your soil is good and plants usually grow well, it may be better to avoid fertilizer. But if you’d like to give your tree a boost, some good old 10-10-10 fertilizer, applied to the root zone in March time, is a good way to go.
10-10-10 fertilizer contains equal parts of the essential nutrients nitrogen, phosphorus, and potassium. But if (like me!) you’re the sort of person who likes to find out whether your soil is lacking in any one of these in particular, it isn’t that hard to find out. I used a Rapitest soil test kit, which will give you levels of these three as well as your soil pH.
Hazelnut diseases and pests affecting production
There are a couple of extremely important ailments that hazel trees suffer from. They’re the scourge of the commercial hazelnut industry and huge effort goes into combating them every year. However, they’re quite likely to affect your own trees, and will certainly affect the overall health of your tree and reduce, or even destroy, your nut yield.
Eastern Filbert Blight (EFB) is probably the best known. It’s caused by a fungus, Anisogramma anomala, and can be lethal to trees. It causes rows of small holes (cankers) on branches, and death of infected tissues. Controlled spread from tree to tree (and orchard to orchard) is a huge problem. The US native Corylus americana is a bit more resistant to EFB than its European counterpart, and some cultivars and hybrids between the two species have also shown some promising resistance.
Here’s a very informative short video. From around the 2:55 mark you can see some EFB-infected tree parts.
Another infamous hazelnut pest is the filbertworm, Cydia latiferreana. The female moth lays eggs near the nuts, and larvae burrow in and consume the inner kernel – another cause of empty or blank hazelnuts. They then eat their way out again and continue their life cycle, leading to more tree devastation.
If you have any fallen hazelnuts, check carefully for a small hole in the shell – this is the hole that the worm exits through.
Farmers attempt to limit the success of their reproductive cycle by placing pheromone traps in the upper third of the tree canopy to capture moths. These lures can be bought online on sites like this one.
However, if you think you may have a tree that’s affected by EFB or filbertworm, I would consider a trained arborist as soon as possible. They’ll give expert advice on filbertworm control and can prune diseased EFB parts (usually a large extra portion of apparently healthy branch needs to be pruned off, and the secateurs sterilised between cuts to avoid spreading the infection).
‘Brutting’ and hazelnut production
This in an unusual but very easy traditional method of improving your hazelnut yield.
It involves snapping, but not totally breaking off, new shoots. Identify the greener new shoots in late summer or autumn, and count about 6 or 7 leaf groups from the place where the new shoot has come from the older branch, and snap there!
This improves light penetration and appears to improve flower (and therefore nut) production.
Here’s a video that explains where on the branch to do this. Go to 3:14!
How do animals and birds affect hazelnut yield?
Being an excellent source of protein, hazelnuts are an appealing food for squirrels, moles, birds and mice. You may find you have to lift fallen filberts quickly, or they’ll soon become fodder for these creatures. One way to mitigate this is to try to pick the hazelnuts from the trees just before they fall – when the shells turn brown and they separate willingly from their husks.
The problem is though that squirrels and birds will often go for them before they’re fully ripe. If you’re getting a lot of loss from squirrels… some say making a squirrel buffet works – setting out a table of easy-to-get-to ripe nuts such as peanuts. If you’re lucky, the squirrels will ignore your hazelnuts. But as peanuts are likely to get eaten very quickly by birds, I’d suggest buying a squirrel feeder.
If you live where deer may wander, a tree guard will be necessary for the duration of the tree’s early life, particularly the first 3 years or so.
How to get good yields of hazelnuts – a summary
- Pick a site with good sun and deep soil
- Plant compatible cultivars nearby for wind pollination
- Give the tree time to mature
- Keep the tree irrigated, especially when young
- Consider fertilizer in March
- Use the traditional ‘brutting’ technique
- Monitor for Eastern Filbert Blight and filbertworm
- Protect from animal loss
One more question….
Do hazelnuts ever stop producing nuts?
Hazel trees are said to live to around 40 years, and they’re likely to give some of their best yields around the second and third decades. But there have been some that have lived much longer – there are hazels with recorded ages of up to two centuries – and there doesn’t appear to be an age at which the tree stops producing nuts, provided it remains healthy. Why do some trees apparently outlive their quoted lifespan? Check out my article ‘Do trees die of old age, or can they live forever – answered’!