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AUSTRALIAN ROSE BREEDERS' ASSOCIATION

ROOT GRAFTING

 

By Dao Mai, Sydney, NSW, http://roseexchange.biz/roseexchange

 

Root grafting is a rose propagation method used extensively by Dutch growers to propagate roses for hot house production of cut flowers. Perhaps it is not used a lot for production of garden roses because it seems to take a little longer to produce a big plant suitable for sale. The philosophy of this method is to strike way between producing an own-root rose by rooting a rose stem directly and a grafted rose where an understock is used. Eventually the rose will become an own-root rose but it has the advantage of being a grafted rose in the first few weeks or months of its life. And this also overcomes the fact that some roses are very difficult to root. The root graft helps the plant to survive until it naturally grows its own roots from the rose cutting at the top part.

The picture below show a successful root graft baby rose. Note that white callus that formed and connected the root segment and the rose stem.

 

Advantage of root-grafted roses

1.  You only use a 1 node or 2 nodes rose stem. This is a saving on disease-free rose materials

2.  The technique creates a new plant rapidly because the root segment will automatically grow feeder roots in 3 days, and the rose part will produce callus to form the union within 1-2 weeks.

3.  This technique overcomes the fact that some roses are very hard to root. So it allows the new plant to start a new life as a grafted rose.

4.  The mature root segment stores much needed reserve energy to help the rose

part to grow quickly

The only disadvantage of this method is the size of the plant. It cannot be big to start with because the union is unstable. The root segment will probably break away in the future months after the rose part grows its own roots and turns into a completely own-root rose. For this reason it will take longer for it to become a mature rose. And that’s probably the reason why they are best for low wind growing environment inside a hot house for cut flower production. However this would change after 2 years when they are big enough to survive strong wind.

The method cleverly solves the most difficult problem which is the rooting of all kinds of roses in the same environment (low strike rate). This is achieved by using a very simple operation to graft the root segment and the rose cutting.

Root grafting procedure

The procedure is similar to the softwood rooting procedure, and misting is required to get the highest success rate. Softwood cuttings are used at all times.

The slow way is to do it in cool autumn weather with a misting system. There is not enough leaves to create enough sap flow for the root and the rose cutting to unite quickly. This is why we need some morning Sun light and misting to counter the drying effect of the Sun.

1.  Prepare a rooting medium with 80% sand and 20% peat to help retaining moisture

2.  Harvest disease free softwood rose cuttings, small in diameter and with completely healthy leaves. Keep only 1-2 leaf set(s) and trim it back down to about 4 leaves on each leaf set.

3.  Harvest roots from any rose type, but roots from a rootstock is the best. Cut the roots into 3cm segments.

4.  Grafting: simply slant-cut (with a razor sharp knife) the base of the rose cutting and the top of each root segment. (a) Make sure you know which end of the root segment is supposed to be the top end (closer to the trunk of the original plant). This top end must be grafted to the rose cutting. (b) The slant cut must be in the same direction of the stalk of a leaf set. This is important for the cut to get as much sap flow from the leaves as possible. (c) Also make sure the diameter of the rose stem and the root segment are as close as possible.

5.  Bind the two using a cotton yarn for best result (cotton yarn will rot naturally in the soil after a couple of months). Using a strong cloth peg is a possibility but it’s unreliable.

6.  Use a pencil to dip a hole in a medium about 5cm deep, lower the root-grafted rose into the hole and firm up the sand.

7.  Protect the location by using chicken-wire net and clear plastic sheet making a high fence surrounding the rooting bed (create a windshield).

8.  Frequent misting is required to keep them fresh.

 

The root-grafted is expected to grow roots and form callus within 2 weeks. They will grow feeder roots and new leaves very quickly. Therefore they need to be repotted after 4-5 weeks. Alternatively the growing medium can have 2 layers of soil mix. The lower layer is rich soil with plenty of nutrients. The top layer is about 8cm thick. The root-grafted rose stay well above the bottom layer. Eventually the roots will go down to the bottom layer to feed.

I can foresee that the cut can be improved if you have the right tool. The cut must be sweet for the union to happen quickly. A crinkle cut using very sharp tool will help the root and rose segments to bite into each other and make the graft much more stable. Finding a tool that can do this is a difficult matter. The common kitchen potato/carrot cutting tool set does not have razor sharpness to cut rose roots and stems sweetly. This could be a good exercise for a handy toolmaker.

 

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2010 The Australian Rose Breeders' Association, created by Paul Hains
 
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