Hazelnuts aka filberts and cob nuts grow on a bushy tree as opposed to a standard tree like most nuts.
They are at times rather large bushes reaching up to 10 feet high with an equal girth. They remain productive for 30 - 40 years and can be grown successfully in USDA zones 4 to 9. Some varieties under the proper conditions are productive in zone 3. Colder regions do best with the American hazelnuts, European varieties are less cold-tolerant.
They should be planted relatively close to one another within a few yards preferably. They will pollinate at greater distances but the closeness improves the odds in ensuring adequate pollination and a bountiful harvest.
They have an unusual reproductive pattern in that they bloom and pollinate in the winter. Male flowers are present from fall through winter, they hang rigidly from hazelnut branches. Female flowers are wind pollinated during the winter and spring and subsequently develop into nuts in the spring.
Your trees will produce nuts about 3 - 4 years from planting under the proper conditions.
After about a decade their productivity increases tremendously and will continue producing, so long as all other parameters are maintained, for several more decades.
During the summer the nuts mature and are harvested in late summer and early autumn. They are ready to harvest when they have turned from green to brown and they begin falling from the bushes of their own accord. They can be harvested off the ground if you can beat the squirrels to them, as well as hand picked.
Hazelnuts require a cool chilling winter season in order to produce. It will not grow well in regions with warm winters. They tolerate temperatures as low as 10 to 15 F.
Soil should be well drained, avoid low lying areas where water accumulates. They should not be located where the soil is too heavy such as clays or light and sandy.
Soil for the hazelnuts should be in the mildly acidic to neutral range. The optimal soil pH should be 6.0 to 7.0 . Adjust the soil pH with sulfur if it is over 7 with lime if it is below 6. See - Tracking and Adjusting Soil pH
As the plant is maturing, in its first 6 months or thereabouts, irrigation is essential, water at least 3X weekly, more so in dry hot weather. After its first year curtail the watering - Once a week will suffice. The primary purpose of watering thereafter is to offset any excessively dry periods, particularly during the nut filling stage. Hazelnuts are a somewhat drought-tolerant nut , you shouldn't have to worry about regular watering except under unusually hot - dry spells.
Hazelnuts are usually started with saplings purchased from nurseries rather than by planting seeds. Most nursery stock is grafted trees, meaning the root-stock is from one kind of tree and the top branch portion is of a different variety. The nuts and pollen from grated trees will produce nuts true to the variety of the top section, not the root stock. See - Grafting Fruit Trees
Your location should receive full sun and have adequate space to accommodate two hazelnut trees at their anticipated mature height and girth. Keep your trees as close together as possible while still maintaining the parameters required for mature trees. The closeness is necessary to ensure pollination - you should assume a spacing of 15-20 feet between each bush.
Dig a hole almost twice as deep as the root ball, then back-fill it slightly with loose non-compacted soil, a little compost worked in wouldn't hurt none either - just a little. The soil beneath and above the root ball should be uncompacted and loose to allow for root penetration, water penetration and oxygenation. Keep the sapling well watered the first few months when the roots are getting established in their permanent home.
Pruning - Suckering
Hazelnuts are more bush than tree, they sprout abundant useless suckers from their base. Trim away any excess sucker growth or low sprouts as they develop not only to keep the tree trained to a central trunk shape, but to maximize nut production. Useless sucker growth uses the plants energy that could be devoted elsewhere.
Once the hazelnut tree starts producing nuts, you can give it an annual fertilizer feeding . A fertilizer specifically formulated for trees is best, but a general purpose fertilizer will suffice.
Pests and Disease
Caterpillars can be a nuisance in particular the eastern leaf roller moth. The moths are light brown. They lay their eggs in and around the trees, and the caterpillars then spin webs within the leaves. See - Leaf Rollers
Nut weevils will occasionally attack hazelnuts, they bore into the nut itself and lay eggs. The larvae or worms develop within the nut. The adult beetles feed on the buds and leaves of hazelnut trees. See - Weevils
Several blights effect hazelnuts, eastern filbert blight is most noteworthy. It is a fungal disease. See- Eastern Filbert Blight - Cornell
Oak root fungus - See University of California - Oak Root Fungus and powdery mildew are other issues that effect hazelnuts.
Hazelnuts are harvested in mid to late autumn when the their husks have dried and split open. You'll find them dropping to the ground just like acorns. Check the ground frequently as they are also a favorite of squirrels, chipmunks, some birds, rabbits and small rodents.
Home growers generally rake the nuts into a pile for easier collection. I prefer to lay out a tarp beneath the trees in order to collect them. Try not to leave any for the local wildlife as they will continue to return to your plants once they are aware of a food source.
Hazelnuts should be dried before being stored. They can be dried either in the shell or out of it. The quickest way to dry them is to shell them first and spread them out in a warm and well aerated location - where the tree rats can't get to them.
Dried hazelnuts will keep for about a year, in the freezer up to 2 years. Regardless of whether refrigerated or stored dry they should be kept in airtight containers.
Hazelnuts and Truffles - Inter-cropped
The roots of hazelnut saplings are inoculated with truffle spores before planting, they are the preferred host tree. The tree will produce nuts above ground, and you can also harvest truffle below the surface. Truffles in addition to being delicious are very very lucrative See - Truffle Planting Guide.