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In a 6b zone I have to grow some annual and perennial flowers by the end of May, meaning that they must be flowering by then. I have tried to make a rehearsal of some sorts, but we had freezing temperatures until the first days of May 2016, so last year I have transplanted them a little late (they were grown indoors from seed). The result was that they came in flower in mid-July.

Some of the species are Tropaeolum majus (or minus), Centaurea cyanus, Lavatera trimestris and Alcea rosea and I was wondering how to protect them in case I want to plant them earlier, let's say in March.

My plan is to make raised beds and any advice on how to protect them is most welcome. I also have to mention that the land is on a north-faced hill, but the slope is barely noticeable in the area I will make the raised beds.

Alina
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  • 6b gets down to -17 deg C? – Graham Chiu Jan 10 '17 at 22:16
  • -23 deg C. Historical low was -30 deg C. – Alina Jan 10 '17 at 22:25
  • And what temperature are you trying to protect against? – Graham Chiu Jan 10 '17 at 22:34
  • I guess it won't be lower than -5 deg C in March, since the average low is -1. The annuals don't need to survive the cold season and from the perennials I will select species that withstand the winter, that's why I'm interested in their protection only in March. – Alina Jan 10 '17 at 22:45
  • Are you going directly from indoors to in ground in the final location? – mpdonadio Jan 11 '17 at 14:27
  • I will acclimate them, shorter intervals in the beginning and gradually increasing the time spent outside. – Alina Jan 11 '17 at 16:11
  • What country's zone 6b? The -30° C (-22° F.) temperature you gave matches USDA zone 4b. If you're growing perennials (which is what the hardiness zones are for), it's a good idea to go with the historic lows, if you want to be sure they're hardy enough. Average temperatures only help for average years. We're definitely not having an average winter in my town. ;) – Brōtsyorfuzthrāx Jan 11 '17 at 23:46
  • 6b in Romania gets to -23° C, but -30° C is the historical low in January in the city of Cluj-Napoca where I will plant the flowers. What troubles me is March weather because that's when I want to take the plantlets outdoors. After I acclimate them gradually, I will transplant them and let them be if temperatures are above freezing. It is likely that this will happen in the second half of March, when there is a low chance of freezing. However, even then there might be some nights when temperatures fall below freezing and I would like to be prepared and cover them. – Alina Jan 12 '17 at 07:37

1 Answers1

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I don't know about flowers, but for vegetables, I like to use humidity domes. I just cut off the bottom of a milk jug, throw the cap away and put it over my newly transplanted plants, if it still frosts. This seems to work for fairly cold temperatures, in my experience (at least down to 23° F. at the side of our house, if not colder, which is to say -5° C.) There are many kinds of humidity domes.

You might try row covers, floating row covers, certain protective garden fabrics/cloths, a hoophouse, a greenhouse and such, to protect plants from frost. However, they may each have different ratings for temperature.

Brōtsyorfuzthrāx
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    In France, they used to use glass cloches in the market gardens. – Graham Chiu Jan 11 '17 at 06:28
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    Newspaper is an incredible insulator. I use newspaper dampened and then row cloth. Problem with plastic or glass covers is frying your plants. If you don't get back out to the garden and remove these mini green houses, you can easily cook your plants. If you are able to do that then mini greenhouses work as well as row cloth. Newspaper single sheets, dampened then cover all with row cloth. If you forget to cover and if it is still dark, start the sprinklers before the sun comes up. Freeze damage mostly happens when frozen plant cells thaw too quickly. Sprinklers slow the thawing. – stormy Jan 11 '17 at 07:37
  • @stormy Where do you put the newspaper, exactly? There's definitely a certain temperature where the milk jug isn't good anymore. With winter sowing (which is different but still uses milk jugs similarly) people usually gradually increase the size of the opening at the top as it gets warmer, but I just tend to take the jug off when it reaches that temperature, and leave it alone until then. In my area, I don't remember whether it was 71° F. or 81° F, but one of those, I believe. You also need to anchor the jugs with dirt and make sure dogs don't take them off, if you have dogs. – Brōtsyorfuzthrāx Jan 11 '17 at 17:17
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    I tried the sprinkler method once. This is my observation: If you're going to do it, begin before any plants have frozen (or they may still die). It will probably coat your plants in scary-looking ice (the melting of the ice I hear is supposed to produce heat or something to protect the plants; I don't know if it's true). If you don't want to risk extra anxiety over scary-looking ice all over your plants, maybe don't do it. It requires a *lot* of water. If you have city water, that may be a huge expense, since you have to sprinkle for hours. – Brōtsyorfuzthrāx Jan 11 '17 at 17:28
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    I started the sprinkler while it was dark, but after it had already frozen (it didn't work; hopefully it works if you begin before then, but I can't say). If you have clay-type soil, expect a lot of water build-up. For fall frosts, I prefer just to cover them with blankets overnight. It works very well. For spring frosts, you probably want something gentler than a normal blanket; something that will let light and air through. – Brōtsyorfuzthrāx Jan 11 '17 at 17:47
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    @stormy are you saying that plants will cook under glass in near freezing temperatures? – Graham Chiu Jan 11 '17 at 20:06
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    Depends on how much sun there is...I wasn't reading freezing temps for March, zone 6b? I am in zone 1b and with bright sunshine the green house gets up to 80 degrees, in freezing weather. 80 degrees F. Glass is particularly heat enhancing. Plants being grown between straw bales or larger wooden cold frames need supervision as well, opening the tops to allow heat to escape. March 6b is rarely freezing freezing. I do know that newspaper and row cloth work dang well. I wrapped all my house plants in newspaper for a trip in a uhaul to a new home. 16 hours...not one died. -20 F. – stormy Jan 11 '17 at 21:21
  • I had my milk jugs in basically full sun for the high temperature I mentioned (shade for the 23° F. though). I never had a problem with them getting cooked by the sun if it was cool, even if it was really sunny. They could handle higher temperatures in my greenhouse if the vents were all open. Maybe elevation or location makes a difference as to the affect of the sun. I'm at just over 2200 feet, near some northwestern high deserts USA location. Ventilation is key, though. If you don't have any that's going to hurt/hinder the plants, even at cold temperatures; more when hot. Never tried glass. – Brōtsyorfuzthrāx Jan 11 '17 at 23:36
  • Just the light from the sun through glass/plastic can burn plants. In a small environment that energy is enough to cook plants. VENTS and air flow would be the best to include to stop any harm to the plants. That is a lot to deal with, freezing temps outside and inside too high of temps. Ventilation would be the best thing to ameliorate this temp change. There is nothing to stop the temp from reaching the outside ambient temps at night. During the day, even if the temps don't rise to cooking, just the change in temps is wow stressful to the plant. I agree Shule... – stormy Jan 15 '17 at 22:49