Category Archives: Did you know…

Everything’s coming up roses!

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A trip to the Chicago Botanic Garden last week provided a great opportunity to take in the sights and smells of summer roses. Some of the most common types of roses are described below.

peach color rose

 Hybrid Tea

Tea roses, named for their fragrance, are considered “old garden roses” and date back to the mid 1800s. Original tea roses were mostly red, pink, or white and had small weak stems with blooms that drooped. Hybrid tea roses have stems that are longer and stronger.  They are available in a wide variety of colors. Hybrid tea roses have individual blossoms, bloom repeatedly, and are usually grafted onto rootstocks of other types of roses to improve growing performance. Of the 40+ million roses produced each year in the US, almost half are hybrid tea roses. They make excellent cut flowers.

Floribunda

Floribunda roses were introduced at the beginning of the 20th century. They have clusters of flowers at the top of each stem and generally do not grow very tall. Many floribunda roses were developed by Eugene Boerner during his time at Jackson & Perkins. Several of his roses were given the All-American Rose Selections award. Floribunda roses are preferred by landscapers, especially for borders and hedges, for their abundant flowers and small, compact size. Several floribunda roses have intense fragrance.

 Grandiflora

Grandiflora roses are combinations of floribunda and hybrid tea roses. Grandiflora roses are tall, bloom repeatedly, have clustered blooms, and have slightly shorter stems than hybrid tea roses. The term grandiflora was first used to describe a rose developed in the 1950s for Queen Elizabeth.

Miniature

Miniature roses are just like their full-size counterparts except they are smaller. They are available in a wide variety of colors, sizes, bloom types, and growth patterns. Miniature roses are more hardy in colder climates because they are usually grown on their own roots. They are easy to grow and some are very fragrant.

Examples of these types of roses are shown below.

For more information, check out this link:

http://scvrs.homestead.com/TypesOfRoses.html

The McCartney Rose (Rosa Meizeli)

The McCartney Rose (group hybrid tea)

Ingrid Bergman (Rosa Poulman)

Ingrid Bergman (hybrid tea)

Ingrid Bergman (Rosa Poulman)

Ingrid Bergman (hybrid tea)

Ingrid Bergman, Rosa Poulman rose

Ingrid Bergman (hybrid tea)

Rosa Tiffany

Tiffany (hybrid tea)

Gemini, Rosa Jacnepal

Gemini (hybrid tea)

Tropicana rose, Rosa Tanorstar

TROPICANA (hybrid tea)

Rosa Medallion

Medallion (hybrid tea)

Lavaglut, Rosa Korlech

Lavaglut (floribunda)

Mardi Gras rose, Rosa Jacfrain

MARDI GRAS (floribunda)

Sun Sprinkles rose, Rosa JAChal

Sun Sprinkles (miniature)

Love rose, Rosa Jactwin

Love (grandiflora)

Magic Carousel, Rosa Moorcar

Magic Carousel (miniature)

Lawn Care in Spring–Look to Forsythia

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forsythiaforsythiaforsythia

One of the joys of spring is the reappearance of a lush green lawn. Amazingly, the grass survived the winter and is now ready to take in the sunshine. Unfortunately, so are the weeds, specifically crabgrass and dandelions. With a little preventative action, these weeds can be kept to a minimum. Here’s how forsythia can help.

Weed Preventers versus Killers—When to Apply?

Crabgrass is a seasonal weed that grows from seeds produced the previous summer (the crabgrass plant dies off in the winter). The seeds survive the winter and germinate in early spring. A crabgrass preventer, or preemergent herbicide, forms a barrier on the soil that prevents sprouting seeds from sending roots into the soil. The best time to apply a crabgrass preventer is when forsythia bushes are in full bloom, usually sometime during the month of April in northern Illinois. Why? Crabgrass seed germination begins when soil temperatures reach 62 degrees F at a depth of 1-2 inches, just after most of the forsythia blooms have dropped. Applying crabgrass preventer when forsythia is in full bloom ensures the treatment has been applied BEFORE germination begins. After the crabgrass preventer has been applied, remember not to rake or aerate, which will compromise the barrier. Also, wait several weeks before starting new grass seed—most crabgrass preventers also prevent grass seeds from germinating! Read the label on the crabgrass preventer to be sure.

Dandelions are perennial weeds that grow from root systems established the previous year. They are not affected by crabgrass preventers. Instead, they are controlled using weed killers. Weed killers work by coming into contact with the leaves, which is how the weed killer is absorbed. Weed killers must be applied when dandelions are actively growing. The best time to apply weed killers is when the weather is warmer, usually well into May and well after forsythia blooms have dropped. Remember not to mow first because this will remove some of the leaves.

Can’t stand those early spring dandelions? Skip the chemicals and dig the dandelions up by hand, preferably before the dandelion blooms have turned to seed. I like to use a weeder with a sharpened fork tip. Place the tip at the base of the dandelion, just under the soil, and lift. The dandelion and a good portion of the root should pop right out.

For further reading, check out these links:

http://www.hewitts.com/garden-tips/lawn-care/crabgrass-preventer-vs-weed-killer/

http://turf.msu.edu/crabgrass-control-in-home-lawns

Maple Leaf Tar Spot

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maple leaf tar spot

maple leaf tar spot close-up view

Tar spot is caused by a fungus in the genus Rhytisma.1  I first became aware of tar spot when I noticed that my newly mowed lawn was covered the following day with dropped maple leaves…in August!  Upon closer inspection of the leaves on the lawn and on the tree, I noticed the leaves contained varying numbers of the black spots shown in the images above.  As it turned out, several other trees in my neighborhood also had the same black spots.

Tar spots begin as small yellow-colored spots on the upper leaf surface that turn into black raised structures resembling tar.  The fungus that causes tar spots overwinters on infected leaves and then releases its spores from the stroma (black spot) the following spring.  The spores are spread by the wind onto new leaves that are beginning to unfold.  The spots where the fungus colonizes the leaves become visible 1-2 months later, during the summer.   Fortunately, tar spot is not usually detrimental to the tree—it is a cosmetic concern that can be managed by raking up the infected leaves and destroying them in the fall.2

  1. Hudelson B. Tar spot. 8/13/2012.  Available at: http://hort.uwex.edu/articles/tar-spot (accessed 12 December 2013).
  2. Healy R.  Minor leaf spot diseases of maple:  tar spot and leaf blister.  8/8/2007. Available at: http://www.ipm.iastate.edu/ipm/hortnews/2007/8-8/maplespot.html (accessed 12 December 2013).

Pin Oak Tree: Magnificent Marcescent Leaves

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pin oak tree marcescent leaves

Trees may be grouped into two types based on the duration of time with leaves:  evergreen and deciduous.  Evergreen trees have leaves or needles year round and the leaves or needles stay green (due to the presence of chlorophyll).  Deciduous trees, on the other hand, have leaves for only part of the year and the leaves may change color (due to the disappearance of chlorophyll).

Interestingly, some deciduous trees like the pin oak tree pictured above have leaves that change color but the leaves do not drop until spring (this photo was taken in late November).  This characteristic is referred to as marcescence, from the Latin marcescent – beginning to wither.  Botanically speaking, the term refers to leaves or fronds that wither but remain attached to the stem.1   Beech, sycamore, and several species of oak have marcescent leaves.

What causes leaves to fall from trees? The leaves of deciduous trees have an abscission zone or abscission layer that forms where the leaf meets the stem.  In response to changes in the length of the dark period each day, the cells in the abscission layer start to block the transport of nutrients between the leaf and the stem. Eventually, the cells weaken or are digested and the leaf separates from the tree.  In marcescent leaves, the abscission zone is not present or does not fully develop until the start of the next growing season, when buds begin to emerge. The result is a deciduous tree that keeps its brown leaves all winter!  The articles by Andrew Hipp2 and Ted Griess3 provide good overviews of this process.  The US National Arboretum also has a nice summary.4

Not sure what type of tree you have?  Try the searchable factsheets at the Department of Forest Resources and Environmental Conservation at Virginia Tech.

  1. Oxford Dictionaries.  http://www.oxforddictionaries.com/definition/american_english/marcescent
  2. Hipp A.  When oak leaves fail to fall.  Tag Along.  Vol 6 #2. Spring 2007.  Available at: http://systematics.mortonarb.org/lab/publications/Hipp2007_TagAlong6_marcescence.pdf
  3. Griess T.  Yard and Garden.  11-02-2013.  Available at: http://buffalo.unl.edu/c/document_library/get_file?uuid=9419c5cc-3be5-45da-a972-f36d2022d071&groupId=134881&.pdf
  4. The Science of Color in Autumn Leaves. http://www.usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html (accessed 11 December 2013)

Leaf Gall

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hackberry nipple gall leaf

Hackberry nipple gall

hackberry nipple gall leaf tope

Hackberry nipple gall – top of leaf

spindle gall

Spindle gall

spindle gall

Spindle gall close-up

spindle gall

Spindle gall viewed from underside of leaf

I found these leaves on trees growing in my neighborhood.  The photos were taken in early November.  The bumps on the leaves are known as leaf galls.  According to the American Heritage® Science Dictionary, a gall is defined as “an abnormal swelling of plant tissue, caused by injury or by parasitic organisms such as insects, mites, nematodes, and bacteria. Parasites stimulate the production of galls by secreting chemical irritants on or in the plant tissue. Galls stimulated by egg-laying parasites typically provide a protective environment in which the eggs can hatch and the pupae develop, and they usually do only minor damage to the host plant. Gall-stimulating fungi and microorganisms, such as the bacterium that causes crown gall, are generally considered to be plant diseases.”1

What I find interesting about galls is that they look very different from the leaf, but they are formed by normal leaf cells that have gone awry.  The parasite releases chemicals that cause the leaf cells to grow aberrantly and form the gall. In turn, the gall may provide the parasite with a source of nutrients and protection from harsh environmental conditions.  Galls may also protect the parasites from natural enemies, produce antimicrobial agents,2 and release volatile compounds that deter herbivorous mammals.3

There are hundreds of gall-forming organisms.  The photos shown above are just two examples of leaf galls.  Despite their unusual appearance, galls generally are not thought to be harmful to the plant.  More information on leaf galls and other types of galls may be obtained from a local university extension.  I found the publication by Mark Shour and colleagues from the Iowa State University Extension to be particularly informative.4

  1. Gall. Dictionary.com. The American Heritage® Science Dictionary. Houghton Mifflin Company. http://dictionary.reference.com/browse/gall (accessed: November 27, 2013).
  2. Gerchman Y, Inbar M. Distinct antimicrobial activities in aphid galls on Pistacia atlantica. Plant Signal Behav. 2011 Dec;6(12):2008-12.  Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3337195/
  3. Rostás M, Maag D, Ikegami M, Inbar M. Gall volatiles defend aphids against a browsing mammal. BMC Evol Biol. 2013 Sep 11;13:193.  Available at: http://www.biomedcentral.com/1471-2148/13/193.
  4. Shour M, Jesse L, Lewis D.  Insect galls on trees and shrubs.  Available at: http://www.extension.iastate.edu/publications/ic417.pdf