How to Determine Whether to Keep Hardy Perennials in Your Garden

Reader Contribution by The Thyme Garden Herb Company

It is officially spring! The seed and plant catalogs have been rolling in for months, making their way into homes covered in snow and ice. But with the daffodils popping, the swallows returning, and all the other tell-tale harbingers of the new season arriving, it feels like time to dust off those catalogs and get down to planning the 2014 garden. Before getting all crazy about new plantings, it’s a good idea to take stock of what survived and what needs to be repurposed into compost.

Out here in Oregon, we had one of the harshest winters on recent record. As a result, many of our normally hardy perennial herbs didn’t overwinter. One of the most frequently asked questions I’ve been getting this year is “is my rosemary (or lavender, sage, or thyme) dead?” Sadly, much of the time I’ve had to answer yes. I’d like to share a few basic ways to determine the course of action for these four herbs that can be applied to other (usually) hardy perennials as well.


Rosemary doesn’t like to have its root zone saturated with water. Wet winters with extended periods of standing water will kill your rosemary quickly. Likewise, heavy snow will snap branches and freezing conditions will kill the tender growing tips. Sadly, rosemary tends to go through a long, drawn out death. It’s basically the same demise as a Christmas Tree that has been cut: the root system has died, but the plant stays green for a while, then loses some leaves, then loses some of its shine and luster, and finally ends up a fire hazard.

When to prune.If just the tips of the plant are brown and the rest of the plant appears green and vibrant, give the plant a chance. It’s likely that your plant suffered from frost damage. Prune off any dead sections, keeping in mind the end result of your pruning, and wait and see. It is also possible that the roots are dying and the energy is retreating from the tips first.

When to yank. If your plant has an overall dull appearance (ie the leaves are still greenish but appear sort of cloudy and maybe even a little bit crunchy and can be stripped from the stem easily), it is time to yank it. Another way to check if the plant has life coursing through it or not is to take a sharp fingernail or knife and strip away part of the outer bark on the stem. If you see green in there, there is life. If you see nothing but brown, that section is dead. You can also study a cross-section of the stem, looking for a green living tissue. Here’s the deal with rosemary, in my honest opinion, it needs to be replaced every now and then. It’s hard to say goodbye to an old garden friend, and rosemary is my favorite herb, but it gets very woody and scraggly with many pruning’s and it is best to just pop in a new one periodically. It also gives you a chance to try new varieties.


Like rosemary, lavender likes warm weather and well drained soil. A lack of either or both will do it in. It can be tricky to determine if your lavender is worth hoping for a healthy recovery or not because they tend to look a bit scraggly in early spring. There are a few signs to look for, however.

When to prune.If the lower portion of the plant is still silver green, leaves are full and vibrant, and the only brown on the plant is from the previous year’s flowers, you’ve got it made. Prune in early spring, and prune hard. I suggest pruning at least half of the healthy portion of the plant back. This will keep your lavender from becoming excessively woody with time and encourage more blooms. It seems harsh, but it’s good for the plant. An exception to this would be if you like the sort of bonsai-ed look of a lavender with exposed lower branches and tufts of leaves and flowers at the top which can be a neat look for older plants.

When to yank It’s time to get out the shovel when the lower portion of the plant is brown. Look closely. Sometimes you will find that there are new green leaf buds popping along the stem. If there are, then prune as suggested above. Keep in mind that how patient you are with babying your plants along. I have a hard time giving up on plants, but I’m a softie. You can also use the technique of looking for green in the stem.


Culinary sages (examples: Salvia officinalis, Berggarten, TriColor, Golden)  can take the cold pretty well. They don’t love the wet ground so it’s a good idea to plant them on a high spot in the garden, a pot, or in soil amended with sand. We’ve had good luck with some of our more decorative varieties in mild winters, but some of the more unusual decorative varieties like Karwinski’s Red and even Saltillo Sage, will need to be potted up and brought into a warm location for the winter. Some we just treat as annuals and plan to replace each year.

When to prune.
If there is a lot of healthy growth at the tips of each branch, it’s safe to say your sage is coming back for the year. Prune way back, like with lavender, and you will get a flush of healthy new growth. With culinary sages, it’s pretty normal for the bottom leaves of the plant to turn brown and yucky over the winter. If you carefully remove the spent leaves you will find new growth sprouting out if the plant has overwintered. For decorative sages that form a basal rosette, you can expect the upright stalk to completely die-back in winter. New leaves will form at the base of last year’s growth. It’s a good idea to leave part of the stalk or a garden marker where the plant should be showing up. Also, watch for slugs – they are great opportunists of new shoots!

When to yank. If there is no sign of life anywhere on the plant. If you have done the green-stem test and there is nothing but brown. Give a gentle tug a the base of the plant. If the plant feels like it could easily release from the soil, you might as well give it a good firm yank and throw it in the compost heap for some nice woody material.


When spring rolls around, many herbs snap into life and start a beautiful flourish of new growth. Thyme is not always among them. Dead foliage from the previous year tends to hang on to the green coming through at the base – and that’s actually a good thing! The spent foliage forms a protective layer of insulation for the new growth from snow and frost.

When to prune.Prune your thyme when the danger of frost has past (to the best of your knowledge!) Like the other herbs listed in this blog, thyme is in the Lamiaceae or mint family, and it loves a good hard pruning to stimulate new growth. If there is a good base of green on your thyme, it is worth keeping. This is true of both upright culinary and creeping thyme varieties.

When to yank.It’s good-bye thyme (sorry – I couldn’t resist one bad thyme joke!) when the plant has an overall look of brown or if the green lively parts are so few and far between that the plant would look odd if pruned. Rest assured that thyme grows into a harvestable plant the first year and you will soon have thyme in the garden again.

The sooner you can make the decision to prune or yank the better. It’s getting late for seed starting, but we do carry many varieties of lavender, sage, and thyme by seed as well as common rosemary. If you are in Oregon, check us out at our nursery in Alsea – we open for the season April 15th!

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