During spring, a heavy coat of fall leaves or wood mulch isn't a good idea for sages (Salvia spp.), because it can cause fungal problems that attack crown and roots. But in winter, organic mulches are ideal for blanketing the foliage and root area of sages.
Mulch is particularly useful in protecting protect plant roots against injury from freeze-and-thaw cycles, especially for new fall plantings.
Let's say you live in USDA Cold Hardiness Zone 6 and have recently planted some Zone 5 or 6 Autumn Sage (Salvia greggii spp.) that are now about 18 inches tall and wide. However, you are worried that the plant roots aren't established enough to avoid heaving out of the ground when it freezes.
When ground thaws, heaved roots don't always sink back into the ground with the shrinking soil. Often, they are exposed to dry, cold air as well as more freeze-thaw cycles. One way to minimize this problem is to wrap mulch blankets around each plant.
Building a Mulch Tower
Tomato cages are good structures for holding leaf mulch in place when plants are small. Here's how to do it:
To protect a new planting that is larger -- or even an older sage that is cold-appropriate for your zone and has a well-established root system -- apply a thick layer of leaf mulch around the plant's base.
But what do you do if you have a flowerbed filled with beautiful sages that are perennial to warmer zones? Furthermore, what if you don't want to dig them up each year to overwinter indoors?
Creating a Mulch Comforter
We pay close attention to horticultural professionals, but also encounter excellent ideas on gardening social-media sites. For example, the Hummingbird Forum is a great place to chat with experienced Salvia gardeners, such as a Minnesotan who manages to keep Zone 7 plants alive through Zone 4 winters.
Normally, we don't recommend pruning sage in autumn, but this method requires it. It also requires a raised-bed planter amended with sand for excellent drainage, because damp roots are dangerous for sages in freezing weather.
Here is how the Minnesota gardener puts his Salvias and companion plants to bed for the winter:
Quick Digs and Questions
This is the second article in our current Quick Digs series on preparation for winter in the Salvia garden. Each Quick Digs series selects a central issue about gardening and provides a series of brief articles suggesting ways to deal with the issue.
Another way to deal with questions about winter mulching is to contact us. We can't offer any works-every-time solutions for overwintering, but we are glad to share ideas.
Updated October 26, 2015