Potted Rosemary Left Outside in Snow: An Update

18 years ago

I thought my experience with leaving a few herbs, especially rosemary, outside in very cold weather might help answer some questions many people seem to have about hardiness and when to bring plants inside.

As I mentioned in an earlier post, I brought most of my potted herbs inside in October, just before our first frost. But, I left a few plants outside in pots until last weekend, when I finally brought them inside. Being in Zone 5 in NH, weÂve had below freezing temps since 25 October and temps have gotten down to 12F/-11C with three measurable snowfalls. All the pots were frozen solid and snow covered. The plants were: a standard rosemary, about three feet tall, a dwarf, prostrate rosemary, Blue Boy, a pot of Profusion chives and a lemon verbena. When I brought them in the rosemary plants looked fine, the chives had died back to the dirt and the lemon verbena had dead leaves. I thawed the pots and the rosemary plants went right into south-facing windows. The chives went into an eastern-facing window, trimmed of all their dead leaves, of course. The lemon verbena went into the basement.

One week later the rosemary plants look very healthy with no signs of damage. Tips are green and thereÂs new growth on all stems. The chives also look fine and are already putting out new growth. The jury will be out on the lemon verbena until probably March, but I think it may be toast, since it really doesnÂt like to freeze. We shall see, but thatÂs what experiments are all about.

So, it looks like rosemary can take some pretty cold weather, even in a pot, and just shrug it off. I will try to put them out earlier in the spring, too, since they really seem to prefer it outside. Why did I bring them in when I did? Because temps got down into single digits the next night, and I felt that that was pushing it for potted plants. I do have a Madeline Hill rosemary and an Arp rosemary in the ground in a protected spot on the southern side of my house to see if they can take below 0F temps, but thatÂs another experiment.

As for the rest of the herbs that I brought in last October, everyone seems to be doing fine, even the basils. Some plants, like Mexican tarragon, African and holy basils, and VickÂs plant are even blooming.

narcnh

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Comments (6)

Heathen1
18 years ago
Yeah, I'd think the lemon verbena is toast... I grow a lot of tropicals, so I know they can be more hardy than people think, but I think LV is not very hardy.
jenny_in_se_pa
18 years ago
How big are your pots?
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Hi chocolateis2b8, Nice nic, by the way. Glad the info is useful. I will keep updating on the status of the outdoor plants. The new growth on my indoor rosemary plants is more tender than the older growth, which as you know gets pretty tough with rosemary, but it is not weak or floppy. I think that is a function of light - the plants are in south-facing windows and get full sun most of the day. If the new growth on your plants doesnÂt firm up by spring, just cut it all off. The plants will put out a flush of new growth that will be even fuller than before, and you will collect a whole lot of rosemary sprigs that you can dry or use for potpourri. I water when the plants get very dry, maybe every two weeks, even longer sometimes. This is for rosemary, which likes it dry; other herbs that like it more moist I water more frequently. When I do water, I do so until the water comes out the bottom of the pot, so I'm sure that the soil was thoroughly soaked. I use those plastic trays that are available at any box store under all my pots, just so I can soak them, yet protect the furniture underneath. All my pots have built-in water reservoirs, so those have to fill before the pots overflow into the plastic trays. I feed VERY infrequently, since most herbs, especially the Mediterranean types, for the most part are tough-environment plants and make do with very little. Basil is an obvious exception. Usually, I use a dilute houseplant fertilizer that is added to their water a couple of times during the winter. I just bought some time-release fertilizer that I will be adding to all my pots today. This will be the first time I have ever really fertilized them, when they are indoors. But, all the plants are really growing this year and the rosemary is completely covered in blooms (even more than are in the pic above), so I think they could all use a few extra nutrients. I also misted all my herbs with a micro-nutrient spray recently, because I had some left over from misting my citrus trees. Normally, I don't mist to minimize the risk of powdery mildew. But, as a rule, I have been pretty miserly with the fertilizer indoors. All my potted herbs get a good dose of time-release fertilizer, when they go outside in the spring. I hope this helps. Rosemary is one of my favorite plants to grow indoors, because it smells so great and has such a solid, live-forever look about it. When it blooms, it almost looks like lavender. narcnh
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Hi Flora, If it's not outdoors, I just don't have any other options beyond "the temp we keep the house," which is 70F when we're up & about, 60F when we're away at work, and 65F while we're sleeping. On the plus side, this plant did survive indoors last year, and it wasn't nearly as healthy when it started, nor was it in the sunniest window available. Because of this, I'm hopeful. It was somewhat pale and spindly-looking by the end of it, mind you, but by golly, it was alive, and several months of outdoor sunshine did wonders for its health. It's positively thriving now. One of the upstairs rooms might be somewhat cooler, at least some of the time, but there's also the danger of "out of sight, out of mind" and it could get ignored, never get watered, and die that way. I think one of the things that kept it alive last Winter was that it was in the kitchen, poor light and all, but that meant we saw it every day, and if it looked horribly dry, it got watered. This is a difficult problem, to be certain, but last year's success (my first ever) keeps me optimistic.
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narcnh
Original Author
18 years ago
jenny,

Standard rosemary: 12-inch
Lemon verbena: 10-inch
Profusion chives: 8-inch
Blue Boy rosemary: 6-inch

narcnh
ozarkmtman
18 years ago
Last year we had an arctic blast here that brought sub-zero temperatures along with high winds. Shame on me, I forgot to cover my Arp rosemary. Never the less it survived with only a moderate amount of damge that I was able to prune out in the spring. It has recovered nicely.
In an endeavor to find an even hardier rosemary I went by the cold hardiness reference in the Well Sweep catalog. It lists quite a few cultivars that they have found through their own experience to be hardier than Arp. I tried two of those, 'Blue Spire' and 'Logees Blue'.
The 'Logees Blue' is just wonderful, with its lemon-thyme undertone to the rosemary fragrance but, alas, it bit the bullet when we had a zero degree night last week. So much for that one.
The 'Blue Spire' survived that frigid night with only a modest amount of tip damage, so I assume that it will make the winter here, I hope. Sadly, it is not nearly as appetizing as the 'Logees Blue' or the 'Arp'.
All three plants are in the same area of the garden, and fully exposed.
Next year I intend to try the varieties 'Salem' and 'Hill Hardy'. I had been told by one source that 'Hill Hardy' and 'Madeline Hill' are one and the same but, I see in the Well Sweep catalog that they have different flower colors.
I would assume that if they are seperate cultivars that they would both be worth growing, having been selected by Madeline, herself. I had been told this some time ago. Now I am confused over their identities, and I do not want to order two plants that go by different names that are essentially the same. At some point I would like to try 'Madeline Hill' if it is a cultivar seperate from 'Hill Hardy'. Does anyone here have any input on that?
By the bye; The USDA lists my zone as 6. I list my zone as 7a at the GWF because I have found that some zone 7 plants make the winters for me here, regardless of the stray mid-winter zaps.
Blessings to all.
martieinct
18 years ago
If a frozen LV makes it Take Cuttings and get it out to market. LOL It's probably toast -- scratch the trunk to be absolutely sure (where there is any sign of green there is hope) but I doubt there's much hope.

Many varieties of Rosemary can take *some* freezing weather if it warms up during the day to keep the fluids moving. It is when there is sustained freezing weather that the plants die.

OMM: It is my steadfast belief that Madeline Hill and Hill Hardy are one and the same having grown both. I rarely go by flower color to finally identify plants, as new bloom can be different than old bloom, light can play a part, and the nutrition the plant receives matters a lot. Go by the foliage color and habit, instead. Though Well Sweep is a reputable vendor, it is better for them to sell two plants rather than one, so they can take advantage of very subtle differences between parents and name varieties whatever they'd like. A very common practice .....

Even the hardiest of plants will die if they go through too much freeze/thaw/freeze/thaw. It could be that the Rosemaries alledgedly hardy to Z5 did that, and it wasn't the temp that killed them, it was the *change* in temp.

Martie
jjaymccabe_gmail_com
12 years ago
I'm trying this for the first time but so far so good...I bought deep ice cube trays on amazon 6 two inch cube per rack.here's the trick: cut the herb or pepper in the size you will use it. Pack the cubes with herb or pepper only half way, and fill with water ONLY half way, then freeze. Remove and finish filling the trays with water for a second freezing! This covers any material that floated to the top and would have been exposed to air! Place fully frozen cubes into a sturdy freezer bag (don't go cheap here), label with herb and date, and use whenever. If replacing dry herbs with fresh remember to double the amount of fresh. Good luck!

Potted Rosemary Left Outside in Snow: An Update

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Potted Rosemary Left Outside in Snow: An Update

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narcnh
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