These plants are grown as tubelings because:
The nuts (seeds) are too precious to plant outdoors. A fact of life hazel
growers must contend with is that hazelnuts are delicious. They are not
only the subject of cravings by humans, they are dramatically more attractive
to wildlife, of all sorts, than beginners ever believe.
Far more attractive
than the crop seeds like corn or wheat that we are used to. Animals, and
birds, will work 24 hours a day to get at a supply of hazelnuts, and they
will succeed, in spite of all efforts to stop them. Usually, they succeed
in the first 24 hours.
Wild hazel seed is cheap; nurseries can afford to have animals eat most of it; hybrid hazel seed is perforce expensive, and feeding 85% of it (a real number from years of trying) to the mice, raccoons, and woodpeckers is not economic.
Another serious economic barrier to bare-root dormant hazels is the fact that they start to leaf out with the very earliest trees. Very quickly in the spring, they are not dormant anymore; experience has shown us that most often, hazels grown in the field will be leafed out before the ground is "workable"- digging them for transplant in the spring is extremely risky. Fall digging might be possible; but it requires expensive refrigerated climate controlled storage over the winter; and our experience with experimental trials is that hazelnuts do worse than most other plants in such storage.
If this crop is going to develop, there must be many new growers, and many
tons of nuts produced annually- one factor in making that happen is simply
the cost of the plants; they must be as inexpensive as we can make them,
so that regular folks, regular farmers, can actually afford to plant them.
Grafted trees at $20 apiece is not a route that will allow farmers to plant
acres.
The tubelings are much cheaper to grow, ship, and plant than bare root dormant plants can be. (Once you have a mouse-proof greenhouse...) They are still not cheap, but we work on getting the price down every year.
Also, standard bare-root tree transplanting must be done as early as possible in the spring. We're used to that, but in fact that's an expensive proposition. Other urgent chores must be postponed; or if they are urgent enough, the tree planting must be interrupted, leading to higher tree mortality. When the season has moved from spring to summer, it is too late; they can no longer be successfully transplanted- their minimal root system cannot grow new roots fast enough to keep the top watered when it is hot, and the tree will die.
The standard tubelings are not dormant when they are planted. They have small leaf areas that have been toughened by being cut back, and a small but intact and actively growing root system. Planting requires a more gentle hand than bare-root transplanting, where we are taught to stomp the trees in, and pack the soil well around their roots. That will kill a tubeling, by smashing its root system. But it's basically identical to the gentler planting long integrated into agriculture in tobacco and tomato crops- it can be done by anyone willing to learn, and it can be done by machines.
Once used to the idea, the fact that tubelings do not have to be planted in early April, but can be planted in May, June, July, August, September... is liberating. Plantings can be planned for times when the ground is ready, the necessary labor is available, and other urgent need are not conflicting. All this means that planting can be done more cheaply.
Having made the case for standard tubelings, we must now point out that another category of planting stock has just become available; the "bare-root dormant tubeling". Hopefully we can avoid confusing the reader on this point.
These have only now become available as we have learned some things about hazel "dormancy". While they tend to die if kept in dark refrigeration for several months, they not only tolerate being kept in a warm greenhouse over the winter, they thrive. This is not the usual expectation. Many plants kept in continuously warm circumstances will break dormancy and start growing- a bad thing if you are wanting to transplant in early spring. The hazels, however, as part of their extreme cold-hardiness, truly require a substantial number of cold hours before they will break dormancy- kept warm, they do not get them; consequently they stay dormant, and happy, sitting in the sun in the greenhouse. In February they are pulled from their tubes and put into cold storage for a month- not a mortality problem, and giving them their cold requirement.
This kind of planting stock is now available in quantity; allowing plain old-fashioned early spring plantings. They are shipped, handled and planted just like any bare-root tree. However...
An economic drawback is that they are more expensive- since someone must
care for them through the winter. In general, standard tubelings are 3-5
months old when shipped and planted into the field; bare-root dormant tubelings
are 8-14 months old- it unavoidably costs more to produce them.
Cloned cultivars-
Most fruit and nut crops are based on genetically identical plants: clones,
of one kind or another. Cloning of trees is an ancient practice, normally
accomplished by grafting or layering. Most hazels in the Pacific NW are
propagated by layering, the hybrid tree hazels being planted in Michigan
are grafted. All the apples you buy at the store are from cloned trees-
grafted, to 
produce identical fruit.
The great majority of hybrid bush hazels planted to date are not clones, but grown from seed.
Finding an economic way to clone bush hazel has been a difficult task.
Grafting is both expensive and in the case of bush hazels, a waste of time
rootstocks will tend to sprout and overwhelm the graft; alternative use
of Turkish tree hazel rootstock would put us back in the tree business,
which we do not want; bushes are more economic. Also, testing such cross
species grafts is a matter of decades, to find out if such plants will actually
survive over time. Rooting cuttings has been extensively investigated, in
a project funded by The Agricultural Utilization Research Institute (AURI),
by Dr. Harold Pellett; some success was obtained, but it was not easy, and
has not encouraged further work. Layering is possible, but also is time
consuming. taking years per plant, and is thus not economically very attractive,
always resulting in plants that cost many dollars, where our goal is to
produce planting stock that only costs pennies.
Tissue culture cloning has that potential, and BRC has been investing substantial resources into developing this process; success has been coming fast. The advantages of using tissue culture clones over seedlings for new plantings are manifold; first, the result will be a field of uniform plants with a uniform crop much easier to harvest and process; second, simple overall productivity of a clonal field should be considerably higher than from a seedling field, since only strong plants will be cloned and any seedling field will inevitably contain some weak plants, and third, the cost of producing the cloned plants it potentially much less than for any other propagation method. Since there is no nut involved, all problems with animals disappear, and the full range of automated greenhouse technology becomes available to us. Potentially, the cost to the farmer for commercially produced clonal plants could well be as low as 50¢/plant, making the crop available to a much wider range of growers.
"The state of the art" in hazel tissue culture when we began
this research was very primitive; every stage of the culturing process was
pretty much hit or miss; occasional success was possible, but rarely, and
with nothing like reliability. Over the past several years, Mr. Mehmet Nuri
Nas, working in Dr. Paul Read's laboratories at the University of Nebraska,
has moved hazel tissue culture all the way to commercial feasibility. 
As the project stands today we have 4 different hazelnut clones that can be produced at will. They are stable in culture, proliferate well, and can be regularly and easily rooted and "grown out". There are now clones growing in field test plantings at Badgersett, 2 other sites in Minnesota, 2 sites in Wisconsin, and one in Ohio. Total number of clones growing in the field is now approaching 1000 plants.
The oldest of the clones in the field have only been outplanted for some 18 months, but several critical things have already been learned about them; they are highly vigorous, appear to grow quite normally, develop new sprouts from the crown of the plant in normal fashion, including after being cut entirely back (coppice), and 2 different clones, G-029-N-Cl and E-295-S-Cl, have already developed flowers; both male and female. That means we can realistically expect to reach the day when harvest from clonal hazel plantings can begin when they are only 3 years old; perhaps, indeed, only 2 years old. The clones will not only eventually be cheaper to propagate than seedlings, but will produce nuts much sooner, since physiological maturity is retained.
Primarily what remains to be done is to refine the process of "initiation"; ie. getting new clones "into culture". Hazelnuts have proven particularly difficult to initiate; unlike other woody plants, they appear to have a substantial microbial population that grows inside their tissues. In order for tissue culture to be successful, we must be able to grow cultures free of microorganisms; getting new cultures started continues to be difficult.
As a consequence of this barrier, the 4 clones now in successful culture are more the result of chance than choice; a standard part of the learning process. In seeking a workable technique, hundreds of attempts at initiation were made, using many different methods and plants; but the success rate was, and continues to be, low. In my own opinion, it is unlikely that any of these 4 will prove to be a truly commercial cultivar- 3 of them have known flaws; the 4th is untested, having been derived from a newly germinated seed.
Initiation protocols need to be developed to the point where we can regularly take any interesting new plant and clone it. And cloned plants must be tested in the field, to be sure they perform up to expectations, before suggesting farmers plant them as crops (this will take some years).
All caveats included, it is still only a matter of a few years before tissue culture clones are commercially produced, and added to the arsenal of available plant types.
Layered or stooled plants are another kind of clone, in both these techniques a stem of an existing mature plant is induced to form roots, by burying part of the stem for a long period of time. Usually the period is at least a year, making this a relatively expensive pathway. At the moment, such clones are only being produced for experimental reasons, and are not available for sale to the public. A great advantage of this kind of cloning, however, is its extremely low technology- basically, bury it, and wait. Anyone can do it.
This is a highly useful technique for individual farmers to clone one or two plants they find interesting, or to increase their own best plants for their own use. There is also an opportunity here for smaller growers to find a niche market producing moderate numbers of clones in this way.
Larger/older transplants, ie. hazel plants that may be 4 years old, for example, are not available at present. There is some demand for them, particularly from homeowners interested in a few plants for their yard, but BRC has not had the resources to expand into this kind of nursery operation. This could be another niche opportunity for existing nurseries. BRC expects to continue to focus on producing mass numbers of plants, as inexpensively as they can be delivered to growers intending to get into serious nut production. Older transplants have uses there, also, for example to fill in holes in an older planting; but the costs of such plants will always be very high in comparison to tubelings or tissue culture starts.
"Crowns" are an alternative nursery stock type that
BRC has experimented with for several years. Essentially these are hazels
that are 2-4 years old, but their handling is different from standard transplant
methods. The plants can be dug at any time when the ground is not frozen;
then their tops are removed entirely. This leaves just the root system-
it can be planted out at any time of the year, and since there are no leaves
to support, the root system is not under drying stress even if not irrigated.
The plant will now send up shoots and put out leaves, but only as the root
system is prepared to support them. This kind of regrowth from a total loss
of the top is intrinsic in the genetics of the native hazels, which are
adapted to ecologies which include frequent fires. This system was investigated
as a possible method for establishing hazel plantings in very difficult
circumstances, eg. in dry sands, in ground subject to frequent flooding,
or in situations with extreme animal pressure. The 2-4 year old root system
contains very substantial resources and energy reserves to help the roots
get reestablished, and the top, being entirely new, grows uniformly and
without stress. Tests of the process were very successful; however at present
nursery stock of this type is not being produced, simply because BRC does
not have the equipment to do it in an economic fashion. Digging 3 year and
older hazel root systems is a job that requires fairly powerful machinery-
the roots are large and deep, and hand labor is not an option for a business.
Ground Preparation
Requirements will vary greatly depending on your soil. Because these are deep rooted woody plants, more thought needs to be given to the state of the subsoil than with row crops; subsoiling, at least below the row of plants, is a good idea. This is likely to leave the soil blocky, however, and may require more than one pass with a disc or similar implement to remove air pockets and generally smooth the soil.
For the silt loams at Badgersett Farm, these are our present practices
For recent row crop land: 2 weeks before planting, spray Roundup® strips ~ 8' wide. Subsoil down the middle of the row, twice, in opposite directions, if the compaction seems serious. Disc twice to break up clods and firm. Immediately before planting, the row is bladed and rolled simultaneously- the blade is set to level the soil with the adjacent untilled strips, and the roller is pulled behind the blade, providing a firm smooth track for the transplanting machine.
For old hay ground, or heavy sod: well before planting, Roundup®, either strips or whole field depending on needs, then moldboard plow the sod. Preferably, the sods should have several months to break down before planting proceeds; the transplanting machines work badly and/or slowly in tough chunky sod.
For small hand plantings: by preference, strip spray or spot spray Roundup® so that an area about 3 feet in diameter is cleared of weeds. If planting in sod, sometimes the less disturbance the better, tillage bringing more weed seeds to the surface to germinate. Undisturbed killed sod can act as a good mulch for as much as a year.
Planting
These plants do not need a big hole; just enough to get them into the ground. We use several tools depending on the looseness of the soil; a "bulb planter" that cuts a plug out, a "dibble" bar, that punches a hole exactly the size of the tube-pot, or a shovel. Standard tree planting "bars" are not good; they are designed to pack soil hard around bare roots; with our plants, they crush the root ball and destroy roots.
The plants handle best if they are NOT watered just before planting; soaking-wet root balls crumble easily. Grasp the base of the stem just above the soil, & gently pull the root ball straight out of the tube. Occasionally a plant may not pull easily; though it sounds strange, we may blow these out; put our mouth over the holes on the bottom and blow hard. Hold the stem as you blow, or it will shoot out! Once out, handle carefully; the plants are tough, but roots and new buds are tender.
Planting Depth. Plant so the root ball is slightly deeper than it was in the pot; 1/2 to 1 inch deeper is best. Covering the roots with soil is necessary to prevent drying out; any exposed potting soil will act as a wick and dry out the whole root ball. Planting deeper than 2" could hurt the plant; some of the plants may die. If the soil you are planting into has been extensively cultivated, or "fluffed" by tilling, be aware it will settle quite a bit, and may expose the roots of the plants unless they are set deep enough to compensate for settling; 2" may not be too deep in this case.
Water well right after planting. Ideally the ground around each plant should receive 1/2- 2 gallons. Don't dump water right on the plant; water around it. Try to water so the roots of the plant get wet, but by absorbing water from the nearby soil- this helps get air out of the hole, and insures good root-soil contact. Make sure the root ball is still covered with soil after watering!
Weather- If you have a choice, it can help to plant as a cool, wet weather system moves in. Avoid planting in hot sun if you can; try to plant only after 2-3 PM if you can't.
Remove the nut? Mice, squirrels, chipmunks, groundhogs, and other critters will still find the nut attractive on newly planted tubelings. If you are planting in an area where there is a lot of wildlife pressure, it may be best to gently pull or snip the nut off before or right after planting. The plant doesn't really need the nut for nutrition at this point, though it will certainly use it if the nut survives. In most cases if a squirrel goes after the nut on a newly planted tubeling, it will just pull the nut off, leaving the plant unaffected. Animals are individuals, though, and sometimes plants may be pulled out of the ground- be on the lookout for this; particularly in very sandy soils, where a new plant may be easily pulled before its roots grow and anchor it. If in doubt, plant a few and watch for several days to see how they do before planting the rest.
Weed Control. Try to keep weeds at least 1 foot away from the plants in the first years. A tractor mounted corn cultivator has worked very well. When it is too wet to cultivate, mow. In our largest plantings, mowing is all the weed control the plants get, or need. The few weeds remaining in the row don't hurt, and in fact help, by distracting deer and rabbits from the young hazels, and providing a little wind protection.
Herbicide use is possible, but very difficult because of the high probability of damage to the seedlings; they have leaves and green bark right down to the ground. Both Roundup® and Princep® have been used on these plantings, but Princep® was found to be too difficult to control, frequently damaging the hazels. "Wick" applicators can be used to apply Roundup without danger of drift, and are recommended. They are still dangerous to your plants, however, if you hit a stem accidentally, or put herbicide on a grass stem that the wind will blow so the grass touches the seedling before the herbicide dries.
Mulches can be beneficial in dry years and for weed control, but some kinds encourage mice and steal nitrogen from the plants. Mulches keep soil cool in summer, and warm in winter; this may not be good for best growth and hardiness. "Landscape fabric", has yielded mixed results. It requires precise installation and considerable maintenance; storm winds can rip it up if not very carefully anchored.
"Tree shelters" are simply too expensive for very large plantings. To be effective; they must be staked, weeded, tended, and lifted in fall to allow the plants to go dormant in time for winter. They can kill bluebirds, and in wet years, they can make the environment inside the tube too wet. On the other hand, several plantings report they definitely helped the seedlings get established. If you are interested in them, try a few on your site first, before investing in large numbers of tubes. 12" or 18" tubes are fine for young hazels, don't have to be staked, and can be removed after a year.
Fertilize at or soon after planting, or spray plants with a foliar fertilizer solution. Hazels can be fertilized at any time, including fall. Mature leaves should be dark green until they turn color in autumn. New leaves can be light green, or reddish. A general purpose fertilizer like 10-10-10 is fine the first year; individual soil requirements vary greatly. Be sure your fertilizer does not contain any herbicides, as "weed and feed" lawn fertilizers do. Long term fertilization needs are more complex. In general, hazels are short of nitrogen and potash more often than other nutrients.
Pink or red young leaves are common, and do not indicate any nutrition imbalance, in fact we think this indicates good fertility; some young hazels normally have a red spot in the center of the leaf.
Once hazels have been growing more than a month, they will survive all sorts of disasters, from drought to being stepped on or accidentally mowed. Of course they will be hurt, but a healthy plant should sprout again from the roots: you will not have to replant.
Animals- Egg spray to discourage deer has proven effective: Liquefy 1 doz. eggs in a blender, mix in 5 gal of water and spray on the young plants until just wet. This won't wash off in rain, and is effective for 2-4 weeks. Do this the same day you plant if possible, to prevent "curiosity browsing". Don't use a heavier mix than this; several instances have been reported where raccoons pulled out newly planted tubelings after they were sprayed with heavy egg mixes; probably looking for an egg. If you have a lot of raccoons, don't spray egg at all, until 2 months after planting; use an alternative commercial deer repellent if necessary.
Rabbits & Mice may attack young seedlings; for chestnuts,
spiral plastic tree guards are very effective in stopping them. Put the
guards on in early fall, and remove them in spring. Young hazels may sometimes
be snipped off by rabbits or mice; a commercial repellent such as Hinder®
will help. Be on the lookout for animal damage as the seasons change. Weed
control helps; rodents would rather not feed where they are exposed to predators.
The plants will survive in any case, resprout, and in a few years outgrow
the critters; once established, hazels are rarely damaged.