How to Grow Mediterranean Herbs in a Cold Climate

It all started with the rosemary. I had written a blog post quite some time ago, recommending ‘Salem’ rosemary as being particularly good for wintering over indoors–and yet I had never grown it myself. Since moving to our new house, I had been puzzling over a narrow strip of soil between the attached garage and a stone walk.

With its southwestern exposure, this bed made the hostas happy in early spring, and miserable in summer.

It got sun for three-quarters of the day and runoff from the garage roof. The hostas that the previous owners had planted there appreciated that runoff, but during the driest part of the summer, they really started to flag. I suppose a different gardener would water them all through the summer, but that’s not my style. I would rather find a place for the hostas where they are happy without the extra help from me. So then I asked myself,

What likes it hot and dry?

Answer: Perennial Mediterranean herbs! Specifically, rosemary, lavender, thyme, tarragon, oregano, and sage. After this light-bulb moment, I realized it was time to try ‘Salem’ rosemary. ‘Arp’ rosemary is reputedly the hardiest, but it just wasn’t that attractive of a plant, and it finally died on me. I was currently growing a nameless rosemary from a big box store. ‘Salem’ was not that easy to find, but I finally located it at The Grower’s Exchange. I contacted the owner, Briscoe White, to pick his brain about the hardiest rosemary.

Salem is a tried and true variety. It does not sell as well as other better known varieties, but I kept it on our list just because it is a very reliable rosemary. It would need winter wind protection in your climate. It can be kept indoors, but we always have recommended that they be taken from indoors after holiday season and kept in a cool room or cold frame to allow dormancy. Arp, I agree is a specialty variety. The very sparse needles look gray/green, they are not very fragrant. It has the reputation among gardeners to be the hardiest rosemary. This may be, but from my experience in Virginia, Salem is just as hardy, and is fine for culinary use.

I asked him if there were any other rosemarys he would recommend for wintering over.

As an indoor rosemary, Tuscan Blue is my long time favorite. It is not reliably hardy even here in Virginia. BUT, it has the largest and most dark green needles of any other rosemary. It is very aromatic and does well indoors. It is great for cooking. If you are committed to bringing in a potted rosemary inside every winter due to severe temps, hardiness is not a critical factor. Why not select for best foliage and fragrance? Tuscan Blue does require a cool dormant period, so a cool room with southern or western exposure would be perfect. Tuscan Blue’s foliage is beautiful, making plants useful for Xmas holiday decorating.

Rosemary is definitely not hardy in my climate; it will be grown in a pot. That was a given. But what about the other herbs? I had tried growing tarragon and sage before, and they hadn’t made it through the winter. A inexperienced cold climate gardener might think that the winter was too cold, but what I have learned over the years is that poor drainage will kill a lot of plants that would otherwise survive the cold just fine. They rot, and it’s usually mud season that gets them. Briscoe agreed. “Drainage is vital to herb plant health. Especially in winter.” The soil here is acid clay, and especially during snow melt it can be sodden.

Typical early March. A previous sunny day has caused the snow to start melting in this warm microclimate. Melted snow dripping from the roof has carved out a line in the snow under the drip edge.

It was the runoff from the drip edge that concerned me. It could provide too much moisture to the soil. But, considering my other options, this was still the best place to grow Mediterranean herbs in my garden. So, I tried to make the soil more freely draining by adding amendments.

First, I added 3 bags of crushed oyster shell.

I spread it evenly.

This is what crushed oyster shells look like, in case you were wondering. It’s one of two things called chicken grit.

The “other chicken grit” is made out of granite. One brand is called Grani-Grit. Both products are available at poultry supply stores, but usually not both at the same shop. In this case I wanted the oyster shells to offset the acidity of the soil. Most of these perennial herbs like a soil that leans toward alkaline.

Once I had spread all the chicken grit, I decided that wasn’t sufficient to improve the drainage. I availed myself of the surplus grit (or sand or gravel or whatever it’s called) used as the base for the front stone walk.

I don’t know the technical name for this stuff, so let’s just call it “construction grit.”

Here’s what “construction grit” looks like up close.

You know, if you didn’t need to moderate the pH of your soil, you’d do better to use “construction grit” for a project like this. An entire pickup truck load of this stuff cost less than one bag of the chicken grit, and the color of the construction grit blends in with the native soil much better. (I didn’t know about the price difference when I started this project, or I might have just used construction grit for the whole thing myself, and added lime if I thought it was needed.)

Here’s the “construction grit” dumped on top.

Here’s how it looked after I mixed it all in. See how conspicuous the white chicken grit is?

Now for the fun part: planting!

Here’s what went into the original planting in 2013.

In addition to ‘Salem’ rosemary and ‘Tuscan Blue’ rosemary (both Rosmarinus officinalis), Briscoe sent me ‘Lemon Carpet’ thyme (Thymus herba-barona), tarragon (Artemisia dracunculus), Italian oregano (Origanum majoricum), and Greek oregano (Origanum ‘Kalitera’). Besides Briscoe’s plants, I had chives, garlic chives, and anise hyssop (Agastache foeniculum) from my old garden. I had been sent a trial plant of ‘Elizabeth’ lavender from Skagit Gardens. A friend gave me the borage (Borago officinalis). And I purchased the golden sage (Salvia officinalis ‘Aurea’).

What lived and what died?

One of the reasons I didn’t write about this garden right away is I wanted to make sure it actually worked–that is, I wanted to be able to tell you what made it through the winter. This planting has been through four winters now and I’m confident that my soil amendment was sufficient for most of these plants. Here’s how it all went down.

• Rosemary: I planted my old rosemary in the ground as an experiment. If it had pulled through, I would have tried one of my “good” rosemarys. (The old rosemary had a self-sown flowering tobacco in the same pot.) The ‘Tuscan Blue’ did fine that first summer, but died almost immediately after coming inside for the winter. I think that was operator-error, and I want to try it again, as it was really gorgeous. ‘Salem’ is still going strong and needs such a big pot that I no longer keep it near the other herbs.
• Oregano: Both oreganos are doing fine. They always look dead in the spring but after the new growth shows up I trim back the dead stuff.
• Thyme: The ‘Lemon Carpet’ died out. Not a surprise since it was listed as hardy to Zone 6. I replaced it with ‘Golden Variegated’ thyme (Thymus x citriodorus) which has no lemon scent (that I’ve noticed) but is hardy to Zone 5 and has been doing fine. I have also added creeping thyme (Thymus pulegioides) grown from Renee’s Garden seed and ‘Elfin’ thyme to grow between the stones in the walk.
• Tarragon: it barely squeaked through for a couple of years but finally gave up last year. I guess it needs even better drainage, as it’s listed as hardy to Zone 3!
• Lavender: ‘Elizabeth’ is still going strong. Later in 2013 I received a sample plant of ‘Phenomenal’ lavender and that is also doing quite well. They both look dead in the spring and I wait until the new growth is visible and then cut out everything dead.
• Sage: the golden sage died that first winter. Since then I replaced it with regular non-fancy culinary sage which comes back every year after looking dead.
• Anise hyssop: some years it comes back, sometimes it doesn’t. It is great brewed with green tea and served iced, so I keep trying. Also a favorite with kids to just nibble.
• Borage: it came back for a couple of years but then died out. I never used it in cooking but the flowers are a real pretty blue.
• Chives: These are thriving and are one of the few things looking alive this time of the year. As a matter of fact, vigilant dead-heading is required to keep them from seeding everywhere.
• Garlic chives: I have a lot of friends in warmer climates who have given garlic chives weed status. Mine needs to be babied, and I didn’t baby it enough because it didn’t come back this year. I will get more because it is my favorite addition secret ingredient in deviled eggs. It has white flowers and blooms in late summer/early fall. I will have to figure out what I need to do to make it happy.

The plants that survived up until now are in their same spots. The replacements have been tucked in where there was room. (October 2016)

In 2015 there was one poppy that somehow snuck into the bed. In 2016 there was half a dozen. The ‘Goodwin Creek’ lavender was a gift from my sister and isn’t hardy. It winters over with the ‘Salem’ rosemary in the room above the attached garage.

It’s no longer just an herb garden

Once I successfully created a warm, free-draining microclimate, I could hardly stand to reserve it exclusively for herbs!

Arum italicum ‘Marmoratum’ was the first plant to get “tucked in”.

I got it from a friend in Tennessee, and I was afraid it wasn’t cold-hardy here. Now that it’s bulked up a bit, I’m trying it in the Cabin Fever Bed, because it has attractive foliage throughout the winter–when it’s not buried in snow. Know what else likes a hot, dry summer?

Tulips!

I kept finding the odd tulip here and there, and I just “tucked them” into the Herb Garden. I think the previous owner planted out tulips that she received blooming in pots. They weren’t blooming in their former locations, but they bloomed the following year in the Herb Garden. Time will tell if they bloom this year. So far I see leaves but no buds.

These ‘Valerie Finnis’ muscari were getting overrun in their former bed, so I moved them here to keep them safe.

Besides, as you can see, the Herb Garden doesn’t look like much in May. It could stand a little color in spring. Even in June in some years, the more woody plants struggle to get growing.

This is mid-June of last year. The lavenders and the sage got hit hard by the April polar vortex after the extremely mild mud season.

The labeled photo of the current plants (above) is the same bed last October, where you can see the lavender and sage did come back eventually.

Last fall I screwed up my courage and acquired some “iffy’ colchicums that I planted in this bed.

Colchicum munzurense, pictured above, is described as hardy to USDA Zone 5 but needing a gritty soil. It bloomed in February, yes, February–before the snowdrops in that same bed. Oops. I had forgotten about those snowdrops.

Here they are. ‘S. Arnott’ snowdrops, an early-blooming variety.

They were blooming a mere four days after the colchicum did, but still–the very first flower of the year is always a thrill. The Merendera sobolifera (label in picture) was supposed to bloom this spring as well but so far there’s no sign of it.

The takeaway

• You need a warm microclimate. Check where the snow melts first.
• You need good drainage. If you don’t already have it, you’ll have to create it.
• Some plants will die. They might make it the second time you try them.
• Some plants look dead for a long time, but eventually grow back.

Have you grown these perennial herbs in your garden? I’d love to hear how they do for you!

As mentioned in the text, six herb plants were donated by The Growers Exchange in support of this project. The opinions are my own.

P.S. Don’t forget to register for Jaw-Dropping Flowering Shrubs, Kerry Mendez’s upcoming webinar on April 27th. Click here for details.

from Cold Climate Gardening http://ift.tt/2ovYgie