Lab II. T-budding
For information about the use and commercial applications of T-budding,
including links to several Web sites which describe it in detail, go to T-budding
in the List
of Grafting and Budding Methods.
B. T-budding Exercise Check List
For information about the use and commercial applications of T-budding, including links to several Web sites which describe it in detail, go to T-budding in the List of Grafting and Budding Methods.
B. T-budding Exercise Check List
1. Rootstock preparation.
- Choose a hibiscus stock plant that is actively growing (to insure that the bark will be slipping), and locate a straight section of stem at least 10 to 15 cm above the soil line, or higher if you prefer highworking.
- The diameter of the stock should be approx. 7 to 10 mm (pencil thick, at least) at the point you wish to insert the bud.
- There should be a sufficiently long internode at that point to insert the t-bud without involving a node. Nodal tissue, where leaf and bud join the stem, tends to be more difficult to cut and the bark more difficult to peel away from the underlying wood, than it is at internodes.
- Using your knife, cut off any leaves for at least one or two nodes above and below, so that you can see clearly and have plenty of room to work. Remove these leaves by cutting the petiole about 1 cm out from its point of attachment..
2. Cutting the stock plant
Note: The upright T-bud is the most common approach, especially in the temperate zone. In regions of high rainfall, an inverted T-bud is often used, so that rain water can drain from the bud pocket.
- Make the first horizontal cut with your grafting (or budding) knife, by pushing the blade of the knife through the bark, down to, but not deeply into, the underlying wood. This can be done with a rolling motion rather than with the tip of the knife. This horizontal cut should extend no more than half way around the stem, and should not exceed about 1 cm in length.
- Next make a vertical cut from the center of the horizontal cut and perpendicular to it, downwards, 2.5 to 4 cm long.
- Using the back (dull) side of the blade of a grafting knife (or the blunt-ended tool at the end of a budding knife opposite the blade), gently separate the two flaps of bark, created by the T-shaped cut, from the underlying wood, to create a "pouch". It is critical that the bark be slipping as described above; otherwise the bark will tear.
- Making First horizontal cut. Note Field T-budding is done very close to the ground. Outer bark has been scraped away before T cut is made
- Inverted T-budding, used in areas of high rainfall, so excess water will drain from pocket.
- Pulling back bark flap. Field T-budding several inches above soil line.
3. Preparing the Scion bud
- Select a healthy looking bud (incipient shoot) from a scion donor plant, preferably of another hibiscus variety, and remove the leaf by cutting its petiole approx. 1 cm out from its point of attachment with the stem.
- Starting 1 to 2 cm below this scion bud, cut the bud shield (scion bud) by drawing the knife upwards, underneath the bud, and reemerging 1 to 2 cm above it. The knife should pass just under the bark and slightly into the underlying wood (xylem). Some budders remove the sliver of wood from the back of the bud piece before inserting the bud into the rootstock pocket.
4. Inserting the scion bud into the stock
- Holding the bud shield by the "handle" formed by its petiole stump, insert it into the rootstock pouch by sliding its bottom (pointed) end downwards from the top of the "T" and under the bark flaps.
- Once the bottom end of the bud is pushed all the way into the T-shaped pocket of the rootstock, any (upper) portion of the bud shield which does not fit into the pocket, and protrudes out above the horizontal cut, should be cut off with a rolling motion of your knife, so that the bud fits entirely within the pocket. This is to ensure that the cut surface of the bud makes tight contact with the underlying wood of the rootstock.
5. Tying the bud
- Begin tying a few millimeters below the bottom of the bud. Trap the bottom end of the budding rubber beneath the first turn by holding the end at an ascending angle with the thumb and forefinger of your left hand while simultaneously stretching and wrapping the band in a counter clockwise direction, creating an "X". Continue turning, overlapping each turn by about half the diameter of the budding rubber. Go around rather than over the bud itself, or small lateral shoot in the case of hibiscus, continuing up about 1 cm above the bud. In some cases with apple and other fruit trees, if the bud is small and hard, it may be completely covered by the budding rubber.
6. Post budding management of the T-budded plant
- Place the budded hibiscus under shade in the greenhouse for several weeks. A good early sign of a successful graft union is abscission of the petiole stump attached to the scion bud piece. If it dries up, but remains attached to the bud, the graft has probably failed.
Question: Why is non-abscission an indicator of failure to form a graft union?
- After several weeks, if the graft has taken, callusing of the graft union should be apparent. New shoot growth from the bud may also occur, but often the bud remains dormant. It can be forced into growth by bending the stem of rootstock over (but not breaking it off entirely) several cm above the bud graft. If you have chosen to place a T-bud on the same hibiscus rootstock as you have done a top wedge graft on, you will not be able to force the bud in this fashion (without destroying the top wedge graft).