Most trees begin to emerge from dormancy in late winter-sometimes as early as late January even in the North — when there is still snow on the ground. Nurseries couldn't dream of getting their digging equipment onto the land before then, which means that near-convenient time in mid-spring, most are held in artificial dormancy many weeks (or even months) longer than they would remain somnolent in nature. That’s why planting an orchard in fall is much more natural: it permits rain and snow melt to compact soil around the roots and have your trees awaken slowly in their new home, rather than all at once, months late, and in much warmer weather than is natural.
No matter when planted, a little bareroot tree has been ripped from its nursery, leaving behind its original feeder roots — the microscopic hairs that grow from rootlets and make the actual connection between plant and soil. It must grow an all new set, and if given the chance, will get started underground long before any top growth is visible. A fall-set tree can have as much as a year's head start on a spring-planted counterpart if it is set in right.
First of all, don't treat a newly acquired bare root tree tenderly by "heeling it in" moistening the roots, packing them in damp soil or moss, and leaning the tree in a shady spot as you would in spring. This could break dormancy, initiate growth, and severely set back or even kill the tree. Keep it as dry as it came, in the dark, and as cold as possible while you prepare a planting hole.
The Hundred Dollar Hole
As the old saying goes, you oughta "dig a hundred dollar hole for a ten dollar tree." Of course, top-quality fruit or ornamental lawn trees cost more than $10 these days, so the hundred dollar hole is worth more. In truth, it costs nothing like a hundred bucks, though. It is the work that you put into preparing a planting hole for a new tree that gives it value, offering a good start and firm foundation for decades of growth and production.
Most bare-rooted specimens, from a foot-tall slip to a 24-inch sapling or a yard-high two- to five-year-old, will come with a root mass no bigger than your two hands formed into a fingertip-to-fingertip basket. Small as it may be, dig it a hole the size of a bushel basket, about 18 inches around and deep. For a larger tree, or any specimen that comes with roots baled in soil, make the hole two feet around and two feet deep.
First, cut out sod and set to one side. Remove dark, loamy topsoil and put in a pile. Then, dig out and discard light-colored subsoil down to planting depth. If any tree roots are growing through the hole, grub them out mercilessly. Though if the roots are so big they require an ax or saw, you may want to spare their parent tree... and you are probably planting too close to an adult tree anyway. (Many trees, poplars and nut trees in particular, actually secrete plant poisons in the soil within their drip lines to deter competition.)
You can return the sod to the hole, bottom-side up, but you must compact it exceedingly well or the grass and roots can cavitate under the tree as it decays and the soil will sink. Better is to knock off as much soil as you can and compost the sod itself.
Dish the surface around the outer rim of the hole to hold rain water, and stake it for support. Toss on the retained topsoil. Remove rocks and roots. Add in as much compost as you can spare and/or well-rotted stable manure and/or sacks of composted cow manure to a pile no more than one-and-a-half times the volume of the hole. Add a quart-size sack of cottonseed meal (for nitrogen), green-sand (for potassium, aluminum, and iron) and seaweed meal for boron, magnesium, and 20 or so other trace elements that all life needs in small and varying amounts, but needs absolutely. Have on hand, but don't mix in yet, a quart of bone or blood meal for phosphorus.
Top the pile with equal amounts of water-retaining peat moss and vermiculite to make a pile of loose soil mix that's twice the volume of the planting hole. Sprinkle with enough wood ash or ground limestone or a combination to make the surface a dirty gray-white (but not so thick that the soil mix is so well-coated it is obscured). Mix thoroughly with shovel.
Fill the hole a quarter-full with loose mix, add half the bone meal and mix that in. Stomp this first layer of loose-mix well. Make up another batch with the rest of the meal and stomp. You will be burying the meaty-smelling animal meal so your dogs and wild creatures won't dig it up and possibly die from phosphorus poisoning. The hole should be about half full. Then add bone-meal-free mix in layers, stomping well between each till the hole is full.
Now, dig a planting hole in the compacted SuperSoil and set in the tree according to instructions that came with it. In general, you want to set the tree a little deeper than it grew in the nursery, spreading roots at the bottom of the hole and firming soil around them well and soaking the soil thoroughly. Most grafted trees must be set with the graft well above soil level. But requirements vary, so follow instructions.
When the tree is in, dish the surface around the outer rim of the hole to hold rainwater. Pound a stake into the soil beside the tree and fasten trunk to stake every few inches with lengths of twine tied tight to a notch whittled in the stake, but looping loose around the young tree. If you are planting a larger tree — say a six-foot-tall lawn specimen — guy the tree with three twine cables fastened to stakes sunk in a circle at least six feet out from the tree, and looped through soft fabric or foam-rubber tubing where it bends around the trunk.
One danger to fall-set trees is dehydration through the still-tender young bark due to dry winter winds. A second hazard is rodents — mice, voles, rabbits — that are especially fond of sweet fruit tree bark and will gnaw it down to bare wood, girdling and killing the tree. Field mice and voles will attack under the snow and you won't see the damage till too late.
To prevent desiccation, enclose the tree in trunk-wrap plastic strips or tar paper that comes in an easily applied spiral. This will keep moisture in, but let the trunk breathe (or "transpire;" to be botanically accurate), as plants constantly exchange gases with the atmosphere just as animals do. To deter the destructive little creatures, remove both ends from several tin cans (small-size tomato paste cans are ideal for young trees). Slit them up the sides with metal shears. Spring them open just enough to clamp around the trees (being extra careful not to let the sharp cut edges gouge tender bark). Apply duct tape all around if they don't close back up. Push the bottom can well down into the soil and stack others atop it two feet above the ground — or three feet or more if your part of the country gets a foot or more of snow for hungry bunnies to walk on top of. It is best to remove the cans once more conventional wild rabbit food is greened up in spring and re-install them each fall. Lengths of aluminum flashing (allowed to keep the natural curl they have coming off the roll) will serve as well as cans, but not as cheaply. Nurseries sell anti-rodent trunk-guard, but that is more expensive still.
For more on fall planting see the following:
Fall Planting Guide for the Garden
Planting a Lawn in Fall