Some gardeners in my area can manage to overwinter rosemary outdoors. Only the most hardy rosemarys, like arp, have a chance.

I was rezoned from 5 to 6 the last time the hardiness zone map was redone. Some zone 6 plants make it here, some don't. I just have to see on a plant-by-plant basis for that. But the success of those borderline plants all depends upon the microclimates you have.

I've tried arp three times unsuccessfully. That's generally my limit for utter failures. I know of a gardener only a few miles from me that successfully overwinters rosemary outside. I'm sure she is experiencing the same sub-zero degrees F weather that I've been experiencing. But that is not unusual for zone 6. We get sub-zero every winter.

So while I can't offer any personal anecdotes of success, I know it is possible.

FataMorgana

I think we're pretty firmly in zone 6, between being in the city, and not being particularly far from the ocean.

I'm not convinced that the place where I planted my own Arp is the best microclimate available in my yard, but it's a decent location for the plant. When I got my Arp plant, I bought extras and gave them to other folks, so there are 3 others that could possibly make it if mine doesn't. Then again, I really hope that mine is one of the survivors, since I pinned down some branches in an attempt to propagate the plant by layering, and I doubt that anyone else did. If my plant survives, there may well be 3-4 plants in Spring.

One of my extras went to my mother, who is actually in zone 5, but she says she has it in a very sheltered location, where she has some gladiolas that have survived several winters without digging.

I've been dreaming of a rosemary that's hardy in my zone for as long as I can remember, so I really want this to work out. I'm finding it difficult to wait until Spring to get the verdict!

If this one doesn't survive, however, I'll take fatamorgana's advice to heart, and try it again in another location in the yard. If it does survive, I may transplant one of the babies to a very different location, in the hopes of increasing my chances.

I had one survive for several winters here in Pennsylvania, but it then expired. It was in heavy clay soil in a spot where direct sun was limited, though. Your soil is probably sandier and drier, and that may help, especially if you are giving it full sun.

I do get jealous when I hear of people able to make actual hedges of it in more Southerly locations.

Well, my soil isn't sandy. I'd call it loam-y. Definitely not clay. Plenty of pieces of shale in the spot where I planted the Arp, seemingly more shale than dirt, but I painstakingly dug a good, deep hole and picked out the stones before planting. That spot does have full sun, or near enough to it.

As for hedges, here's my thought. If I can grow one Arp, why can't I grow two? Or five? And if I grow five Arps, all in a row, isn't that hedge? Just sayin'.

I am lucky that I can grow rosemarys year round down here on the Texas Coastal Bend, zone 9b. I do not think that I would not even try planting Arp further north than Zone 6. FYI, just in case you are not aware, Arp rosemary is named after a small town in east Texas. Here is some information about Arp rosemary. Here is what Madalene Hill has to say about rosemary:

Rosemary Rosmarinus officinalis

Rosemary is a tender perennial, but if properly located, it will thrive in the Zone 9 climate of the Upper Gulf Coast of Texas. It can become a bushy shrub five to six feet tall and wide.

Rosemary needs a loose, well-drained soil with a pH of 6.0 to 7.5. It prefers full sun but will tolerate partial shade. Indoor container plants like to be root bound and need four hours of direct sun or 12 hours of strong artificial lighting per day. Both indoors and outside, the soil needs to dry between irrigations. Seeds germinate very slowly, so the best method of propagation is to root or layer cuttings. Cuttings root easily in a self-watering propagation system.

There are many known varieties, but the two most common are R. officinalis, an upright species with blue flowers, and R. prostrates that grows one foot high by two to three feet wide with intensely fragrant foliage.

VARIETIES
"Arp" is a variety discovered by Madalene Hill in 1972 in Arp, Texas. It is hardy to Zone 6 and the answer to prayers of herb growers in colder climate zones.

"Hill Hardy" is a sport of "Arp" rosemary. It is salt tolerant, deer resistant, butterflies love the flowers, and also a good choice for a xeriscape.

"Madalene Hill" was named in honor of the great herb gardener.

From website: http://aggie-horticulture.tamu.edu/Galveston/publications/Herb-Book.pdf

Check this thread out for more information on rosemarys including Arp.

I'm in the borderline zone 5/6 area, rezoned 6, but I don't trust a solid 6 here. My rosemary (arp) is doing great. I mulch with pine needles, which is my favorite. (we have alkaline soil, so the acidic pine is ok...rosemary likes neutral to alkaline). I haven't yet, but am told by a master gardener that if you bend down the branches and weigh them with dirt or something, then mulch over them, they will survive very cold temperatures.

This is my first winter for my little arp, in a very sunny dry spot under the eves of my front porch, in Providence RI, a little farther up the bay than Portsmouth. We are considered zone 6 but have significantly gentler climate extremes than MA. It was very happy this summer and I'll pile up some insulation for the winter--@seahorsehurt's story gives me hope!

The little arp made it to March but died soon after pruning. I'm unsure conditions were right, I will try again!

ARP should be hardy for you in 6b. I am a tad milder in Zone 7A/NJ and mine have survived multiple winters. My issue has been bugs bothering them the last two seasons. Remember, when it's warmer PESTS also have an easier time surviving!! Always something.

@subtropix I've seen recommendations to plant in spring, not fall. fingers crossed

Interesting. I have had an Arp rosemary in a 1/2 barrel for the last 3 years but I do bring it into the unheated garage from late November until sometime in February. I have a few branches layering at the moment to get a few more plants going by fall.

Maybe I'll try to put one or 2 of the new plants into the ground next spring and see if they make it here. I have some area on the south side of my house that would be somewhat protected in the winter but blazing hot in the summer months. We can get sub-zero here for short spurts.

update: the arp didn't make it through winter. I thought it was in a high spot but now suspect cold eddying around the plant, also even though there was no wind it could have suffered desiccation, also the freeze/thaw cycles are reported to be very hard for them, and unfortunately that's a signature element of New England spring! I'm considering trying again this year and using a bell jar.

I tossed my original Arp that I had in the half barrel in the winter of 2018-2019 because it was getting root bound. I took a few of the rooted cuttings from it and planted one in the ground on the south side of my house and the other in a 2 gallon pot last spring. The one in the ground grew decent last summer but appears to have croaked over the winter as expected. The one planted in the pot that I overwintered in the garage is now blooming. I need to pot it up to the half barrel this weekend. It's supposed to rain most of the weekend so I need to bring the barrel into the garage to do it.