Breeding Hardy Rhododendrons in Finland
Kristian Theqvist, 16-Apr-2016, rev. 028

This is my hobby and I love what I am doing when I cross rhododendrons. May be some day my hybrids get to the commercial market for everyone to enjoy.

Elepidotes

• Criteria for selection as mother: Hardy Finnish hybrids
  • 'Elviira' Dense, well branching compact habit. Deep red flowers with faint dark spotting. Weak points: Leaves are somewhat curved and needs protection from the early spring sun.
  • 'Mauritz' Dense, well branching compact habit. Cherry red flowers with darker red spotting. Sister of 'Elviira'. Seems to be easier to please than 'Elviira'.
  • 'Kullervo' A hardy yaku hybrid. Compact and round growth. Pink flowers fading white, upper lobes spotted green. Weak points: Flowers could be larger.
  • 'Haaga' An upright, well branching plant, reaching 1.5 to 2 m height when fully-grown. Bright pink flowers, red-orange freckled. Weak points: Subject to snowload damage until 1m high.
  • 'Helsinki University' An upright, well branching plant, reaching more than 2 m height when fully-grown. Light pink flowers, red-orange freckled. Weak points: Subject to snowload damage until 1m high.
  • 'Mikkeli' also known as 'St. Michel'. An upright, well branching plant, reaching more than 2 m height when fully-grown. Leaves are glabrous, dark green, underside with yellowish indumentum. Light pink flowers, green or green-brown freckled. Weak points: A bit shy flowering when young.
  • 'P.M.A. Tigerstedt' also known as 'Peter Tigerstedt'. An upright spreading plant, reaching more than 2 m height when fully-grown. White flowers have blood-brown blotches. Weak points: Straggly growth in full shadow.
  • 'Pekka' A strong growing plant, reaching more than 3 m height when fully-grown. Large attractive leaves. Pink flowers, brown freckled. Weak points: Grows large for a small garden.
  • 'Hellikki' An upright, compact plant, height 1.2 m in ten years. Purplish red flowers. Leaves are glabrous, dark green, underside with indumentum. Weak points: Needs almost full shadow to grow nice leaves.
  • 'Elsie Maria' R. dichroanthum hybrid, that I have named for my mother. A low growing plant, 60 cm height in 15 years. White flowers with pink edges, greenish yellow area with brown spots on upper lobe. Leaves are glabrous, dark green.
  • 'Eino' A wide growing plant, height 1.2 m in ten years. Dark flower buds open in purplish pink flowers with yellow-brown spottings.
   

• I have tried to emphasize the super hardiness of the brachycarpum var. tigerstedtii hybrids in my selections. I have intentionally left out the Finnish hybrid 'Pohjola's Daughter' from my plans as not hardy enough. My favorites as mother have been 'Kullervo',  'Mikkeli', 'Pekka' and 'P.M.A. Tigerstedt'. Link to pictures and information on Finnish Rhododendron Hybrids.

• Criteria for pollen giving elepidotes: pollen available / specially beautiful flower / compact, nice growth / good leaves / at least marginally hardy.
   
• The tables include only crossings with Finnish hybrids as mother. I have done also several other elepidote crossings but they are not documented on this page.

Explanations of the symbols in the table
02 OK crossing done in 2002 and germination was succesful
02 F crossing done in 2002 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
03 OK crossing done in 2003 and germination was succesful
03 F crossing done in 2003 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
04 OK crossing done in 2004 and germination was succesful
04 F crossing done in 2004 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
05 OK crossing done in 2005 and germination was succesful
05 F crossing done in 2005 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
06 OK crossing done in 2006 and germination was succesful
06 F crossing done in 2006 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
07 OK crossing done in 2007 and germination was succesful
07 F crossing done in 2007 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
08 OK crossing done in 2008 and germination was succesful
08 F crossing done in 2008 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
09 OK crossing done in 2009 and germination was succesful
09 F crossing done in 2009 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
10 OK crossing done in 2010 and germination was succesful
10 F crossing done in 2010 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
11 OK crossing done in 2011 and germination was succesful
11 F crossing done in 2011 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
12 OK crossing done in 2012 and germination was succesful
12 F crossing done in 2012 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
13 OK crossing done in 2013 and germination was succesful
13 F crossing done in 2013 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)
15 OK crossing done in 2013 and germination was succesful
15 F crossing done in 2013 but germination failed (sterile pollen, not enough pollen, pollen not good, bad timing in pollination, polyploidy, ..)

Elepidote crossings table 1, pollen from species

(1) Annoying mixup in pollination or marking. Pollen could be either from arizelum or sinofalconeri.

Elepidote crossings table 2, pollen from hybrid

Elepidote crossings table 3, statistics on species and hybrids combined

2004
This is a learning process for me and in 2004 I had more patience to wait for the covered stigmas to be wet before I applied pollen. However, the weather was very cold in June and some pollinations probably failed partly because of too low temperature. This was specially the case with 'Elviira'. The temperature dropped to -6°C (21°F) on one of the nights after pollination.

2005 and 2006
In 2005 and 2006 I did continue the same line of hybridization work as in previous years. I have got pollen of several rhododendrons from Bjarne Dinesen (Denmark). Thanks Bjarne! See his marvelous pictures at Asperupgaard.

From 2002 to 2006 I've done 265 crosses in which the mother plant has been a hardy Finnish hybrid. Out of these 188 crosses have yielded seed.
I have high hopes that some of these could result in hybrids that have qualities worth for naming.

As of 22nd of November, 2006 I have myself 2277 plants cross plants growing and there are probably a lot more plants around the world from the seeds I've distributed to various Seed Exchanges.
Since my resources are limited (this is my hobby!) I sow only max 30 seeds per cross. This is not enough to get the whole variance of a cross. On the other hand this justifies the distribution of seeds to Seed Exchanges.

2007
In 2007 I made a lot less crosses than in previous years.
Based on the ARS Seed Exchange Pollen-to-Seed Program I ordered pollen from RSF and formed a small hybridizer team here in Finland. The two other hybridizers in addition to me were Osmo Jussila from Naantali and Jaakko Saarinen from Arboretum Mustila. To optimize the amount of seed we made R. brachycarpum var. tigerstedtii crosses with two separate plants, one at Naantali and another at Arboretum Mustila.
The main aim was to to get hardy big-leaf hybrids by using use the super hardy R. brachycarpum var. tigerstedtii and hardy proven Finnish hybrids as seed parent and pollen from big-leaf Rhododendron species. In addition there are side goals for yellow flowers, late flowering and good indumentum.
I have reported my own crosses on this page and other crosses of the hybridizer team on page The seed list for ARS 2008 Seed Exchange.

2008
Based on the Pollen-to-Seed Program I had formed in 2007 a small hybridizer team in Finland. The results in 2007 were good and the hybridization work was continued in 2008. The two other hybridizers in addition to Mr. Theqvist were Osmo Jussila from Naantali and Jaakko Saarinen from Arboretum Mustila. The main aim in the hybridization program was to to get hardy reds by using the super hardy R. brachycarpum var. tigerstedtii and hardy proven Finnish hybrids as seed parent and pollen from Rhododendron species with red flowers. In addition there were side goals for beautiful leaves and good indumentum. I have reported my own crosses with Finnish hybrids on this page and other crosses of the hybridizer team on page The seed list for ARS 2009 Seed Exchange.

2009
The hybrization team continued the third year in the ARS Seed Exchange Pollen-to-Seed Program. Each team member chose his favorite pollens from the RSF list. Results: The seed list for ARS 2010 Seed Exchange.

2010
The hybridization team decided not to participate in the Pollen-to-Seed Program due to personal workloads in other activities. I had also decided to reduce the number of crosses. However, on my travels I got some pollen and could not but make some 20 crosses for fun. I have added the crosses on the tables with the marking 10 OK or 10 F.

2011
I did make only 4 elepidote crosses in 2011 due to workload in other activities. I have thousands of plants growing from my crosses from previous years. The plants consume a lot of space in my arboretum and because of this I need to focus in new crosses only to the most interesting ones.

2012
I made in summer 2012 a total of 52 crosses on elepidotes and 42 crosses on azaleas. The list of seed giving crosses can be found from the page Seeds from summer 2012 to various Seed Exchanges.

2013
I made in summer 2013 a total of 35 crosses on elepidotes and 17 crosses on azaleas.

2014
I made in summer 2014 a total of 4 crosses on elepidotes and 8 on azaleas.

2015
I made in summer 2015 a total of 54 crosses on elepidotes and 9 on azaleas, but most crosses were now maternally on other than named Finnish cultivars.

Pictures and links to results

My Registered Rhododendron Hybrids
Unnamed or Non-registered Elepidote Hybrids

Figure 1. Pollen in small gelatin capsules.

Figure 2. The seed pods on 'Helsinki University' are swelling. I got from Jens Birck an excellent idea of using Micropore Surgical Tape (3M) to protect the pollinated stigmas. I use the same tape to label the crosses with code numbers from my pollen database.

Figure 3. 'Helsinki University' x dichroanthum hybrid 'Elsie Maria' seed plant.

Figure 4. 'Helsinki University' x 'Calsap' seed plant.

Figure 5. 'Kullervo' x 'Ken Janeck' seed plant with variegated leaves.

Figure 6. The seed plants need good protection for their first winter. This 9-window cold frame can take some 2000 seed plants. I have another cold frame for large but tender plants.

Figure 7. The rhododendron plants have been planted in rows for their second winter. They are shaded with a green net and get sprinkled water (Netafim) on dry summer weeks.

Figure 8. 'Mikkeli' x makinoi cross plants have usually long and narrow leaves typical to makinoi.

Summer 2008: I have been pleased to see great variability and interesting leaf forms in the hybrids.
Pictures on Rhododendron hybrid plants, leaf forms and growth habits in 2008

Summer 2009: Several hybrids have flowered for the first time. Most have as expected non-interesting pink flowers or miniature flowers.
However, there are a couple of plants that may be worth a small volume propagation for testing in various climatic conditions.

Figure 9. 'Kullervo' x 'Golden Coach' cross gave nice looking flowers. More pictures and information on this and other hybrids: Unnamed or Non-registered Elepidote Hybrids