by Joe Harvey - December 1999
This year the scope of the list has been extended to include some of the groups of plants in which I have an interest. In particular there are many shrub and tree seeds. Among the latter are maples from Hatley park which were planted in 1912 by Isaburo Kishita when he laid out the Japanese Garden for James Dunsmuir. (He also laid out gardens for Mrs. Jeannie Butchart and Mr. L.G. Barnard.)
I have found that maple seeds germinate well but require stratification (see below). The maples at Hatley contain several forms not included among the commercial cultivars currently available. Hence they have been assigned numbers which is not sexy but I have been unable to discover possible cultivar names. Maple #15 is slow growing with particularly small leaves and would make good bonsai.
Among the hand pollinated rhododendron seed are dwarf indumented hybrids, many never offered before. Since the reason for producing these and their place in gardens is widely misunderstood in Victoria there will be an explanation of my reasons for breeding these, in a future newsletter.
There was a disappointing response to the seed list last season. Three people ordered seeds. I have been pondering the reasons for this lack of interest. Possible reasons include: seeds too expensive, the seeds on offer of no interest to members, nursery plants are so cheap in Victoria that there is no incentive to start seeds, members consider themselves too old to start growing plants from seed, members’ gardens are mature with no room for new plants, members do not trust their own skills, people like the assurance of a cultivar name. No doubt you can add your own reasons.
I’ve thought about the charge of $2 per packet. Should it be $1 or 50 cents? I was going to reduce it but then last summer I had to rush out to buy a packet of my favourite lettuce - winter Density. It cost me $2.60 plus tax. Now if ordinary lettuce seed costs nearly $3 then I think $2 is a modest fee for all seeds on our seed list. Like the dollar table the money raised goes to running the Society.
As I type this list I am ordering peony seeds from Josef Halda at $5 US for 6 seeds. So we stay at $2 for this year, but do let me know your feelings on the subject. Many of the plants on the Victoria list will be available from the ARS on their very extensive offerings available in January. All keen growers should have the ARS list. Write to George Woodard and John Nicolella for your own copy.
DM David Mackas OP Open pollinated
FG Finnerty Gardens HP Hand pollinated
HC Horticulture Centre of the Pacific WC Wild collected
JH Joe Harvey S Require stratification
KW Ken Webb cv cultivar (i.e. a clone)
RH Robin Hopper v variety (i.e. distinct plant but not a clone)
RR Hatley Castle
(Maple leaf colour is given: spring/fall)
1. Acer campbellii? green/red. Leaves larger
than A. Palmatum
2. japonicum v aconitifolium green/red. Large divided leaves S RR
3. griseum green/red. Paperbark maple S RR
4. palmatum v. dissectum red/orange. Weeping branches, cut leaves S RR
5. cv ‘Hogyoku’ green/yellow-orange, compact tree S RR
6. cv ‘Shigitatsu-sawa’ green/yellow. Small bushes S RR
7. cv ‘Osakazuki’ green/scarlet. Tall tree S RR
8. cv ‘Umegae’ red/red. Divided leaves, tall tree S RR
9. cv ‘Villa Taranto’ green/yellow. Linear left segments S RR
10 cv #15 green/yellow-orange, very small leaves, dwarf tree S RR
11. cv #16 green/yellow, tall, larger leaves SRR
12. Agapanthus ‘Headbourne’ hybrid. The hardy deciduous form - JH
13. Arbutus menziesii, the famous tree of Victoria, Colwood strain ? JH
14. unedo, the strawberry tree. Smaller than our own arbutus ? JH
15. Camassia leichtlinii v alba, white camus, drought resistant S JH
16. Digitalis purpurea yellow variety - JH
17. Euonymus alatus v compactus, dwarf spindleberry bush S HC
18. Genista aetnensis, Mt Etna broom, wonderful cascading branches S HC
19. Hamamelis xintermedia ‘Arnold Promise’ witch hazel, yellow S JH
20. ‘Jelna’, orange S HC
21. mollis, the Chinese species, early yellow S HC
22. Helleborus xhybridus #24 Pictoee x Picotee HP S JH
23. #27 White S JH
24. #32 Yellow HP S JH
25. #34 Large red S JH
26. #40 pale pink HP S JH
27. niger ssp macranthus, extra large white flowers S JH
28. Menziesia ferruginea, false azalea, WC Kathleen L. Smithers BC - JH
29. Oplopanax horridus, WC false azalea devils club, wet soil S JH
30. Paeonia lutea v ludlowii, yellow tree peony, vigorous S RR
31. Sorbus hupehensis ‘Pink Pagoda’ pink rowan, true from seed S JH
32. ‘Joseph Rock’, yellow fruited hybrid, seedlings may differ S FG
33. sitchensis WC Kathleen L. Smithers, large bush, red fruit S JH
34. Spartium junceum, Spanish broom, fragrant, friendly non-spreading ? JH
35. Stewartia pseudocamellia, Japanese stewartia, white, smooth bark S RR
36. Styrax japonica, Silverbells. A small tree S FG
37. Wisteria floribunda cv ‘Shiro Noda’, the white, graceful form - JH
38. the blue form, also true from seed - JH
39. Yucca filamentosa, HP Unnamed x ‘Ivory Tower’, drought resistant - JH
Rhododendrons Open Pollinated
40. R. calophytum #1460 Vaartnou
41. decorum #1461 Vaartnou FG
42. decorum sn FG
43. degronianum ssp yakushimanum cv ‘Whitney form’ FG
44. fortunei #1129 Vaartnou FG
45. fortunei hybrid Buchanan-Simpson garden, large pink-peach flower DM
46. R. fulvum Stuart Holland RH
47. insigne JH
48. macrophyllum WC Shawnigan Lake, Vancouver Island KW
49. makinoi (as "adenopodum" sic) #983 FG
50. oreodoxa #2032 (mislabelled "rex") FG
51. pseudochryanthum sn FG
52. schlippenbachii sn FG
Rhododendrons Hand Pollinated
53. R. degronianum ssp heptamerum cv ‘Enamoto’ x clementinae
54. makinoi JH
55. pachysanthum JH
56. pseudochrysanthum JH
57. roxianum v cucullatum JH
58. tsariense JH
59. degronanum ssp yakushimanum cv ‘Exbury’ x clementinae JH
60. deg hept ‘Enamoto’ JH
61. insigne JH
62. pachysanthum JH
63. pseudochrysanthum JH
64. wiltonii JH
65. degronianum ssp yakushimanum cv ‘Yaku Angel’ x makinoi JH
How to Obtain Seeds
The problem of dormant seed is much misunderstood. You sow some seeds, they fail to come up, so it was obviously bad seed – problem solved. Many people have thrown out pots of such seeds only to have them come up on the compost heap the next year.
The advantage to the plant of a delayed germination is that it prevents the seed sprouting in the summer or fall as soon as it is scattered. Germination is thus delayed until a more advantageous time in the spring.
The mechanisms causing delayed germination are various. Some are as simple as a tough seed coat which has to decay before the seed can germinate. For instance, the tough seeds of the dove tree, Davidia, can sometimes have their sprouting accelerated by giving them a good whack with a 2 pound hammer.
More frequently there is a physiological mechanism involved. For instance, hellebore seeds are shed with the embryo at a very immature stage but surrounded by a mass of endosperm (a nutritional tissue). If the seeds are kept moist and sown as soon as they are shed, the embryo will continue to grow and the seed will germinate the next spring. However, if the seeds are dried, the embryos go into a state of suspended animation and when remoistened may take two years to germinate.
Most of the seeds from the north temperate zone with delayed germination require what is called cold stratification. This is achieved most simply by sowing the seed in the fall in a soil-less mix and keeping the pots cool over the winter. This usually does the trick. Sometimes it takes two winters.
One problem is that many people obtain their seeds in the spring and then get annoyed when nothing comes up. The solution is to keep the pot until the fall and then keep it moist over the winter. There have to be cool temperatures and moisture.
There is some incredibly bad advice handed out on the subject of cold stratification. I have heard over the radio and seen in magazines that putting seed packets into the fridge or freezer for a few days or a week or two will aid germination. Well the process as I said is a physiological one so moisture has to be present. Putting dry seed into cold does nothing – except that keeping seed dry and cold is the best method of storing it.
The temperature at which cold stratification takes place is in the region of 4-8o C. The vegetable crisper of the fridge is often used. The time period is months, not days. Three to five months in the fridge may be required, i.e. about the length of winter. I have a lot of seeds and a hostile wife so I use one of our outbuildings, which are unheated, for the purpose.
The bad news is that some seeds may take two or more years to germinate. I have had Japanese maples germinate the first spring and then neglect to transplant the seedlings (a common failure of mine). The next spring a whole lot more of the seeds come up. As a biologist who studies evolution, I should point out that a delayed or irregular germination such as this will be an advantage to a plant in that it spreads out the risk. The longest I have had to wait for seeds to germinate is five years. These have included violets, Iris versicolor and Cyclamen rholfsianum.
I just sow my seeds in soil and wait. With over 200 pots on the go at any one time each spring gives me plenty to do. For the less patient I can recommend putting the seeds into a sealed plastic bag with a spoonful of moist Perlite. Throw the bags into the bottom of the fridge and inspect them every few weeks. At the first signs of germination put the seeds into a pot with seedling soil and bring into warmth and light. In the seed list the seeds requiring stratification are marked ‘S’.
There is a problem of how to label pots with seeds obtained from clones, i.e. cultivars which should have names written in single inverted commas (not always done). Since a clone has to be a graft, cutting, or tissue culture, the seedling offspring cannot have the parent’s name. Best get over this problem by putting ex in front of the name. For example ex-Joseph Rock, from Latin meaning from.
Germinating Rhododendron Seeds
Use a soil-less mix such as 3 parts peat to 1 part Perlite. It is important to avoid unsterilized soil because this introduces spores of damping-off fungus and if you get this little beastie in your pots the seeds germinate and then a few days later keel over, dead. Some people water with the proprietary anti-fungal agent No-Damp to avoid damping-off.
Whichever method is used moisten the mix, press into the pots to make a level surface and sprinkle the seeds very thinly over the soil. I like to just cover the seeds with 1 mm of dried sphagnum leaves rubbed through a fine kitchen sieve. Lacking sphagnum, fine sand may be used and even leaving the seeds uncovered works quite well. Cover the pots and put them into a warm cupboard until signs of germination – generally 2-8 weeks. Inspect the pots every few days and if they show signs of drying, spray them with water from a mister.
Newly germinated rhododendron seedlings are delicate with thin leaves. Do not expose them to direct sun. They shrivel up in minutes. Fluorescent tubes are the best form of light to use for the first nine months. Fluorescent lights give off a cool, diffuse light which has proven useful for getting young delicate seedlings through their first stage. I use ‘cool white’ tubes. The more expensive Gro-Lux etc. tubes do not seem to produce any better growth.
Prick out the young seedlings at about the four-leaf stage with a tooth pick and move them to a larger pot or tray spaced a centimetre or two apart. The Plant Propagators Group produces an excellent soil mix which accelerates seedling growth. Continue to keep the pots covered and mist frequently. At this stage very dilute soluble fertiliser may be given.
Only when the plants are 2-3 cm. high should they be moved to open, less humid, conditions. They may then be transplanted again and moved outside in shade.
Arbutus and Menziesia are treated in the same way as Rhododendron. It
is a little uncertain whether they need some stratification.