Fall in Delaware

Cooler temperatures and lower humidity and (thank goodness) some rain have come along with the start of fall this year.  On a recent trip downstate, I saw sweeps of yellow from sweet goldenrod (Solidago odora)—our state herb.  Goldenrod often gets a bad rap as the cause of fall allergies.  In fact, goldenrod pollen is extremely heavy.  It is pollinated by bees, butterflies, moths etc., but not by wind.  It blooms at the same time as the inconspicuously green-flowered ragweed.  Ragweed has light pollen, is wind-pollinated and is the most likely cause of many fall allergies. Contributing to the roadside yellow were also tickseed sunflower (Polylepis bidens) and swamp sunflower (Helianthus angustifolius).  Warm season grasses, switchgrass (Panicum virgatum), Indiangrass (Sorghastrum nutans) and little bluestem (Schizycharium scoparium) are also blooming in great sweeps along our roadways.  Fall is the season in which Delaware’s native vegetation shines.  Along Route 1, groundsel bush (Baccharis halmifolia) is poised to burst into bloom with white fleecy flowers.  Soon our native sumacs (Rhus typhina, Rhus copallina, Rhus glabra and Rhus aromatica) will turn bright red and make a great combination with groundsel bush.  The first fall color we see in Delaware is the crimson color of black gum (Nyssa sylvatica).  At the northern end of Route 1, the black gums are just starting to show hints of red.

Goldenrod, Delaware’s state herb, blooming in community common land in Northern Delaware.

Goldenrod, Delaware’s state herb, blooming in community common land in Northern Delaware.

If you want to do more than view our beautiful fall landscape, there are plenty gardening activities best accomplished in the fall.  Fall, once we get some consistent rainfall, is a great time to plant most trees and shrubs.  Trees and shrubs put energy into root growth in fall, so plants quickly become established in their new sites.  One exception is with evergreens, which do not grow many roots as the weather gets cooler and the day length shorter, so avoid planting evergreens in the fall.  Perennials can be planted in fall, but if you are planting very small plants or plugs, it is best to wait until spring.  Alternate freezing and thawing during winter, pushes small plants out of the ground.

Fall is the best time to renovate your lawn.  Start by evaluating how you use your lawn.  Where do you need circulation? Play areas? Gathering spaces? Or green carpet to unify the scene?  If lawn is not serving a purpose, get rid of it.  Allow it to become a meadow or forest; or plant landscape beds or vegetable gardens in place of unused lawn.  For those areas you do use, a thick, dense lawn will keep the weeds out and serve the intended purpose fully.  Grass seed requires good contact with the soil to germinate.  If you are over-seeding a relatively weed-free lawn, use a hard rake or core cultivator to expose soil before spreading the new seed.  If you are renovating a poor quality lawn, it is best to kill the existing vegetation before seeding.  You can smother the existing grass and weeds with black plastic, but if the area is large and full of perennial weeds, it will be more effective to use an herbicide, such as glyphosate. Take a soil sample to determine pH and nutrient deficiencies.  Correct pH with lime and add nutrients following the recommendations of the soil test.  Next core aerate or till to expose soil.  Then spread grass seed.  Turf type tall fescue is the preferred grass for all of Delaware.  It is drought tolerant and tough enough to withstand modest play and traffic.  Cover your newly seeded lawn area with a light layer of straw or salt hay to help keep the soil moist.  Water frequently (daily at first) until the grass becomes established.  Cut when the grass reaches 3-4 inches with a sharp mower blade.  Dull mower blades may pull the seedling out of the soil instead of making a clean cut.  Fertilize again once grass is established, usually by mid-fall.

More meadows

The trend is growing.  Longwood Gardens has a meadow.  Mt Cuba Center has a meadow.  Winterthur has several meadows.  Isn’t it time YOU manage a meadow too?  As people become concerned about pollinators and bee decline or just want to see more songbirds in their gardens, they are turning to landscaping with native plants and one of the cheapest and easiest ways to get more native plants in your landscape is to manage a meadow.   Dr. Doug Tallamy, professor of Entomology in the College of Agriculture and Natural Resources at UD and author of bestseller, Bringing Nature Home, was the keynote speaker at the recent American Society of Horticultural Sciences meeting in Atlanta Georgia earlier this month.  He spoke about the role native plants play in supporting native insects and more importantly life as we know it.  His talk was the buzz of the meeting (no pun intended).

I just met with a couple who live in Middletown, DE on about 5 acres.  They are tired of cutting grass and managing a lawn plagued by crabgrass.  Instead, they plan to focus on maintaining a small healthy lawn right around the house where they want to entertain and play sports.  The rest of the property is destined for meadow and maybe ultimately a forest.  They started last week manipulating hoses to get the mow lines for the meadow just right.  Then, they plan to kill the existing turf with glyphosate (sold as Round Up or other generic products).  They will core cultivate to open up holes in the soil and improve seed/soil contact when they seed.  They may use the sawdust method, which involves mixing meadow seed with sawdust and spreading a one-inch layer over the entire site.  The sawdust provides a good germination medium for the seed and prevents light from reaching crabgrass and foxtail seed reducing their germination and encroachment into the new meadow.  The best time to seed a meadow is late spring, but now is a great time to start deciding where your meadow will go.  Just stop mowing the sections of your lawn that you want to turn into meadow and see how it looks.  You will get a sense of the shape and feel of the meadow, before it is time to seed next spring.   The gardens I mentioned earlier do a great job of using cues of care to indicate meadow management.  Mow edges around your meadow and mow curving paths through the meadow.  You can add artwork to the meadow or plant native perennials at key intersections or edges.


Path mowed in a backyard meadow.

Path mowed in a backyard meadow.

I have a bee-keeper friend who is taking the simpler route to meadow establishment.  He simply stopped mowing his lawn.  He is still mowing a circular area off the back patio, but the rest of the backyard is starting to grow tall and will hopefully provide nectar for his bees in a year or so.  He needs to apply those same cues of care, by mowing a path from the end of the driveway to the mowed section.  The clean crisp line between mowed grass and meadow is critical.  It will take a bit longer to establish a native plant meadow with this method, but eventually native warm season grasses and perennials, like common milkweed, will grow.   A middle-of-the-road strategy to jump start the meadow is to open up the soil and plant pockets of native grasses and perennials, either from seed or plugs into the now tall lawn.  These plants will eventually produce seed and spread into the surrounding meadow.  You can’t just throw seeds onto an existing lawn, though and expect them to germinate.  Only seed that stays moist and is in contact with the soil will grow.

To manage a meadow, plan to mow once a year in early spring, and possibly again in late June.  This will keep woody plants from taking over the meadow and still allow the native plants to flower.  Jump on the meadow bandwagon; do your part to encourage wildlife; and help provide the ecosystem services we need right in your own home landscape!

Rose rosette and microscopic mites

A writer from the News Journal heard about invasive microscopic rose bud mites in Delaware that are killing plants.  She became concerned and wanted to learn more about this situation.  These are very small eriophyid mites that spread rose rosette disease, also known as witches’-broom of rose, which is caused by a virus (Emaravirus sp.). The disease is limited to plants in the genus Rosa but some roses are believed to be resistant. Its main host is the multiflora rose, which is considered an invasive plant in Delaware. Multiflora rose has a small white flower in early spring and has taken over many natural areas in Delaware.  It can grow as a shrub or a vine and become intertwined with other shrubs and trees in the woods.  Interest in rose rosette has been generated by the threat to garden roses and also its possible use as a biocontrol for multiflora rose.

Rose rosette disease starts as a red color on the underside of leaf veins and quickly progresses to sharply increased growth at branch tips.  The growth is more succulent than normal and colored in various shades of red. Leaves often become deformed, crinkled, and brittle with yellow mosaics and red pigmentation. As the disease progresses, leaves become very small, petioles are shortened, and most lateral buds grow, producing short, intensely red shoots (witch’s broom). The disease causes the plant to be exceptionally susceptible to freeze damage. Symptoms on cultivated roses are typically less severe than on multiflora rose. Symptoms can be confused with some forms of herbicide damage.

The disease is transmitted by an eriophyid mite, a wingless mite that can travel passively in the wind as well as on contaminated clothing and equipment. The mites feed and reproduce in the tips of rose shoots. Females overwinter under bark or on bud scales of living roses. The females move to newly developing shoots where they lay one egg a day for about 30 days. The young hatch in 3-4 days. They can reach adulthood in about a week depending upon temperatures. Multiple generations occur each year until fall when females seek overwintering sites.  The mites are hampered by low humidity and can only survive about 8 hours without being on a host plant.

The virus is transmitted most readily between May and mid-July when plants are actively growing. Symptoms from new infections usually start appearing in mid-July. In general, smaller plants go through the disease stages more quickly than larger plants. Small plants are usually killed in about 2 years, while a large plant may survive for five years in a deteriorated condition.

To control this disease, you can:

  1. Remove ornamental roses with symptoms. Remove and destroy the entire plant including the roots by burning or placing in a plastic bag. Take care when working with diseased plants as you can spread the mites that spread the disease. Bag the plant before removal, cut it at ground level and then dig out the plant’s roots. Soil need not be removed. Clean tools and put on fresh clothing before moving to a disease-free plant or area.
  2. Plant ornamental roses as far away as possible from known stands of multiflora rose. Maintain at least 300 feet between your roses and any stands of multiflora rose. Even greater distance is preferred especially if they are upwind of your desirable rose plants.
  3. Control the disease by controlling the mite. Start mite control early by pruning your roses hard in late winter (back by 2/3) to remove as many overwintering mites as possible and then spray with horticultural oil to kill any remaining mites. Use horticultural oil or soap, which are less harmful to natural predators that feed on the problem mites. Apply weekly during the months of June and July paying particular attention to the new growing tips where the mites will congregate. Refrain from using leaf blowers around roses as they can spread mites.
  4. Help to isolate your roses. Do not plant roses too close together. With extra space between the plants mite movement can be reduced. Also, consider interplanting roses with other ornamental plants.
  5. Using rose rosette disease as an IPM strategy. The multiflora rose is an exotic invasive species that is responsible for the degradation of millions of acres of farmland and recreational areas. Using the disease to control this invasive weed can cut costs and be considered environmentally friendly for reducing the amount of synthetic chemicals used. However, the disease also affects cultivated roses. One should be extremely cautious and good neighbor-minded when it comes to rose rosette disease.

    Multiflora rose growing at the edge of the woods. It would be great if this virus killed multiflora rose without harming our desirable garden roses, but that does not seem to be the case.

    Multiflora rose growing at the edge of the woods. It would be great if this virus killed multiflora rose without harming our desirable garden roses, but that does not seem to be the case.

Weed Control in the Vegetable Garden

With July 4th approaching many Delawareans are anxiously awaiting the first home-grown tomato from the vegetable garden.  You probably have most of your summer crops planted, so now is the time to focus on weed control.  Weeds steal moisture, nutrients, sunlight and growing space from crop plants.  Their presence can reduce crop growth, quality and yield.  They can also make harvest difficult and they provide cover for diseases, insects and animal pests.

The first line of defense is to plant crops in combination, using sprawling crops like squash, pumpkins, cucumbers, potatoes, etc. to shade the ground around taller crops like corn, pole beans, peppers and tomatoes.  This is the concept between the native American planting of the three sisters—corn, beans and squash.  Corn provides structure for beans to climb.  Beans fix nitrogen from the air and put it back into the soil and squash covers the ground to reduce weeds.
Fall planted cover crops that you till in prior to spring planting, like winter wheat, will reduce winter annual weed germination and as a bonus, improve soil by adding compost.

Use mulch to suppress weeds in the vegetable garden.  Many annual weeds require light to germinate, so a relatively thin covering a mulch can reduce many weed problems.  For tougher weeds, use a thicker layer of mulch (3-4 inches).  Organic mulches, like grass clippings, yard waste, shredded newspaper or straw provide some flexibility because they can be raked around existing plants.  Do not use straw with weed seeds.  Salt hay is a good alternative that will not contain seeds.  If you use grass clippings, know their source and make sure the grass has not been treated recently with an herbicide.

Landscape fabric that allows water penetration is an excellent inorganic mulch to use in the vegetable garden.  Install the sheets of fabric at the time of planting.  Landscape fabric can be used for many years if you carefully remove it in the fall and store it indoors over the winter.  Be sure to by good quality, name brand landscape fabric. You can also use black plastic to cover areas of the garden you are not currently using.  Don’t put black plastic around growing crops because it will exclude water.  If you have a fallow section of the garden, even for a few weeks prior to the next successional crop, black plastic can kill existing weeds by excluding light and raising the soil temperature, so that section of the garden is ready for planting when you are ready to use it.

Tilling is another important method of vegetable garden weed control.   It is easier to kill weeds by tilling when they are young.  Seedlings can be dug up and their roots exposed to air with a hoe.  Once weeds get to be 3 inches tall, they cannot be easily tilled and should be hand pulled, using a trowel to get the entire root system.  Once you have hand weeded an area of the garden, cover it quickly with mulch to reduce the need to continue weeding all summer long.

Herbicides can be used with great care in a vegetable garden.  Before a crop is present, glyphosate (commonly sold as Roundup or other generics) can be applied to kill all the present green growth.  Once you have crops in the ground, avoid using glyphosate in your garden.  Treflan can be used to control germinating weed seedling before the crop emerges.  Poast is a grass herbicide that will kill grass plants without harming broadleaf crops.

Weeds are best controlled preventatively in the garden.  Once you have a lush stand of weeds, you will spend many hours removing them.  But, a few hours spent applying mulch or tilling seedling weeds will prevent problems later on.  Never allow weeds to go to seed in the garden.  That increases your weed pressure for later in the season or the following year.

Tomatoes and peppers planted with weed control fabric are completely weed free.

Tomatoes and peppers planted with weed control fabric are completely weed free.

Enjoy those first ripe, red tomatoes!

Container Gardens are HOT

Container gardens are “in” and have been for several years.  Planting in a container allows you to grow plants where you can’t otherwise.  Containers allow apartment dwellers to grow tomatoes, but they also brighten the deck or patio of any home.  Combination planters achieve the look of a “bouquet with roots” providing color all season long.  Even where there is ample room for a garden, well-placed containers provide seasonal accents.

Choose a container that fits your décor or style.  Containers can be amusing, valuable, clever, loud, quiet, classy, creative, solid, sophisticated, stylish, primitive, homespun, friendly, understated, matched or anything you want them to be.  But, they MUST have a drainage hole.

Soils for containers must be well aerated and well drained while still being able to retain enough moisture for plant growth.  Don’t use garden soil in your containers, it is too heavy and won’t drain properly.  Purchase a soilless mix designed for use in containers.  For succulents, herbs and perennials, select a coarse soilless mix with more bark, perlite or sand because these plants need good drainage and you don’t want the mix to retain moisture over long periods of time.  For tropical and foliage plants, choose a media with more peat and less coarse material as these plants tend to prefer moister growing conditions.  Moisten your media slightly before planting by filling a tub with media, adding water and mixing.

Think of your container garden as a living flower (and foliage) arrangement.  Include a tall plant in the center or back of the container.  Select filler plants to provide interest and use cascading plants to soften the edges.  Consider plant requirements when planning combination containers.  Use all shade plants for shady locations and sun-loving plants on a sunny patio.  If you use a combination of sun-loving and shade-loving plants in a single container, there will be no appropriate exposure for the container.  Also, think about moisture requirements.  Don’t combine plants that like it moist with plants that require good drainage.  You can combine shrubs, perennials and annuals, but the annuals will need to be replaced the following year.  Depending on the size of the container and exposure, the shrubs and perennials may overwinter in the container.  Tropicals are fun to add in a combination container, but they will need to be brought indoors to survive the winter.  If you combine a shrub and a tropical, you will have a conundrum—bring it in and the shrub will suffer; leave it outdoors and the tropical will die.

Once you have selected your container, growing media and plants, fill the container (almost full) with media.  Arrange the plants on the surface and play with the design until you are happy with the combination.  Remove each plant from its plastic pot and loosen the roots, especially if they are circling within the container in which it was grown.  Add a bit more media and water thoroughly.  Watering after planting settles the media and eliminates air pockets.  You may need to water several times to insure the media is thoroughly moist.  Make sure water drains out of the hole in the bottom of the pot.  A waterlogged container will not thrive unless you are growing water plants.  Remember to water container plants frequently throughout the summer.  Soilless media dries out more quickly than garden soil.  Fertilize containers a few times during the summer.  Annuals and tropical will need more frequent fertilization than shrubs and perennials.

Evergreen and deciduous shrubs are combined with perennials and annuals in this sumptuous planter combination at Longwood Gardens.

Evergreen and deciduous shrubs are combined with perennials and annuals in this sumptuous planter combination at Longwood Gardens.

Striking architectural container set by the pool at Chanticleer.

Striking architectural container set by the pool at Chanticleer.

If you want inspiration for designing container plantings, visit a local public garden.  Longwood Gardens in Kennett Square, PA and Chanticleer in Wayne, PA have spectacular planted containers throughout the gardens.  You can also buy combination containers already planted and ready to place on your deck or patio from most local garden centers.

Pears on the roadside – Beauty or Beast?

Sue Barton

Roland Roth, retired Entomology and Wildlife professor from the University of Delaware, wrote a short piece in the New Journal on Friday highlighting the invasive callery pear that is so prominently blooming on Delaware’s roadsides this April.  He said while they may seem pretty, they are crowding out native plants that once existed on natural land in Delaware.  He went on to suggest that everyone do their part to cut down invasive plants (especially pears, but also burning bush, barberry and butterfly bush) on their properties and replant with native plants that support native wildlife.

A few days later another article appeared in the News Journal.  It seems Patricia Dougherty took a ride downstate and never enjoyed it so much.  “The white trees that were blooming on both sides of the road were beautiful.  Some even looked like white Christmas trees.  I do not know what kind of trees they are.  I would love to know.”  Those trees are callery pears

Pears along Delaware's roadside in April.

Pears along Delaware’s roadside in April.

In fact, callery pear is spreading like wildfire on Delaware roadsides.  Once we just planted the cultivar ‘Bradford.’  This tree has a nice conical habit, white flowers in the spring and attractive maroon fall color.  What is not to like?  Well, Bradford pears have a nasty habit of branch splitting when the trees reach about 15 years of age.  Large limbs can break out of trees and fall on cars, even pedestrians.  This became such a problem that about 10 years ago, Newark removed all the Bradford pears on Main Street and replaced them with other tree species.  The nursery industry responded to the problem of weak branches by breeding other callery pear cultivars that have better branch structure.  Some examples include ‘Aristocrat’, ‘Chanticleer’ and ‘Redspire’.  While Bradford alone produced a small amount of fruit, the fruit production of callery pears skyrocketed with all these new cultivars for cross pollination.  That is when callery pears started escaping into disturbed areas along our roadways and crowding out native species.  At one time, not too long ago, when you drove past a wooded stretch in Delaware and saw a white tree blooming at the edge of the woods, you could be pretty sure it was a serviceberry (Amelanchier canadensis), a beautiful native trees sometimes also called shad bush; and you knew the shad would be running on the Susquehanna. Now, there are few serviceberries remaining and LOTS of callery pears.