CO-Horts Blog

Wednesday, May 31, 2017

Don't Bug Out! Educate Yourself!
Posted by: Sherie Caffey, Horticulture Coordinator, CSU Extension-Pueblo County

I’m sure at some time in most of our lives, we have reached for a pesticide to help us out with a yard or garden pest. Being a new homeowner, I found that I had a lot to learn about the proper use of pesticides. Here’s some of the most important things I have discovered:

The new EPA advisory box
 Most people think of pesticides to be insecticides, but the actual definition of a pesticide is any chemical that controls a pest, whether it is an insect, a weed, a fungus, a rodent, or any other thing that is “pest”ering you.

There are many categories that pesticides fall into. One of the broadest is natural or synthetic. Natural pesticides are derived from biological ingredients, and synthetics are man made. If keeping your garden organic is important to you, look for an OMRI (Organic Materials Review Institute) label on the product you are using, this means it is certified to be used in organic production. Even though a product may be natural or organic, it may still be harmful to humans and beneficial critters in high concentrations, which brings me to the most important point about using pesticides, ALWAYS read the label! We will come back to this…

Too late for pre-emergents on this guy
There are a couple of other categories that pesticides are separated into. For herbicides in particular, they may be pre-emergent, meaning they can only control weeds before they germinate, or post-emergent, meaning you use them after the weeds have sprouted. Broad spectrum products are not picky, they kill everything, whereas selective products are meant to control one certain pest. Some pesticides are soil applied, and others need to be applied to the actual plant. Finally, protective pesticides prevent the pest of interest, and eradicants get rid of pests that are already present.

Signal words
The most important information that you can get about safely and properly using a pesticide is on the label. It is against the law to use any pesticide in a manner inconsistent with its labeling. There are many things that you will generally find on the product label. First of all, there will be the product name. There is usually a brand name (e.g. Roundup), and a common name (e.g. Glyphosate).

The next thing you should look for is the signal word, which tells you how hazardous the product is. These are the signal words you will see, in order from least toxic to most: Caution, Warning, and Danger/Poison. 1 to 3 drops of a product labeled Danger/Poison can kill an adult. You should also pay attention to any hazard or precautionary statements. These statements are meant to protect the applicator and the environment.

Last but not least, you will see the directions for use. You must use the product as directed on the label. The directions will tell you which plants it can be used on, which pests it is for, application rates, re-application times, and how long to wait until you harvest if you are using it in a vegetable garden.

So next time you reach for a pesticide to control a pesky garden problem, educate yourself before you use it, and remember, the label is the law!

Monday, May 29, 2017

Ascochyta Leaf Blight on Lawns – 2017 Version

Mowing drought-stressed lawns can make
Ascochyta worse. Notice no disease at top
of photo - shadier and no drought stress here!
Tony Koski
Extension Turf Specialist

The appearance of Ascochyta Leaf Blight has become an annual springtime event on lawns in Colorado. We have written about Ascochyta before: see our 2013, 2015 and 2016 blogs on this lawn disease. For more detailed information on Ascochyta in lawns, read those blogs because I’m not going to repeat everything that we've already written about it.

What I do want to talk about is WHY the Ascochyta disease appeared so suddenly over the last week. We’ve been inundated with calls, emails and texts with a common theme: “My lawn was perfectly green, and now you should see it! What happened?”. The explanation of why – that the disease is incited by drought stress –  doesn’t make sense to people because it appeared after the very wet (2 plus inches of water) snowy/rainy storm that came on May 16-18. That abundance of moisture (here’s what people DON’T remember) was preceded by two WEEKS of above-normal temperatures and very dry weather (red flag weather, if you recall?). And while everyone who has seen this happen to their lawns claims they were watering, I saw a lot of drought-stressed turf in the week before the storm. All it takes to turn Ascochyta on is a day or two of drought stress and heat during the spring – which this graph clearly shows was probable in home lawns this May. Those who REALLY were watering their lawns (or have shady lawns, or north exposure lawns) are not seeing Ascochyta. 

Much of first half of May was warmer (red line) than average (green line).And there was almost no precipitation May 1-16. This is a perfect "recipe"for Ascochyta on lawns that aren't irrigated enough during warm springs.The disease cycle began BEFORE the wet storm, with the symptoms appearing immediately after the storm. The moisture came a couple of days too late!

Here are some pics of what we’ve seen the past week.

In these 2 photos, there is less/no Ascochyta in parts of the lawn that are shaded or receiving a little more water from gutter downspouts. Ascochyta is turned on by heat and drought stress in the spring

Some quick bullets on the disease (go here for more details):

  • As bad as it looks, it isn’t dead!
  • Affected turf will take 1-3 weeks to recover, depending on severity and turf species.
  • It is NOT spread by mowing equipment – so there is no need to sanitize your mower.
  • Fungicides are NOT EFFECTIVE for preventing or curing the disease – so don’t apply them!
  • Adjust watering (and fix sprinkler coverage issues) to maintain consistent soil moisture, but not so that it is swampy (which will slow down recovery).
  • This appears to be a disease that occurs when cool weather turns into hot weather (hence a spring disease), so it will pretty much disappear as we become consistently warm in the summer.
Ascochyta doesn't kill the grass plant. You will see new growth
under the dead leaves almost immediately following an outbreak
of this disease. Recovery can take 1-3 weeks, depending on
severity and grass species.

While you can see mowing patterns with Ascochyta, mowing and the mower
doesn't spread the fungus. The mowing is an additional stress when turf is
heat and drought-stressed - so the Ascochyta and mower stress combine to
cause the browning of the turf.

Friday, May 26, 2017

Trees in the Land of Dr. Seuss

Posted by Mary Small
Master Gardener Coordinator
Colorado State University

Visiting the land of Dr. Seuss recently brought back some pretty old memories. Like many kids of my generation, my sisters and I grew up with the rhyming words, lessons, and odd-looking creatures and trees of his books. In traveling to San Diego and La Jolla, CA, area you can sure see how Dr. Seuss got his inspiration.

This coral tree (Erythrina coralloides) near Seaport Village reminds me of the three tree. The coral tree is among the pea family members found in tropical and subtropical regions. It’s often used as street and park trees because of its shade. The tree branches grow to resemble coral branches. Many species also have bright red flowers, so there’s some debate about just how the common name came to be.

Below is one of the many varieties of Eucalyptus (Eucalyptus spp.) trees in the area. (I’m not even going to try to guess which one!) Do you think they were inspirational to the story of “Horton Hatches the Egg”? Or maybe the truffula trees of “The Lorax”?

Eucalyptus trees are not native to California; they were imported when miners from Australia told stories of the large, quick -growing trees that would grow almost anywhere. Dreams and eyes grew large as entrepreneurs visualized the fortunes that could be made from growing much needed shipbuilding  lumber in a short period of time. It’s believed eucalyptus was first planted in San Francisco during the 1850’s.

Remember the expression - “if it sounds too good to be true, it probably is?”  That’s what happened in this story. The wood split and curled and was useless for lumber. Australian shipbuilders used old-growth eucalyptus that apparently didn’t have this performance issue.
Eucalyptus was growing in San Diego by the 1880’s for fuel, railroad ties and to spiff up the landscape. The railroad tie venture was a failure for the same reason that the wood failed as lumber. Some might argue that the trees don’t really beautify the landscape. Today, eucalyptus are considered an invasive pest tree that crowds out native vegetation.

Did palm trees inspire this (and many other versions) from “The Butter Battle"? I believe this is a Senegal date palm (Phoenix reclinata) which is originally from Africa. It has a suckering habit and tolerates drought and dry heat. It’s usually used as a specimen planting, particularly since the plants often lean outward a bit and so take up even more space than the clump itself.  On the down side for us in cooler climates – it’s only hardy to about 23 degrees F. But looking at the bright side, we don’t have to remove the old leaves- a good thing- since they have 8” long, sharp thorns!

So remember next time you’re reading a Dr. Seuss story that the weird looking trees have real- life inspiration. There’s something to the old adage about truth being stranger than fiction!

Friday, May 19, 2017

Cool Season Trial Garden Winners

Posted by James E. Klett, Professor and Extension Landscape Horticulturist

The 2016-17 Colorado State University Cool Season Trials are completed and the winners have been announced.  In this trial we evaluated 119 different varieties of pansies and Violas for their performance in the fall of 2016 and winter and spring of 2017.  We evaluated them on April 19, 2017 and sixteen varieties were given high honors.  Overall, the Cool Season Trial was probably the best one we had in the past ten years.  Plants were planted in October 2017, watered and fertilized initially and hand watered throughout the winter when temperatures were above 40° F and when there was no snow cover.  The plants still look excellent and we will keep them in the trials till after Memorial Day 2017.  We then will remove them since we need the space for our annual flower trials.

Five of the outstanding varieties in this trial include:

Best of Show Pansy – ‘Cool Wave Morpho’ from Pan American Seed
This pansy stole the show in our trial with vibrant flower colors which were a striking contrast between blue and yellow and were held up high for easy viewing.  The flowers were numerous totally covering the plant which attributed to the larger spreading growth habit.  The entire Cool Wave Series was noted to have exceptional vigor and flower power but ‘Cool Wave Morpho’ was considered the best of the series.

Best Yellow Pansy – ‘Matrix Yellow’ Improved by Pan American Seed
The huge flowers alone draws attention to this plant.  The clear yellow flower creates this plant.  The clear yellow flower creates an array of bright and sunny looking flowers.  This pansy would brighten up any landscape in the winter and early spring.

Best Purple Pansy – ‘Inspire Plus Denim’ by Benary
This pansy had a unique flower color which was shades of blue and purple on sturdy stems with excellent green foliage.  This pansy had an attractive face with eyes adding character to upward facing flowers.

Best of Show Viola – ‘Endurio Blue Yellow with Purple Wing’ by Syngenta
The spreading growth habit makes this viola very attractive for borders and nostalgic looking flowers that bring back the idea of old-school violas.  The eye catching blue yellow with purple wing flower color is guaranteed to make everyone feel happy.  It was also designated as the “Best Novelty” Viola.

Best White Viola – ‘Admire White’ by Benary
This viola demonstrates a uniform and tidy growth habit with a petite flower size.  Flower are a pure white and very floriferous.

These are just five of the fifteen winners and a complete listing can be viewed on and click on the Cool Season Trial tab.

You will want to include some of these varieties as you plan your cool season garden for the 2017-18 season.

Thursday, May 18, 2017


By Irene Shonle, CSU Extension in Gilpin County

Epiphyllums are wonderful and mostly low-maintenance houseplants. Epiphyllum is a genus in the cactus family CactaceaeThey’re also called “orchid cactus” (even though they are not orchids) -- and to the afficianados, they are affectionately dubbed “epis”. Epiphyllum are tropical (rather than desert) cacti, from oak forests and rainforests across Mexico and Central and South America. They are epiphytes (which are plants that grow on trees, but are not parasites).

 I have a big specimen that stuns me every year with knock-out flowers.   Mine just got done blooming a few days ago (sadly, each enormous bloom only lasts a couple of days).
Epiphyllum "Unforgettable" in full bloom.
However, I always have a problem with some of the buds dropping off before they bloom.  As the buds form in late winter, I gleefully count them in anticipation of a big show, but I’m usually met with some disappointment, since all but about 4 or 5 of them usually shrivel up. 
Shriveled bud about to fall off

 This year, I decided I don’t want to put up with that in the future, so I looked more carefully into their care.

The first tip is to make sure the soil is well-draining, yet holds some moisture.  One suggestion is to use three parts potting soil mixed with one part of coarse non-organic material such as perlite. Check. 

The second is to stop watering entirely in November until buds start to form in March (this is only for blooming-size plants). I have been following this practice for years, although the first year I was nervous that I would kill the plant. Once the buds form, the advice is to water regularly, imitating the rainy season, but to not overwater the plant. Thinking I may have inadvertently overwatered last year by giving them their regular watering, I watered quite sparingly after bud formation this year, and still had the same issue. The rest of the year, water when the top part of the soil dries out.  Check.

The third is to keep the plant in an area with cool nights (mid-thirties to mid-fifties) and bright, indirect light while buds are forming in in the winter. Check. The room they are in gets down to the high fifties every night, and that seems to work fine.

Next tip is that the plants bloom best when they are root-bound. One group of 'epi' fans say to only re-pot if absolutely necessary, and another suggests repotting every year to replenish the soil. I have followed the advice of the first group, probably mostly due to laziness.

The last tip is to fertilize regularly during the growing season, and I think this is where I need some fine-tuning.  I fertilize pretty minimally, and have never paid too much attention to it, so I think here might be some room for improvement.  The flowers form on the active growth from the previous summer, so a regular fertilizer and watering regime is supportive at this stage. 

After researching a bit, I plan to feed each watering time from May to late August with a balanced formulation like 10-10-10 or 5-5-5. From August to November, I will try only fertilizing every other watering time (that’s going to be a challenge to remember!). Because epiphyllums are used to low nutrient environments, I plan to only use about one-third to one-half the amount of fertilizer that is recommended on the label. From August to November, I’ll use a low or no nitrogen fertilizer ( i.e.; 2-10-10 or a 0-10-10 formulation).

And we’ll see what happens sometime next May!

Tuesday, May 16, 2017

Cold snap alert: cover those plants

By Carol O'Meara, CSU Extension Boulder County

The cold snap predicted for Thursday and Friday is not going to be kind to the garden.  Yes, we can use the rain, but the snow and below freezing temps means gardeners should get ready to cover up.  Grab tarps, plastic sheets, buckets, and keep your therapist on speed dial for the inevitable call to cry on their shoulder; this freeze is catching us after we’ve planted.

Tender vegetables like tomatoes, peppers, eggplant, cucumbers, napa cabbage, or squash should be capped with an extra bucket, coffee can, Mason jar – anything that will trap the heat from the soil.  If the planted area is too large for individual buckets, set up a tent to cover the plants with plastic.  The trick is to trap the soil heat, so ensure that the plastic reaches the ground on all sides.  Weigh it down so the wind doesn’t blow it to Kansas and keep the plastic from touching the plants you’d like to protect.

Potatoes, onions, beets, and other root crops nosing up from the soil will be fine under a thick, warm blanket of mulch.  Pile the straw or grass clippings up over the plants to keep them snug under at least six inches of mulch.  You can uncover them after the freeze is over.

There’s not much we can do for the trees but if you have smaller perennials or roses you’d like to protect, swaddle them in plastic as well.  If possible, pull containers into the garage to protect them or cover them with buckets or plastic.  To keep pots from freezing, group them close together and stack bales of straw around them, then cap them with a blanket or tarp.

Make sure that you uncover the plants as soon as the cold snap passes by; things heat up very quickly under plastic and you don’t want to steam cook your plants.


Thursday, May 11, 2017

April Frost brings May concerns

Mother’s Day is fast approaching and away should go the chance for frost and freezes in the Grand Valley and other low lying areas of Colorado.  Unfortunately the last weekend of April and three weeks prior we had some late cold temperatures.  Many plants were a good month ahead on growing because our February and March had been so warm.  The first of the frost/freeze wasn’t too bad.  Most of our fruit crop just had a good thinning and some just the lower limbs were affected.  Areas that were lower, like my residence in Fruita, got much colder.  I lost all my peaches and plum fruit for this year and my apples were thinned heavily.  We tend to forget that cold settles.  I had tried covering my smaller trees, but when you get down to 21 degrees F, a cover doesn’t do it.  

The Palisade area was much warmer (29 plus) and with orchard fans running were able to avoid great damage; then came the second frost April 29th and 30th.  I didn’t see much more fruit damage; it is dependent on the bud or fruit stage and how cold it gets for several hours or more.  But I did see many large ornamental trees get hit hard by the cold.  They were just at the right point of expansion of the leaves. I have noticed cold damaged foliage on cottonwoods, sycamores, elm, honey-locust and oak.  
Cold damage on a baby Kentucky Coffeetree in our Nursery area- SLC

Even Siberian Elms showed some cold damage- notice the larger leaves on the tips-
New foliage is now emerging- SLC

My potatoes had damage to the edges of the top leaves and we have had some shrub samples come in with cold damage.  I found a good handout for preventing frost damage from Arizona Extension.

SO what do you do if you had cold damage?  Many people at first want to cut off some of the damage or fertilize.  If the tree was in good health, a second set of leaves should emerge.  Give it time.  Patience has its virtue.  Don’t prune until new shoots have emerged; then remove the dead.   And don’t fertilize.  This plant is under stress from the frost damage.  We don’t want to try to force it to grow and cause more stress.  

Susan's potato plant with frost damage

Here is a link to how and when to fertilize: Keep the tree watered but don’t overdue. With some patience and good basic care, your tree and other damaged plants can come back as long as they had some reserved energy and the temperature didn’t get too cold for the particular plant.  So now that we have gotten the freezing temperatures out of the way, it’s time to plant our tomatoes in Grand Junction and wish mom Happy Mothers Day!
Plant Select plant: Scutellaria resinosa 'Smoky Hills'
Didn't see any cold damage on it.
Happy Mother's Day

By Susan L Carter, Horticulture Agent, CSU Extension, Tri River Area