Overwintering of Tropical and Subtropical Container Plants Before you decide to overwinter a plant, ask yourself the following questions: Is the plant really worth saving? Is it readily found in garden centers? Would it be relatively inexpensive to replace? Do you have a suitable place to overwinter it? Is it fairly easy to propagate? If so, consider propagating it. Develop a plan! If you decide to overwinter your plants, it’s good to have a plan in advance. This will include where you will store them, even if it’s only temporary and how you will move them to that location. If you need help doing this, you will want to make those arrangements in advance. If you have decided to overwinter a plant, here are your options for providing a suitable winter environment. Depending on the plant, you may need a bright, cool environment, a bright but warm environment, or a dark environment. You may need to add moisture on a regular basis. Naturally, this will vary with the plant. As a general rule you will either skip the fertilizer or use it very sparingly. 1. Propagate the plant and discard the original, but not until the replacements “take”. This works well with smaller plants, such as pelargoniums and plants that are easy to propagate. It does not work with most large plants, which can take more than one year to get to blooming size. For instance, a Brugmansia needs to grow to a size of 3 feet to bloom and it needs more than 1 year to get to that size. 2. Treat as a houseplant and overwinter indoors in a sunroom, enclosed porch or bedroom near a window. Do not use this method for plants that get too buggy indoors, such as brugmansias. Don’t forget your basement window sills are ideal for smaller plants such as pelargoniums. They may not get a huge amount of light because most people have foundation plantings, but if you prune these back, it can help. 3. Use a heated greenhouse if you have one, but keep in mind that this is a very expensive way to overwinter plants! 4. Grow under Fluorescent or HID lights. Although the new T-5 compact fluorescents penetrate better, in general, fluorescents are not suitable for tall plants because the light does not penetrate down to the lower leaves, as with HID lights. 5. Store in an unheated garage with or without windows and monitor the temperature. Provide supplemental heat in the form of heat lamps when it is needed. Most of these are 250 watt and need a fixture with a porcelain socket to minimize fire hazard. Power costs can add up, assuming you run them at least 12 hours daily. There is an alternative to using heat lamps. Garden writer and columnist Marcia Tatroe puts her plants on the “house side” of the garage and covers them with frost blankets. These are similar to row covers, but thicker. Most give you an extra 6-8 degrees of protection, some as much as 10 degrees. The lighter ones allow light and water to pass through. 6. Store in basement in semi-darkness. 7. Store in a dark root cellar. Unfortunately not too many people have these. Overwintering Individual Plants Unless the information on overwintering specific plants is found in our handouts, consult the books below. All but one of these books are now out of print, however they are still available from Amazon and other online vendors. Branies, Monica Moran and the Editors of Sunset Books. Landscaping with Tropical Plants. Menlo Park, CA: Sunset Publishing Corporation, 2004. Provides information on how to design and garden with tropical plants in northern climates with overwintering information for roughly 80 plants. McGowan, Alice and McGowan, Brian. Bulbs in the Basement and Geraniums on the Windowsill: How to Grow and Overwinter 165 Tender Plants. North Adams, Mass: Storey Publishing, 2008. 208pp. Former nursery owners Alice and Brian McGowan provide useful information for a larger number of tropicals and tender perennials more at home in the warmer temperate zones. McGowan, Brian and Alice McGowan. Saving Container Plant: Overwintering Techniques for Keeping Tender Plants Alive Year After Year. North Adams, Mass: Storey Publishing, 2014. This book contains some of the information of the McGowan’s earlier book, but focused entirely on overwintering. Roth, Susan A. and Dennis Schrader. Hot Plants for Cool Climates: Gardening with Tropicals in Temperate Zones. Boston, New York: Houghton Mifflin, 2000. This excellent book by a writer with horticulture credentials and a landscape designer and nurseryman teaches us how tropical plants can enhance our northern gardens. Discussions of individual plants provides details on overwintering.

Overwintering of Tropical and Subtropical Container Plants

Before you decide to overwinter a plant, ask yourself the following questions:

Is the plant really worth saving?

Is it readily found in garden centers?

Would it be relatively inexpensive to replace?

Do you have a suitable place to overwinter it?

Is it fairly easy to propagate? If so, consider propagating it.

Develop a plan!

If you decide to overwinter your plants, it’s good to have a plan in

advance. This will include where you will store them, even if it’s only temporary

and how you will move them to that location. If you need help doing this, you will want to make those arrangements in advance.

If you have decided to overwinter a plant, here are your options for providing a suitable winter environment. Depending on the plant, you may need a bright, cool environment, a bright but warm environment, or a dark environment. You may need to add moisture on a regular basis. Naturally, this will vary with the plant. As a general rule you will either skip the fertilizer or use it very sparingly.

1.Propagate the plant and discard the original, but not until the replacements “take”. This works well with smaller plants, such as pelargoniums and plants that are easy to propagate. It does not work with most large plants, which can take more than one year to get to blooming size. For instance, a Brugmansia needs to grow to a size of 3 feet to bloom and it needs more than 1 year to get to that size.

2.Treat as a houseplant and overwinter indoors in a sunroom, enclosed porch or bedroom near a window. Do not use this method for plants that get too buggy indoors, such as brugmansias. Don’t forget your basement window sills are ideal for smaller plants such as pelargoniums. They may not get a huge amount of light because most people have foundation plantings, but if you prune these back, it can help.

3.Use a heated greenhouse if you have one, but keep in mind that this is a very expensive way to overwinter plants!

4.Grow under Fluorescent or HID lights. Although the new T-5 compact fluorescents penetrate better, in general, fluorescents are not suitable for tall plants because the light does not penetrate down to the lower leaves, as with HID lights.

5.Store in an unheated garage with or without windows and monitor the temperature. Provide supplemental heat in the form of heat lamps when it is needed. Most of these are 250 watt and need a fixture with a porcelain socket to minimize fire hazard. Power costs can add up, assuming you run them at least 12 hours daily. There is an alternative to using heat lamps. Garden writer and columnist Marcia Tatroe puts her plants on the “house side” of the garage and covers them with frost blankets. These are similar to row covers, but thicker. Most give you an extra 6-8 degrees of protection, some as much as 10 degrees. The lighter ones allow light and water to pass through.

6.Store in basement in semi-darkness.

7.Store in a dark root cellar. Unfortunately not too many people have these.

Overwintering Individual Plants

Unless the information on overwintering specific plants is found in our handouts, consult the books below. All but one of these books are now out of print, however they are still available from Amazon and other online vendors.

Branies, Monica Moran and the Editors of Sunset Books. Landscaping with Tropical Plants. Menlo Park, CA: Sunset Publishing Corporation, 2004.

Provides information on how to design and garden with tropical plants in northern climates with overwintering information for roughly 80 plants.

McGowan, Alice and McGowan, Brian. Bulbs in the Basement and Geraniums on the Windowsill: How to Grow and Overwinter 165 Tender Plants. North Adams, Mass: Storey Publishing, 2008. 208pp.

Former nursery owners Alice and Brian McGowan provide useful information for a larger number of tropicals and tender perennials more at home in the warmer temperate zones.

McGowan, Brian and Alice McGowan. Saving Container Plant: Overwintering Techniques for Keeping Tender Plants Alive Year After Year. North Adams, Mass: Storey Publishing, 2014.

This book contains some of the information of the McGowan’s earlier book, but focused entirely on overwintering.

Roth, Susan A. and Dennis Schrader. Hot Plants for Cool Climates: Gardening with Tropicals in Temperate Zones. Boston, New York: Houghton Mifflin, 2000.

This excellent book by a writer with horticulture credentials and a landscape designer and nurseryman teaches us how tropical plants can enhance our northern gardens. Discussions of individual plants provides details on overwintering.