Category Archives: Indoor plants

Now that the holidays are behind us, decisions must be made regarding the plants we used to decorate our homes or received as gifts. Poinsettias, amaryllis, Christmas cactus, and cyclamen are traditional holiday flowers. Some are quite easy to keep as houseplants and will flower again if given the right conditions. Others are a bit more challenging; maybe it’s best to toss them onto the compost pile after flowering. You be the judge.

Christmas cacti are easy to grow and force into flower year after year. Photo c Alice Raimondo.

Christmas cacti are easy to grow and force into flower year after year. Photo © Alice Raimondo.

Perhaps the simplest to care for is the Christmas cactus. Many of these cacti are actually hybrids, called Zygocactus, and are not true Christmas cacti which belongs to another genus. In any case, the Christmas cactus can be forced to flower anytime from Thanksgiving through Christmas, provided that starting in September you withhold water from it and it experiences 13-hour nights and cool temperatures in the 55-60 degree range. This is fairly easy to accomplish as this is what normally happens outdoors.

Begin by putting the plant outside in late May in a shaded location, water it once a week or so, and fertilize it every other week with a water-soluble fertilizer. Move your Christmas cactus back into the house in late October when the threat of frost occurs. By then these plants are usually full of flower buds. To prevent bud drop, keep your plant in a cool room until the first flowers open; after that you may place it anywhere to enjoy. Once it has finished flowering, water your Christmas cactus lightly and give it bright but indirect sun. Be careful not to over water as it will rot if watered too heavily.

Another really easy plant to care for is the amaryllis. After it flowers, simply cut off the flowering stalk when it yellows, and keep the bulb watered and in a sunny or bright location. Amaryllis leaves are produced either after or along with its flowers. These leaves need to stay healthy and growing throughout the winter, spring, and summer; they nourish the bulb so it can bloom again. Like the Christmas cactus, amaryllis enjoys summer vacation outdoors in a sunny location. Water your plant a few times a week as needed, and fertilize it every other week or use a slow release fertilizer on the soil surface.

In September it is time to stop watering your amaryllis. I find the easiest way to do this is to move the plant into a garage and simply forget about it. This treatment forces the bulb into dormancy, a rest period during which the leaves dry up. After about ten weeks, the pot can be brought indoors and placed in a bright location. Give it a light drink of water and then hold off watering again until you see the flower bud start to emerge from the bulb. Amaryllis bulbs can be kept alive for years this way, and their flowers are very rewarding.

Poinsettias and cyclamen are a bit more challenging, so typically I don’t keep them from year to year. Poinsettias often are host to whiteflies, and cyclamen often suffer from corm rot or weak growth. Rarely do either of these plants put on the same flower show if saved as they do when they were originally purchased. Having worked at a greenhouse for several years, I can honestly say that maintaining healthy poinsettias and cyclamen is best left to the grower unless you have lots of space in your home and lots of time on your hands. That said, care information for both plants as well as for Christmas cactus and amaryllis can be found in the following fact sheets: Care of Holiday Plants and Forcing Bulbs for Indoor Bloom.

Alice Raimondo is Horticulture Consultant for CCE Suffolk. She can be reached at aw242@cornell.edu or 631-727-77850 x335.

Winter Care of Tropical Houseplants

During the chilly dark days of winter, our houseplants and overwintering tropicals remind us that green life still exists, which gets us crazy gardeners through what can be a depressing time of year. Living with indoor plants is a subject near and dear to my heart, and I have lots of experience to pass along to you. I thought I’d start by talking about how to overwinter the large tropical plants that many people buy in spring, such as hibiscus, elephant ears, cannas, lantana, brugmansia, and mandevilla, and provide some sound advice for houseplant care so you may fully enjoy your indoor garden all winter.

Bird of paradise makes a cheerful indoor winter companion. Photo c Alice Raimondo.

Bird of paradise makes a cheerful indoor companion. Photo © Alice Raimondo.

As I write this, it is a relatively mild mid-December day but far too cold outdoors for tender tropicals. Summer provided all the things they needed to survive: sunlight, humidity, water, and lots of air circulation. How can we give them what they need indoors for the next several months before moving them outside once more? I’m sure I’m not the only one whose tropical plant’s leaves all turned yellow and dropped off a few days after bringing it indoors in the fall. A common mistake is waiting too long to bring these plants inside; it’s better to bring them indoors in late August before nighttime temperature start to drop. This is especially true for hibiscus or mandevilla; however, some leaf drop with them should be expected. Indoor environments have low humidity, particularly during winter when the heat comes on frequently, so plants drop leaves to reduce water loss.

Fear not, your plants will adjust, provided you site them properly. If placed near sunny south-facing windows and away from radiators, hibiscus plants will perform quite well as houseplants for a while, at least until whiteflies or aphids likely arrive. Mandevilla can be a bit trickier as a houseplant, often losing all of its leaves during the winter and going semi-dormant. Be very careful how you water them then; I have killed several, I fear, from overwatering alone. Mandevilla can also be a magnet for scale and mealybugs in the home, so if other houseplants are nearby, beware! Lantana is best not brought indoors unless you have a sunny, dry, cool location where it can grow.

Much of my garage has nothing to do with cars during winter. Photo c Alice Raimondo.

My garage is home to dozens of plants during winter. Photo © Alice Raimondo.

Elephant ear tubers and canna fleshy rhizomes can be stored dormant in an unheated location with no light, provided it gets no colder than the upper 40s. If your cannas and elephant ears were dug from the ground after the first frost, they will overwinter very well in paper bags or in cardboard boxes in temperatures in the low 50s. Another plant that stores equally well in garages where it will go dormant is brugmansia. No need to water it but a few times, very lightly, throughout the winter so its root ball doesn’t dry out completely. Keep brugmansia cool at temperatures in the upper 40’s to near 50 degrees; any warmer, and it will break dormancy and begin to grow. You can store this large woody tropical indoors from year to year until the plant is too big to fit in the garage. Even then, you can lay them down in the garage after they’ve grown too tall; these plants are indestructible! I currently have flowers on mine, as they haven’t yet gone to sleep yet for the winter.

Phalenopsis orchids love humidity. Photo c Alice Raimondo.

Phalaenopsis orchids do fine with enough humidity. Photo © Alice Raimondo.

If you aren’t brave enough to try overwintering these large tropical beauties, which are often sold as annuals, there are many houseplants to grow that are just smaller counterparts of their larger cousins. Peace lily, African violet, phalaenopsis orchids, and many foliage plants will chase your winter blues away as you garden indoors. Or perhaps you have space to grow large palms or bird of paradise. Plan your indoor garden as you do your yard: consider sun exposure, water requirements, and home temperature. One word of advice: water. Overwatering is the most common mistake when it comes to houseplants, so be careful to not kill your plants with too much love. Drooping or yellowing leaves is a symptom of too little water, but it’s also a symptom of watering too frequently.

The Horticulture Diagnostic Lab often receives calls regarding sick houseplants during the winter. If you have questions about caring for specific plants, call us at the Horticulture Information line (631)727-4126. In the meantime enjoy your little bit of the tropics indoors, and dream about spring.

Alice Raimondo is Horticulture Consultant for CCE Suffolk. She can be reached at aw242@cornell.edu or 631-727-77850 x335.

Rosemary for Remembrance

Rosmarinus officinalis is a wonderfully aromatic plant with a wide range of uses. An herb steeped in folklore and tradition, “There’s rosemary, that’s for remembrance,” Ophelia says to Laertes in Shakespeare’s Hamlet. The plant has long been used as a memory strengthener, and in Elizabethan times appeared at both weddings and funerals as a token of remembrance. Besides the beliefs that add to the lore of this beautiful plant, rosemary provides great culinary flavorings, is used in toiletries and potpourri, and appeals to gardeners as a simple decorative container plant. With all these accolades, its only drawback is that it cannot survive cold Long Island winters outdoors. With some preparation, however, you can ensure your rosemary plant will follow you indoors and out throughout the years.

In-ground rosemary thrives in coastal California, but not in colder Long Island gardens. Photo c Sandra Vultaggio.

To understand how best to conserve your plant, consider where rosemary thrives. Its botanical name, Rosemarinus, comes from the Latin words ros, meaning dew, and marinus, meaning sea. “Dew of the sea” probably refers to the herb’s native habitat among the misty cliffs of the Mediterranean seaside. Rosemary is winter hardy to USDA Zone 8-10, just shy of our cooler, Zone 7 climate. The herb enjoys growing in light, slightly acidic, dry-to-medium, well-drained soils in full sun. Much like the lavender you may already grow, rosemary has very good drought tolerance and cannot abide wet, heavy soils that usually prove fatal to it.

If you intend to keep your rosemary plant alive during winter, bear in mind its Mediterranean home. Since we aren’t able to grow rosemary in our landscapes, keeping it in a pot is often better than planting it in the ground. A well-draining clay pot gives its roots the breathability they crave. Use a high-quality, lightweight potting mix, and consider amending it with additional perlite. This will aid in drainage and keep the media loose, which helps mimic the conditions where the plant grows naturally. Provide a water-soluble fertilizer every two weeks if the growing media doesn’t already contain fertilizer.

During winter, keep the soil in the pot evenly moist: not wet and not dry. A clay pot allows the soil to dry out sooner than non-porous pots do, so use your finger to test soil moisture and decide when to water. Water the plant deeply, allowing water to run through the pot and into the catch tray. Discard the water that runs through.

The two most important factors you must remember about growing rosemary indoors during winter is that it will not tolerate wet feet or dry air. Forced hot-air heat inside the home can dry out its foliage quickly, so misting the plant weekly is important. Keep rosemary indoors somewhere where it gets bright light but also stays on the cooler side.

Follow these tips, and come the spring thaw, your rosemary plant should still be thriving. Once all danger of frost has past, take the plant out of the pot, tease its roots apart a bit (cutting out a small portion of them if necessary) and add some fresh potting soil. Place the re-potted rosemary outdoors in a full-sun location for the remainder of the growing season, and enjoy its beauty again for another year!

Sandra Vultgaggio is Horticulture Consultant for CCE Suffolk. She can be reached by email at sib7@cornell.edu or by phone at 631-727-7850 x387.

CCE Suffolk Long Island Gardening

Cornell Cooperative Extension of Suffolk County

Category Archives: Indoor plants

Summer Session for the Advanced Training for LI Gardeners is Back!

It’s Not too Late to Join our Spring Gardening School!

Caring for Holiday Plants in the New Year

Winter Care of Tropical Houseplants

Rosemary for Remembrance

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