Eric W. Sanderson, Ph.D., is Vice President for Urban Conservation, and Lucinda Royte is the Manager of Urban Conservation Data, Tools, and Outreach at The New York Botanical Garden.
Between us, we have been studying the historical ecology of New York City for nearly 30 years and thinking about what it means for the city’s future. We can tell you a lot of things, but one thing is for sure: Water will go where water wants to go.
We see evidence of this every time it storms. A little bit of rain isn’t a problem; it flows down the buildings through downspouts, off streets into gutters, through the drain pipes to the wastewater treatment plants.
What if it rains harder? Then there is more water in the streets, in the subways, and sometimes in our homes. When there is more water than the infrastructure can accommodate, we get floods. Floods that kill, floods that destroy property, floods that spread disease and pollution. Floods that are not good.
There are a places where floods are not a problem. In wetlands. In streams. In ponds. In oceans. These ecosystems are designed to receive water, process it, and move it along in what elementary school teachers and highly trained scientists both call the water cycle. Remember the water cycle?
The key quality of the water cycle is that it is water in motion. Water moves from the ocean to the clouds to the raindrop to the stream and back to the ocean. Plants, it turns out, play a pivotal role in that movement.
Plants can move water in ways that downspouts, gutters, and drain pipes can’t. Trees can move water up into the sky. We like to think of them as huge straws stuck in the ground, powered by photosynthesis to pump water from the soil zone to the atmosphere through the process of evapotranspiration.
Evaporation is the natural movement of a liquid into a vapor, think steam rising from a hot pavement after a rain. The same happens from leaf surfaces. Transpiration is the process for plants to carry water from the root zone and putting it into the sky zone.
Plants also facilitate water movement down, into the soil. Their roots create spaces, their actions aerate the soil, and their aboveground physical structure provides a conduit for water to flow: leaf-flow, stemflow, and trunkflow are the subjects of scientific study. Some plants also drop their leaves onto the ground and the resulting leaf litter helps slow infiltration into the soil.
Once the water is on the soil surface it can flow overland; we call that a stream. Where surface water pools, we call that a pond. The places between a stream and a pond where water collects, where the soil is saturated, are wetlands.
In streams, ponds, and wetlands, plants have evolved special adaptations to withstand flooding. Flooding not only drowns people, but can drown plants. (Sound familiar? Your houseplants are not immune.) That’s why plants that survive in wetlands have means of getting oxygen to their roots. They have specific adaptations to the chemistry and physical characteristics of wetland soils. Carnivorous plants, for example, eat insects, not for the energy in their bodies, but for the nitrogen, which is hard to come by in soggy sediments.
Meanwhile wetland plants are helping in other ways. Their leaves, stems, roots hold back the water, literally slowing the movement of water. They hold down the sediments when the floods come. They contribute to the overall picture of biodiversity in a place.
Collectively, these-designed-by-nature wet ecosystems, which vary by type depending on how often they are inundated and how deep the water is, help slow floods, absorb floods, and prevent floods downstream. As an added bonus, when the clouds clear, wetlands slowly release water back into streams and the groundwater, so it can continue to cycle to other places.
What about on the shore? Here nature has another trick. Where we live in New York, long sandy islands and beaches used to line the shore. We know them as Coney Island, Rockaway Beach, the South Shore of Staten Island. Every day waves from the ocean deposit sand, and the wind blows a portion of the sand up the beach, where it piles so that plants could grow. Ammophila breviligulata, or beachgrass, loves nothing more than to root into the dunes, capture the sand, be buried by the sand, and grow up again. The dunes grow taller, the grass grows deeper.
Until large storms come and whack the grassy dunes with surges of tremendous force. The dunes yield, and the waves, robbed of their energy, give up their water to the tidal marshes that grow in the salty lagoons behind the dune line. Beaches, dunes, salt marshes are nature’s way of protecting the coast and inland ecosystems while at the same time allowing the coast to change as the sea levels change.
Today we face more frequent and extreme floods than we have before. We face more powerful storms than we have ever seen. The expectations are, because of climate change, that we will get more rain, not less, at least here in New York. We may be on track for more frequent coastal storms. Other places might get less water, not more, and some may have fewer storms, not more. Changing the climate is tinkering with the fundamentals of nature; it alters many things…
In those alterations, nature can help us, but only if let nature do its part of the job.
Recently Dr. Sanderson participated as an ecologist and a historian in a Rainproof NYC initiative to help New York City prepare for the worst. The team of experts from within and without of government described 10 things to know about rain, developed recommendations, and adopted a set of principles to guide adaptation efforts.
Nature is the first layer of our stormwater infrastructure. We need to protect the existing ecological systems, which means investing in parks and open spaces in quantities of attention and funds like what we invest in emergency services and the sewage system.
Taking care of what have is only the beginning. We also need to expand natural systems by way of building “bluebelts,” daylighting streams, and restoring wetlands. Some of us will need to move from places that climate change has made untenable to live – old beaches, wetlands, and ponds, come to mind – and we need those moves to be facilitated by society at large with support and justice in mind. Even places that are not in danger of flooding may need to change to accommodate the people who are endangered.
Finally, we need people to understand why plants are so important. This is a combination of education and experience. Plants can give so much if we give some space back to them.
Severe flooding, from rain and from storm surge, has the potential to damage our city, kill folks and destroy stuff, and fuel social unrest, but only if we don’t act.
At the New York Botanical Garden, with our many partners and friends across the city, we have the expertise, the science, the passion, and the plant power to adapt to and mitigate the devastating effects of our changing climate. It is time to act, and quickly.
Next time you find yourself caught outside in the rain, take a moment to watch it flow down the street. Consider how you might use the power of plants to usher it down into the soil, out to the sea, up into the atmosphere, back into the water cycle… and out of your basement.
The elegant Alice du Pont mandevilla vine is prized for its abundant pink trumpet-shaped blooms that add tropical flair to gardens. However these vines sometimes start drooping, causing their leaves and flowers to wilt. If you notice your Alice du Pont mandevilla vine inexplicably drooping, it likely indicates an underlying issue that needs attention.
Drooping in mandevilla vines can have various causes, ranging from cultural problems to pests and diseases. By identifying the specific reason your plant is drooping, you can take targeted corrective actions to revive it
Here are the most common reasons an Alice du Pont mandevilla vine may start to droop and what you can do to get your plant looking perky again
Underwatering
Lack of adequate water is one of the most frequent causes of drooping in mandevilla vines. These plants need a consistent supply of moisture, especially in hot weather. If allowed to dry out too much, the leaves will start to wilt and the vines will droop.
Check the soil moisture by inserting your finger an inch deep – if it’s dry, it’s time to water thoroughly. Provide enough water to moisten the entire root zone, then allow excess to drain away. Ensure the plant receives sufficient water going forward, about 1-2 inches per week.
Overwatering
While underwatering causes drooping, so can overwatering. Excess moisture suffocates roots leading to root rot and lack of oxygen. This damages the roots’ ability to uptake water, resulting in wilting.
Allow the soil to partially dry out between waterings. If soil is soggy, reduce watering frequency. Improve drainage by amending dense soil with compost or switching to a well-draining potting mix.
Insufficient Light
Mandevilla vines thrive in full sun to partial shade. Without adequate sunlight, the vines can become spindly and weak, leading to drooping.
If possible, move the plant to a brighter location receiving at least 6 hours of direct sun daily. Dappled shade under a sun-blocking structure is suitable if full sun isn’t feasible.
Nutrient Deficiency
Lack of essential nutrients causes poor growth and flowering in mandevilla vines. This stresses the plant, eventually causing it to wilt and droop.
Apply a balanced fertilizer every 2-4 weeks during spring and summer. Alternatively, repot in fresh potting mix to provide a nutrient boost. Avoid overfertilizing which can damage roots.
Pests
Sap-sucking pests like aphids, mealybugs and spider mites infest mandevilla vines, leading to stippling, yellowing and wilting of leaves.
Check for signs of pests like honeydew droplets, webbing or insects under leaves. Remove with jets of water or apply insecticidal soap. Keep plants isolated until pests are eliminated.
Diseases
Fungal diseases like botrytis, root rot and powdery mildew are common in mandevilla vines. The infection can spread to roots and block water transport, resulting in wilt.
Improve airflow and avoid wetting foliage to prevent disease. Remove any infected parts immediately. Treat established infections with appropriate organic fungicides.
Environmental Stress
Excessive heat, cold drafts and sudden changes in weather conditions can stress mandevilla vines, causing temporary drooping.
Try to keep the plant in an environment with stable temperatures between 65-85°F. Shield from hot sun/cold winds. Acclimate to any weather shifts gradually.
Root Damage
Accidental root damage from transplanting or cultivation can instantly disrupt the vine’s ability to take up water, leading to drooping.
Carefully inspect roots and trim away any that are crushed or broken. Repot gently in fresh soil, water well and allow time to regenerate new root growth.
Pot Bound Roots
As mandevilla vines become pot bound, the limited soil and root mass cannot provide enough moisture, causing drought stress and drooping.
For plants in small containers, shift to a larger pot size in fresh potting mix. Alternatively, remove lower leaves and bury vine deeper to allow more root growth.
By assessing the likely cause and taking appropriate corrective actions, you can get your drooping Alice du Pont mandevilla vine perky again. Consistent monitoring and care tailored to the plant’s needs will help prevent future drooping episodes. Enjoy the full beauty of your mandevilla vine with healthy, vigorous vines adorned with abundant pink blooms.
k
Alice Dupont Mandevilla
FAQ
Why is my mandevilla drooping?
What does an overwatered mandevilla look like?
How to bring a mandevilla back to life?
How often should mandevilla be watered?
Why is my Mandevilla plant dying?
Mandevilla plant shows dying signs often due to Nutrient deficiency, Poor drainage, or Spider mite infection. Southern blight bacteria and Aphids may deteriorate the plant’s health too. Anthracnose and Powdery Mildew are also commonly seen in Mandevilla plants. ‘Mandevilla’ is a group of tropical and subtropical plants.
Why does my Mandevilla plant wilt?
Southern wilt is also called Southern Blight. This disease is caused by bacteria. When it infects your Mandevilla plant, the leaves become yellow. Leaves may turn yellow, brown, and then fall off. If you suspect this disease in your plant, destroy the plant to prevent its spread in your garden.
Why do Mandevilla leaves drop?
If the temperature is too high or too low, it can also cause leaf drop, so make sure your Mandevilla is in an area with a consistent temperature. Wind can damage the plant and cause leaves to drop, so make sure it’s in a sheltered area or provide support if it’s a climbing vine. Pests and diseases can also cause Mandevilla leaves to drop.
How to prevent premature leaf drop in Mandevilla plants?
To prevent premature leaf dropping in Mandevilla plants, it is important to provide them with optimal growing conditions. Here are some tips: Adequate sunlight: Mandevillas thrive in full sunlight. Ensure they receive at least 6-8 hours of direct sunlight each day to promote healthy foliage and minimize leaf drop.