DECIDUOUS HARDWOOD CUTTINGS. PlSc 300 Lab Compare root initiation and bud growth of cuttings in two different propagation environments.

Transcription

1 0 DECIDUOUS HARDWOOD CUTTINGS PlSc 00 Lab REFERENCE: Text pp. - 0; 7-8. OBJECTIVES:. Learn how to make deciduous hardwood stem cuttings.. Compare root initiation and bud growth of cuttings in two different propagation environments. INTRODUCTION: Deciduous hardwood cuttings refer to woody stems used for cuttings, and these cuttings are taken during the dormant period. Hardwood cuttings often have advantages over other types of cuttings because they:. are least expensive and easiest to handle. are not readily perishable. are easy to ship. require little special equipment Many deciduous ornamental and fruit species can be propagated by this method. Cuttings are made from current season s wood and are always taken during the dormant season. Cuttings made from stocky but not overly vigorous shoots grown in full sunlight often root and survive the best. Use the center to basal portion of such shoots; avoid the thinner, flimsy shoot tips. Cutting length is usually unimportant to rooting. At least two buds (the second bud is a safety factor since the first bud will occasionally not develop), however, should be in a position where you can depend on them to develop into a new shoot. Therefore, the buds must be kept away from bottom heat when it is used and usually kept out of the wet medium where they can rot. If bud

2 orientation is difficult to see (not obvious), make the distal (top) cut 90º and the proximal (basal) cut º. Straight cuttings are most common, but heel and mallet cuttings are also used. Many variations exist for handling deciduous hardwood cuttings (see text pages cited above). Which variation is used depends partly on the severity of the winters in a given region. We will study two handling methods (involving two different propagation structures) in this laboratory exercise. Regardless of the structure used, the key is to encourage rooting while discouraging bud break. New leaves will quickly wilt and die if roots are absent because the leaves lack a supply of water. Also, rooted cuttings that have leafed out are more difficult to transplant. Method I. Hotbed: The principle is to use bottom heat to maintain the root zone around ºC (70ºF) to promote rooting while maintaining the air temperature just above freezing to slow bud development drastically. Cuttings should be started in winter and be transplanted by early spring before air temperatures get too warm. Good ventilation is essential, as the sun will quickly heat the air in a plastic covered hotbed or cold frame even on a cold winter day. Method II. Refrigerated (cold) Room: Bottom heat is again used to promote rooting. By locating the cuttings in a refrigerated room, however, air temperature is controlled much better than in a hotbed or cold frame. After roots form and bottom heat is discontinued, bud break can be slowed by maintaining a low temperature so that transplanting can be completed when convenient. Light is unnecessary for leafless cuttings; darkness, in fact, slows bud break by some species.

3 Plants Propagated by Hardwood Cuttings. A. Ornamental trees and shrubs. Arrowwood (Viburnum dentatum), multiflora rose (Rosa multiflora), privets (Ligustrum sp.), weigela (Weigela sp.), mockorange (Philadelphus sp.), and forsythia (Forsythia sp.) are some of the many deciduous shrubs propagated by hardwood cuttings. Trees commercially propagatged this way include poplars (Populus sp.), willows (Salix sp.), and mulberry (Morus alba). B. Greenhouse crops. Roses grown in greenhouses for cut flower production are usually budded or grafted onto rooted hardwood cuttings of Rosa manetti. The roots of this species maintain good activity even in the low light available during the winter months. Hydrangeas, which used to be propagated by softwood leaf-bud cuttings, are now propagated principally from hardwood cuttings. C. Fruit crops. Hardwood cuttings of fruit trees are harder to handle successfully than those listed under A and B above. In the U.S., all propagation is by grafting or budding onto seedlings or clonal rootstocks (propagated by layering). Hardwood cuttings can be rooted, but transplant with great difficulty. In areas with more moderate climates, apple rootstocks, peaches, and plums are often propagated from hardwood cuttings. PROCEDURE A. Form a group of three people. B.. Take uniform whips of ONE species (either willow or poplar).. Make 70 uniform 6 to 8 cuttings, each with at least two nodes (three nodes are best). Note: - Make cuttings from current season s wood (0) - Avoid thin, weak shoots

4 - Use º (proximal - at the base) and 90º (distal - at the top) cuts when polarity is difficult to discern or easy to forget.. Wound all cuttings uniformly. Wounding may enhance rooting by some species. One suggested method might be to make two to four vertical cuts/slashes at the base of the stem of each cutting. The cut can be up to one inch long. Please make certain that you use a cutting board to avoid cutting the table top.. Make bundles of cuttings with each bundle containing cuttings. Hold bundles together with rubber bands if you would like to do so.. Treat the bundles as follows: a. First bundles dipped in tap water for seconds (water control). b. Second bundles receive a second dip in,000 ppm K-IBA solution c. Third bundles receive a second dip in 8,000 ppm K-IBA solution. d. Fourth bundles receive a second dip in 6,000 ppm K-IBA solution. e. Fifth bundles dipped in an 8,000 ppm IBA talc (Hormex #8).* f. Sixth bundles dipped in an 6,000 ppm IBA talc (Hormex #6).* g. Seventh bundles receive plain talc (no auxin treatment - talc control).* *Cuttings to be treated with talc should have their bases dipped in tap water and then the bottom inch treated with powder. Tap the cutting to remove excess powder. 6. Label all bundles completely. - species - treatment - your names, lab section/group - date

5 7. One bundle from each treatment will be stuck (lined out) in the appropriate section of the flats (bottom heated flats) to be put in the cold room. One bundle of cuttings from each treatment will also be lined out in flats to be placed in the hotbed. 8. Cuttings should be stuck in rows from front to back close together in your appropriate section of a flat. Use a trowel or ruler to mark the row and stick the cuttings into the medium without removing the talc. The medium should be firmed down around the cuttings after they all have been stuck. Label cuttings clearly. Lightly water the flats and place them in the appropriate propagation facility (hotbed or cold room). 9. Fill in the top left side of the following table before leaving lab. 0. Your group should check the cuttings twice a week to determine if the rooting medium needs to be watered. RESULTS: You can tell when rooting begins by feeling resistance when very gently tugging on cuttings. When terminating experiments, stick your hand or a trowel underneath the cuttings and push them up to minimize root breakage. Always keep the roots covered with wet paper towels, as they desiccate rapidly. Rooting is evaluated by scoring each cutting as follows: Score Observed Rooting 0 no roots or callus callus only, no roots one or two roots a few roots (-) moderate root mass (-0) heavy root mass (+)

6 Enter the score for each cutting into the following table. Add rooting scores to determine totals for each treatment-environment combination, and then divide by five to determine the average rooting score for each species in the hotbed or cold room. Enter the means onto the class data sheet as well. data are significant because greater accuracy is obtained when the results of a large number of groups are averaged. summary data will be posted for you to copy the next week after taking the data. In addition, be sure to tell the root percentage for each treatmentenvironment combination. For instance, if three cuttings rooted in a treatment, the percent rooting success was 60% ( rooted cuttings divided by cuttings made). C. Devise Your Own Cutting Experiments.. Have your group select one plant species to use.. Plan an experiment with your chosen plant material.. Consider testing at least two factors to investigate a. Wounding (try a couple methods such as vertical cut vs. peel the epidermis or other type of wound) b. Cutting type (straight, heel, and mallet) c. Liquid IBA dips d. Hormex,, 8, 6, 0, and e. Cutting size (diameter or length) f.. Age of cutting wood (-yr-old vs. -yr-old wood) g. Polarity h. Your own idea

7 6. Be sure to use the appropriate controls for each treatment. See the lab instructor for help if you need it.. Make two bundles of five cuttings for each part of each treatment. One bundle could be placed in the cold room and the other could be placed in the hotbed (optional step). 6. Follow the procedures described in lab or in this exercise when making and sticking the cuttings. 7. Carefully label the cuttings. 8. Test the cuttings for rooting as described above (Section B Results). 9. For results from your experiments, devise a table that relates the appropriate information: Species, Treatment, Time (duration since treated) Results controls versus treated cuttings Amount of callus formed (if any) Pattern of callus development Percentage of cuttings forming roots length of roots Effects of wounding Number of roots per rooted cutting Degree of open buds or shoot growth Effect of hotbed versus cold room Site of wound appearance in relation to callus (if any) 0. Other data or important observations should be written in the report CONCLUSIONS: Examine the class summary data and then comment briefly on the following:. What is the significance of callusing for the species (willow or poplar) you used?

8 7. Comment on the effects of the different treatments to induce adventitious root formation.. Compare the hotbed vs. the cold room with respect to: a. Rooting: If you saw differences in the numbers of roots formed on cuttings in the different environments, what do you think caused the differences? Please explain your answer. b. Bud break: Rooting Score: Group Data Species & Cutting Rooting Score Callus Present ( + / - ) Treatment Number Cold Room Hotbed Cold Room Hotbed

9 8 Rooting Score: Group Data Species & Cutting Rooting Score Callus Present ( + / - ) Treatment Number Cold Room Hotbed Cold Room Hotbed

10 9 Rooting Score: Group Data Species & Cutting Rooting Score Callus Present ( + / - ) Treatment Number Cold Room Hotbed Cold Room Hotbed

11 0 Rooting Score: Data - Mean Scores* Species & Group Rooting Score Callus Present ( + / - ) Treatment Number Cold Room Hotbed Cold Room Hotbed * Greater accuracy is obtained when the results from large numbers of groups are averaged.

12 Rooting Score: Data - Mean Scores* Species & Group Rooting Score Callus Present ( + / - ) Treatment Number Cold Room Hotbed Cold Room Hotbed * Greater accuracy is obtained when the results from large numbers of groups are averaged.

13 Rooting Score: Data - Mean Scores* Species & Group Rooting Score Callus Present ( + / - ) Treatment Number Cold Room Hotbed Cold Room Hotbed * Greater accuracy is obtained when the results from large numbers of groups are averaged. Plsc00\lab hardwood cuttings-.doc