The fascination of hybridizing rhododendrons and azaleas

Rhododendrons colours:

index

white

orange

yellow

Rhododendrons colours:

Because of the hybridizing work of thousands of plant lovers, we now can enjoy an overwhelming number of beautiful and different flowers and plants. Suppose there was only one color of a rose: red, and that's it. Wouldn't it be a shame?!! Dull and boring!!
We can propagate and graft a new plant and get thousands of the new one. Even quicker is tissue culture, so that in just a few years we have many thousands of the new introduction to be spread for the joy of all who love fine plants.
But why all this hybridizing work? What is our goal? Better or more beautiful flowers and plants. But what does 'better' mean? Let me mention some reasons:
A. bigger flowers
B. prettier flowers
C. double flowers
D. flowers which don't fade or wilt in the sun
E. plants that have a later flowering time - better because of the late frosts
F. plants that are more coldhardy
G. plants that don't grow leggy
H. plants with better dark glowing leaves
Etc.

Seedling Z. 517, a cross with 'Sappho'

a cross with 'Emperor Waltz'

What do you need?
The way I do it:

A. a greenhouse is very useful
B. a small pair of (nail)scissors;
C. (mosquito)netting to keep insects out of the greenhouse
D. small pots (jars) for the stamens;
E. a pair of tweezers, which open if you pinch them!

How does it work?

         Suppose I have an early flowering rhododendron, very hardy with pretty white flowers. If I want a later flowering plant, hardy with a fine
flower and a dark blotch (I like blotches), then I have to cross it with a late flowering plant which has a dark blotch. We want a double red flower? That's not so easy. I use 'Queen Anne's' with double white flowers (therefore without stamens) and I cross it with, for instance, 'Erato', the father, with dark red flowers. I can't do it in reverse, remember, because 'Queen Anne's' has no stamens. Oh, yes, it's not that easy. You need to know what you are doing.
        It also is not always as simple as it seems. When I want an orange flower I could cross a red one with a yellow one. The result? We could expect orange, but it will be just pink, because the color red is dominant.
Studying the ancestors of a plant can be very useful!
            Phenotypical refers to what we see. For example, a plant may have pink flowers. Genotypical means the genome, the "inside". Colors can be red and/or yellow. We call this the "sleeping" characteristics . And which are dominant? Hardiness? Late or early flowering? Or double flowers? It is just a matter of trial and error. For instance, the blotch of 'Sappho' is very dominant. If you don't want it, don't cross with it!!
            This is the fascinating thing about hybridizing - you never know exactly what you will get. Always surprises. And that's better, than knowing before what the results will be! This keeps us going. You can hardly improve a terrific plant, but you can change one or more of the characteristics.
For example the rhododendron 'Hachmann's Charmant' - hardly improvable. Fine flower on a good hardy plant, white with a dark blotch and red margins. But you might want to change it. Not white, but yellow. This can be the challange!

'Eruption' x 'Janet Ward', Z. 556

Z. 700 again a further cross with 'Sappho'

Pollen storage:

A. using immdediately is the best way;
B. pre-dry the anthers on central heating;
C.keep the pollen stored in the freezer in a jar with dessicant (calcium chloride or silica
   gel dessicants) at 0 F (-18C)
D. my experience: freezing directly till 0
     F, -18 C; then using directly!

The Germans could call me “Pflanzensexualbearbeiter”. They like long words. In this case meaning "Plants-sex-worker". Of course you can let the bees do the crossing job, but this is only for "lazy hybridiziers". For those who are willing to do the labour, it is an easy job. Then you also know the parents.J

Looking at the picture( also left below) you see how I make a cross with an own new hybrid. Supposing that I am not satisfied with it and I want a darker blotch, then I cut off some of the ripe stamens with the anthers, using them as the male parent. Mostly I put them in a small jar (of a fotofilm f.i.)

Then I hold the stamens with a pair of tweezers and go to a flower of the other plant with a dark blotch and shake out the pollen onto the stigma of this flower. The tip of a ripe pistil of the stigma is sticky and the pollen will adhere as soon as the pollen touches it

Next? Well, you have to take care that no insects can 'destroy' or mix your cross with other pollen, keep the flower out of the rain (therefore I cross in my greenhouse!). Years ago, when I crossed outdoors, I used bamboo sticks around the plant and put some lace over it. Now I use my greenhouse, which is safer and easier. See the step-by-step procedure below.

I put the capsules with the label in a jar on the central heating (radiator) and within a week the capsules will open themselves or I break them open. I
use a sieve to separate the capsule pieces from the seeds. Try to get the seeds as pure as possible, otherwise you get a lot of fungus when you sow them. Mostly I directly sow the seeds on beds in my greenhouse with daylight tubes and bottom heating. You can also wait until the end of February or March to sow. Then the sunlight gets brighter. There are a lot of ways to germinate the seeds. For example: in your living room near the window. Take care that the seeds or small seedlings never dry out! No direct sunlight!

TIP: never cover the rhodo seeds (or any seeds of any Ericaceae plants) with soil! They need light to germinate. Besides in all the things with rhododendrons the keyword is: MOIST!!! I wish you good luck!!

Step-by-step procedure: see picture
The way I do it:

A. make a plan for the objectives you have and which crosses you want to make
B. make sure that no insects can 'visit' your greenhouse!
C. put the plants for hybridizing in the greenhouse
D. collect the stamens with anthers in jars from plants in the greenhouse and also from plants in the garden
E. make a note about which plant you take the pollen from
F. take the stamens with pollen with the tweezers and shake out the pollen onto the tip of the stigma of the receiving flower. Sometimes you have to squeeze out the pollen between your finger and thumb.
G. repeat the cross if the pollen did not stick on the stigma
H. make a label on the flower-branch with the names of the parents - the mother first!!
I. harvest the seed capsules and label them in September or October

general	information	practice:	propagation	Azaleas	my own hybrids	miscellaneous:
home	rhodo-info	planting	sowing	evergreen	first ##	leaves and buds
about myself	extra info	care	cuttings	deciduous	## 2002	parks and gardens
ordering photos	new Huisman Rhodos	hybridizing	grafting	native azaleas USA	## 2003\4	Articles

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