Ericaceae

[Lesley Cox]

In fact, if you look carefully there is a dead liverwort at the lower edge of the keleticum pot but I painted it very carefully with vinegar solution (half plus half water) and it did for that little bit. Mosses do eventually come but they take a long time.

The keleticum has been outside in all weathers all its life but I started the camschaticum in my airy tunnel until I saw the first speck of green then put it out so it was sheltered in winter, mostly because we had so much wind this year and I thought the grit and seeds could blow away.

[nicheplanthead]

Leslie,

     beautiful seedlings...
I always first sprinkle small seed on top of grit then spray them in..I see seed clusters together... same problem I have.. makes hard to separate but if the soil mix is loose there is less damage separating.

wish I could find nice grit like you have... I also tried for seed of r. Kamchatka..

Is your ph fairly low in your mix as growth looks very healthy?

I find all the sand around here is very alkaline so I can't add much of that and use turface and perlite with peat moss..

I won't be able to put any seedlings out until late march until the freeze ends here.

[ranunculus]

... And not a sign of moss or liverwort, Lesley ... superb!

? ? ? ? ? ? ? 

Many of my seed pots (especially those kept outside without cover) attract moss and liverwort within weeks of being sown, usually engulfing any tiny seedlings that condescend to appear ... and yes, it is raining again ...

[nicheplanthead]

Here is what I have tried so that they don't dry out and get them to planting out size.
I put a few in a large 20" pot and over winter them in a plunge in my veggie bed.
R Ferrugineum vintage july 2004 about ready for the rockgarden coming spring.
In smaller pots they seem to grow to slow for me as I tend to forget watering

Any ideas what book would give me reliable minimum temperature hardiness for rhodo's
also give a good treatment of the species.

this one has -10C listed on the american rhodo society but it survived -20C  here outside.
I have killed so many so called hardy ones some due to poor drainage trying to keep soil
moisture retentive over winter.

[johnw]

Any ideas what book would give me reliable minimum temperature hardiness for rhodo's
also give a good treatment of the species.

this one has -10C listed on the american rhodo society but it survived -20C  here outside.
I have killed so many so called hardy ones some due to poor drainage trying to keep soil
moisture retentive over winter.

Stuart -  Poor drainage will knock out any rhododendron below and above freezing and quicker still in summer heat.

Writers are quick to tell one to which minimum temperature a rhodo will survive even when they live in a mild area. It is an excerise fraught with pitfalls. Will the plant survive to -18c but lose the flowers buds at -12c? One has to ask when does the cold arrive, is the ground frozen solid when the coldest temperature occurs, were the plants stressed from summer heat, did proper ripening occur in the autumn etc etc etc. It's a bloody minefield.

If you PM me a list I can give you an idea of what they will take here (with caveats understood!) or post here and we can see how others feels about the ratings.

johnw 

[nicheplanthead]

John,

    To get the growth rate up on seedling over the summer in earlier years I used a very moisture retentive mix.  I just left them on the patio in a big 20" pot then the winter thaw would come with the surface in water and the rest of the bottom of the pot frozen then of course it all froze again solid on the surface. My little seedlings with surface roots perished in the spring.  Now I plunge them at a sloping angle over winter and have improved my own soil mix after reading was it John Gyer's book?.

Good moisture retention and drying out is hard get as we have a 2 week droughty period here...and even some I planted out that reached one foot died. I mulch with pine bark and cedar..

Its the smaller ones like fastiganum and wren.. that make it for two or years then used to die but my solution in growing out is progressive larger pots seems to be working.  My list is in a earlier post.

The little one is a fastigatum and large without much foliage is kiusianum cheji island form rescued from snow load and stepping on. 
 

[Lesley Cox]

My potting mix is quite acid I think - I've never tested it - but a local Agresearch place did, some years ago and said it needed some lime for optimum plant growth. I never bothered with that. The grit itself, is sieved builders' sand which is quarried as solid rock locally and crushed. I buy it by the cubic metre and sieve out the larger stuff to put on my seed pots, the rest going into the potting mix or the garden, so it's probably acid to neutral as well.

Most of my seed are outside through the year in all weathers and I put shade cloth over the pots from mid spring though mid autumn, taking it off when it rains, which it isn't doing lately, or to water. But my lowest temps are around -6 or 7C so nothing to compare with Canadian or North American cold.

[johnw]

Stuart - Moisture retentive mix is okay but you must get air into the mix which is critical.  50% ground pine bark or pine bark mulch, some perlite - say 10%, 40% coarse peat or better still 50/50 peat/coconut fibre (available at most big garden centres - Better Than Peat - and go for a coarse form of it) to make up the 40% required.  For a 5 gallon pot a teaspoon of 0-20-0 superphosphate (Vigoro/So-Green brand, the others are treble superphosphate and far too hot). A little potato fertilizer.

Might I suggest you get your seed pots under cover for the winter as we do here. Plunge the pot to the rim in woodchips (available by the bale at Feed stores) in a cold frame. We pot high to avoid water lodging at the top of the pot when we remove the cover in March. Cover the frame  tightly with white plastic after a thorough autumn soaking, this will keep the rain off and there will be virtually no drying out.  We have very few loses unless the plants or crosses are too tender.

Now we plant directly into frames and cover with white plastic in early December. After 2-3 years the plants are planted out. Now that the snow has gone covering the frames will be this weekend. The Gunnera will get its winter home erected too.

I will post a shot of the frames if I can locate it.

If you need acidic grit try a local feed store, there are various grades - turkey grit, hen grit etc. - all okay as long as the grit is sharp (crushed - not smooth and roundish) which impairs drainage according to gritophile Steve Doonan. 

johnw

[nicheplanthead]

John,

    yes the key in the rhodo book by john gryer I think his name is he is a phd rhodo grower in the usa said air space was key and the first thing I did was add perlite as I was using too much pine mulch which compressed after a few years decomposing..

I the local farmer suppliers of chicken girt is a marble type grit which is alkaline again.


What I like to do to get the growth up fast is liquid feed in the spring and have already added earlier to the soil as you suggested and I also use sulfur pellets to get the ph down. I'm getting fairly good growth since I changed by formula. I hand test them all..


The snow load is too heavy here for anything but a sturdy cold frame which I now leave open for my seedlings which has a coarse sand base.. last winter we had over 6 feet of snow.. the sloped pot plunge works nicely here.

What I really need now is a reliable way to get the ph lower without overshooting on the downside which I once did in a garden area or clay soil which I tried to also amend.. but it grower ericaeia ok.

Now that I got the soil mostly figured out I now am trying to get them in more sun so that they will flower better as the sun is at a low angle for most of the growing season except the midsummer when it can become droughty and kill most rhodo's.

I remember seeing someone with a rhodo plunged in a sand bed and in spring it was dead... lack of oxygen!

I'll post a pix tomorrow to show how I angle plunged on a mound some of my large and medium sized pots.
I used to have them in covered cold frames that I built but I still had the same problem of the midwinter thaw and rain!! soaking the pot and freezing it solid until spring when it would still be frozen in but with melting water on top. I could have put a plastic sheet over the frame cover but it would have frozen to the top shade cloth.

You have very good suggestions and a little more space than I have to overwinter seedlings.

[johnw]

Stuart - These are observations from here only and assumptions as well.

Rhodo  hanceanum v. nanum   0F – not hardy in Halifax, the rating sounds about right as an absolute bottom.               
Rhodo aborescens – never damaged even inland at Kentville, NS where it has flowered after at least -25F                       
Rhodo Algo – not quite as hardy as PJM, brittle when young, needs sharp drainage as do all the PJM types, -20F or lower 
Rhodo Autumn Velvet – could this be Violet instead of Velvet?                   
Rhodo canadense  -   native here and have seen it in western Newfoundland where it must see -35 or less (very heavy snow cover there)                   
Rhodo complexum ss. Lapponica -10F,  about right, buds maybe -5F, never damaged here                 

Rhodo Counterpoint -30F   - a deciduous PJM, possibly as hardy as PJM but no experience here   
Rhodo fastiagatum -15F, plant and buds                 
Rhodo ferrungineum -  buds -15F, the plant probably colder circa -25F                   
Rhodo Girard's Hot Shot – not reliable long term in Halifax, rated around -15F but ripening in the fall can be an issue               
Rhodo groendlanicum – must see -40F and lower in the north.                     
Rhodo Hellikki – Helsinki hardy but a very poor performer here.  Peter Tigerstedt told me he wishes it had not been released, a poor commercial plant for container production, buds can move in the fall, rated to -34F, ok in southern New Brunswick to Fredericton.                   
Rhodo impeditum -15F about right, buds maybe a few degrees less, never damaged here                 
Rhodo intricatum -15F,  about right, buds maybe -5F, never damaged here                 
       
Rhodo July Joy    - bakeri x prunifolium, probably -20F or lower           
Rhodo Kermesina Rosea – kiusinaum hybrid doing well in colder parts of NS where lows can go to -15F               
Rhodo kiusianum   -15f maybe a few degrees lower (and less with snow cover) – for an evergreen azalea second only to pukhanense in hardiness. I believe it’s ok at Alpines Mt Echo in Sutton, PQ       
Rhodo Lemon Drop - nice plant, has taken -20F inland here.                         
Rhodo mucronulatum  - see below, about the same           
Rhodo mucronulatum (Cheju Island form) – has taken -15F inland here with no problems, can’t recall plant damage on any mucronulatum in NS, needs a dryish site here or at least sharp drainage, blooms very early and can be caught by late frosts where prevalent.
Rhodo Nova Zembla – bud hardy to at least -15 but can blast buds in mild winters here, have seen it defoliated here in mild winters and perform perfectly in extremely cold winters, the one rhodo I love to hate               
Rhodo Narcissiflora - -20F, no problem in NS but must have hardiness issues as it stays mainly below the snowline in PEI         
Rhodo Patty Bee – plant -15F, buds -5 to -10   
Rhodo Pink Dawn - the Shamarello hybrid? - if so think it is very very tough but some of his hybrids are bad actors here. Have never seen a Sham hybrid as good-looking as those growing in his native Ohio.   
             
Rhodo PJM compacta – slightly less hardly than PJM itself. I believe, maybe -30F
Rhodo Pohjola's Daughter – another Finnish hybrid and a bad actor, again I have seen this damaged here in several gardens after a long autumn followed by a not so cold winter,                           
Rhodo Popsicle  - a late Weston azalea, should easily take -25f             
Rhodo prunifolium – considered in the books to be tender but inland has survived -17F here, buds may be more like -5                           
Rhodo Sericho – didn’t know this and couldn’t find it anywhere. Then realized it must be Jericho, a Leach hybrid between carolinianum and keiskei. Another cranky one for drainage and isn’t a particularly good do-oer here but is hardy enough. Have seen two good plants about. Theoretically should be hardy to -25F or a bit less.                           
Rhodo Thunder -  a very tempermental dark leafed PJM, highly susceptible to root rot, needs sun and extremely good drainage here. Not believed to be as hardy as PJM itself  but the plants cited may have died from cultural conditions rather than cold.                       
Rhodo Towhead – another tempermental plant needing exceptional drainage. I know of only 2-3 good looking examples of it locally. Buds -10F, plant maybe -15 or lower are my guesses                         
Rhodo Wren – a star performer for me but many consider it cranky, good drainage and half day of sun. Has never missed a year here. -10 plant, buds -5 or lower.                       
Rhodo Apricot Surprise – rated to -35F, Minnesota hardy. Complaints of autumn flowers in the USA.
Rhodo NorthernStarburst  - a tetraploid PJM and a nightmare to grow, needs very sharp drainage, ploidy levels have significantly reduced the hardiness it should have. Some say -10 to 15F usually dead before winter arrives.
                       
Rhodo Oudijiks Favourite – Leonardslee rates it at +5F which sounds reasonable given the parentage                       
Rhodo Patty Bee - -10F plant, -5 or aq bit less for the buds                     
Rhodo Pink Discovery – actually a selection of poukhanense by Weston Nurseries, should easily take -20F or less. Have never seen a pouk damaged here on the coast.

For what it's worth.

johnw

[nicheplanthead]

John,

   A big thank you.

That explains a lot of hits and misses... can't seem to keep impetatum alive killed 3 but my neighbors survives for years..on a slope

You are right on the bud hardiness a there is unreliable flowering on many, and with my mainly clayey soil and giving up on trying to water these plants are more for my appreciation of their form and foliage.

What is your minimum temperate and it is drought by midsummer there and do you experience same freeze and dry winter cycles or are you a mostly maritime climate?

[johnw]

What is your minimum temperate and it is drought by midsummer there and do you experience same freeze and dry winter cycles or are you a mostly maritime climate?

Stuart - The coldest winter ever was 1993 when we dropped to -15F in late January after a mild start to winter. Intense cold and wind continued into early April, old Ilex aquifoliums in the city froze to the ground and then recovered. Mercifully we had a foot of snow the night before the cold came so the ground was not frozen.

We are plagued every winter by storms (every 5 days or so) accompanied by wind. Snow cannot be relied upon, we 40" in one day several years ago.  We have wild temperature fluctuations during the winter as these storms roar through and out.  Rain changing to snow and vice versa.

We are a schizoid maritime climate. Spring and summer are quite maritime with no really hot days and cool nights. It can be briefly continental in winter when the storms suck in cold air to the north and northwest, then we are back to maritime.  So cold (below 0F) usually occurs only at night and rarely lasts long. Normally our low is around 0F or slightly less.

Our rainfall is substantial and both it and our fog (114 days a year here in Halifax!) help the rhodos out a great deal.   Once one leaves the coast by even a kilometer the moderating effect of the ocean in winter can evaporate.

I also have a planting near Yarmouth, NS where spring comes earlier, summer is cooler and winter cold is very brief - probably the mildest area east of the  lower mainland of BC where species like rex are happy as clams.  More fog than Hfx. Maggi finds fog spooky!

johnw

[Maggi Young]

Maggi finds fog spooky!

That's because fog IS spooky!

Stuart, you mention repeatedly about summer drought in your area..... is this not much more likely to be a problem than the freezing in winter? 
Of course, some species are more susceptible to frost than others but if the plants are also subject to great stress in summer, through drought, then they cannot possibly be strong enough in the winter to withstand the bad conditions then. 
At the momen here in Aberdeen is i bright sunshine and the temperature is approx. -4 degrees C...... outside the window as I type this I can see the leaves of rhodos rolled up like cigars and hanging ow...... I can see bureauvii, williamsianum, a taliense x lacteum cross, yakushimanum  and smirnowii...and even this last one, which is really a tough cookie, is rolled today 

[nicheplanthead]

John,

    we have similar cold hardiness in winter and variations but your advantage is cooler summer on coast... so your hardiness the bursting of moisture in cell walls of woody structures without enough naturally adapted antifreeze would be similar at 0F
barring exposure to colder winds.

Maggi,

    The fall is usually quite damp and rainy here.. I lost one due to drought as it was hidden behind another larger rhodo... and I was not in the ground more than a year altho it was one foot tall and I must have forgot it in the watering can run...
I think the sun is important to harden it off after summer growth, but the culprit is likely the neighbors huge maples at the fence line in the back sucking out moisture at a faster rate than replenishment requires.. 

 I have 3 small cold frames I built, one thing is that they should not be in too shady a location as 2 are here and they are in one of the last places to defrost in winter so I keep one less shady one for cutting and some saxifrages or other slow and moisture requiring plants and a few woodies, the floor has a sand base. The other one in more shade is holding area for overwintering seedpots which get moved to more shade and then I use it for a first stage hardienng off area for plants coming from the basement lights in springtime, and transplants and cutting growth.

Its john greer's book I used for hardiness that I used and wondered if that is about right.

[johnw]

Maggi finds fog spooky!

That's because fog IS spooky!

Maggi - Mysterious maybe but not spooky. You've been reading too much Sherlock Holmes.

johnw