Caring for Holiday Plants in the New Year

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.

Vole Control: Time to Be Vigilant

Have you had trouble with voles over the past few years? Our harsh, snowy winters have created ideal environments for voles to thrive. Voles can wreak winter-time havoc on young trees, shrubs, perennials, and your lawn. Fall and early winter are the best times to implement controls for mitigating the damage these small creatures can do.

The meadow vole is common on Long Island. Photo by John Mose.

The meadow vole is common on Long Island. Photo by John Mose.

A vole is a small rodent resembling a mouse but with a stouter body, a shorter, hairy tail, a slightly rounder head, and smaller ears and eyes. Two species of voles reside in New York State: the meadow vole (Microtus pennsylvanicus) and the pine vole (Microtus pinetorum). You can read descriptions of each and more about their biology and habits in this Voles fact sheet on our website.

Hidden from predators, voles happily travel under snow cover, feasting on blades of grass and the bark of trees and shrubs. Voles like to gnaw around the circumference of woody plants until they are completely girdled. Once the snow melts, the damage is clear: long, 2-inch wide runways of beaten down, damaged turf grass, and woody plants that suddenly die after the first flush of spring growth.

Here are a few ways to deter voles and protect your plants by reducing their favorite winter habitats:

  • Clean up piles of leaves and branches.
  • Remove grass and weeds from around trees and shrubs (this area should be clear of grass anyway to prevent injury from mowers or line trimmers).
  • Bare soil is ideal within the first few inches of ground that surround plant bark. At most, put only a very light layer of mulch there.
  • Don’t mulch excessively in flower beds as this will favor vole activity.
  • Before it snows, install fine-gauge hardware cloth around tree trunks to prevent voles from chewing young wood.
  • Make your last lawn mow of the year slightly lower than normal to discourage voles from creating surface trails through longer grass. Lowering the mower deck to 3” works well.

If you find you need to control the population of voles on your property, try using snap-back mouse traps placed in boxes with holes on either side; this is one of the more effective control methods. Populations of voles tends to be highest in the fall and before our first snowfall, so act now!

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.

“Waterwise Landscapes,” the 2016 LI Gardening Calendar

Now’s the time to buy the Long Island Gardening Calendar, a perfect gift or stocking stuffer for the passionate gardeners in your life.  The theme for our 2016 calendar is “Waterwise Landscapes,” and it is filled with sustainable gardening tips and beautiful photographs every month. Be inspired by the many landscape and gardening choices we can make to protect Long Island estuaries and water supplies.

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This high-quality calendar features information on drought-tolerant plants, correct use of mulch, drip irrigation, rain barrels, healthy soil, rain gardens, green roofs, and more, including a resource page about local and national organizations that focus on native plants and sustainable horticulture. Purchase calendars at the front desk at CCE Suffolk, 423 Griffing Avenue in Riverhead for $7 each; or use this order form to have them mailed to you for $9 each to cover their cost with postage. Buy your calendars soon while supplies last!

Robin Simmen is Community Horticulture Specialist for CCE Suffolk. She can be reached at rls63@cornell.edu or at 631-727-7850 x215.

Simple Ways to Protect Plants Now from Winter Injury

Weather conditions for the past two years have favored all sorts of winter injury to landscapes; this year may be no different. Droughty summers and autumns followed by long winters filled with wide temperature fluctuations can wreak havoc with plants and soil. But fear not! Here are some simple ways to help your plants come out of this winter unscathed.

Needled and broad-leaved evergreens such as arborvitaes, cherry laurels, and rhododendrons often suffer severe winter discoloration, browning, and even death from several causes. Winter sun (think southern exposure) combined with wind can create excessive transpiration, or foliage loss of water, at the same time as soils are frozen so plant roots can’t replace the lost water. This can be particularly disastrous for late season plantings in October, November, and December if plants aren’t well watered and if roots haven’t had time to grow out of the existing root ball. That’s why September is best for fall planting, not November!

Bright sunny winter days when leaves warm up may trigger cellular activities such as photosynthesis and cellular respiration. This break from dormancy can result in severe plant injury when nighttime temperatures drop abruptly, for example from the 40’s down to the teens in the course of a day or so. These conditions also bleach evergreen foliage, for example on boxwood, when chlorophyll is destroyed in plant tissue and then not rebuilt due to low temperatures. Late pruning in October, which generates new late season growth, is another cause of injury or death when cold temperatures occur. This sort of injury also occurs in May when light frosts settle into low areas during the time of tender new growth.

A piece of burlap posted in front of these inkberry plants will protect them from winter sun and wind. Photo c Alice Raimondo.

A piece of burlap posted in front of these inkberry plants will protect them from winter sun and wind. Photo © Alice Raimondo.

Protecting your evergreens from these sorts of winter injury is easily done. First and foremost, consider where you locate plants. South, southwest, and windy sites may not be the best places for evergreens. For plants in such sensitive conditions and for those that are less winter hardy, consider constructing a burlap barrier on the southern and/or windy side of the plant to shade it from the harsh winter sun and keep temperatures consistent, thereby reducing the injuries described above. Place the screen in front of the plant; don’t wrap it completely with burlap.

Water loss is by far the most important and misunderstood aspect of winter injury. Established plants shouldn’t be over watered in September as this will slow down their hardening off process, but they need to be well watered through October and into November if there isn’t regular, measurable rainfall. This regular watering in the autumn is particularly important for trees and shrubs in the ground for less than three or four years. Anti-desiccant and/or anti-transpirant sprays offer protection that is limited at best, but these can be applied in conjunction with correct watering and sun/wind screens.

Sunscald of thin-barked trees (cherry, maple, linden, and plum) is another common winter injury. Sunscald creates sunken, cracked, or dried areas on the trunk, which are elongate in shape. Young, newly planted trees are particularly sensitive to this damage as their bark is not well developed. Shading tree trunks from the harsh southern winter sun helps keep their living cambium tissue dormant, protecting it from freezing temperatures following a thaw. On young and newly transplanted trees, consider not pruning their lower branches for a season or two to help shade their trunks.

Cold that follows relatively warm temperatures is common on Long Island and often kills or damages less winter-hardy flower buds such as those of Hydrangea macrophylla. This is why many of us haven’t seen flowers on these beloved plants for the past two winters! The big-leafed a.k.a. mophead hydrangea has a bad habit of breaking dormancy as early as late February in sunny locations. Constructing a sun screen similar to that suggested for evergreens may help reduce this sort of cold temperature injury.

Our winters often bring heavy wet snows and ice storms that cause significant injury to plants from extra weight bending and breaking their branches. Protect plants in dangerous locations, such as where snow falls off roofs or where drifting and blowing snows accumulate, by tying or wrapping them to hold them together. If possible, carefully remove heavy, wet snows from plants before the snow freezes solid, encasing the plant in heavy ice.

For those of us with new landscapes, a real concern is frost heaving. Our soils tend to freeze and thaw and then freeze and thaw again, sometimes popping smaller shrubs and perennials right out of the ground. This is a big problem for those fall-sale beauties you may have planted in October or that late season perennial dividing and replanting you did the first week of November when it was 70 degrees. You can protect your plants by insulating the ground around them with mulch. Apply a layer of mulch three-inches thick, being careful to not bury the crowns or stems of the plants. Wait until the ground freezes before applying mulch to keep the ground frozen and discourage rodent activity. Consistent soil temperature will reduce the likelihood of frost heaving.

For more information, read the fact sheet on our website about Winter Injury. Hopefully, some of these simple tips will help your plants survive the winter and thrive come next spring. Putting in a little extra time now will reduce spring cleanup of winter-injured plants that need to be pruned or replaced. There’s still plenty of time to prep plants for the ravages of winter!

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

Cornell Courses for Beginning Farmers Available Online

Winter is a great time for farmers to rest, slow down the pace, and build new skills for the coming growing season. The Cornell Small Farms Program, whose mission is to foster the sustainability of diverse, thriving small farms that contribute to food security, healthy rural communities, and the environment, is pleased to announce a winter roster of online courses available through its Northeast Beginning Farmer Project. These courses help practicing and would-be farmers learn from the latest research-based education available from Cornell University.

Photo c Robin Simmen.

Photo © Robin Simmen

Since 2006, the program has offered high quality, collaborative learning environments online and each year educates hundreds of beginning and established farmers through these courses. From aspiring to experienced farmers, there is a course for nearly everyone. If you are interested, a handy chart on the course homepage can direct you to the right courses for your experience level. And you may qualify for a 0% interest loan to finance your farm! Participants who complete all requirements of one or more online courses are eligible to be endorsed for a 0% interest loan of up to $10,000 through Kiva Zip.

The courses consist of weekly real-time webinars followed by homework, readings, and discussions on your own time in an online setting. If you aren’t able to attend the live webinars, they are always recorded for later viewing. Each course costs $200, but up to four people from the same farm may participate without paying extra. Courses often fill up quickly, so if you’re interested, visit the Cornell Small Farms Program website to learn more today.

Robin Simmen is Community Horticulture Specialist for CCE Suffolk. She can be reached at rls63@cornell.edu or at 631-727-7850 x215.

Sample Soil Now for Healthier Landscapes Next Year

Spring is by far the busiest time for gardeners. Between selecting plants, starting seeds, and preparing beds, we often forget about what’s basic: the soil. Suddenly remembering, in April gardeners furiously submit handfuls of soil to our Horticulture Diagnostic Lab for testing, expecting immediate turnaround, and then realize, “What!? It takes how long for limestone to change the pH of my soil!?”

This is why autumn is the perfect time to start preparing your gardens for the growing season ahead. Submitting soil samples to us now allows you enough time to collect your samples properly, understand the test results, and if you need to make amendments to the soil, time for them to activate before next spring.

Using a soil auger makes collecting samples easy, but a trowel will work just as well.

Using a soil auger, shown above, makes collecting samples easy, but a trowel will work just as well. Photo by Robin Simmen.

Maintaining the proper soil pH is just as important for maximum crop yields as fertilizing, watering, and pest control. The decision to add lime to raise the soil pH and the amount to apply must be based on a soil pH test and the crop species to be grown. Do not guess. Some plants, like rhododendrons, azaleas, and blueberries as well as other members of the Ericaceae family grow best in acid soil (pH 5.0). Most vegetable garden plants grow best in soil with a pH in the 6.2 range. The recommended range for a lawn is between 6.0 and 7.0.

Instructions for taking a soil sample

First determine how many samples to take. Different gardens/beds, lawns, areas with different soil types, places where such amendments as limestone were added, areas with plants having different pH requirements, and good/bad areas should be sampled separately as described below:

  • In gardens or areas planned for new plantings where the soil will be turned under or rototilled, individual samples should be taken from the upper 6 to 8 inches of soil.
  • In established plantings or lawns where the soil won’t be turned under, individual samples should be taken from the upper 3 inches of soil.
  • Each soil sample should be comprised of 5 to 10 individual samples obtained by walking back and forth diagonally across the area to be sampled.
  • Use a trowel to dig a small hole to the desired depth. Remove a slice of soil from the entire side of the hole and place this in a clean plastic container. Repeat this procedure at each of your 5 to 10 random spots, and place the soil from these spots in the same container, discarding any stones, grass, or other debris.
  • Next, remove two 8-ounce cupfuls of the soil in this container and place them in a plastic bag. Secure the bag. This is your soil sample for that area. Mark the outside of the bag with an identification (i.e. #1, #2, or “A”, “B”, or “East”, “West”). Keep the identification simple.
  • Repeat this entire procedure for each additional garden, landscape bed, and/or lawn area you wanted tested.

You can find soil testing submission forms to accompany your samples on our website at http://ccesuffolk.org/agriculture/horticulture-diagnostic-labs. The cost of a soil pH test is $5 per sample; if you submit five or more samples, they cost $3.50 each. Mail or drop off your samples at 423 Griffing Avenue, Riverhead, NY 11901. Our office hours are Monday through Friday 8:30 a.m. to 4:30 p.m.

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.

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.

In-ground rosemary thrives in coastal California, but not in colder Long Island landscapes. Photo © 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.

Managing Landscapes Sustainably

Remember when autumn meant making a pot of soup, pulling out the leaf rake, and spending an afternoon raking leaves into backyard piles for kids and dogs to enjoy? Life in the fast lane has changed all that, degrading the quality of life on many fronts. According to Quiet Communities –a national non-profit organization dedicated to protecting our health, environment, and quality of life from the excessive use of industrial outdoor maintenance equipment—tasks once done manually are now often done with gas-powered machinery. A manicured aesthetic has become the new norm in many communities that barely tolerate even small amounts of leaves or debris. As a result suburban landscapes have lost critical “messy” habitat that insects and other vital species need to live, leading to a loss of biodiversity.

No one wants to breathe in the polluted air created by gas-powered leaf blowers. Photo c Quiet Communities.

No one wants to breathe in the polluted air created by gas-powered leaf blowers. Photo © Quiet Communities.

The deafening roar of gas-powered leaf blowers (GLBs) has replaced the “woosh, woosh” of the rake, and painful noise is just a small, if most noticeable, part of the trouble GLBs cause. Their motors send particulate matter into the air at 200 m.p.h., spewing forth dust, mold, pollen, pesticides, rodent feces, lead, arsenic, other heavy metals, fertilizers, fungicides, and herbicides right into our lungs. These particles aggravate asthma, bronchitis, emphysema, and allergies; in fact, particulates have recently overtaken second-hand smoke as the second greatest cause of lung cancer after smoking.

One GLB produces as much smog as 17 cars and blows 5 pounds of particulate matter into the air per hour, affecting the air of 8-14 neighboring properties. “Every time the leaf blowers are in our neighborhood, my son starts wheezing and has to use his inhaler,” said one father in Huntington, New York. Those are just a few of the reasons a group called Huntington C.A.L.M. (Citizens Appeal for Leafblower Moderation) has formed to educate local citizens about the harm caused by unregulated two-stroke Gas Leaf Blowers. The group’s goal is to limit the use of GLBs by commercial landscapers during summertime when more people are outdoors. Suffolk County received a grade of “F” for air quality for the last 14 years, and this group hopes to improve our air by placing a summertime restriction on GLBs in Huntington.

To learn more about how you can make healthier landscape decisions, come to CCE Suffolk’s Managing Landscapes Sustainably conference in Ronkonkoma on November 12. One of the speakers includes Jamie Banks, PhD, MS, Executive Director of Quiet Communities, an environmentalist and health-care scientist dedicated to promoting clean, healthy, quiet, and sustainable landscaping and agricultural practices.

Robin Simmen is Community Horticulture Specialist for CCE Suffolk. She can be reached at rls63@cornell.edu or at 631-727-7850 x215.

Native Plants Champion Biodiversity

Ever wonder whether it really makes a difference whether or not you plant native species? Do native plants do a better job of hosting local insect communities than their non-native counterparts? Now a University of Delaware study shows that not only are natives much better at sustaining local insects, planting non-natives actually compounds the problem of declining species diversity because non-natives support fewer herbivore species across our landscapes.

A yellow swallowtail enjoying a purple coneflower. Photo by Mary Howe.

A yellow swallowtail enjoying a purple coneflower at the Children’s Garden at Suffolk County Farm, part of the National Pollinator Garden Network’s Million Pollinator Garden Challenge. Photo by Mary Howe.

The research was conducted by Karin Burghardt and Doug Tallamy, who is professor of entomology at University of Delaware and author of the bestselling book, Bringing Nature Home. Together they published their findings in a recent issue of Ecology Letters: http://onlinelibrary.wiley.com/doi/10.1111/ele.12492/abstract To conduct their study, they planted imitation yards with different common garden selections of both native and non-native tree species, and then collected data over a three-year period, measuring the herbivore communities and species found on those plants.

Tallamy said that finding young herbivores on a plant is a good indication of how that plant is supporting the local ecosystem, as opposed to finding adult insects, which could be on a plant for a number of reasons, such as resting or looking for a mate. “The relationship between the adult and food is far weaker than the relationship between immatures and food, so when you find adults on the non-natives, it doesn’t mean that much. When you find immatures, that’s what you should be measuring,” Tallamy said. “Those are the plants that are creating those immatures, and so we do get significant differences between the immatures that are using native plants versus the immatures using non-natives.”

He also stressed that that native plants always do the best job per tree of supporting herbivore communities when compared to their non-native counterparts. This study expands the understanding of that fact by looking at whether that lower per tree diversity is magnified further by non-natives hosting more similar communities across trees species and locations.

Burghardt said the goal of the research was to understand how the composition of the plants that homeowners plant in their yards affects herbivore communities. “What the gardens we constructed for the study are trying to replicate are landscaping decisions that people might make if they wanted to support native insect communities that in turn support much of the diversity around us.”

Learn more about how what you plant affects biodiversity at the Long Island Native Plant Initiative’s biennial Native Plant Conference on Saturday, October 24, at Farmingdale State College. LINPI’s Registration Flyer includes a symposium agenda and list of speakers.

Robin Simmen is Community Horticulture Specialist for CCE Suffolk. She can be reached at rls63@cornell.edu or at 631-727-7850 x215.