Potted Rosemary Left Outside in Snow: An Update

narcnh(z5nh)December 11, 2005

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.


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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.

    Bookmark   December 11, 2005 at 10:56AM
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jenny_in_se_pa(USDA7 Sunset 32)

How big are your pots?

    Bookmark   December 11, 2005 at 4:17PM
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Standard rosemary: 12-inch
Lemon verbena: 10-inch
Profusion chives: 8-inch
Blue Boy rosemary: 6-inch


    Bookmark   December 11, 2005 at 8:11PM
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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.

    Bookmark   December 14, 2005 at 4:12PM
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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.


    Bookmark   December 17, 2005 at 10:38AM
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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!

    Bookmark   July 24, 2011 at 8:39AM
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