For some gardeners, bringing outdoor plants inside to ride out the chill of winter is a practical matter. You want to save money by helping favorite tender perennials survive from one season to another. For others, plants are a bit like pets. You feel tender about your tender perennials and can't bear to think of a lovely sage dying from exposure to harsh weather.
For both types of gardeners there is also the underlying challenge of attempting to win against nature.
This fourth article in our Quick Digs series on preparation for winter in the Salvia garden suggests ways to overwinter sages indoors. The series began here and moved on to posts about winter mulching and overwintering in containers outdoors.
At Flowers by the Sea, we understand about experimenting and pushing the limits. We certainly enjoy it when a plant exceeds our expectations for cold hardiness or other abilities. So we have some tips for inviting tender perennials indoors and helping them to make it through to another growing season.
Increasing the Odds in Your Favor
No matter what technique you use for overwintering a plant indoors, you will increase the odds of plant survival if you take cuttings in fall before frosts weaken the plant. This is called vegetative propagation.
Be advised that propagating patented varieties is generally prohibited by law, even for one's personal use.
Snip off pieces about 3 to 4 inches long with a minimum of three leaf nodes on each cutting. Pinch the leaves off the bottom two nodes. Then dip the stems in rooting hormone and plant them in soilless potting mix covering the stem to a point above the pinched-off leaves. A clean, recycled 6- or 9-pack bedding plant tray works well.
Keep the potting mix moist but not soggy. Place the trays near a sunny window in a pan to capture any residue that drains out when you water.
Once these starts roughly triple in size, move them into bigger pots, such as 3 1/2-inch containers. You may have to move them to larger containers at least two more times before spring arrives.
By now, you are likely asking, "But what about the parent plant?" Following are some indoor techniques for overwintering mature plants.
Repotting and Relocating Fleshy-Rooted Salvias
Salvias with fleshy, tuberous or rhizomatous roots will likely be most successful staying indoors during winter. These include Anise-Scented Sages (Salvia guaranitica spp.) and Gentian Sages (Salvia patens spp.). Their indoor survival is increased by their flexibility in adapting to a variety of indoor settings, including unheated sun porches and sunny but cool spare bedrooms, basements, root cellars and garages.
The garage -- or another cool, dark place -- is a possible storage location after one of these sages loses its leaves. Tender perennials appreciate winter temperatures in a range from about 45 to 60 degrees Fahrenheit, but can tolerate colder temperatures that stay above freezing.
Of course, if a plant doesn't lose its leaves, then keep it in front of a sunny window. But if it goes deciduous or you want to reinforce dormancy, here are three possible storage methods for tuberous or rhizomatous sages:
First Method: Dig up the plant, then hose off its foliage and drench its soil to encourage any garden critters to evacuate instead of hitchhiking indoors. Place the plant, dirt and all, in a container.
Put this pot inside a second, larger container that allows room to pack insulating materials -- such as Styrofoam beads or crumpled newspapers -- in the space between the two pots.
If the plant goes deciduous, trim back its foliage to a few inches tall and store its double pot in the garage in a plastic bag for an added layer of frost protection. Be sure to snip small holes in the bag to allow ventilation so condensation doesn't cause root rot.
Wherever the plant is stored, check it periodically to make sure the soil doesn't completely dry out. Water it lightly. Overwatering can encourage growth during dormancy when it should be resting. Too much moisture can also cause rot.
Second Method: Many gardeners store the roots of tuberous and rhizomatous perennials in slightly damp sawdust or sand in the garage over winter. To do this, trim the foliage to about 2 inches above the tubers and clean off all the soil before putting them in the storage medium. Check occasionally for shriveling and lightly moisten the bedding.
Third Method: This technique, which pioneers used to preserve geraniums, may work for storing the dahlia-like roots of Gentian Sages. Dig up the plant outdoors, remove all dirt from its roots and hang it upside down inside the garage, basement or root cellar. Check the roots periodically to make sure that they aren't shriveling. Dip them in water a few times during the winter.
Indoor Digs for Other Kinds of Salvias
You can, of course, try the insulated pot method for other kinds of Salvias that may go deciduous indoors. However, some may retain their greenery all winter when grouped with other outdoor expatriates in a cool yet sunny indoor location.
Here are some other general rules for indoor overwintering your huddled masses of perennials:
Finally, keep notes as you go.
Yes, there is one more article in this series, and it covers the choice that many gardeners make to treat tender Salvias as bedding plants to replace in the spring. But if you try some of our overwintering ideas, please contact us as spring unfurls to report how your plant babies fared. Meanwhile, we're rooting for their success.