CO-Horts Blog

Tuesday, August 25, 2015

Hort Peeves: The "More is Better" Attitude

Posted by: Alison O'Connor, Larimer County Extension

Hopefully you did a double-take of the Japanese maple photo above. Perhaps a thought came into your mind that starts with, "What the _____?!" (You fill in the blank.) This photo was taken by my brother, Jeffrey, in Oregon. His text said, "What do you think? A few more scoops should do it?"

In case you're wondering what's wrong, that poor Japanese maple is covered (smothered, really) in Osmocote, a slow-release fertilizer. And this brings me to my hort peeve: the mentality that, "A little is good, so a lot more is better."

Here's the thing..."a lot more" can actually do damage to your plants. Whether it's fertilizer, pesticides or even water. Too much fertilizer can cause burning, salt build-up and excessive succulent growth that is more prone to insects, disease and damage. Overuse of pesticides is wasteful and not environmentally responsible.
Weed death by drowning.
Yes, we've all done it. Even I've done it. But it's not the way to approach sustainable (and legal) gardening.

The bottom line: Read the label and apply the product according to the directions. In terms of pesticides, the label is the law. If the label suggests to apply the product so that the foliage is "lightly dripping", do not pour the product on the plant. If the product suggests 2 teaspoons of product per inch trunk diameter, do not use 2 cups of product.


I realize that we're an instant society and we want to see immediate results. If we use Roundup, we want that plant dead within hours. As a point of clarity, glyphosate (the active ingredient in Roundup) usually takes a week or more to work, depending on conditions. But ingredients have been added (like diquat) so that you see foliage burn in a couple hours.

This also brings up another peeve: apply the product in the time frame suggested. If the label says wait 14 days before reapplying, then wait 14 days. Don't reapply at 7 days and think you'll "get a jump" on the problem. Give the product time to work.

Going back to the Japanese maple, Jeff has assured me he will keep an eye on it. I suspect the poor tree will show signs of leaf burn and dieback over the coming months/years. Poor tree.

Saturday, August 22, 2015

The Leaves They Are A’Fallin’

Posted by: Mary Small, Colorado State Master Gardener Coordinator and Jefferson County Extension Office
Time to get out the rake....
Okay, can I just say I am sick of aspen and cottonwood dropping their leaves already?!
We’ve received numerous leaf samples from these trees and nearly all of them have been infected with either Marssonina or Septoria leaf spot diseases. It’s so severe in some places that some trees are already defoliated or darn near. It’s causing a lot of concern and unfortunately we can’t do much for the trees or their owners!

Caused by fungi, these diseases develop readily in cool, wet weather (like we had this spring).  Fungal spores are released from last year’s infected leaves.  Spores (the “seeds” of the fungus) are then blown or carried by splashing water to susceptible new tissue, causing infections. 
Septoria leaf spot on cottonwood
Although leaves are infected in the spring, symptoms usually don’t appear until mid to late summer. Leaves will drop prematurely.  Trees can be stressed during severe outbreaks due to reduction of photosynthesis and food production.

Symptoms vary between these two diseases. Marssonina leaf spots are dark brown dots with yellow halos.  In prolonged wet weather (which we’ve also had), smaller spots may fuse to form larger black patches. Septoria spots form under similar conditions and often occur alongside Marssonina. Septoria start out as dark sunken flecks that may enlarge and form larger dead areas or spots are tan and circular with dark margins. 
Marssonina leaf spot on aspen
One of the best times to manage the diseases is now, from late summer into fall. Where it is practical (such as in a landscape, rather than a forested setting), rake up fallen leaves and dispose of them in the trash. The diseases over-winter in the dropped leaves and raking and disposing removes that inoculum from the site for next year. (Unless of course, infected leaves/spores blow in from somewhere else!)

In the landscape, space plants according to recommendations for the species.  Trees planted too closely increase the humidity within the canopy, creating conditions ideal for infection. Keep sprinkler water out of leaves, so they stay dry.  Splashing water from sprinklers can also spread spores between leaves, causing secondary infections.  Prune to thin trees. This increases air circulation, keeping leaf surfaces dry. 

I could say we might hope for a drier year in 2016, but I won’t. Sorry, aspen and poplar. 

Thursday, August 20, 2015

My Lawn is Turning Red?

Tony Koski, Extension Turf Specialist

Rough(stalk) bluegrass (Poa trivialis) will turn purple or
red when it becomes heat-and/or drought-stressed,
and then brown when completely dormant.
It’s been an interesting year for lawns. The cool wet spring gave us perfect growing conditions for bluegrass and other cool-season grass lawns – and perfect conditions for some diseases we don’t normally see here. Then it turned hot and dry, causing Ascochyta leaf blight to break out in epidemic proportions. I’ve written about yellow lawns and brown spots. Now we are getting calls and emails about red and purple spots in lawns.

Rough bluegrass turns brown when completely dormant.
While it looks dead, it will revive itself when cooler
weather returns in the fall.
The red grass people are seeing is rough(stalk) bluegrass (Poa trivialis) reacting to the very hot weather we’ve had the past couple of weeks. This cool-season relative to Kentucky bluegrass likes hot weather even less than our bluegrass lawns do – so it will often go dormant when we get long stretches of 90+ degree weather. Most often it just goes from green to brown, but it sometimes turns a bright red or purple before browning out. These red grass plants may have stopped producing chlorophyll in advance of becoming dormant (a “smart” thing for a plant to do), leaving red pigments behind – giving the plant a red appearance. Or they are producing extra xanthocyanins and carotenoids (red, purple and pink colored pigments) to protect the leaves from excess light (kind of a sunscreen that the plant produces to protect itself). Either way, the Poa triv patches in some lawns (usually in the hottest, sunniest parts of lawns) take on a reddish or purple cast – before turning a dead-appearing brown.

While it may appear to be dead, dormant Poa triv
will come back from live stolons on the soil surface. You
can find these green stolons when you dig down into
the patches of dormant, brown grass.
In spite of the dead appearance, the grass is only dormant. When cooler weather returns, it will green up again. Triv will often go dormant when it’s hot, in spite of generous irrigation. It’s not a drought-induced dormancy, but rather a heat-induced one.

This happy, green Poa triv is growing in a shady spot
just a few feet away from the brown patch pictured
above. It is aggressively and successfully crowding out
the original grass - turf-type tall fescue.
When you have a lawn full of Poa triv, you either learn to love it (or at least tolerate it), or you kill it and reseed or re-sod. There is no selective herbicide that will eliminate this weedy grass without harming the bluegrass or ryegrass in the lawn. Poa triv spreads easily and quickly by creeping stolons (runners) to form large patches - especially in lawns that are kept on the wet side. Shade favors its growth, but it can grow quite well in full-sun (but is more likely to go dormant in the sunnier parts of lawns). It is an aggressive, smothering grass under optimal conditions (wet, cool, shady), but less aggressive in drier, sunnier lawns.

I’m hoping for some cooler, wetter weather that will give us healthy, GREEN grass again.

Monday, August 17, 2015

Why I love floating row covers

Posted by Irene Shonle, CSU Extension in Gilpin County

As a mountain gardener, I believe that floating row covers are my vegetable garden’s best friend.   I wrote an “ode” to them in the Mountain gardening blog:

This year, I have a new reason to love them: hail.   We got a spectacular hail storm in July, with about an inch of graupel and a couple inches of rain falling in less than an hour.  We still had a pile of hail under our downspout three days later.

The weight of the hail pulled the row cover off a corner of my row cover, and where the tender spinach and lettuce was exposed, it turned to mush:

The spinach underneath was untouched (which, thankfully, was most of the bed).  Hooray for floating row covers! 

I had tried an experiment this year where I planted red mustard and squash in the same bed.  I figured I’d be harvesting the mustard as the squash grew larger, so it was a good use of space. Just as the squash was starting to flower, I took the row cover off to allow for pollination.  I was planning on cooking up a mess of greens for dinner, but the hail hit before I harvested.  Bad timing!  Shredded mustard.  I tried salvaging a few of the leaves to cook, but the rain had been so intense, it was impossible to wash all of the imbedded grit off.    The squash leaves were skeletonized as well. Fortunately, almost everything recovered pretty well within a couple of weeks.  

This is probably one of the only downsides to floating row covers – the need to remove them for plants that require pollination.  Okay, and the cute factor goes down a bit, too – but I’d rather have nice greens than cute.

Wednesday, August 12, 2015

Colorado Native Plant Society annual conference Sept 12

Many gardeners are also native plant enthusiasts. Please join the Colorado Native Plant Society at the annual conference - it's for anybody who is interested in native plants, from beginner to advanced!

Native plants and pollinators Saturday, September 12th in Golden, CO with field trips on Sunday, September 13th. 
The early bird registration of $35 for a full day of speakers, plus a field trip, is set to end on Aug 15th, and then it will go up to $45.  You can register online at: NOTE: if you are not an existing CoNPS member, there is a membership fee of $25 added to the registration. 

Hope to see you there!


Thursday, August 6, 2015

Scenes from a Cemetery Part II (and the Garden District): New Orleans

Posted by: Alison O’Connor, Larimer County Extension

I’m in New Orleans for the American Society of Horticultural Science annual meeting. First of all, it’s hot. Like really hot. I described it as being hugged by a furnace. The heat index is well north of 100 degrees. Second of all, for a first-time visitor, New Orleans is an incredible place. History, fun and great food! What more can you ask for!?

Today I toured the Lafayette Cemetery No. 1 in conjunction with a tour of the historic Garden District. The cemetery is the oldest in the city of New Orleans and dates back to 1832. It is a municipal cemetery and doesn’t have a religious affiliation, so anyone could be buried there. I loved what the tour guide, Sarah, said about visiting cemeteries—“It’s where the history is.” I couldn’t agree more if you remember my other blog about the cemetery in New Jersey last fall.

The oldest cemetery in New Orleans, dating back to 1832.

Lafayette Cemetery No. 1 (New Orleans, Louisiana) 
The magnolias, which were replanted in the 1970s, were a welcome relief from the sun. There was a lot of “hardscape” in the cemetery, which added to the heat index.
Magnolias casting welcome shade in the cemetery.
What is most fascinating is that the people of New Orleans are buried in a very different way than what we typically experience in the west…and often with their entire family. In the same tomb. I’m not sure about you, but that’s a whole lot of "family time" for everlasting eternity.

The tombs are located above ground—the highest point in the cemetery is nine feet above sea level. Burying the dead above ground is out of necessity—caskets would float to the surface after being buried. (Yikes!) The tombs are constructed from various stone, but the most basic are brick covered in plaster. Many of the name plates on the tomb entrance were marble.

The tombs have two levels. The upper level is where the most recently deceased is placed (in a simple casket). The bottom level is where the deceased were placed after their one year period on the top floor. So you have an above-ground tomb, constructed of brick, in New Orleans. Yes, it gets hot and as a result, creates rapid decomposition of the body. After a year, the bones are placed in a muslin bag (where the term “bag of bones” comes from) and placed below. The next body goes to the upper shelf.
Don't worry--this tomb has never been used. But you can see the two levels. The top shelf is for the most recently deceased. The bottom is where individuals are placed the year after burial.
With this process, dozens of family members can be buried together. There were people, from the same family, buried in the 1800s and as recently as a couple years ago.
Twenty two people are buried here together.
One of the most precious things on many of these tombs are the resurrection fern (Pleopeltis polypodioides), aptly named for their growth habit. These true ferns, which are epiphytic, can lose up to 97% of water and still live. With the smallest addition of water, the ferns spring back to life. Native to Africa and parts of the Americas, some resurrection ferns have lain dormant for over 100 years. These ferns take nutrients from the air and any precipitation that falls to live and grow. Talk about a tough plant! These ferns were tucked in various pockets on the tombs, ground and on trees in the cemetery. I even saw some growing on a brick wall in a parking lot.
Resurrection fern growing on a tomb in the cemetery.
Following the cemetery, we took a stroll around the Garden District to ooh and awe at the magnificent homes. As a girl from the Midwest, seeing houseplants (like cast iron plant, cycad palm and bird of paradise) planted as landscape shrubs still fascinates me. And the best part—I haven’t seen one juniper since my arrival!
A gorgeous home in the Garden District.
The live oaks are spectacular. There are some live oaks in the southern part of Louisiana that are hundreds of years old. They probably aren’t the best street tree, since their roots eat sidewalks and heave the concrete, but are incredibly attractive.
I'm sure any arborist would agree that this is a pretty good trip hazard.
Lawns for the most part, are not in front of many homes. Disease (brown patch!) and insects (chinch bugs!) tend to wipe out the hardiest of turfgrass, though a select few homes had bermudagrass, St. Augustinegrass and centipedegrass.

And one home had a wrought iron fence that brought me back to my days at Iowa State. This home, where the lady of home was from Iowa, had a corn fence, painted to authentic green. Our tour guide informed us that the fence needs to be painted every two years, or it would essentially disintegrate due to the weather.
The cornstalk fence at the Cornstalk Fence Mansion, 1448 Fourth Street, New Orleans.

The house is for sale! For a cool $6.5 million, you could own this fence.

For you Peyton Manning fans, he grew up in New Orleans and this is his childhood home. His father, Archie, still lives here.
Eli Manning grew up here, too.
Is it time to eat again? I’m hankering for another po’boy!

Wednesday, August 5, 2015

Hort Peeve: New Sod Torture

Tony Koski, Extension Turf Specialist

The lawn before mowing; that blue flag is 12 inches tall!
This turf peeve is about the mowing of newly planted sod. For some reason, the principles of proper mowing height and frequency are often totally neglected with new sod - sometimes for weeks on end. I’ve been watching the sod that was planted during the renovation of the old Fort Collins post office landscape over the past 6 weeks. The old lawn was replaced with new bluegrass sod – and then taped off as if it were a crime scene. The new sod went unmown for about 3-plus weeks – but was liberally irrigated during that time. As you might expect, it grew tall….VERY tall. So tall, in fact, that it began flopping over (aka “lodging”).

The lawn an hour after mowing torture
The lush, floppy, dense grass was recently mowed to a height of about 3 inches. What was left behind is not pretty – a mess of wet, matted, rutted brown and yellow grass. Mowing in this fashion will kill roots – roots that have been formed in just the previous few weeks. The stressed turf must not only grow a bunch of new leaves and shoots to replace those that were hacked off during mowing – but also will have to produce new roots to replace the ones that died as a result of the severe mowing.

This first mowing left few green leaves...and what happens
when the 1/3 rule is violated so egregiously!
This turf torture occurs all too frequently when new sod is planted. For some misguided reason(s), mowing of the newly planted sod often doesn’t happen for 2-4 weeks following planting. Sometimes the sod supplier tells a client it is better to leave the sod unmown for weeks on end because it will form better roots than if mowed “too soon” (not true). More often it is out of laziness, neglect or fear that new sod isn’t mowed. Because new sod should be irrigated daily, the water must be turned off for a day prior to mowing to give the sod a chance to dry out a little. This temporary drying out of the new sod takes planning and coordination with the person doing the mowing – and it creates the (unjustified) fear that the short-term drying will harm the turf.

The truth is, grass should always be mowed when it needs it – to avoid removing any more than 1/3 of the turf height at a single mowing (we call this the “1/3 rule”) – even if it is new sod.  Luckily, newly planted bluegrass sod is amazingly forgiving of neglect and mismanagement – so this lawn will likely survive and (eventually) look good. I will keep you updated.

Here is the lawn 1 week after its first mowing. Still recovering
from misinformed (stupid?) management. This is someone's
idea of proper turf management?

Saturday, August 1, 2015

Ash leaves Curling?

Posted by Eric Hammond Adams County

The wet weather which much of the state has experienced this year has been great for water bills, lawns and many plants in the garden.  However, it has also created some challenges.   One pest which has thrived under the moist and humid conditions is the ash leaf curl aphid (Prociphilus fraxinifolli).

Curling leaves on a mature ash
These insects are a type of wooly aphid which begins feeding on the underside of terminal leaves of green ash (Fraxinus pennsylvanica) in the spring.  Their feeding causes the leaves to curl (thus the aphid’s name).   Late in the summer winged individuals are produced which migrate to the roots of ash trees.

Leaves curled by ash leaf curl aphid

The damage caused by this pest is showy and often alarming to tree owners.   However, it is mostly a cosmetic issue and is normally not a serious concern to the tree’s health.   Normally treatment with insecticides is not warranted and sprays are ineffective once the leaves have curled, providing protection for the aphids within.   There are systemic treatments available but they can take several weeks or more to be affective and, again, are not normally necessary for the health of the tree.   If the curled appearance of the terminal leaves is distressing they can be removed from the tree.


Another nuisance associated with the insect is the sticky excrement they produce which is known as “honeydew”.   This sugary substance drips from affected trees in such quantity that it can coat cars, patio furniture, sidewalks or any other element of the landscape which is unlucky enough to be below the trees.   The honeydew is not only sticky and unpleasant but it is also commonly colonized by gray sooty mold which give it a black appearance with often appears to stain whatever it has dripped on.
Ash leaf curl aphids produce a white waxy substance as well as a sticky excrement
know as "Honeydew"


However, while all of this is a pain (pain in the Ash?), the issues associated with ash leaf curl aphid are still mainly aesthetic nuisances and it is not a serious threat to the tree’s health.  In most cases tolerance is the best option for dealing with the pest.   More information can be found in the “Aphid on Shade Trees and Ornimentals” Factsheet located here.