 |
|
Albas |
Hints
for Successful Grafting and Budding Reprinted from the 1/94 issue of The Cherokee Rose After Diann Giles' excellent and expert presentation on budding and grafting at our November meeting, I thought it might be helpful to provide some complementary pointers or "tips for success" for first-time grafters or budders, and a couple alternative methods you may wish to try. So, the following is a slight modification of an article I wrote for the January/February 1991 issue of Fine Gardening magazine. It is printed here with the kind permission of the Taunton Press, publishers of Fine Gardening. The article was written for gardeners in general, not just rosarians, but the concepts and techniques presented are as valid for roses as they are for any other plant. Grafting Basics: Advice and Methods for First-Time Success. As a college teacher of horticulture, one of the skills I have the privilege of teaching is how to graft woody ornamental plants and fruit tree species. I find that many people are fascinated by the idea of grafting plants and that many have attempted a few grafts in their own gardens. In most cases, such attempts have resulted in failure, leading to the idea that grafting is an exceedingly difficult process that most people simply don't have the talent to learn. I disagree with that idea; I find that most people can become proficient at grafting, once the common reasons for failure are understood. In this article, I hope to explain the most common errors committed by beginning grafters, and how to avoid them. "Grafting" is a process in which a part of one plant (e.g., a piece of stem) is surgically attached to a part of another plant (e.g., a root or a stem with roots). These parts grow together to form a single "grafted" plant. The part which will eventually grow to form the top of the plant, producing stems, leaves, flowers, and fruit, is known as the "scion" (pronounced "sigh-on"). Stems from which scions will be cut are called "budsticks" or "budwood." The bottom portion of the graft, which will produce the root system, is known as the "rootstock," "understock," or simply, the "stock." The point at which the scion and rootstock were joined and healed together is the "graft union" or "union." "Budding" is merely a type of grafting in which the scion is quite small, consisting of just one axillary bud (from the point on a stem just above where a leaf was attached), and a small shield of bark. The mere fact that a plant is grafted does not make it better than a non-grafted plant. Rather, it is the fact that a superior, selected scion was attached to a root system ideally suited to its growing conditions, which makes the grafted plant superior. With rooted cuttings or air-layers, you also get a selected cultivar, but these methods don't allow for any selection of the root system. The production of grafted plants requires more skilled labor and considerably more time than are involved in producing plants from seeds or rooted cuttings, so grafted plants are usually more expensive than those produced by other means. Still, there are good reasons to graft some plants. I'll list a few, here: 1. Grafted plants are usually more uniform in their growth habit, flower color, flowering season, fruit size, shape, and quality, etc., than seed-grown plants. If you planted seeds from a 'Golden Delicious' apple, the resulting trees would produce fruit of varying types but none of them would bear 'Golden Delicious' fruit. Grafted trees, using scions cut from a 'Golden Delicious' tree, would all produce typical, 'Golden Delicious' apples. 2. They often begin to flower or bear fruit much sooner than plants grown from seeds. In the case of some fruit tree species, you can save several years of waiting time, through grafting. This is because seedlings of most woody plant species have a juvenile period, during which they are unable to flower or bear fruit. Even if you don't grow your own trees or shrubs from seeds, nursery-grown plants of many species are seedlings. A good example would be the southern magnolia (Magnolia grandiflora), which is nearly always sold by nurseries as seedling trees. Gardeners who buy such trees have to wait 5-10 years for the first flowers to appear, after the tree has grown quite large. On the other hand, grafted trees usually flower the first year after graftage, often while still in a 1-gallon pot. Apple trees behave in a similar manner; seedling trees may take many years to begin to bear fruit, but grafted trees will bear when quite young. The reason for this difference is that in a grafted plant, the scion is cut from an old, mature tree. The scion physiologically "knows" that it is mature, and continues to behave as a mature stem (flowering and fruiting), in spite of the fact that it is now part of a small, grafted plant. 3. Grafting a plant allows you to select a root system adapted to your climate and soil, or resistant to local pests and diseases. THIS IS THE MAJOR ADVANTAGE OF GRAFTED ROSES IN FLORIDA. 4. Some rootstocks produce extreme vigor in the scion. Others may cause the scion to be dwarfed. 5. A skilled grafter can propagate more species or varieties, often with better success, than could be accomplished by rooting cuttings or air-layers. Because of these advantages, most fruit and nut tree species are commonly grafted, including apples, pears, peaches, plums, cherries, citrus, some grapes, walnuts, pecans, and avocados. Some woody ornamental plants are also commonly grafted, including blue spruce, some magnolias, most roses, gardenias, camellias, and tree peonies. Grafts are usually most successful between members of the same species (apple on apple, peach on peach). Some plants can be grafted onto other species in the same genus (oranges on lemon roots [both genus Citrus] peaches on plum roots [both genus Prunus], or nearly any rose species or hybrid on any other species or hybrid [all in the genus Rosa]; or much less commonly, to another genus in the same family, such as orange on trifoliate orange roots (genus Poncirus but still in the citrus family, Rutaceae). Grafts between different plant families (orange on apple roots, grape on walnut roots) usually don't form a union at all and in any case, never survive long enough to make a desirable plant. Tips for Successful Grafting: 1. Use a sharp knife. A grafting knife needs to be literally razor-sharp. I test my knife by shaving some hair from my arm. If it won't shave cleanly, the knife isn't sharp enough. (Don't test a properly sharpened grafting knife with your thumb, or you may need sutures!) We have our knives sharpened professionally at a local shop, and I frequently touch-up the edge with a leather razor strop. A dull knife will almost guarantee failure at grafting. You can use nearly any style of knife but I would recommend one designed specifically for grafting. These knives are honed on only one side, leaving one side flat. With such a blade, it is easier to make a very smooth cut in a woody stem. Because of the one-sided edge on grafting knives, they come in right- and, left-handed models. Be sure you have the correct type for your dominant hand. 2. Budsticks should be collected from young but firm stems of the plant you want to graft. I like to use stems which are no longer succulent, having produced some wood. For roses, the stems are at an ideal stage for grafting when the flowers are fading and dropping their petals, but before the buds have swollen for the next growth flush. For many fruit trees, the most recent growthm flush can be used, after it has hardened. Some recalcitrant species graft best if the wood is cut just as the buds are beginning to swell for a new growth flush. Budwood should immediately have all the leaves removed, to avoid wilting. Wilted budwood usually won't make a successful graft union. Place the sticks in a plastic bag with a few drops of water, a damp paper towel, or a bit of moist peat moss, and seal the bag. If left in the sun, the wood may die within minutes, but in a shady, cool spot, it should last several days. Budsticks of many plant species can survive for several months in the refrigerator, if kept moist. 3. Rootstock plants can be grown from seeds, or may be rooted from cuttings in some cases. ['Fortuniana' rootstock for roses is virtually always produced from cuttings.] They should be well-watered for several weeks before and after grafting. As with wilted scions, wilted rootstocks often result in failed grafts. 4. When cutting the wood, use your entire knife blade: Start at the base of the blade, moving out to the tip in a single, sweeping cut. This results in a smoother cut than you would get by whittling, sawing, or pulling a single spot on the knife blade through the entire scion or rootstock cut. Splinters, bumps, or other imperfections in the cuts will tend to prevent a good match of scion to stock, and will reduce your success rate. 5. Unprotected cut surfaces may dry out in a matter of seconds, preventing a good graft union from forming. So, it is important to make your cuts, match them together, and wrap the graft as quickly as possible. I like to wrap a graft within 5 to 10 seconds of the time I start to cut the wood. Beginning grafters tend to hurry, ending up with a splintered, bumpy cut, or they take far too much time making smooth cuts. But they find it difficult to make perfect cuts quickly. The only remedy for this problem is practice. I usually use roses when teaching beginning grafters, and I take long canes of a climbing variety to class for practice grafting. The students cut scions from the canes and reattach them elsewhere on the same cane, pretending that it is a rootstock stem. They can make 10 or even 20 practice grafts on a long stem, without feeling pressured by the knowledge that their grafts will fail if they don't hurry. When they've become adept at making good cuts, they throw the practice wood away and move on to a "real" scion and rootstock. No precious rootstock plants or scions have been wasted, and they are remarkably better (and faster) grafters than they were, 15 minutes earlier. I would suggest that if you try this method, practice on the species you intend to graft. If you are budding roses, don't practice on apple wood, which has an entirely different feel to it, under your knife. 6. In addition to working quickly, you can prevent the cut surfaces of your scion from drying by making those cuts first, then storing the scion cut-side-down on your tongue while you work on the rootstock. Of course, scions of toxic species or plants you've recently sprayed with an insecticide shouldn't be placed in your mouth, but most commonly grafted plants are harmless. I use this trick with roses, citrus, and magnolias (which taste bad!). Commercial citrus budders often cut large numbers of scion buds at once, storing them in their cheeks for later use. Saliva is harmless to the buds and doesn't seem to promote rotting or other problems for the graft. 7. Cut surfaces should not come in contact with the soil, which contains rotting organisms. Unless scions are in scarce supply, it is usually wise to discard any that are dropped on the floor. 8. I wrap grafts with 1/2-inch, clear polyethylene budding tape (not gummed). The wrap should be quite firm, stretching the tape almost to the point of breaking. Another wrapping material which has gained popularity in the last few years is parafilm, which is a very stretchy, waxy material, originally developed for sealing laboratory glassware. It has the advantage of not having to be unwrapped later, as does tape, since the growing scion will eventually stretch and split the parafilm. Also, if you stretch it correctly, parafilm sticks to itself, making it unnecessary to tie off the end of the wrap. Plastic tape must be tied securely. 9. In warm weather, I usually leave a graft wrapped 3-6 weeks, depending on the species being grafted. If callus tissue has developed on all the cut surfaces, the graft is probably ready to be unwrapped. (Callus is the wound-healing tissue of the plant, and looks like a small blob of white or pale tan spongy material.) In cold weather, grafts should be left wrapped longer. Fall-grafted plants may be left wrapped until spring, in colder climates. There are many methods of budding and grafting from which to choose. Two of my favorites are veneer grafting and chip budding. Veneer grafting is more likely to be successful than are most other methods, especially with difficult plant species. It is therefore a good method to use when learning to graft. In this method, a thin strip of bark is removed from the side of a rootstock plant. Rootstocks can be slightly thinner than a pencil, to slightly thicker than your thumb. The scion is a short (3 inch) twig. The bark is removed from the entire length of one side of the scion, and the cut side is placed against the rootstock cuts, aligning the cambium layers, which are located just beneath the bark. Chip budding is really just a type of veneer grafting, but uses a tiny, one-bud scion. This "chip" of bark replaces a similar chip, removed from the rootstock stem. Once you've mastered veneer grafting, chip budding is quite easy to learn. The big advantage of budding is that you can produce two or three times as many plants from the same amount of budwood as you could by veneer grafting. Both methods can be used at any time of year but I think the best time would be about a month before you want the scions to begin active growth. Malcolm M. Manners
There
have been |
|
