Weather Woes

2018 has been a tough year so far for plants. A tally of monthly data from DEOS (the Delaware Environmental Observation System) indicates most areas in the state are already over the average yearly rainfall (41 inches of rain per year in Delaware) and we are only three quarters of the way through the year!  We were 5-10 inches ahead in May depending on the location in the state. Planting and plant growth were delayed this spring due to cold and wet soils. Temperatures increased in June and July, but rainfall amounts were still above average. We had about 47 rainy days out of 100 this summer.  That is unpleasant for us humans, but it is also really bad for plants.  We also had a two-week dry period in early July with high temperatures that resulted in stressful dry conditions.

All this rain led to saturated soils.  Soils are comprised of minerals (sand, silt or clay), organic matter (decaying plants and animals), and some combination of air and water. Soils with good structure have equal parts air and water leading to healthy plants.  Clay soils tend to have small pore spaces resulting in more water than air.  When clay soils receive excess rain, the percentage of air decreases and water increases even further.  Plants need both oxygen and water for growth.  When roots sit in water logged soil the result will be poor root development and plant health problems, especially with newly transplanted trees and shrubs. Low lying and wet areas are conducive to root rot microbes. Regular rain also results in a constant coating of moisture on the leaves, which encourages the spread of diseases.  So, we have had a summer of many plant diseases from root rots to leaf spots and everything in between.

Let’s talk vegetable gardens.  Most got off to a slow start with poor seed germination due to waterlogged seedbeds. The constant film of water on leaves meant more leaf diseases than normal.  Tomatoes really struggled and the tomatoes we did harvest were watery and less flavorful.  The only plants that grew well in my vegetable garden this summer were the weeds!

Plants are most susceptible to excess water when they are actively growing.  Root tips begin to die within a few days of waterlogging.  Shallow root systems develop that have a limited ability to take up nutrients (particularly nitrogen) and water.  It is ironic that excess water can cause plants to exhibit symptoms of drought stress.  There is plenty of water, but a lack of healthy roots to take the water to plant leaves, so wilting occurs.  Nitrogen is lost from waterlogged soils by leaching and denitrification (nitrogen lost as a gas to the air).  These losses combined with less ability to absorb nutrients due to compromised roots systems may cause older leaves to yellow.  Even plants that normally fix their own nitrogen (peas and other legumes) are impacted by waterlogged soils.

What does this mean for landscapes this fall and in the future?  Be careful with trees in saturated soils.   Trees with compromised root systems may fall over with strong wind gusts. Prune or remove dead or damaged trees near homes and buildings.  My sister thought she heard gunshots and then fireworks as a tree fell on her property in August.  I heard “fireworks” in the woods behind my home about a week ago only to find a fallen tree the next day.

Unfortunately, the effects of this bad weather summer may be with us for a while.  Plants take time to grow new roots.  If fall dries up a bit, we may get some root recovery since fall is a good time for root growth in most plants.  But, evergreens do not grow roots in the fall, so they will really suffer next year.  It is possible newly planted or stressed trees and shrubs may die as they try to leaf out next spring.  Hopefully, we can chalk this growing season up as an anomaly and expect better growing conditions next year.  Look at it as an opportunity to replace plants that die with native species that promote wildlife and a regional sense of place.

Flooded mower tracks in the UDBG this September. Photo credit: N. Gregory

For more information about horticulture in Delaware follow me on Instagram at sbartonhort.  For information about plant health follow Nancy Gregory at http://extension.udel.edu/ag/hot-topics-plant-disease/.

Surviving Salt

One of the many problems plants encounter in the landscape is salt damage. The two major problems are saline soils and salt spray. Saline soils are a general problem with less than 20 inches of rainfall per year, but Delaware gets 43 inches of rain per year, so why are we concerned? While we do not have saline soils throughout the state, we can have specific site problems such as coastlines with seawater over wash or salt accumulation in the soil from salt spray. Flooding from brackish tidal rivers and estuaries happens in wooded wetlands. Sidewalks and roads where deicing salts are used may have soil affected within 30 to 50 feet of the roadway. Over application of fertilizer (especially animal manures), irrigation with high salt water and high ground water tables can also cause specific site problems.

High salt soils cause plant injury because plant membranes allow water to pass through but prevent salt from entering the plant. Lots of salt makes it hard for water to pass through the membrane. Especially high salt may even draw water out of root cells. Salt also changes soil structure. It binds with clay soils and causes compaction resulting in less room for water and air in the soil. Seedlings and young transplants are more sensitive. The amount, duration and concentration of exposure to salt matter and damage is more severe during dry weather.

Saline soil injury to plants will show up as stunted growth, dead leaves, dead areas on leaf edges, early fall color or leaf drop and buds that fail to open.

How do you know how much salt is present in the soil? One strategy is to look for injury in plants. You can also take a soil test and anything greater than 2000 ppm is a problem.

Plants injury can also be due to salt spray. Waves break and throw tiny droplets of salt water into the air. Salt laden water droplets land on leaves. When droplets evaporate, sodium and chlorine ions penetrate stems, buds and leaves, causing injury.

Symptoms of salt spray injury include bud death and twig dieback producing a witch’s broom appearance to the branches. Leaf burn or scorch on foliage can also occur. Sometimes there is even a white residue on leaves once water evaporates. With salt spray damage, the plant injury is usually on one side of the plant—the side facing the roadway or ocean.

Why are we talking about salt injury in August? This seems more like a winter problem, right? The reason to think about salt injury now is that selecting tolerant plants for landscape situations prone to high salts is the best method of preventing injury and we are coming up to the best planting time of the year—fall. Fall is good for planting because we normally get adequate rainfall (certainly not an issue this year, but…); plants tend to grow roots in the fall, so they become established more quickly; and the weather gets cooler throughout the fall providing great conditions for growth. Evergreens are the exception because they do not grow roots in the fall, but most other plants establish quickly when planted in the fall, giving them a great start for the spring growing season.

So, what makes a plant salt tolerant? Salt tolerance is the ability of plants to grow and complete their life cycle in substrates with a high concentration of soluble salts. These plants are called “halophytes.”  There are several different mechanisms of tolerance. Plants use avoidance to keep salt ions away from the parts of the plant they might harm. Salt exclusion means filtering salt at the root membrane, allowing water in, but keeping salt out. Red mangroves use this method of salt avoidance. Salt excretion involves removing salt into glands, bladders or though leaf cuticles. Tamarix secretes salt through its leaf cuticle. Succulent plants use salt dilution.  By having plenty of water in the leaf, they dilute the salt content. High salts are compartmentalized in plants.  Groundsel bush, a common beach and roadside plant in Delaware, has vacuoles (large open structures between leaf cells) filled with salt. Some plants have biochemical mechanisms that allow them to tolerate salt.

To reduce salt injury from salt saturated soils, improve soil structure by adding organic matter to soils exposed to salt. Leach the soil with irrigation, applying two inches of water over a two to three hour period. If runoff occurs, repeat in three days. Always irrigate thoroughly, rather than lightly. Mulch to reduce evaporation. Fertilize only as needed and keep plants healthy to reduce stress. If you have control over de-icing, use cinders, fly ash or sand, rather than salt.

For salt injury caused by salt spray, design sites with windbreaks to prevent salt spray from hitting plants or use salt tolerant plants as windbreaks. Rinse salt spray off plants after a storm that might have caused excessive spray.

If salty soil or salt spray is a problem for your landscape, select salt tolerant plants for planting this fall. Here are two good references that list many salt tolerant plants.

https://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/430/430-031/430-031_pdf.pdf

https://www.ces.ncsu.edu/files/library/71/Salt%20Tolerant%20Plants.pdf

Highly tolerant large trees include southern magnolia and willow oak. For smaller trees,  use Japanese black pine. Highly tolerant shrubs include groundsel bush, wax myrtle and yucca. Lyme grass and muhly grass are both highly salt tolerant. Blanket flower and daylily are flowering perennials with high salt tolerance. There are many more moderately tolerant trees, shrubs and perennials on the referenced lists.

Groundsel bush (Baccharis halmifolia) is a highly salt tolerant shrub that grows along the Delaware coast and sequesters salt in large vacuoles within the leaves to prevent injury. (Photo credit: Rick Darke

Plants – they are everywhere!

Well, duh, of course plants are part of our every day life.  They are the beginning of the food chain, making food from the sun.  They exchange carbon dioxide for oxygen – pretty handy trick.  They clean the atmosphere and help manage water.  But, ornamental plants are also an important part of our lives.  Nowhere is that more evident than in Europe.  Europeans have populated their countries for so long and space is at such a premium, they seem to appreciate plants more. It helps that a bouquet of flowers costs as little as 3-4 Euros, so it is easy to have fresh flowers on the table always.

As I write this column from Brodenbach, Germany on the Moselle River, I am reflecting on 10 days in the Netherlands, Brugges and Alsace and thinking about all the great examples of horticulture I’ve seen.  Colorful annuals are simply a part of every city or town’s atmosphere.  Overflowing baskets of annuals hang from lampposts or cascade over window boxes in town squares and small alleys. People are paid to care for those plants because it is important to have flowers brightening up the environment.

Restaurants take local produce to a new level.  One café in Colmar, France had planters surrounding their outdoor dining space full of herbs, cherry tomatoes and peppers that were picked and used in the dishes they served.  More vegetables were grown in a garden outside a windmill at Kinderdijk in the Netherlands, demonstrating how windmill keepers lived back in the day.

And of course, the wine.  Living in a vineyard and making wine is not just a job, it is a way of life. A vintner in Geuberschwihr, France describes how the soil, rain, sun, insects, fungi and everything in the environment must be considered to make a great wine. In Alsace, where one side of the mountain range is perfect for wine grapes, every square meter is planted.

We could all learn a little from the conscious appreciation of decorative plantings observed in Europe.  Let’s celebrate what plants do for us and enjoy their beauty in public spaces, private gardens and on the dinner table every day!

Town square overflowing with annuals in Eguisheim, France

Private home display on street in Heusden, The Netherlands

Wine grapes occupying every square meter of space on this premium hillside in Alsace, France.

Vegetable garden outside a windmill in Kinderdijk, The Netherlands.

Restaurant in Colmar, France with herbs and tomatoes defining the dining space.

 

More Meadows

Will she ever stop writing about meadows, you ask. The answer is “no.”  I keep learning more about converting mowed lawn to meadow.  I will not stop sharing these ideas until suburban Delaware has converted most of the lawn space (except gathering spaces, paths and play areas) to some other type of planting.  Meadow is one of the best alternatives to lawn because it is relatively inexpensive to install and while not maintenance free, does not require weekly mowing, like a lawn, or routine weeding, like a landscape bed.

This week I saw three different beautiful meadows.  DelDOT is continuing to plant meadows to benefit pollinators, reduce mowing along the roadside and beautify the state with native plants.  Two new meadows along I95 between Newark and Wilmington are blooming with black-eyed Susan, lance leaved coreopsis, butterfly weed and more.  These were seeded in summer 2017 and are just starting to come into their own.  Both sites are also planted with native trees and shrubs to provide a woody backbone.  One site is just north of the I95 rest area and the other is on southbound I95 after the 141 exit. Check them out next time you are driving between Newark and Wilmington.

Black-eyed Susan blooming in the DelDOT meadow at the north end of the rest area on I95.

Working with summer interns from the Landscape Architecture program at UD, I had the opportunity to visit Laurel, DE.  They have been using green infrastructure to revitalize the town, bring in tourism and provide ecosystem services to Laurel residents.  Jules Bruck is working with a group of interns this summer to document the process of installing a planned wetland and seek SITES certification for the project.  SITES is a national organization that certifies sustainable landscape projects, similar to LEED for buildings.  A few years ago, Jules installed a meadow in Laurel and it looks fantastic after three years of growing pains.  It really brings home the message that meadow installation often requires patience.  It is important to set realistic expectations about what the meadow will look like in year 1, 2, 3, and 10!  The Laurel meadow was seeded with many flowering perennials and includes very little grass, usually the backbone of a meadow.  It meets the desires of Laurel residents with its colorful blooms.

A wide variety of blooming perennials provide a riot of color in this Laurel, DE meadow.

The third meadow I visited recently was at a friends’ house.  They are amateur beekeepers and wanted a place for their bees to forage.  With the help of entomology graduate student, John Menz, they tried another approach for establishing a meadow.  They had struggled with the “meadow in a can” concept last year and were unhappy with the results.  A bad nutsedge infestation among other weeds kept the meadow from fulfilling expectations.  Menz suggested trying a cover crop, buckwheat. Buckwheat is a warm weather plant that grows in ordinary garden soil and has minimal nutritional needs.  It germinates quickly and flowers in 5-6 weeks. Once seeds mature, it can be cut and tilled in. The brittle roots are easy to chop up with a hoe.  Because of its dense growth, it can smother out even the most tenacious weeds.  It has completely covered the nutsedge that was so prevalent in my friends’ meadow.  The seeds should resprout and provide multiple crops in one year.  I am curious to watch this approach to a small residential meadow develop over the next year.  I will keep you posted as well!

Buckwheat surrounding a pine needle path to a suburban garden and bee hive.

Follow me on Instagram at sbartonhort.

Wet, Wet, Wet

What does all this rain mean for the landscape? In most cases, it means growth is lush this spring (weeds included).  You should be cutting your lawn about every five days to keep up with the growth.  One of the best things you can do for your lawn is to follow the rule of one-third, which means remove only one-third of the leaf tissue with every cut.  That allows the grass to photosynthesize in the remaining leaf tissue and make sugars for healthy root growth.  When you remove more than one-third of the leaf tissue with each cut, you stress the grass.  In addition, clippings tend to clump up so they are unsightly and exclude light from reaching the grass below the clump.  Most people cut their grass once a week, so every 5 days means changing your routine while growth conditions are so favorable.

Weeds are growing too and I have seen some of the largest dandelions ever this spring. You can hand pull weeds, but be sure to get the entire root system.  When you pull up a weed, you disturb the soil and bring up additional weed seeds. One school of thought recommends spot spraying weeds with herbicides instead of hand pulling to control the weed, but keep the weed seeds buried so they are not exposed to light and allowed to germinate.  If you put a preemergent crabgrass herbicide on your lawn this spring, you might need to make another application.  Crabgrass preventers work by setting up an herbicide barrier in the soil.  When crabgrass seeds germinate, the young sprout hits the barrier and dies so the crabgrass never actually emerges from the soil.  That barrier can be washed away with lots of rain and that has probably happened this spring.

One problem with lots of rain is prevalence of fungal diseases.  Fungi spread when there is a film of water on the leaves.  Most disease control must be preventative, so once you see a disease it is too late for treatment.  In most cases, dry weather and good air circulation will clear up a disease outbreak in the landscape.  Hand picking spent flowers or pruning out diseased foliage is usually a good idea and reduced disease spread.

Lots of moisture is good for some vegetables and not so good for others.  Peppers like hot, sunny weather, so pepper plants might be looking a little sorry after the rain we have had this spring.  As soon as temperatures get solidly hot and we get a dry spell, their growth should take off.  Most of the vegetable garden should be responding well to all the moisture.  Be sure to add fertilizer as plants grow rapidly, they will use the fertilizer you applied at planting and start depleting the soil.

If you have done a lot of new planting this spring, the wet weather has been great for your landscape.  Think of all the time you would have wasted watering newly planted trees, shrubs and perennials.  Mother Nature took care of that for you.  However, remember, plants are not fully established for several months to a year, depending on their size at planting.  When we hit our inevitable dry spell, check your newly planted specimens to make sure they are not drying out.  They may require supplemental watering at that point.

Poorly drained landscape sites may be waterlogged this spring. A surprising symptom of waterlogged plants is wilted foliage.  You see the wilted leaves and think they must be dry, so you add water.  In fact, the plant is wilting because the wet conditions have rotted enough of the roots to prevent water uptake even though there is plenty of water in the soil.  Inventory your landscape looking for plants that are suffering and consider replacing them with a more water tolerant plant.  Buttonbush (Cephalanthus occidentalis) is the most moisture tolerant shrub I have seen.   This brochure from Delaware Cooperative Extension recommends plants for a rain garden that tolerate moisture (http://s3.amazonaws.com/udextension/lawngarden/files/2012/06/live_eco_final.pdf).

 

Buttonbush and the ground cover, creek sedge (Carex amphibola) thriving in a wet border planting.

Cephalanthus occidentalis flower – A close up of the flowers of buttonbush.

Great Plants for Your Garden

Looking for ideas for new garden plants?  Many organizations highlight special plants each year.  The Perennial Plant Association’s pick for 2018 is Allium ‘Millenium’.  This ornamental onion is heralded as a butterfly magnet.  It grows best in full sun and produces a clump of upright glossy deep green leaves that reach 10-15 inches tall in spring.  By midsummer, it with have two to three flower stalks each sporting a 2-inch sphere of rose-purple florets.  Flowers can last as long as four weeks and then can be picked and dried holding on to a blush of their rose-purple color.  Allium ‘Millenium’ has no serious insect or disease problems, plus deer and rabbits usually avoid this great perennial.  What’s not to like!

Allium ‘Millenium’ in full bloom. Photo credit: Perennial Plant Association

The Delaware Nursery and Landscape Association (DNLA) picks a woody plant and an herbaceous plant each year.  The 2018 picks are marginal wood fern (Dryopteris marginalis) and common pawpaw (Asimina triloba); both native to the region.  The DNLA selects plants that are typically underused or unknown and are particularly well suited to thrive in Delaware. The marginal wood fern forms tidy clumps and can be easily identified by the spores along the outermost edges of the fronds.  Leathery leaves are evergreen and twice compound resulting in a lacy texture.  Leaves are blue-green on the upper surface with a light green underside and reach a height of 18 to 30 inches. Marginal wood fern requires good drainage and grows best in shade or partial sun.  It tolerates dry shade and like all ferns is deer tolerant. It is extremely cold hardy, but may need a protected location to keep the evergreen fronds looking good. Stands of marginal wood fern provide valuable habitat to small wildlife.  The dramatic feathery foliage makes marginal wood fern a great accent for a shade garden or in the right conditions, a lush, verdant groundcover.

Common pawpaw is a small to medium sized tree or large multi-stemmed shrub (10-40 feet tall).  It is native to the eastern United States, but has an exotic feel due to large, tropical-looking foliage. Pawpaw is the northernmost member of a primarily tropical family (Annonaceae; Custard Apple Family). Thick, bright-green leaves turn yellow-green for interesting fall color.  Purple, six-petaled flowers are borne singly in leaf axils in early spring before leaves emerge.  They are not particularly showy, but reward the keen observer as a harbinger of spring. Fruit are large, cylindrical and edible. They have a soft texture and flavor often described as strawberry banana-like. Fruit are not commercially available because they bruise easily and do not withstand shipping. Therefore, if you want to taste pawpaw, you need to grow one. Pawpaws make an excellent grove-forming understory tree. They provide food for birds, butterflies and small mammals and give an exotic touch to a native garden.

Paw paw in full yellow fall color. Photo credit: R. Darke

Interesting maroon flowers of the pawpaw tree. Photo credit: R. Darke

Delicate fronds of the marginal wood fern. Photo credit: R. Darke

The Native Plant Center at WestChester Community College in New York has its picks as well.  Blackhaw viburnum (Viburnum prunifolium) is the native woody plant of the year and Eastern bluestar (Amsonia tabernaemontana) is the native perennial of the year.  Blackhaw viburnum is a large shrub, reaching 12 to 14 feet at maturity.  Large, creamy white flower clusters are born above the foliage in late spring to early summer.  These are followed by pinkish-red berries that turn blue-black as they mature.  Flowers provide nectar for pollinators and a host of beneficial insects and fruit provides food for birds and small mammals.  Fruit is edible by people and can be made into preserves.

Eastern bluestar has multiple seasons of interest.  Powder blue five-stared flowers are born in clusters in spring, providing nectar for pollinators.  Bright green, shrubby foliage is makes a great background for other summer-bloomers.  Then in the fall, the leaves turn golden yellow.  Amsonia hubrictii (Arizona bluestar) is another bluestar with even more dramatic fall foliage color. This perennial is a member of the dogbane family and has a milky sap that makes it unpalatable to deer, rabbits and groundhogs.

Bluestar blooming along I95 at the gateway to Delaware from Pennsylvania.

If you want to learn more about horticulture in Delaware, visit my blog (http://sites.udel.edu/suebarton/)  and follow my instagram (sbartonhort).