Getting Large Container Plants Through the Winter Adapted from articles appearing in the October 2007 issue of Mein Schoener Garten, with added information from the book Hot Plants for Cool Climates. By Paula Szilard Though most commonly grown tropical, subtropical and Mediterranean container plants thrive in the sun, many can adapt to low light conditions during winter. Most of our patio container plants cannot tolerate a night of frost out in the open. For some tropical plants, such as Hibiscus, even temperatures of 50 F may be too cold. (Paula’s note: This has not been my experience here in Colorado. Recently when night-time temperatures dipped just below 40 F, I noticed the leaves on the hibiscuses farthest from the house were limp, but the plant seemed to recover later in the day.) Mediterranean container plants, such as oleanders, figs or laurels can often tolerate a very light, brief frost when left out on the patio. These plants should stay outside as long as possible. It keeps them healthy and prevents pests. If a cold spell lasts only a few days, these plants can be put back outside. In our Colorado climate, close monitoring of daily weather forecasts is a must. Container plants can be divided into those which can be overwintered in low light conditions and those that must be overwintered in a bright, well-lit environment. Some plants can be stored either way. Plants that tolerate low light: Angels Trumpets (Brugmansias): To store for the winter, you must induce dormancy by keeping them in temperatures just above freezing to about 45 F or so. They can be kept in bright light or in darkness. Garages with additional heating or protection, such as frost blankets, root cellars and dark basement rooms are ideal storage places. These popular container plants will lose their leaves and this, of course greatly reduces their need for light and water. It also helps keep down spider mite and whitefly populations. Water only lightly, to prevent desiccation. Here in Colorado, this is about once a month. Edible Figs (Ficus carica): Bring these indoors and treat them as houseplants or store in a cool, dark or semidark place, such as a garage, root cellar or dark basement room, but temperatures must be above freezing. In milder climates they can be planted out in the garden as long as they are protected. This is generally not the case in our Zone 5 Colorado climate. Pomegranate (Punica granatum) Both the prolifically blooming ornamental varieties and the larger fruited varieties tolerate low-light winter conditions because they can shed leaves in the fall. However, if kept at higher temperatures and high light conditions, they just keep on blooming and fruiting. Coral Shrub (Erythrina): This shrub is related to the coral tree (Erythrina crista-galli). The branches generally die back in the winter. This plant may be stored in a cool, dark location, but the potting mix should be kept very slightly moist. Laurel (Laurus): This classic laurel has leaves used an herb. Even though it remains evergreen, it tolerates a poorly lit winter environment, provided temperatures remain under 50 F. It can remain outdoors only in areas where temperatures do not go below freezing. Palms Most palms are overwintered as houseplants, conservatory plants or in heated greenhouses. Their need for bright light does not diminish in the winter. There are a few commonly grown palms that are more shade loving: Chamaedorea (parlor palm), bamboo palm (Chamaedorea erumpens) and Kentia palm (Howea fosteriana). Although many palms thrive in the summer sun, some can adapt to lower light conditions in the winter months. Cold tolerant Chusan or windmill palms (Trachycarpus fortunei) can handle a poorly lit environment for about two months. They generally can take temperatures down to about 20 F, but should be wrapped for protection. Agapanthus If these subtropical lilies are overwintered in a well-lit place, they keep their leaves. In darkness, the leaves wilt and die, sprouting anew in the spring. As a consequence, their bloom time is delayed. Plants that like it bright: Keep in mind that window glass itself can cut out anywhere from 30-70 % of the sun’s rays, particularly low-e glass. Also be mindful that every foot you move a plant back from the glass reduces available light by roughly 50%. The best place for some of these sun lovers is right in front of a south-facing window. The plants below need a lot of light in the winter. Too little light draws on energy reserves and forces plants to conserve energy by dropping leaves. They will usually recover, but it’s an added stress. Citrus: Most citrus plants are evergreen and need a spot close to a bright window. They will lose leaves if they are placed in insufficient light, but they will leaf out again in the spring. Plants with fewer leaves will need less water, so make sure to adjust your watering practices. Olives: Though evergreen, olives do lose leaves in the winter. This is because they may be kept too dry or are located in a place with insufficient light. The damage from dryness may not be evident until ten or more days later. Hibiscus: This plant will keep its leaves in environments above 65 F. It should continue to bloom intermittently throughout the winter. When exposed to cooler temperatures, it may lose its leaves and can be then stored in a cool, poorly lit environment. Just remember to keep it on the dry side. Bird of Paradise (Strelitzia): If kept in warm, sunny living spaces, especially directly in front of a south window, these plants will continue to bloom. To grow them to flowering size requires about seven years or so of indoor/outdoor cultivation. If, on the other hand they are placed into a cool environment for the winter (35-50 F), they do not bloom until summer. Oleander (Nerium oleander): Since this is an evergreen, it likes a place close to a bright window, preferably south. It does better in a cool room, with temperatures hovering slightly above freezing. These conditions also keep scale insects at bay. You can induce dormancy if necessary by placing oleanders into a cool, dark place where temperatures are just above freezing. Bananas (Musa): Bananas make excellent sunroom conservatory or greenhouse plant for the winter. They can also be grown as a houseplant. Do exercise caution however, because they drip a brown liquid from the leaf tips which can stain furniture, carpeting and some flooring. Bananas need very bright light, and considerable humidity so that leaf edges don’t become brown. If you really don’t have room inside, then Susan A. Roth and Dennis Schrader recommend cutting the pseudostem off right at pot level after the foliage is withered by the first frost, then storing the container in a cool, but frost-free dark place until spring. Water it occasionally. In the spring, when new shoots come up from the sides of the central stem, you can return the plant to its usual place. In Colorado, you may have to bring it in if frost threatens. If the container is too heavy to transport, then dig it up before the first frost. Leave most of the soil around the roots and wrap it in a large plastic bag. Do not cut off the stem and leaves. Store it in a cool, frost-free place, such as a basement or a garage Bougainvilleas: In non-tropical environments bougainvilleas often lose their leaves in the winter. They also do this when they are allowed to dry out too much. So check to be sure that they really need that water before you start pouring it on. Overly wet soil can cause root rot. Store in a well-lit environment at roughly 50 F. Keep the soil only slightly moist. Another option recommended in Hot Plants for Cool Climates is to cut the canes back to about 6 inches and store the plant in a cool, dark place at about 40-45 F. Plumerias: Plumerias are best placed in sunny spaces, preferably in front of a south-facing window and stored at temperatures of 60 F or above. Some types of plumerias lose their leaves seasonally, even in the tropics. Plumeria obtusa, also known as the Singapore plumeria generally does not. When the plants shed their leaves, they need a lot less water and you can cut watering to once every 2-3 weeks. Even then, apply water sparingly to prevent the stems from rotting. Do not apply fertilizer until spring. Alternatively a procedure recommended in Hot Plants for Cool Climates is to store plumerias in a dark location at temperatures between 40-70 F, allowing the soil to dry out completely. When watering is resumed in the spring the plant will leaf out. Sources: Roth, Susan A. and Dennis Schrader. Hot Plants for Cool Climates: Gardening with Tropical Plants in the Temperate Zone. Boston: Houghton Mifflin, 2000. “Saisonende fuer Kuebelpflanzen” Mein Schoener Garten, Oct 2007, pp 62-63 “Waerme und wenig Wasser” Mein Schoener Garten, Oct 2007, p. 69

Getting Large Container Plants Through the Winter

Adapted from articles appearing in the October 2007 issue of Mein Schoener Garten, with added information from the book Hot Plants for Cool Climates.

Paula Szilard

Though most commonly grown tropical, subtropical and Mediterranean container plants thrive in the sun, many can adapt to low light conditions during winter. Most of our patio container plants cannot tolerate a night of frost out in the open. For some tropical plants, such as Hibiscus, even temperatures of 50 F may be too cold. (Paula’s note: This has not been my experience here in Colorado. Recently when night-time temperatures dipped just below 40 F, I noticed the leaves on the hibiscuses farthest from the house were limp, but the plant seemed to recover later in the day.)

Mediterranean container plants, such as oleanders, figs or laurels can often tolerate a very light, brief frost when left out on the patio. These plants should stay outside as long as possible. It keeps them healthy and prevents pests. If a cold spell lasts only a few days, these plants can be put back outside. In our Colorado climate, close monitoring of daily weather forecasts is a must.

Container plants can be divided into those which can be overwintered in low light conditions and those that must be overwintered in a bright, well-lit environment. Some plants can be stored either way.

Plants that tolerate low light:

Angels Trumpets (Brugmansias):

To store for the winter, you must induce dormancy by keeping them in temperatures just above freezing to about 45 F or so. They can be kept in bright light or in darkness. Garages with additional heating or protection, such as frost blankets, root cellars and dark basement rooms are ideal storage places. These popular container plants will lose their leaves and this, of course greatly reduces their need for light and water. It also helps keep down spider mite and whitefly populations. Water only lightly, to prevent desiccation. Here in Colorado, this is about once a month.

Edible Figs (Ficus carica):

Bring these indoors and treat them as houseplants or store in a cool, dark or semidark place, such as a garage, root cellar or dark basement room, but temperatures must be above freezing. In milder climates they can be planted out in the garden as long as they are protected. This is generally not the case in our Zone 5 Colorado climate.

Pomegranate (Punica granatum)

Both the prolifically blooming ornamental varieties and the larger fruited varieties tolerate low-light winter conditions because they can shed leaves in the fall. However, if kept at higher temperatures and high light conditions, they just keep on blooming and fruiting.

Coral Shrub (Erythrina):

This shrub is related to the coral tree (Erythrina crista-galli). The branches generally die back in the winter. This plant may be stored in a cool, dark location, but the potting mix should be kept very slightly moist.

Laurel (Laurus):

This classic laurel has leaves used an herb. Even though it remains evergreen, it tolerates a poorly lit winter environment, provided temperatures remain under 50 F. It can remain outdoors only in areas where temperatures do not go below freezing.

Palms

Most palms are overwintered as houseplants, conservatory plants or in heated greenhouses. Their need for bright light does not diminish in the winter. There are a few commonly grown palms that are more shade loving: Chamaedorea (parlor palm), bamboo palm (Chamaedorea erumpens) and Kentia palm (Howea fosteriana). Although many palms thrive in the summer sun, some can adapt to lower light conditions in the winter months. Cold tolerant Chusan or windmill palms (Trachycarpus fortunei) can handle a poorly lit environment for about two months. They generally can take temperatures down to about 20 F, but should be wrapped for protection.

Agapanthus

If these subtropical lilies are overwintered in a well-lit place, they keep their leaves. In darkness, the leaves wilt and die, sprouting anew in the spring. As a consequence, their bloom time is delayed.

Plants that like it bright:

Keep in mind that window glass itself can cut out anywhere from 30-70 % of the sun’s rays, particularly low-e glass. Also be mindful that every foot you move a plant back from the glass reduces available light by roughly 50%. The best place for some of these sun lovers is right in front of a south-facing window. The plants below need a lot of light in the winter. Too little light draws on energy reserves and forces plants to conserve energy by dropping leaves. They will usually recover, but it’s an added stress.

Citrus:

Most citrus plants are evergreen and need a spot close to a bright window. They will lose leaves if they are placed in insufficient light, but they will leaf out again in the spring. Plants with fewer leaves will need less water, so make sure to adjust your watering practices.

Olives:

Though evergreen, olives do lose leaves in the winter. This is because they may be kept too dry or are located in a place with insufficient light. The damage from dryness may not be evident until ten or more days later.

Hibiscus:

This plant will keep its leaves in environments above 65 F. It should continue to bloom intermittently throughout the winter. When exposed to cooler temperatures, it may lose its leaves and can be then stored in a cool, poorly lit environment. Just remember to keep it on the dry side.

Bird of Paradise (Strelitzia):

If kept in warm, sunny living spaces, especially directly in front of a south window, these plants will continue to bloom. To grow them to flowering size requires about seven years or so of indoor/outdoor cultivation. If, on the other hand they are placed into a cool environment for the winter (35-50 F), they do not bloom until summer.

Oleander (Nerium oleander):

Since this is an evergreen, it likes a place close to a bright window, preferably south. It does better in a cool room, with temperatures hovering slightly above freezing. These conditions also keep scale insects at bay. You can induce dormancy if necessary by placing oleanders into a cool, dark place where temperatures are just above freezing.

Bananas (Musa):

Bananas make excellent sunroom conservatory or greenhouse plant for the winter. They can also be grown as a houseplant. Do exercise caution however, because they drip a brown liquid from the leaf tips which can stain furniture, carpeting and some flooring.

Bananas need very bright light, and considerable humidity so that leaf edges don’t become brown. If you really don’t have room inside, then Susan A. Roth and Dennis Schrader recommend cutting the pseudostem off right at pot level after the foliage is withered by the first frost, then storing the container in a cool, but frost-free dark place until spring. Water it occasionally. In the spring, when new shoots come up from the sides of the central stem, you can return the plant to its usual place. In Colorado, you may have to bring it in if frost threatens. If the container is too heavy to transport, then dig it up before the first frost. Leave most of the soil around the roots and wrap it in a large plastic bag. Do not cut off the stem and leaves. Store it in a cool, frost-free place, such as a basement or a garage

Bougainvilleas:

In non-tropical environments bougainvilleas often lose their leaves in the winter. They also do this when they are allowed to dry out too much. So check to be sure that they really need that water before you start pouring it on. Overly wet soil can cause root rot. Store in a well-lit environment at roughly 50 F. Keep the soil only slightly moist. Another option recommended in Hot Plants for Cool Climates is to cut the canes back to about 6 inches and store the plant in a cool, dark place at about 40-45 F.

Plumerias:

Plumerias are best placed in sunny spaces, preferably in front of a south-facing window and stored at temperatures of 60 F or above. Some types of plumerias lose their leaves seasonally, even in the tropics. Plumeria obtusa, also known as the Singapore plumeria generally does not. When the plants shed their leaves, they need a lot less water and you can cut watering to once every 2-3 weeks. Even then, apply water sparingly to prevent the stems from rotting. Do not apply fertilizer until spring. Alternatively a procedure recommended in Hot Plants for Cool Climates is to store plumerias in a dark location at temperatures between 40-70 F, allowing the soil to dry out completely. When watering is resumed in the spring the plant will leaf out.

Sources:

Roth, Susan A. and Dennis Schrader. Hot Plants for Cool Climates: Gardening with Tropical Plants in the Temperate Zone. Boston: Houghton Mifflin, 2000.

“Saisonende fuer Kuebelpflanzen” Mein Schoener Garten, Oct 2007, pp 62-63

“Waerme und wenig Wasser” Mein Schoener Garten, Oct 2007, p. 69