Tree Planting in Michigan By Douglas Lantagne and Melvin Koelling

    Each year trees are planted on s several thousand acres of Michigan land.  Most are planted on cutover forest land or abandoned agricultural fields, and more recently on highly erodible agricultural land covered under the Conservation Reserve Program.
    Trees are planted for many purposes, including timber production, windbreaks, erosion control, Christmas tree production, wildlife habitat improvement, future investment, aesthetics and other land-owner objectives.  Tree plantings enhance the natural beauty of the state, protect watersheds, and enable forests to contribute to the state's economy by assuring a stable supply of wood and providing for recreational opportunities.
    Each year many trees are planted by private forest landowners.  Often these individuals are unfamiliar with planting techniques that will assure high survival and good growth.  To have a successful tree planting program, particular emphasis must be given to soil and species selection, soil preparation, nursery stock selection and handling, planting technique and follow-up care.  Each of these aspects of tree planting is discussed in this bulletin.

PLANTING CONSIDERATIONS

Species and Soil Selection
   Many trees grow under a wide range of environmental and soil conditions, but best growth in most trees is attained within a rather narrow range.  Tree species should be selected for their ability to grow on the proposed planting site.  Not all trees perform satisfactorily on all soils, although they may grow well on different soils in the same area.
    Tree species planted on unsuitable sites suffer high mortality, grow poorly and are more susceptible to insect and disease problems.  To help insure a successful planting, evaluate the soil-species combination before threes are purchased and planted.  Recommendations for coniferous species for various Michigan soil conditions are discussed in Extension Bulletin E-721, "Selecting Management Groups."  Important soil and site factors include air temperature (average, minimum and maximum), air drainage, soil texture and soil fertility.  As a general rule, hardwood species are better suited to loamy and clay loam soil types where soil moisture and fertility are generally higher.  although conifers will grow on heavier soils, they are more commonly planted on drier, coarser textured, and less fertile soils.   All things considered, tree growth is most rapid where soil drainage is good and competing grasses and weeds are controlled.
    Table 1 contains a list of tree and shrub species suitable for planting in different parts of Michigan.  A brief description of some of the commonly planted tree species follows.

Table 1: Planting guide for various forest trees and shrubs under Michigan soil and climatic conditions.

DRY UPLANDS

WELL DRAINED UPLANDS

WET LOWLANDS

SPECIES

Very Coarse

Moderately Coarse

Medium

Fine

Mineral Soils

Organic Soils

Loamy Sand, Sandy Loam

Fine Sandy Loam, Loam, Silt Loam

Sandy Clay Loam, Silty Clay Loam, Clay

Dune Sands, Sands

Level

Exposure*

Level

Exposure

Level

Exposure

Sands to Clays

Muck or Peat

N&E*

S&W*

N&E

S&W

N&E

S&W

CONIFERS (Evergreen)

Douglas-fir

Fir, balsam

Larch, European

Pine, jack

Pine, red

Pine, scotch

Pine, white

Spruce, black

Spruce, Norway(4)

Spruce, white

White-cedar, northern

BROADLEAVES (Deciduous)

Ash, green

Ash, white

Basswood

Cherry, black (4)

Cottonwood

Elm, American

Hickory, shagbark(4)

Honeylocust(4)

Locust, black(4)

(2)

(2)

(2)

Maple, soft

Maple, sugar

Oak, red

Oak, white

Walnut, black

Willow

Yellow-poplar(4)

SHRUBS

Ash, mountain

Blackberry

Black-haw(4)

Coralberry

Crab, wild

Dogwood, gray

Dogwood, red-osier

Dogwood, silky

Elder

Hawthorn

Hazel

Honeysuckle

Juniper, prostrate

Nanny-berry

Ninebark

Olive-Russian

Pea, Siberian

Plum, wild

Rose, wild

Shadbush

Snowberry

Sumac

Pines
   Red pine ins the most extensively planted reforestation tree in Michigan.  It has a high survival rate, grows well on a variety of upland soil types and is relatively fee of serious insect and disease pest.
    White pin grows well on well-drained  sandy loam or clay loam soils, but it is not well suited to dry  soils.  It is susceptible to both white pin blister rust and white pine weevil.  The former is a canker disease that often kills the tree.  The latter, more of a problem in the northern part of the state, causes bushy growth or crooked stems by attacking and killing the growing terminal leader and branches. Nevertheless, white pine is a fast growing tree that does well on good soils in the southern part of the state.
    Jack pine is well adapted to growing on droughty, infertile sandy soils.  It is often planted on sandy cutover sites where other trees do not grow or grow poorly.  Recently it has been planted in several northern Lower Peninsula counties to create nesting habitat for the endangered Kirtland's Warbler.
    Scotch pine is extensively planted for Christmas tree production.   Because it is highly susceptible to insect and disease damage, it is not recommended for reforestation purposes.  Older Scotch pine plantations found in Michigan generally originated as Christmas tree plantations, but were abandoned over time.   Today, these plantations act as a breeding ground for many tree insect and disease pests.  Extension Bulletin E-1155, entitled "Recommended Species for Christmas Tree Planting," lists several recommended seed sources of pine, spruce and fir species which are planted for the production of Christmas trees in Michigan.

Spruce
   White, black and Norway spruce are well suited to fairly acid clay loam soils.  Do not plant them on dry upland soils, especially in the southern part of the state.  Black spruce is p preferred for planting on poorly drained or wet soils, particularly in the northern part of the state.  White and Norway spruce can be planted for Christmas tree production on cooler, more moist north and northeast facing slopes with fine to moderately coarse textured soils.  White spruce plantations for timber production are also planted on some soils in the Upper Peninsula.
    Blue spruce is extensively planted for Christmas tree production throughout the state.  Blue spruce grows best on well drained fine textured soils, although it is adaptable to a wide range of soils.  As with Scotch pine, there are several seed sources available for planting which are described in Extension Bulletin E-1155.

Firs
   Balsam fir, Fraser fir and Douglas-fir are planted as Christmas trees on well drained, fine textured soils similar to those used for  spruce.  Balsam fir and Douglas-fir often have new growth killed back my late spring frosts.  Plant fir species on protected upland areas to ensure proper air drainage and to minimize frost damage or winter kill.  Fraser fir and Douglas-fir are more susceptible to injury from very low temperatures than Balsam fir.   In many areas of the northern Lower Peninsula and in the Upper Peninsula, Balsam fir is recommended.  However,  do not plant Balsam fir in areas with a high concentration of spruce budworm.  Fraser fir is less susceptible to spruce budworm damage.

Hardwoods
   Hardwood plantations are typically more difficult to establish than conifer plantations.  In general, hardwoods require a more fertile soil than conifers.  Preferred soil textures include sandy loams, loamy sands, loams or clay loams.  Because fertile soils typically have higher levels of grass and weed competition, intensive weed control is required to successfully establish hardwood plantations (figure 1).  Hardwoods may also require protection from rodents and may need corrective pruning to produce quality trees.   Hardwoods planted most often are black walnut, oaks, maples, poplars and ashes.   In addition to timber value, hardwood plantations can be designed for wildlife habitat, aesthetics, windbreaks and firewood production.

Mixed Species Planting
   Special emphasis must be given to species selection in mixed plantings.   Differences in species survival, growth rate, and shade tolerance, and soil-site requirements are often responsible for uneven and unsatisfactory plantation development.   While mixtures of hardwoods are generally compatible, conifer-hardwood and conifer-conifer moistures usually do not develop good timber stands, although they are satisfactory as aesthetic or wildlife plantings.
    In most mixed species plantations, weed control is difficult and often restricted to mowing.  Many of the registered herbicides do not control undesirable woody and herbaceous competition in mixed conifer-conifer or conifer-hardwood plantations without damaging or killing one or more of the planted tree species.
    Examples of successful hardwood-hardwood plantations include autumn olive with any other hardwood species and black locust/black walnut plantations.   Autumn olive and black locust stimulate self pruning of the hardwoods with which they are planted.  Furthermore, since both are legumes, they release nitrogen into the soil.  Autumn olive is also a food source for wildlife.  Black locust will produce firewood.  The combination of these species with higher value species, such as red oak and black walnut, reduces establishment costs because fewer of the more expensive oak and walnut trees are needed to plant the site.

Mixed Species Planting
   Special emphasis must be given to species selection in mixed plantings. Differences in species survival, growth rate, shade tolerance, and soil-site requirements are often responsible for uneven and unsatisfactory plantation development. While mixtures of hardwoods are generally compatible, conifer- hardwood and conifer-conifer mixtures usually do not develop good timber stands, although they are satisfactory as aesthetic or wildlife plantings.
    In most mixed species plantations, weed control is difficult and often restricted to mowing. Many of the registered herbicides do not control undesirable woody and herbaceous competition in mixed conifer-conifer or conifer- hardwood plantations without damaging or killing one or more of the planted tree species.
    Examples of successful hardwood- hardwood plantations include autumn olive with any other hardwood species and black locust/black walnut plantations. Autumn olive and black locust stimulate self pruning of the hardwoods with which they are planted. Furthermore, since both are legumes, they release nitrogen into the soil. Autumn olive is also a food source for wildlife. Black locust will produce firewood. The combination of these species with higher value species, such as red oak and black walnut, reduces establishment costs because fewer of the more expensive oak and walnut trees are needed to plant the site.

Planting Season
   Bare rooted seedlings and transplants must be planted during the dormant season if good survival is expected. Weather and soil conditions conducive to planting occur in both early fall and late spring. The spring season is generally considered the best time to plant, especially if planting is to be done on heavy loam or clay soils. Trees planted on heavy soils in the fall are susceptible to frost heaving and winterkill from dry winter winds. Winter damage from rodents and other wildlife is also greater in fall-planted than spring-planted trees.
    Start spring tree planting as soon as the soil is free of frost. Do not plant when the soil is excessively wet, or on hot, windy days. Dull, overcast, cool days are most favorable since evaporation and moisture loss from the planted trees is reduced. However, trees planted in the spring are susceptible to drought.

Tree Spacing
   The distance between planted trees is determined by the species and the purpose of the planting. The goal is to plant a sufficient number of trees to fully utilize the site, but provide sufficient growing space to avoid a noncommercial thinning to maintain plantation vigor. No single spacing is ideal for satisfying all planting objectives. A distance of 6 to 12 feet between trees within planting rows will result in maximum growth and maintenance of tree quality for most species. Spacings of less than 6 feet require thinning before the trees are of commercial size and value and are not recommended. Tree spacings greater than 12 feet are also not recommended as the site is not fully utilized while the trees are young and weed control problems are prolonged.
    Wide spacings also contribute to the development of trees with large branches and por form.  In general, hardwood seedlings are planted at wider spacing than conifer seedlings or transplants and are pruned to produce high quality stems.   Access roads should be evenly spaced throughout a newly established plantation to facilitate future management. 
    General planting density recommendations for specific planting purposes are in Table 2.  Typical tree spacing to reach recommended planting densities are listed in Table 3.

Table 2:  Tree Planting Density recommendations for common planting purposes.

Table 3:  Common tree spacings used to reach recommended planting densities.

* 8 X 10 spacing is used to establish windbreaks and shelterbelts in three staggered rows.

    In general, rectangular spacings are advantageous because they require fewer passes over the site with planting or tending equipment, and they create corridors of access for future operations.  Rectangular spacings are not recommended for wildlife and aesthetic plantings.

SITE PREPARATION

PLANTING STOCK

Types
   Planting stock is available in a variety of species, sizes and ages. Seedlings usually are described as 1-0, 2-0 and 3-0. The first number refers to the number of years grown in a nursery seedling bed and the second to the number of years in a transplant nursery bed. Seedlings may be bare-root planting stock or container grown stock (Figure 3). Transplants are commonly designated as 2-1, 2-2, and 3-2. The total age of the plant is the sum of the two numbers. For example, 1-0 refers to a 1-year-old seedling and 2-2 to a 4-year-old transplant.
    Transplanted stock is more expensive than seedlings, but survival and growth after planting are often better. The improved survival and growth is attributable to the more fibrous root systems of transplanted planting stock. Order spruce, fir, and Douglas-fir as transplant stock to help insure planting success. For most pines, standard 2-0 stock is usually satisfactory.
    Some seedlings and transplants are sold by height class. This has the advantage of establishing a plantation which should develop uniformly. This is important for Christmas tree plantings where uniform growth is desired. Available sizes may range from 6 to 12 inches. A rule-of-thumb for planting success is to buy the biggest or oldest seedlings you can afford. In all cases avoid small (less than 6" tall) spindly planting stock. For hardwoods, look for seedlings with at least a % inch stem caliper and at least six vigorous lateral roots. Avoid hardwood stock with a single large taproot.
    In the past several years, container grown seedlings have become more commonly used for establishing plantations in Michigan. Container seedlings usually are grown in a greenhouse to reduce the time necessary to produce a seedling or transplant. Depending on the species, container grown seedlings often are ready for outplanting into a nursery bed or plantation in less than a year. This compares to the 2, 3 and 4-year old trees produced in standard outdoor nurseries. For most species, seedlings are started in containers in the greenhouse and then transplanted and grown for an additional time in regular nursery beds. If the seedling remains in the nursery bed for one year, it is referred to as a plug-1 seedling. A plug-2 seedling remained in the nursery bed for two years. This practice reduces the amount of time required to produce stock for these tree species and results in a plant with a better root system.
    Container grown seedlings experience less shock than bare-root stock at planting time because the seedling roots are not disturbed when outplanted.   Containers come in various sizes to accommodate the rooting habit of the species being grown. Conifer shipping containers may hold 2 to 4 cubic inches of soil compared to upwards of 75 cubic inches of soil in large containers used for taprooted hardwood species such as walnut and oak. Again, avoid planting small container-grown trees.
    Order planting stock well in advance of the planting season to insure availability of correct species, size and quality. Many of the nurseries which produce Christmas tree seedlings and transplants are sold out of preferred planting stock the summer before the planting season. Planning is important and essential to a successful planting season.

Characteristics
   Inspect tree quality before accepting seedlings or transplants from the seller. Tree, seedlings and transplants are typically packaged and shipped in rolls or boxes (Figure 4).  Inspect boxes and rolls for crushed appearance and coolness.  Figure 5 shows ideal examples of conifer and hardwood planting stock.  Inspect trees for:

• healthy green color
• fibrous root system and/or many lateral roots
• good stem caliper (diameter)
• single versus double stems

Transporting and Storing
   Improper care of planting stock upon receipt often contributes to poor survival and growth of trees. To curtail damage to planting stock follow these recommendations:

• never expose shipping containers to direct sunlight
• keep the temperature of the shipping containers near 35 degrees F during transport
• do not stack shipping containers during transport or storage
• keep one side of each container exposed to open air
• do not allow containers to touch
• transport and store containers on pallets

HOW TO PLANT

Seedlings and transplants may be successfully planted by either hand or machine.  Where conditions are favorable, machine planting reduces both time and labor.  On particularly steep, rough or stony areas, or for interplanting between established trees, hand planting is often the only practical method.  hand planting is also somewhat better suited for planting certain hardwood species, such as walnut and various oaks, which have long taproots.

Handling Planting Stock
   Bring only the number of trees necessary for a single day of planting to the planting site. Moisten planting stock containers before they are removed from the storage area. Shield containers from the sun during the trip to the planting site. At the planting site, immediately place planting stock in a shady location. If necessary, use a vehicle to construct a lean-to for shade. Open only one container at any one time, and close it after the necessary bundles of trees have been removed. This prevents the remaining trees from drying out or overheating. Never sit or place heavy objects on container's so that seedlings are not crushed and damaged.
    Carefully separate the seedlings or transplants in the extracted bundles to minimize, the number of stripped or broken roots. If the roots of the trees were not pruned to an 8 inch length at the nursery, do so with clippers, sharp ax, machete or hatchet before planting. Root pruning makes planting easier and increases survival rates. The actual root length can vary to accommodate the planting tool being used. In general, the depth of the planting hole and the root length should be the same, but not less than 8 inches.
    Keep the tree roots moist and protected from the sun and wind while handling. However, it is usually not recommended to soak the tree roots in water before planting because protective soil particles are removed from the roots, making the roots more susceptible to drying. Place planting stock in white containers containing either moss from the shipping container, wet shredded newspaper, wet burlap or other similar material. This prevents the tree roots from drying out while planting. These materials should also be used in the tree holding boxes on planting machines. No more than one to two hours worth of trees should be carried by the planter.

Hand Planting
   There are two general methods of hand planting: the hole method (Figure 6), and the bar or slit method (Figure 7). The hole method consists of digging a small hole in the soil to hold the roots of the tree. The hole is made large enough for the planter to spread the tree roots out in a natural uncrowded or twisted position. Soil is then added around the roots and tamped firmly to exclude air. Some variations of this method involve the use of a mattock or shovel to make a straight sided hole (Figure 8). The tree is then placed along this straight side and the soil replaced. The soil is then tamped.
    Seedlings or transplants can also be planted by making a vertical slit in the soil with a bar, inserting the roots of the plant and re-closing the slit, both top and bottom. It is important that the tree roots are not crowded and the soil is firmly replaced around the roots. Roots should fall down in the hole to avoid the deformity called J- or L-rooting. Seedlings with J-roots are more susceptible to drought, disease and insect attack because the root system never develops properly. Root systems with a characteristic J or L shape are typically caused by not making the planting hole deep enough or twisting the tree into the hole.

Machine Planting
   A planting machine is attached behind a tractor and creates a slit in the soil as it is pulled along. The seedlings or transplants are placed in the slit. A set of wheels on the back of the planter closes the slit and packs the soil around the tree roots (Figure 9). Many types of machines are available, and each has some special advantage. Some are equipped with furrowing attachments to clear away competing vegetation. Others have spray attachments to apply chemicals for controlling weed growth around newly planted trees.
    Planting machines are very helpful and efficient when planting large areas. During operation, check them occasionally to make sure trees are being planted at the correct depth and that the soil is being packed firmly around the roots. Changes in soil type and topography also may call for minor adjustments in the machine planter.

Summary of Planting Rules

• Plant trees one inch deeper than they were in the nursery.
• Plant trees upright, not at an angle.
• Plant trees in mineral soil, not in loose debris.
• Pack the soil firmly around planted tree roots.
• Keep tree roots cool and moist.
• Do no plant in excessively wet or sticky soil.
• Plant tree roots in a natural uncurled position.
• Make the planting hole deep enough to fit the roots.
• Remove or suppress competing vegetation on the planting site.
• Remove trees one at a time from the planting container.
• Do not remove trees from the planting container until the hole is prepared.

FOLLOW-UP CARE

SPECIAL CONSIDERATIONS

    Trees and forests greatly contribute to the quality of our environment. Therefore, many individuals plant trees for purposes other than producing forest products. Some of these purposes are wildlife habitat, Christmas tree production and aesthetics.

Wildlife Habitat
   Many kinds of wildlife depend on the cover, food and environment trees provide. In fact, the amount and diversity of wildlife in many areas is determined by the amount, type, variety and extent of local forest conditions. Large and varied wildlife populations are not found in barren areas, nor are they found in large, old-growth forests. In general, the greater the variety of plant species and the greater the variety of plant sizes and ages, the better the habitat for a wide variety of animals and birds.
    Plantings for wildlife need not be large. Actually, they are of highest value when planted in scattered groupings throughout a property. Leave open spaces and use irregular shapes in plantings. Plantings of a single species are not as valuable as mixed group plantings which contain hardwoods, conifers, and food-producing shrubs. Wildlife packets, containing a variety of tree and shrub species, are available from many local soil conservation districts. The composition of the packets is varied to match the location in the state where they will be planted.

Christmas Trees
   Michigan produces about one of every five plantation grown Christmas trees in the United States. Growing Christmas trees has become a highly intensive business that requires significant knowledge, time and effort on the part of growers.
    Christmas trees require consistent monitoring and care after planting. They require annual shearing, beginning in the third or fourth year, and protection from insects and diseases each year.
    Several species of conifers are used as Christmas tree stock. The most common are Scotch pine, Colorado blue spruce, and Douglas-fir. For more information on growing Christmas trees, contact your local county Extension office.

Aesthetic Considerations
   Trees and forests are important to the quality of the environment. Tree cover moderates air temperature, suppresses noise, collects dust, dissipates odors, balances carbon dioxide and oxygen levels, and can even warn of dangerous levels of air pollution.
    When planting trees to improve aesthetics, it is well to plan for future growth of the trees. Mixing species, such as conifers and hardwoods, leads to diversity. Planting low growing and tall trees in different locations adds contrast. Consider tree form, flowering habits, foliage patterns, and fall colorations when planting selections are made. Many of these features will increase the attractiveness of any planting in later years. In congested urban areas, select trees that possess some tolerance for confined conditions, and are resistant to certain pollutants. In all plantings, consider soil properties, water availability, space and nutrient requirements before selecting and planting trees. Consult your local county extension office for further information on how to select the right tree species for your situation.

If you have questions or would like additional information, please contact
Dr. Karen Potter-Witter, Professor, MSU Department of Forestry