Zone, Heat and Sun challenged

SouthCountryGuy Zone 4b-5 SE BC(Zone 4b-5 SE BC Canada)July 8, 2013

Hi all, first time posting to this forum and looking for a little advice. I am looking for a shrub to anchor a bed along my house and have a few challenges.

1) we often get -35C (-31F) for a week or so a year and our summers are usually around 30C (86F) from late May through September. Frost safe (June - end August)
2) it gets sun at 8:30 then shade from the house creeps across the bed (8' wide) and it is totally in shade by 2pm
3) Need a tall variety it will be 'behind' some astilbe and I prefer to not have white
4) Soil is alkaline but I can amend if needed

I have been researching and searching this forum and have a list in order of what I think will work the best.

1) PJM Elite
2) PJM Victor or Regal
3) Nova Zembla
4) Manitou (although probably not tall enough)

Any further suggestions or advice would be greatly appreciated.

Thanks

Lance

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akamainegrower

The number of rhododendrons hardy to -30 is pretty limited, but it's likely that the temperature would be somewhat modified by the protection afforded by the house. So a few non-white ones listed as hardy to -20 to -25: Henry's Red, Aglo, several of the hybrids developed in Finland, Olga Mezitt, Edith Bosley, Fire Storm, English Roseum. Since the area gets direct sun until 2 PM, you'd likely be better off with a tough small leafed variety such as the PJM types than with the larger leafed sorts.

    Bookmark   July 9, 2013 at 5:16AM
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rhodyman(SE PA, USDA Z6)

The alkaline soil is a BIG problem. All rhododendrons need acidic soil. You are probably better off using a raised bed with a good mix of garden soil with organic matter adjusted to a pH of 5.5 to 6 with powdered sulfur. Also, make sure you don't water the plants with alkaline water. Rain water is usually acidic and safe.

Sun from 8:30 to 2 pm is good for most all varieties except those that need some shade.

Elviira, 2', -30F. This rhododendron is very hardy. It grows to a height of 2' and width of 18" to 24". It grows well in shade. A very low growing rhododendron cultivar. Densely branched, it is covered with flower buds that are hardy to -30F and open bright red. From the group of Marjatta hybrids developed at the University of Helsinki, Finland.

Regal, 5', -30F, is a vigorous grower with a broad, spreading habit that bears an abundance of showy, vivid, light purplish-pink flowers beginning in mid-April. Tolerant of sun and shade.

Nova Zembla, 5', -25F. This rhododendron has true hardiness in a red. A vigorous plant that has good foliage and will grow in more difficult areas. This hybrid exhibits some outstanding characteristics. Of course, hardiness tops the list. A nice looking contrast with other plants. Extremely showy, red flowers make a real display in the spring.. Dark red flowers in a ball-shaped cluster. Broad, bushy plant. Cold and heat tolerant and sun and shade tolerant. It grows to 5' tall and is hardy.

    Bookmark   July 9, 2013 at 11:38AM
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SouthCountryGuy Zone 4b-5 SE BC(Zone 4b-5 SE BC Canada)

Thanks for the very good info folks.

Rhody, how big is the expected root ball of Nova Zembla? I dug a hole 8' wide by 6' deep (tapered sides to 4' at bottom) to admend my soil. What I am planning to add tests at a ph of 6.1 so I think I can get in the good range easily. Should I go bigger? Or should I make this into a pot...i have the means to concrete the sides..

Again thanks for the advice. This is one of the few forums that are great.

Lance

    Bookmark   July 9, 2013 at 11:02PM
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SouthCountryGuy Zone 4b-5 SE BC(Zone 4b-5 SE BC Canada)

Thanks for the very good info folks.

Rhody, how big is the expected root ball of Nova Zembla? I dug a hole 8' wide by 6' deep (tapered sides to 4' at bottom) to admend my soil. What I am planning to add tests at a ph of 6.1 so I think I can get in the good range easily. Should I go bigger? Or should I make this into a pot...i have the means to concrete the sides..

Again thanks for the advice. This is one of the few forums that are great.

Lance

    Bookmark   July 10, 2013 at 10:51AM
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akamainegrower

Nova Zembla and any other rhododendron for that matter, even one in a large seven gallon pot will have a rootball no larger than the pot size. If you have enough material to fill the hole you've created, by all means use it but be aware that subsidence is likely to be a problem. A 4' depth is way more than you need. Do not use concrete. It's highly alkaline and would defeat the purpose of introducing acid soil.

I'd also respectfully disagree with a couple of rhodyman's points:

Direct morning sun is fine for many rhododendrons, but combine it with extreme subzero temperatures and even the hardiest large leaf varities such as Nova Zembla will suffer from severe leaf burn and damage to the dormant flower buds. That's why I think you'd be better off with a small leafed PJM type or perhaps deciduous variety. If anyone in your area is having success with rhododendrons, follow their lead.

'Elviira' is an interesting variety with an unusual shade of red which I've grown for many years. It may even be as hardy as claimed. It is, however, a miffy plant and painfully slow growing. It would be invisible behind the astilbes for 20 years or longer.

    Bookmark   July 11, 2013 at 5:28AM
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rhodyman(SE PA, USDA Z6)

I agree wholeheartedly with aka, winter sun and winter wind are real problems for any broad leaved evergreen when the ground is frozen. However, during the growing season, many hardy rhododendrons cope quite well with sun and wind. However some don't handle full sun well and one needs to know this.

Since the sun angle in cooler climates is usually very low in winter, it is often easy to assure that plants receive shade in winter but still receive some sun in summer. Also, windbreaks are very helpful in raising broadleaved evergreens in cold climates, especially when starting them out.

The more one can refine the growing conditions in very cold climates, the more diversity one can get. Many of us have micro climates were we can grow things that we shouldn't be able to grow. The trick is to discover and exploit these areas.

    Bookmark   July 11, 2013 at 9:32AM
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SouthCountryGuy Zone 4b-5 SE BC(Zone 4b-5 SE BC Canada)

Thanks Rhoda and aka. You have brought a lot of good info to the table I would never have thought of. Fortunately, the location I want this shrub in is totally protected from all but the strangest storms. Unfortunately I don't know anyone with rhodo's in this area to get info from. I could talk to the folks at the nursery but I like to be a little educated first. Although we have very knowledgable folks in all nurseries I am a beginner and not sure if I am talking to the summer student or a horticulturist. Thanks to you folks I can arm myself with enough information to ask intelligent and more importantly the right questions.

I was able to put a hold on a nova zembla at a local nursery. Surprisingly it is the last Rhody within a hundred miles.

Thanks again.

    Bookmark   July 12, 2013 at 6:53PM
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