Question
I live in a Zone 6B area of Ontario, Canada.  I am growing an Arp Rosemary perennial as I have done in the past. Is it possible to winter this plant over without bringing it indoors?  If so what care does it need to do so?
Thanks kindly,
Norma

Answer
Rosemary officinalis 'ARP' takes its name from the Zone 6 Texas town where an herbalist first found it 35 years ago.

Theoretically, you should be able to grow this more hardy 'Zone 6' Rosemary, in your Zone 6 Ontario climate.  But there's more to this than its cold tolerance.  Much depends on factors like wind, snow, rain, and 10 different things about the Soil.  In fact, everything depends on those factors.

Back in its home country, ordinary Rosemary was a simple Mediterranean weed with simple tastes.  Dr William Welch of Texas A&M points out that it 'will thrive even on poor, dry rocky Soils' around the Mediterranean.  In fact, he points out, 'Rosemary flourishes in coastal regions so arid that a significant part of the plant's moisture comes from the dew absorbed through the foliage.'

The key to keeping Rosemary comfortable: 'poor, dry rocky Soils'.  This is a taste it shares with its fellow Mediterranean natives: Lavendula, Grapes, Olives.  This is NOT a plant that fares well in a water-retaining, rich, humusy growing medium.  That, as much as the over-chilly Winter air, does much to determine the fate of any Rosemary plant.

Drainage is esential, enhanced with high ratios of Sand to a rich, organic Soil.  No Peat Moss allowed.

You probably get a ton of Snow each Winter and take it for granted, but if you topdress Arp with Sand you may raise the odds of Winter survival when there is a lack of consistent snow cover.  Find the right R. officinalis-happy micro-climate in your plot.  A foundation, a stone wall, a hedge with a Southern exposure -- any of these will be several degrees warmer in Winter.  Wind chill affects plants, too; anything that blocks it on frosty, dark, Winter days pays off when growth resumes in Spring.

If there's anything in the past decade that's come to the forefront that you could call Plant Survival Edges it's conditions around the roots, in the Soil -- namely, the mycorrhizal Fungi.  These are the secret allies no one knew existed until recently around the Soil of the vast majority of organisms in Kingdom Plantae.

If there's anything that boosts plant vigor, it's those mycorrhizae.  And there's nothing that makes mycorrhizae more miserable than disturbance.

Digging and lifting a Rosemary plant, or even just growing it as a potted specimen, cuts off all connection to the Fungal hyphae of these underground organisms -- the threadlike, delicate strands that connect roots to Fungi and serve as trade routes.

You have no way of providing these beneficial Fungi for a potted plant.  Growing it in the ground, on the other hand, opens a whole new set of choices, none of which will involve you but which allow Arp to use these mycorrhizae and all the mysterious things they do for one another.

In 6 months or even a year, there will be negligible differences.  But 18 months, and nothing is the same... That is, IF you can grow it outdoors in your climate.  This remains to be seen.  Arp is too new to know what results you can expect.  It should be interesting.

THE LONG ISLAND GARDENER