Maligned plants

By Irene Shonle, Gilpin County Extension

Today, as I was trying to convince someone yet again about how goldenrod (a great late-summer native pollinator plant) is probably not to blame for their fall allergy woes, I got to thinking about other plants that get maligned, either by mistaken ID or by mistaken causation.

Native goldenrod

First, let’s get back to goldenrod (Solidago spp): people are often horrified when I recommend planting it.  They look at me as though I’ve just suggested that they invite a serial killer to bunk with them.  They shake their heads vigorously, and talk about how allergic they are to goldenrod.  But here’s the thing.  Goldenrod is an insect-pollinated plant, and therefore has less pollen, and the pollen is usually a bit heavier. It has the misfortune of blooming at the same time as ragweed, a wind-pollinated plant that sends out copious amounts of pollen, and is a proven allergen. It’s just that ragweed is an inconspicuous plant, and so when people are looking around for something to blame, they see the bright blooms of goldenrod just starting to bloom, and blame it. Granted, there are a few people who have genuine goldenrod allergies, but most people (unless they’ve had it tested), are blaming the wrong plant.  Chances are, you could safely enjoy this plant in your garden.

Another plant that people often mistakenly blame for their allergies is cottonwood – specifically, the “cotton” that flies every June.  This is something that I  believed as a child – I was genuinely frightened of the cotton because I blamed it for my itchy eyes, scratchy throat and sneezing.  I even once made my family move away from a perfect campsite under a huge cottonwood with flying cotton one time to a much less desirable spot in full sun.  Sigh.  If only I had known then that there is no pollen in the cotton – just seeds.  The pollen comes much earlier in the season. However, the cotton is a very attention-getting phenomenon, and it usually occurs about the same time that many grasses are beginning to release pollen, which is usually the true allergen (for me, smooth brome was the culprit). It's possible grass pollen could collect in the cotton, which would then turn it back into a potential problem.

Another plant suggestion that receives skeptical looks is sumac (Rhus spp). People who come from the Eastern U.S. instantly think that all sumacs are poison sumacs and thereby deprive themselves of a lovely native that contributes much color to the fall garden.  While some people are very sensitive to all members of the family, including mangoes, most people have no trouble with our native species (Rhus trilobata and Rhus glabra).

Native three-lobed sumac

Finally, with the advent of social media, I get calls many times a year with people who have read about the dangers of giant hogweed, and think they have found a population and want it taken care of immediately. This is because of all the Facebook and other social media posts warning people about the dangers of Giant hogweed.  And it is indeed dangerous: Heracleum mantegazzianum is a Federally listed noxious weed. Its sap can cause severe skin and eye irritation, painful blistering, permanent scarring and blindness. People can be exposed to the sap by brushing against the bristles on the stem or breaking the stem or leaves.  The problem is that it does not occur in Colorado (at least not yet). What people are finding is our native Cow parsnip (Heracleum sphondylium), which is related and looks somewhat similar.  Cow parsnip is a native plant (not a noxious weed), and doesn’t usually produce any rashes, and many people consider it an edible plant. Just to make things confusing, though, some individual plants mah produce fouranocoumarins, which can cause phototoxicity; most of the reports seem to come from European populations. I have not heard of issues with Colorado populations, but there may be some.  For more information on hogweed and lookalikes, this page has good information: http://www.dec.ny.gov/animals/72766.html.

Cow parsnip, Heracleum sphondylium, a  native plant (photo:easterncoloradowildflowers.com)

 Can you think of other maligned plants?

Time for a Tree Checkup

Posted by Carol O’Meara, Boulder County Extension

Trees this summer dealt with many challenges, from wet feet to intense heat, and some are starting to throw in the towel.  Although temperatures continue to bake us, symptoms of stress on our trees from a summer of strange weather are showing up all over town.  Help your trees go into fall with a late summer tree inspection.

“We do a tree survey every summer; it’s how we’ve picked up on problems,” said Kathleen Alexander, City of Boulder Forester. “It’s a (health) checkup.  Trees need routine maintenance like pruning or pest control.”  Alexander shared pointers for giving your tree a checkup yourself:

- Is there anything different or unusual about the tree?  Stand back so that you can see the tree from top to bottom.  Does the canopy look full all the way around, and is it the same as in previous years?

 - Check for broken branches that might not have been obvious earlier in the year.  “If the tree has a hanger (a partially broken branch dangling within the canopy) you might not see it until the leaves on it turn brown.  Then you look up and see the branch is cracked,” she said. Large, broken limbs are hazardous, so contact an arborist to have them remove it.

- Is the crown thinner; can you suddenly see daylight through it?  Loss of leaves could be due to stress on the tree or from frost early in the year that prevented the tree from having a full set of leaves. A third reason is mid-summer leaf drop.

Mid-summer leaf drop is characterized by trees leafing out normally in spring, then dropping leaves in late July or August for seemingly no reason.  When trees lose a lot of fine roots during dry winter, they can’t support summer's lush canopies. Leaf tips brown and leaves drop from the tree.

 - Check for changes in the leaves of the tree, such as early fall coloration, chlorosis, or scorched edges.  Scorched leaves show up as evenly discolored areas on leaves that are dry and slightly curled, moving from the tips inward.  These brown areas have no colored rings, called halos, or fruiting bodies of fungus on them. 

 

Scorch

Compounding the mystery of leaf problems this year is the cool wet weather followed by heat, then cool moist weather followed by more heat. Leaf spot diseases, such as Marssonina or Septoria thrive in the type of weather we had.  Infection spread during the cooler weather and symptoms are showing up now.

Fruiting bodies of fungi usually show on the leaf as small, pimple-like speckles and often have red or yellow halos around the diseased area.  Bacterial disease on leaves will have this halo as well, along with a slimy or greasy looking center spot.  If your tree develops these ‘leaf zits’, you should suspect a fungal or bacterial disease.