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## 2002

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## 2003\4

Articles

Rhododendrons colours:

index

white

orange

yellow

Rhododendron George's Delight - a nice flower with a mix of colours - yellow, pink and orange.

Rhododendron 'Double Winner' a strigilosum hybrid with hairy leaves and stems - has bright red flowers

Rhododendrons colours:

pink

red

blue

species

other topics      rhododendron photo review

Photography

My (ex)-gardens 'Park der Gärten' Germany ASA Convention 2003 Flowershow ARS Dutch Rhodo. Society
Kalmia latifolia "Indian Summer" in Maine wildflowers Costa Blanca Bernhard Knorr rhodo's Hans Hachmann Rhodo's Joe Klimavic azaleas
a box with prepared cuttings

Rhodoland

Propagating from
cuttings and graftings

detail image of the cuttings

             Propagating from cuttings and graftings is more a subject for professional nurserists and propagating companies. For an amateur like you and me it is worth to give it a try, and for you I write down my experiencies and efforts. To do things rigtht, you actually must have a sort of greenhouse,and if possible, bottom heating facilities and daylight tubes or fluorescent lights. Rooting evergreen azaleas is very easy to do with good results. But to root the other groups of rhododendrons is not so easy. There are so many reasons why things go wrong - the rooting medium is too dry or just too wet - the warmth is too high or the cuttings get rootrot etc. Nevertheless you can try it  and see what happens. By trial and error we can learn much. So, I now tell my story how I proceed and what I use for it. 
And if you want to see how professionals do it, just go to a nursery or propagating business and ask to visit them. In Holland we have the so called "open-nursery-days" to visit and see how they propagate or pot up etc. Very interesting to do!


Cuttings

       Propagating by cuttings and graftings are vegetative methods of multiplying plants. The results will be plants with exactly the same characteristics as the mother plant. And that's just what we want. So, when I have a wonderful new hybrid and want  many more of them, I have to multiply them. Nowadays there are more methods to do this, like "Tissue Cell Culture". Then you need laboratory equipment and know-how about laboratory procedures in biotechnology, far beyond our goal.
Propagating from cuttings has many advantages: it is relatively cheap - it is a quick method with some plants - in large numbers per small surface - the process is not really complicated etc.  
        With rhododendrons we have to distinguish between the 4 main groups: 1.  the large-leaved = elepidote rhododendron; 2. the small leaved = lepidote rhododendron; 3. the evergreen azaleas and 4. the deciduous azaleas. I can tell you a different story with all these groups - yes, it is not that simple. I'll try to keep it short:

Group 1. From July till September, as soon as the new shoots have hardened off. Take cuttings early in the morning and keep them cool. Break out the last bud certainly if it is a flower bud; about 4 to 6 inches long. Take leaves off except for the last 4 - 6 leaves. See photo 1. You can cut off about one third or half of the leaves; photo 2. On the bottom of the cutting slice off  a sliver or wound of the stem, about 1 inch, using a sharp knife.  Photo 3. Use a rooting hormone, f.i. Hormex (ibz-hormone) of about 0.5 % depending of the variety and dip the cutting bottoms in it. Not too much, so tap off the excess!!  Prepare the cutting boxes and fill up with a layer of about 5 to 7 inches of a mix of spagnum peat moss-perlite. This must not be too wet, otherwise the cuttings will rot! See  photos below!  Tap this mix a bit but not too heavy. There must be air spaces in the soil. Now stick the cuttings up to 2-3 inches into the medium - 1 to 2 inches apart. Water with mist, use fine nozzle not to water too much. The key-word for all this is MOIST, not wet..See pictures. Now cover with a thin sheet of plactic to get 100 % humidity! Start with a temperature of about  60 F (15 C) After 2 - 3 weeks you see callus = wound tissue at the bottom of the cuttings. Now you can raise to   68 F (20 C)  NO direct sunlight on the boxes, it will get too warm. Check every week for rootrot and humidity. Be aware that most problems arise wilth a combination of too wet and too warm! If things are going well, you can have the cuttings rooted in 2 to 3 months. For the right hormones check the internet for your country. There are many trade marks.

Group 2. About the same time and the same method. With a bit of luck the rooting time is even shorter. I have had very different results. Sometimes 90 %, another time only 20 %. Now you can or must use a different hormone; here in Holland we use Rhozopon B 0.2 %.  Ask nurserists what they use. Some nurserists use water soluble tablets. Just look (google) with 'rooting hormone'. Don't start too warm. 

Group 3. Evergreen azaleas. If all the rhododendrons would root so easily, this page would not be necessary. Time is July through August. No hormones. Take cuttings early in the morning, about  3-5 inches. Take off the lowest leaves. See picture right below. Most I leave the flower bud - I sometimes get cuttings from friends and I want to know how they flower. It takes about 6 weeks to root, and that is quite fast. I leave the rooted cuttings in the box, also with the other groups!  

my greenhouse a box with rooted cuttings

Group 4. The deciduous azaleas. Their rootability is quite low and difficult. That's my experience, though I know nurserists who are very keen on doing this right with good success. The best method is as follows: put the plants into the heated greenhouse in March to let them sprout with new shoots. Then harden them off a bit. Take cuttings. and stick them in the same rooting medium as with group 1. Now they can root in time in summer and get new sprouts themselves. This is important to survive the next winter. As far as I know there is no need for rooting hormones. Here in Holland most of them are grafted on R. luteum, but this is not managable for us. By the way - I work together with a nurserist in northern Germany, and he has many greenhouses and is very good in propagating. But he has 'somebody' who's job it is to check all the greenhouses all the days. Moreover he works with 'mist-systems'. Well, yes, in this case I could......

Grafting

       Generally speaking it is so, that many nurserists propagate from cuttings, when grafting is not necessary. But I know, that in the USA many nurserists don't graft at all. So, why make graftings, when there is no need for it? It's a lot of extra work and also 'double' work. First propagate a cutting, and then make a graft on it. So twice the chance that something goes wrong. In Germany, even more than in Holland, they do make graftings, "Veredlungen", as they call it. So, why?
       Well, the reason is, that quite some plants don't grow and prosper so well on 'their own roots'. Grafted on f.i. 'Cunningham's White' they will do much better, grow stronger, or can stand soils with a higher pH, can better pull up the nutrients etc.  So, the 'understock' must have better growing qualities than what you graft on it. What you graft on the understock or rootstock, the scion is the plant that we want to propagate. There are many ways to graft, side-grafts (side-wedge), apical wedge, sadle grafting, copulation end more. I won't go through all with you, except copulation, which is the easiest way and most understandable. See the pictures below.
The copulation graftings mean, that you cut off the scion and the understock the same way, slanting\sloping, with the same angle and length. Now the scion and understock must be unified, joined together with raffia or elastic band. The cambium layers of both, scion and understock must grow together. You can leave one or twee leaves on the understock, or cut them away. Leaving them means, that the understock has some own 'growth supply'. See pictures below. 
I used a method combining cuttings and understock together. I 'connected' a scion to an unrooted understock, and put them both into the rooting medium to get roots. I advise you to make your own experiments. I know "rhodo- and azalea-nuts" in the USA, who try out any method they can imagine. Science arises through trying! 
The time of graftings is most in spring if you have the right facilities. Also in winter, January or February, using bottom heating. You must cover your graftings with thin  plastic sheets to maintain high hymidity. Don't let anything dry out. Then it is over and out.....

       Another simple way of propagating for amateurs is 'Tip-layering'. Bring one or more low growing stems down to ground level and remove the leaves here. Dig a trench, put some peat in it and fix the stem into the trench. Put the soil or peat mix back into the trench, and a stone on it. Wait about a year and the stem in the soil will have roots. Cut of the stem, and you have a new plant. Wounding the stem a bit on the 'trench part' will help to get roots. 

How to act now? I mostly leave the rooted cuttings in the boxes. Why? Well, late in fall when they have roots, you can pot them up or so. What happens? It is unavoidable to damage some tender roots.  And there is no growth 'in the air' now and the roots will rot. Therefore I wait till March-April. Growing conditions are good now and I pot them up or plant them out in my garden. One more tip: as soon as the cuttings or graftings are rooted, I take away the plastic sheets and pick out dropped leaves and dirt, otherwise they will rot..
       I wish you all good luck with it. And if you found out a different but good way of propagating, just let me know!

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