Many woody perennials winter over more successfully if the previous year’s growth and bloom stalks are left intact through the cold weather. Generally falling into this category are many of the salvias, echinacea, monarda, achillea, lantana, and buddleia. All of these can be pretty rangy or twiggy by their season’s end and it is hard for me to resist cleaning them up in the late fall just to make the garden’s overall appearance tidier. If trimmed back so late in the season that no new growth has long enough to harden off the plant is left with a plethora of twiggy hollow stems exposed to water by the cuts. Water will fill the hollow stems and can cause rotting down to the base of the plant. We don’t lose many of these plants in my mild winter garden to frost or bitter cold but many could be lost to overzealous fall cleanup! The natural die back of the current year’s growth acts as protective armor for the next year’s new growth.
So, when do you know the time is right to cut back? There is no one size fits all or date to mark on your calendar. As with all plant maintenance the first step is to know how the plant grows. Several of the plants listed above push their new leaves out at the soil level forming a clump of new growth at the base as the soil starts to warm up at winter’s end. Soil temperature is a better indicator of impending spring growth than air temperature. As you walk through your garden finishing up your rose and summer blooming shrub pruning be mindful of what’s going on at the base of your perennials. Today as I raced the rain to get the last of my four ‘Eden’ climbing roses pruned I surveyed a nearby bed and found these specimens giving me the heads up that it is time to tidy them up for the impending spring.
Okay, so I had all ready trimmed a good many of last year’s stems from this Monarda didyma ‘Raspberry Wine’ (Bee Balm) before it occurred to me that this was a good topic for a post! You can clearly see the flurry of new rosettes of growth. The old growth was so ready to be gone that most of it just fell off at my touch.
I decided to wait a few more days to trim back the old stems on this Salvia guaranitica ‘Black and Bloom’ as the very first of the new growth has just appeared.
It’s cousin and neighbor, Salvia leucantha ‘Velour Pink’ was well on its way so I trimmed back all its spent stems.
This Gaura lindheimeri is a relatively new bicolor called ‘Rosyjane’. It is a little more compact than the species but still looks better throughout the season with regular tidying up. This is the first winter for this cultivar in my garden and you can see the remains of the original top growth is about 1/3 the size of the new growth clump. I will carefully trim all of the old stems to just below the new growth or just wait another week or so and be able to gently pull them off.
There is no rocket science here–the first principle of readying woody perennials for spring is to walk your garden regularly and see what your plants are doing! Understand their growth habits and each will tell you in their own time when to clean them up in anticipation of a great new gardening year.