Note: In this lab, you will learn procedures for propagating selected deciduous woody plants by grafting. Turn in lab report on April 28, 2004.

A. Introduction
        Because flowers on trees or shrubs are cross-pollinated, plants grown from seed do not have the same characteristics as the parent. To propagate a particular cultivar, vegetative propagation is necessary. Where propagation by cuttings is not feasible or economical, grafting is done. For fruiting types like apple or pear, scions of several cultivars placed on one tree develop into branches that are true to type.
        Grafting success requires three elements: a) good technique, b) healthy plant material - both scion and rootstock, and c) a sharp knife. A sharp knife has no substitute. Almost any pocket knife that takes and holds a sharp edge will do but regular grafting knives are recommended.

B. Grafting Terms

1. Scion
        A piece of detached twig or shoot (usually from last year's growth) used in propagating the plant from which the twig is taken. The scion usually contains two to four buds. For most kinds of grafting it is the top part of the graft.
2. Stock
        The portion of the graft to which the scion is attached. It may be a piece of root, a seedling, or a tree with part of the top removed in preparation for grafting.
3. Cambium
        A very thin layer of living cells lying between the outer sapwood and inner bark. This cambium is the growing region just under the bark. Because cambium cells divide and make new cells, the cambiums of two different but related plants will grow together if they are fixed and held firmly in contact.
4. Scion Grafting
        Scion grafting is normally used in topworking older trees. It is a convenient method for rebuilding or rejuvenating an old tree, or changing one to a better cultivar. Scions may also be bridged grafted to repair damaged trees such as those girdled by mice or rabbits. For a successful graft, the cambium layers of the scion and stock must be brought together and held firmly in place until they unite and grow as one. Scions are generally cut in the late fall or winter when the trees are dormant. Grafting is usually done in the spring when growth starts and the sap is running.

2. Whip-and-Tongue
        The method of grafting probably used the most in this country is the whip-and-tongue. It is a common method used to propagate nursery stock and is primarily designed to join together plant parts which are under 1" (2.5 cm) in size. When selecting the scion, choose one-year old wood, preferably the same size as the stock. You get contact only on one side when the stock and scion are of different sizes.
        First prepare the stock. Starting about 2" (5 cm) from the butt of the stock, make a smooth, straight cut about 1.5" (3.8 cm) long. Try to make this cut with one good sweeping movement. Position the one-sided wedge so the cut surface faces you and support the wedge on the back side with your index finger. Starting about one-third of the way down from the tip of the exposed wedge and with the knife perpendicular to the wedge cut, make a downward cut about 0.5" (1.3 cm) long. Make the cut approximately parallel with the grain of the wood. Prepare the scion in the same way, leaving two to three buds. Fit the scion and stock together, pushing them together far enough so the cut surfaces match. The toe of the scion then just comes to the heel of the stock. If the scion and stock are not the same size, be sure to match the cambiums on one side only.
        Whip grafts must be wrapped to maintain contact. When wrapping, see that the scion does not move out of position. The tips of both wedges should be bound tightly against matching cut surfaces. When using non-elastic binding material that may girdle or wraps that will not disintegrate as the graft grows, you will need to slit the material a few weeks later after the graft union has healed.

3. Bark Graft
        A simple, rapid grafting method is the bark graft. This type of graft can be readily performed by amateurs, and if properly done, gives a high percentage of "takes". It requires no special equipment and can be done on branches ranging from 1" (2.5 cm) up to 1 foot (30 cm) or more in diameter, although it is not recommended on the larger sizes. Bark grafting can only be done when the stock is actively growing since it depends on the bark separating readily from the wood. Usually this takes place in the spring when active growth of the stock occurs. Dormant scions must be used, necessitating the collection of scionwood for deciduous species during the dormant season and holding it in cold storage until the grafting is done. With this method, scions are not as securely attached to the stock (as in some of the other methods) and are more susceptible to wind breakage during the first year. New shoots arising from the scions should be staked or cut back to half their length in windy sites.
        For small diameter branches, one scion is used. For larger stocks, several scions may be inserted. Cut the stock or branch where the scion is to be attached to form a stub. A vertical knife cut 1" to 2" (2.5-5 cm) long is made at the top end of the cut stub through the bark to the wood. The bark is then lifted slightly along both sides of this cut, in preparation for insertion of the scion. Select a dormant scion 4-5" long containing two to three buds. Make a slanting cut 1.5" to 2" (3.8 to 5 cm) long at the base of the scion. On the side of the scion opposite the long cut, a second shorter cut is made which forms a wedge at the basal end of the scion. The scion is then inserted between the bark and wood of the stock with the long cut towards the wood.
        The finished graft should be wrapped with grafting rubbers, rubber tape or clear grafting tape. When bark grafting outdoors, the scions are often fastened to the stock using small flat-headed nails (0.5" to 1" long). After the stub has been grafted and the scions fastened by nailing or tying, all cut surfaces, including the end of the scions, should be covered thoroughly with grafting wax.

D. Lab Exercises

1. Plant Materials

a. Root stocks: Malus species (Midwest crabapple seedlings)
    Fraxinus pennsylvanica (green ash seedlings)
b. Scionwood: Cultivars of apple, and ash (green, Manchurian, black)

2. Procedure

a. Perform cleft grafts on 2 crabapple rootstocks and 2 green ash root stocks.
b. Make the whip-and-tongue grafts on 2 crabapple root stocks and 2 green ash root stocks.
c. Perform the bark grafts on 2 crabapple rootstocks and 2 green ash rootstocks.
    Label type of grafts, scion cultivar names, date and your name on all grafted plants.

3. Observation
        Place your grafted plants inside a high humidity tent and observe the shoot growth from the scion. Your lab grade will
        reflect the success of your grafts. Check grafts weekly and remove sucker sprouts below graft.

PLSC 368 - Plant Propagation
Spring Semester, 2004
Lab Report 8

1. Draw pictures of three different types of grafting that you performed.
    a. Cleft graft                     b. Whip-and-tongue                         c. Bark graft
 
 
 
 
 
 
 
 
 
 
 

2. Present the result of your grafting exercise.

                                                                         Cultivar
Graft type                 Stock                     Scion                         Results and comments
1. Cleft

Apple 1     _____________ ______________ _______________________________
Apple 2     _____________ ______________ _______________________________
Ash 1        _____________ ______________ _______________________________
Ash 2        _____________ ______________ _______________________________

2. Whip-and-tongue

Apple 1    _____________ ______________ _______________________________
Apple 2    _____________ ______________ _______________________________
Ash 1       _____________ ______________ _______________________________
Ash 2       _____________ ______________ _______________________________

3. Bark

Apple 1   _____________ ______________ _______________________________
Apple 2   _____________ ______________ _______________________________
Ash 1      _____________ ______________ _______________________________
Ash 2      _____________ ______________ _______________________________