Budding and Top Grafting Rhododendrons
B. F. Lancaster
The amateur rhododendron enthusiast not in possession of a greenhouse with grafting benches or other nursery equipment for increasing his stock may derive considerable pleasure and benefit by the simple method of budding or top grafting during the summer months.
Budding may be done from June on to as late as the bark will peel easily from the wood, in ordinary seasons about September 1st. The writer has found the best wood to place the bud is on the preceding season's growth, that has a diameter of ¼ to ½ inch diameter. This wood as well as some 2 year wood will still have thick green bark which is quite tough and works easily. Budding may be done on older wood that has turned brown and is somewhat rough but the bark will be found to be much thinner and will rupture easily.
Suitable dormant buds will be found at the juncture of leaf and stem on previous season's growth or where ever the bark is green. With a sharp thin blade start the cut ¾ to 1 inch below the leaf stem, slicing upward, taking some of the hard wood with the bark. The shield should be thickest at a point below where the leaf stem enters the main branch and gradually come to the surface about ¼ to ½ inch above the dormant bud. Do not attempt to remove any portion of the wood on the under side of the shield as this will weaken it.
The size of the shield will indicate the length and breadth of the cuts to be made in the stock. Make these cuts and peel the bark downwards with a dull blade far enough so that the eye will be at least ¼ inch below the top or horizontal cut when inserted and pressed firmly downward as far as it will go. A small portion of the shield above the eye should project slightly above the horizontal cut when in place and be cut off crosswise in line with the cut. This last operation seems to be important and lets the top of the shield bark meet the bark of the stock smoothly and it is here that the graft union seems to start.
Wrapping comes next for which I prefer 3/16 by 6 inch rubber grafting or budding bands, obtainable at most garden supply stores. I start the wrapping at the top to cover the horizontal cut and wrap downward rather closely, but not too tight, past the lower end of the lengthwise cut, just leaved varieties make a shield bud leaving the dormant eye and leaf stem exposed. The whole leaf may be left intact or up to ¾ of it removed for ease in handling as some of the larger rather top heavy to handle.
The operation is now complete and needs no attention until the following spring, as the bud will remain dormant until growth starts. At that time if the leaf or bud remains green it has taken and the stock should be smoothly cut off just above the rubber band, which may still be left to reinforce the union and removed at any time it seems to be cutting into the bark.
Perhaps a few brief notes of the writer's experience would be helpful here. Some slow to bloom hybrids as Luscombei, have set buds on the first year's growth and bloomed-every year since, when budded on our native macrophyllum stock. Similarity in bark structure and type seems to be important for successful budding.
Top grafting as so ably described by our fellow member, Halfdan Lem in the 1946 Year book seems to be very successful even where the species or hybrids are widely separated in their serial relations. The writer has successfully top grafted the following specie and their hybrids. Auriculatum , barbatum , campylocarpum , croceum , forrestii , falconeri , fulvum , lacteum , williamsianum , kyawii , venator and all of the griersonianum hybrids available.
My experiments along this line have been chiefly because of a lack of patience to wait years to see some species or hybrid to bloom and it has certainly paid off, as I have branched and bloomed many new ones budded or top grafted on single stems 2 foot standards in my own garden. From a 4 inch plant of sinogrande purchased last October I have a plant grafted on a 4 foot ponticum standard with 6 inches of growth, ½ inch in diameter with its corresponding big leaves that should in one more year be 10 or 12 years ahead of the little plant I took the ⅓ inch scion from.
NOTE: The writer will be happy to demonstrate results of any of these experiments to members of the Society who find it convenient to call at his home just north of Camas, Washington.