Gmshack - I have read of using both plastic and Agribon, but haven't gotten around to the plastic part yet. There are two main issues with overwintering and some studies suggest that dehydration is a bigger problem than cold tolerance in cold climates. I used drew 51's technique of Wilt Stop this fall, so we will see if it prevented desiccation. I also used two layers of Agribon. I find that one layer does not provide the protection that the company claims. I start covering mine around late August when our first frost hit. This is both to protect berries and reduce temperature shock from early season frosts. In the spring, I am leaving the Agribon on for a few weeks. This next spring I will leave it on until each variety begins to flower. This substantially increases growth for me (in our very cool Mays) and hastens flowering by a few weeks. I do remove it on days with temps over 70F. Desiccation is a real problem for me since our ground is frozen solid for at least 6 months out of the year. Add to this that preliminary probing this last summer suggested that blackberry roots up here only extend 3 or 4 inches into the ground (it is too cold below that, with an average annual temperature at 3 ft of around 31F). In this situation I believe that the roots cannot take up water to replace what the canes transpire during the winter and they end up desiccating and dying way back (from 8-10 ft long to about 2 ft). We will see. As far as the weed block, it will probably not increase the soil temperature as much as removing it. I'm not sure of this as I don't have experience with it in the Lower 48. Up here, it must be removed in the spring for about 4 weeks to allow the soil to thaw and then reapplied. Your soil is already thawed and substantially warmer, so you shouldn't have to do this. What I think I get from weed block is increased heat above it = though I have no data to show that. I just know that of two Wild Treasure plants I have (that are one year different in age), the one grown over weed block is much more vigorous than the other. I trellised the very vigorous one last year and it continued to grow strong even though most of the canes were not directly lying on the weed block. A study at Oregon State Univ. also supports this. However, Wild Treasure is a crown-forming variety, not a spreading variety like the ones you have, so covering around it with weed block is a simple process. I do not grow primocane blackberries because the season is too short and there is insufficient heat. Everyone of them has died completely. I have one Triple Crown left and a very wimpy (it grew 2 whole inches this year) Chester. Neither has canes that survive - but then I have not covered them. I am guessing that if your TC canes survive and leaf out, but don't flower, that the flower buds are damaged by the cold. Flower buds on many plants are much less tolerant of cold than non-flowering buds. I have two varieties of erect blackberries that I am trialing that might be of interest to you. They are Nelson and Stenulson. Stenulson has been in the ground for several years, but moose have browsed it down each year and voles girdled anything that was left. Thus, I don't have an idea of its ripening season, but it is likely too late for me. It grows pretty well here and is spreading (unlike TC and Chester which only get smaller each year). I have had a few green canes survive the winter and start to leaf out and then die because they were girdled by voles at the base, so it is pretty hardy (though these were covered by snow mid-winter, when air temps dropped as low as -35F). I just got Nelson last year and it actually flowered earlier than any other erect I have. Its berries are somewhat frost tolerant, as well, to at least 28F. It still did not ripen early enough, but it was in a pot and not established. The timing could change in the future, especially if I put an Agribon "sack" over it early in the season. Both of these are thorny. I got Balsor's Hardy Black from the USDA germ plasm repository this fall, but it failed to root before it rotted. This is another possibility, but it is not commercially available in the US. Happy New Year!

@Kristine LeGault 8a pnw, I absolutely agree with you about Julia’s colir range. I love when she picks up a bit of pink in the fall. My Julia Child gets done blackspot, but maintains vigor. Here she was around Halloween. Another favorite yellow floribunda for me is Yellow Submarine. I fell in love eith it at the National Botanic Garden and looked everywhere for it. Pim Ling roses are excellent, but not always easy to come by. I ordered mine from White Flower Farms. It is my favorite yellow. here it was at the botanical garden. The bees love it. Here it was as a first year rose in my garden. My 3rd yellow is Solero. The bush itself has never had a speck of black spot and the roses are lovely, but it has a crazy growth pattern with octopus canes. I plan to move it to s sunnier spot this spring.

Below is the info. that Floweraremusic (zone 5) in Washington gave on her 2020 winter-survival. She has alkaline clay with rocks at bottom like mine & less snow in winter: "My hardiest roses are the Canadians. John Davis, John Cabot, Wm. Baffin, Morden Sunrise, Morden Blush and Morden Centennial, Victorian Memory aka Isabelle Skinner, also a Canadian rose. All these only have tiny bit of tip damage and bloom a lot with no special care. Also, my Hybrid Perpetuals only have tip damage after winter. Magna Charta, Mrs. John Laing, Black Prince and Marchesa Buccella. The only negative is they don’t have long enough cutting stems. All my Austins are very hardy. The one I just can not grow is Jude. Leonardo da Vinci is super hardy and always healthy. Quietness comes through winter very well. Even Rouge Royale survives beautifully. Cinderella Fairy Tale is very hardy. Gruss an Aachen also. Ballerina and Marjorie Fair are both hardy. Poseidon, Princess Charlene de Monaco and Crazy Love didn’t do as well as I’d hoped. The surprise losses this year are Quicksilver, and Dames de Chenonceau who is left with only 1 cane. Versigny is also reduced down to almost nothing. This was a mild winter with very little snow. " Floweraremusic (zone 5). From StrawChicago (zone 5a with hard black-gumbo alkaline clay & less snow but with freezing rain in winter). Versigny didn't survive winter either. So I lost Versigny TWICE. Besides Versigny, other wimpy own-root roses that don't survive winter well: Paul Neyron, Anna's Promise, Pink Peace (own-root died 1st winter, but grafted-Pink Peace survives many winter), Elantyne, Jude the Obscure, Young Lycidas (bought as grafted-on-Dr.Huey, now with only one cane), Mary Daly, and many floribundas don't survive my zone 5a: Pink Chiffon, Sheila's perfume, King Arthur, Deep Purple, Shocking blue, Honey Bouquet (survived 1 winter). Polka Climber (survived 1 winter), Cloutilde Soupert (died twice on me). Sutter's Gold didn't survive winter, same with many fragrant mini-roses from Burlington nursery. Below are my hardy OWN-ROOT roses in my zone 5a alkaline clay, only Double Delight, Young Lycidas and Lavender Crush are grafted-on-Dr.Huey. Bold-faced are the very vigorous ones: Own-roots with 3 feet of green canes: Carding Mill (since 2012), Princess Charlene of Monaco, Duchess de Rohan, Crown Princess Magareta (since 2012), Zepherine Drouhin, Lady of Shalott, James Galway, Lavender Crush, Queen of Sweden (gave away but very hardy), Poseidon (right below the rain-spout, dug down to 2.5 feet), Scepter'd Isle (very big & hardy own-root but gave that away with its lousy scent). Own-roots with 2 feet of green canes: La Reine (many winters), Blue Mist (since 2012), Prairie Harvest (since 2014), Mary Magdalene (since 2011), Evelyn (since 2012), Radio Times (since 2011), Pat Austin (since 2011), Christopher Marlowe (since 2011), Golden Celebration (since 2011), Lilian Austin (gave away but very hardy), the Squire, the Dark Lady, Wise Portia survived 4 winters but died in poor drainage clay, Dee-lish (since 2015), Twilight Zone (since 2016), William Shakespeare. 2000 (since 2011), Comte de Chambord (since 2012), Princess Anne, Sweet Mademoiselles, Aloha climber, Orchid Romance, Bohemian Rhapsody, Marie Pavie, Lagerfeld (since 2017), Frederic Mistral survived 2 winters but died when I didn't winter-protect with leaves, Sonia Rykiel (survived 3 winters) but died in freezing rain winter, same with 1/4 of the street-trees in my neighborhood, Excellenz von Shubert (since 2013), Own-roots with less than 1 foot of green canes: Gina's rose, Tchaikosky (since 2015), Cornelia (since 2018), Bolero (few winters), Peter Mayle, Sharifa Asma, Neil Diamond, Amber Queen, A Shopshire Lad, Strike it Rich, Old Port (since 2012), Veteran's Honor (many winters), Double Delight (grafted on Dr.Huey), Savannah, Tess of d'Uberville, Gene Boerner (since 2014), thornless Yves Seedling (since 2013), Stephen big Purple (since 2012), Louise Este, Mirandy, Crimson Glory, Liv Tyler survived 1 winter but needs winter-protection, Rouge Royal (bought last year with no winter-protection). Annie L. McDowell (survived 2 winters but needs a wet-spot since it's almost thornless), Nahema (survived 1 winter then died during freezing-rain winter), same with Eyes-for-you (drought-tolerant and doesn't like freezing wet winter), Souvenir du President Lincoln, Madame Issac Pererie and Madame Earnest Calvat, Firefighter (survived 2 winters) but died since it's next to tree. Bayes Blueberry (survived many winters but I gave away), Charles Darwin (gave away since it fades badly), Arthur Bell (since 2012 & killed it since I don't like the flowers). StrawChicago.

Sorry I'm a little late to the conversation. I can grow poly's. They do well, for the most part and are healthy and bloom a lot in my no-spray garden. Mine are own-root and most have few thorns. In this day and age of "Smaller Is Better", I don't know why they aren't more popular. These came from Vintage: Tip-Top- Pretty little rose that starts out pale creamy lemon with a deep pink edge (think Mrs. Dudley Cross) that slowly broadens as the bloom ages, till it is mostly pink. The buds have an almost hybrid tea look but the petals quill and twist as it ages till it looks like a pink dandelion. Mine have never been orange in any way. Broader than tall. Nice fragrance. Foliage is different; matte with a gray undertone. Charles Walker's Mignonette- Tough little white rose of many little petals. In cool weather they are tinted pink. Remind me of tiny chrysanthemums. They have a nice fragrance. The bush has stayed short, 18" +/-,. but is wider than tall for me. Super healthy, able to rebound from bad weather, injuries and the like, resistant to blackspot for me in the South East. Think about giving it a try. Anna Marie de Montravel- Blooms in bunches of little cup-shaped white flowers with a terrific fragrance. They really do smell like lilies-of-the-valley in spring on a humid day. It blooms its heart out during the spring flush and then off and on again the rest of the summer. They will pink up a bit in cool weather, but not as much as some of the others. These are from other mail order companies: Lullaby- New last summer, a fragrant white descendant of Cecile Brunner. It is one of my most fragrant polys, rivaling Clothilde Soupert in flower size and fragrance. In cool weather mine has a lavender pink tint. It went through a cold winter and looks good this spring with no die-back. Marie Pavie- Can't say more than has been said. Clothilde Soupert- Reminds me of an old-fashioned rose that has been shrunk. My most fragrant poly. Has a lovely blush center. Many people have this one. Lady Ann Kidwell- New last year, a Cecile Brunner descendant that seems to have her size, if not color. I may have lost her over the winter, but hopefully she has only died back to the mulch line. It may be a more cold tender poly but I hope it will be more hardy over time. Dubious Poly's Baby Alberic- A wonderful little white rose with a lovely form that has handled the cold winter without missing a beat. Mine is always white. It blooms individually, not in bunches. It is a small bush but doesn't look or grow like a poly at all. Polly Sunshine- A Ralph Moore creation that seems much more like a mini than a poly. It's pretty with soft sunshine yellow blooms that fade to cream. My least healthy poly, it struggles with blackspot and I've thought about removing it. Came through the winter OK, though. Honorary Poly's Sweet Chariot- A Ralph Moore creation that should have been a poly. It looks, blooms and grows like one with the poly toughness and good health. There are even poly's in its pedigree. The spring flush covers the bush with lavender blooms in bunches that nearly obscure it. A wonderful fragrance that wafts. In Memorium Mevrouw Nathalie Nypels- Sweet little pink rose, tough and long-suffering that didn't survive the 2nd time it was run over by the city utility truck. Sweet Pea- Lost during the polar vortex Sunshine- Lost twice. Seems too fragile for my garden.