A cool windowsill for overwintering plants
A cool windowsill is ideal for overwintering a few tender plants, such as lewisias. Photo: Viridissima

The Self-Taught Gardener: Second Chances

What plants can overwinter indoors, and when do you take them in? Our Self-Taught Gardener Lee Buttala shares some wisdom.

Fall always comes on more quickly than I expect. And this past week’s near-frost brought me to my annual wavering over what to do as the season cools down. When should I bring in my houseplants that have been summering on the porch and in the garden, and what should I do about other tender plants in the garden? A forecast of three cold nights had me scrambling to respond to the weather report, while a late harvest of strawberries and apples beckoned to be turned into jam and apple butter, a task I love on the first cool days of fall.

This year, I had purchased some beautifully grown potted dahlias from Jenna O’Brien of Viridissima at a plant sale at Campo de Fiori that benefited the Northwest Connecticut Women Support Services (This sale was created to compensate for the coronavirus- caused cancellation of NCWSS’s main fundraising event, Trade Secrets.) At the sale, these tender perennials were not yet in bloom, but Jenna’s description of the range of color and form of the varieties she was growing sold me on them instantly.

I planted them next to the trunk of a fallen maple in our front yard. At the beginning of spring, this area was filled with the remnants of an old false cypress hedge. When we removed their stumps and added some new conifers, the newly planted area slowly began to evolve into a naturalistic border but it still needed a floral display in its first season to give it a push. After all, we wanted our neighbors to see some progress as they passed by on their daily COVID walks. The dahlias were just what we needed. But adding something new in often means removing something old and, in the process of felling the two old hemlocks that hung over the house, we managed to break off the stems of the dahlias just as they were about to go into bloom.

Dahlias will bloom until a hard frost.
Dahlias will blooms straight through to a hard frost. Covering them overnight with a light fleece blanket can protect them from early bouts of seasonal cold. Photo: Viridissima

In six weeks time, the plants came back. They were covered in buds this past week, ready to break into bloom in the season they love most, when the nights are cool and the days warm and sunny. Dahlias like it cool but are not frost tolerant; frost kills and blackens their foliage, a sign here in the northeast that the tubers can then be dug, dried slightly in a cool dry spot for a few days, and set into pine bark mulch in a cool basement until they are replanted in spring. As much as I trusted Jenna descriptions of these flowers, it was my hope to see them bloom before I spent the energy overwintering their tubers. Three nights of covering them with light fleece blankets and uncovering them as each day warmed up held off any frost damage, and the resulting blooms were well worth the wait. When a hard frost takes them down, I will follow Jenna’s advice and dig up the tubers, label the cultivars, and store them for next year.

Jenna is known for her skills at creating beautiful container plantings that have a long season of performing in the garden. She also teaches a class at the Berkshire Botanical Garden on overwintering some of the tender plants she uses in these designs. While many gardeners love to use rare tropicals in containers, Jenna explained to me that she prefers tender perennials and houseplants that do not require tropical temperatures in order to perform. Given that our summer season is so short, plants such as cardoons, tender stonecrops and carexes, and pineapple lilies, that might be hardy only a zone or two south of us, give her container plantings a longer season of interest. Into this mix, she also adds houseplants, such as begonias (including an old-fashioned form that she received from her grandmother), oxalis, and tender ferns that benefit from a season outdoors.

Plants that are hardy further south have a longer season of interest than do tropicals.
Plants that are hardy just a zone of two south of here make for good container plants as their season of interest is longer than that of many tropicals. Photo: Viridissima

Although not attributed to her grandmother, her advice for timing the transfer of the houseplants back indoors has a common sense approach that could have been passed on from generation to generation. Jenna recommends bringing houseplants back inside as the temperatures outdoors and indoors are about equal so that the plants have very little adjustment to make to their relocation. For Jenna, who lives in Becket, this usually aligns with Labor Day weekend. For other plants, such as her pineapple lilies, which will go dormant for the winter, she brings these into cold storage at about the same time as she brings in her dahlias. Still others, which can overwinter at cooler temperatures, will be moved to a cool windowsill at a time in keeping with her houseplant philosophy, when indoor and outdoor temperatures are equalized.

Begonia
This begonia, passed on to Jenna by her grandmother, was brought back inside when the temperatures inside and outside had equalized to minimize any shock from relocation. Photo: Viridissima

While I plan on taking Jenna’s course on overwintering next season, in the meantime her straightforward advice on overwintering has provided me with some solace for this season. And having spent a little time moving in my houseplants and covering my dahlias for a few evenings, I am back in the kitchen making my apple butter and jam before I need to put the rest of my garden to bed.

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A gardener grows through observation, experimentation, and learning from the failures, triumphs, and hard work of oneself and others. In this sense, all gardeners are self-taught, while at the same time intrinsically connected to a tradition and a community that finds satisfaction through working the soil and sharing their experiences with one another. This column explores those relationships and how we learn about the world around us from plants and our fellow gardeners.