CO-Horts Blog

Thursday, March 26, 2015

Onions Anyone?

Posted by Eric Hammond, Adams County

Last week we began planting the 2015 edition of the Northern Colorado Onion Variety Trials.  This project has been going on for over 40 years (the earliest report I can find from the trial is from 1971) and is an annual rite of passage in our office. 

 Each year seed companies submit onion varieties they would like trialed.   With the help of local farmers, volunteers and “onion biologists” (A position we created to be able to pay some of the people who help us) we plant and then evaluate them on several different characteristics.   The process and procedures of the trial provide an interesting glimpse into large scale agriculture that as gardeners most of us don’t  get to experience.


Having no formal training or experience in traditional agricultural production the first year I helped with the trial I was fascinated by the process of planting the onions.  The planter places single seeds at precisely 3.5 inch intervals at a depth of a half of an inch.  This means they expect, and normally archive  close to 100% germination.    As seedlings emerge we evaluate germination as "percent stand" (which is just code for percent germination).
Planting at Sakata Farms in the Spring of 2014

"Onion biologists" evaluating emergence
Teasing apart leaves to expose thrips which tend
to be found near their base
When mid-summer comes around we begin to evaluate the onions for their responses to pests.   The most taxing evaluation we do is an assessment of thrips populations.  Thrips are tiny insects which feed on the leaves of the onions (along with other plants).  They are one of the major pests of onions in the state.   There is some thought that onions which have leaves that are different shades of green or waxier will be less attractive to these insects.   There is also interest in finding varieties that tolerate thrips feeding, meaning that they produce an acceptable yield even when populations are high.  So, we crawl through the onion field on our hands and knees wearing magnifying glasses to count the number of thrips on individual onion plants.  This evaluation is my personal nemesis.  The first year I participated I apparently had a gap between my tee shirt and pants on my lower back.  By the time we were finished in the field I had managed to give myself a sunburn which had the color of a deep bruise (be thankful there is no picture).

Thrips on an onion leaf.  I wonder how many thrips I have eaten in my life?
Note our sweet magnifying headgear.

Counting thrips populations in Hudson

Iris yellow spot
Later in the summer we also evaluate the plants for the incidence and severity of iris yellow spot virus.   If the infection is severe enough, the virus can reduce yields.  Some varieties appear to have some tolerance or resistance to the virus.  Researchers and plant breeders would obviously like to identify such varieties.  So, we note the presence of the oval shaped lesions caused by the virus and rate their severity. 


In the fall, we harvest the onions and sort them to determine yield, size and the amount of doubles for each variety.  Most onions grown in Colorado are stored and used in applications which require a “medium” sized onion.  Larger sizes are desirable for specialty applications (has anyone has a “Bloomin’ Onion” recently?).  Double onions are not desirable for some uses such as onion rings.   Red onions are also evaluated for the quality of their color (which is a fancy way of saying they have their “redness” evaluated).

Harvesting onions last fall
My wife who I have coerced convinced to help
with the trial.  Where else can you learn how to juggle onions?

After yield and size have been evaluated the onions are bagged back up and placed in storage.  In January, we pull them out and evaluate how well they stored.   This can be a very slimy and smelly process for some of the varieties. 

Our retro onion sorter
Onions are evaluated after  storage for firmness and scale quality
Onions in January after storage
I can’t overstate how valuable the cooperation of local farms is in the trials.  Without the donation of space in their fields and storage facilities and time with their very valuable planting equipment and personnel, the trial could not exist in its current form.

So why do we put all this effort into this project?  Well, onions are a valuable and economically important crop in Colorado, nationally and worldwide.  Over 5,000 acres of onions were planted by Colorado farmers last year and our state’s harvest yielded an estimated 26 million pounds of onions.    This seems like a lot until you consider that globally something like 170 countries grow onions on approximately 9.2 million acres.  I guess the take home message is that the world is a big place and a lot of people living on it like to eat onions.  The Northern Colorado trial and other others like it are small but important pieces in contributing to the continued success of the crop.

No, the drone is not real

Tuesday, March 24, 2015

No Seeds, No Weeds

By Jane Rozum

I start each gardening season with the same mantra: I vow to do better this year in controlling weeds that inevitably invade my garden beds and landscape. I vow to not let the dandelions, crabgrass, purslane, etc. take over. I usually start the season with this mantra in my head, but at some point, I forget about area weeds or I just don’t get to them quickly enough before they flower and set seed. After attending a lecture by Dr. Tony Koski (CSU Extension Specialist) on weed management, I learned why one should never let the thugs of the garden take advantage of my garden space again.

During the lecture, Dr. Koski talked about the weed seed bank. A seed bank occurs when weeds are allowed to go to seed and drop seeds into the surrounding soil over many years. Many common species of weeds can produce thousands of seed in a season with just one plant. Take a look at the below table. Is there any doubt that many weeds are good seed producers?
                                                                                        Number of Seeds  
                                                     Weed                        Produced Per Plant
       Dandelion                15,000
       Canada thistle              680
       Curly dock                29,500
       Lamb’s quarter       72,450
       Mullein                     223,200
       Pigweed                   117,400
       Purslane                   52,300
 Think of what one weed is capable of producing as subsequent generations also produce seed, millions of seeds! The true horror, however, is allowing seeds to accumulate in the soil. What is the average viability of the seed; that is, how long is a seed able to persist in the landscape? The table below shows the average number of years that some common species of weed seeds can survive and still germinate and grow:

                                                     Weed           Viability of Buried Seed
Black mustard                  50 years
Curly dock                         80 years
Foxtail                               30 years
Mallow                             20 years
Plantain                            40 years
                                                    Shepherd’s purse            35 years

Say, what?! Not only are weeds proficient at growing and producing seed, the seeds they produce can still germinate and grow 50 years later! Is it any wonder why weeds are so prevalent in our landscapes? A weed seed bank can produce weeds for many, many years to come.
How can you decrease the weed seed bank in your yard? Here are some tips:
1.       The best weed control is applied when the weed is young, or even before seed germination. Crabgrass control in spring prevents the crabgrass seeds from germinating. That’s why it’s important to apply at the right time (like right now). Mechanical control is easier when weeds are young, and herbicides work best at this stage as well.
2.       Keep your garden and lawn healthy to promote weed growth competition. Deep, infrequent watering schedule works well for lawns and gardens, but shallow-rooted weeds don’t do well with this type of watering schedule. Healthy lawn and garden plants will crowd out and compete with weeds for light and nutrients, so keep nurturing your landscape throughout the gardening season.
3.       Apply mulch. CSU recommends 3-4 inches of weed-free mulch so weed seeds can’t germinate. Landscape fabric under the mulch is not necessary and can contribute to lower garden plant vigor.
4.       Most important of all: Do not let weeds contribute to the seed bank in your landscape. If weeds do pop up in your garden, pull or cut off the flower head. The weed may still grow and attempt to flower again, but if you never let a weed flower and set seed, it cannot contribute to the weed seed bank. 

So, as we head into the 2015 garden season, I now have a new mantra: NEVER let a weed set seed! At some point, maybe many years from now, I look forward to depleting the weed seed bank in my landscape.

  For more information, check out CSU’s GardenNotes #351

Monday, March 23, 2015

Spring Already?

Posted by: Deana Wise, Master Gardener coordinator, Broomfield County

I can tell spring is here because I received three different phone calls in the office this week concerning turf diseases. At first I was a little confused, did Kentucky bluegrass break dormancy since I came into the building this morning? Then I thought, Carol was right in her earlier post concerning gentlemen and their engines (see Friday, March 13, 2015). The warmer temperatures had flushed the early birds out and they had old lawn complaints from last summer.

I admit I was a little excited to be receiving my first call as a Colorado Master Gardener Coordinator. I have spent four years as a CMG and have served on the phones for many hours. I am normally fairly confident in my Horticultural knowledge or at least in my research capabilities if I can’t come up with an answer right away. My excitement changed to fear as I realized I was “the expert” now.

My first client (Mr. X) has a large dead spot in his lawn and I attempted to listen, take notes, and recall the correct questions to ask. I tried to remember the Steps of Diagnosis. Step 1- Identifying the plant was easy enough because Mr. X told me what it was. So far so good.

Step 2 involves identifying the pest. This was the reason Mr. X called. I asked him to email me pictures, thinking this would buy me time. Unfortunately, he was very comfortable using modern technology. I had 5 different photos in my email before I could locate my dichotomous key for diagnosing turf diseases.
The mysterious turf disease.
To stall further, I told him I would forward his photos to two of our turf experts (Thanks Tony and Curtis). While awaiting their reply, I finally had time to do a little research. Our experts confirmed my diagnosis of Gray Snow Mold (Typhula). I moved on to Step 3, what type of damage does it do?
Gray snow mold. The best "treatment" is to gently rake and encourage air circulation. (Photo by Tony Koski)
Gray Snow Mold usually requires extended periods of snow cover. Our freaky cold spell kept the snow around long enough for the Typhula to attack. According to NC State Turffiles, “The disease appears in perfect circles or irregular patches up to 3’ or more in diameter. The turf within these patches is white or gray and matted together”. Snow mold can, in extreme cases, cause extensive damage.

Step 4 questions under what conditions will management efforts be warranted? We discussed his treatment options. The turf area affected was relatively small: therefore limited actions needed to be taken.

Step 5 led me to the available management options, are they effective on the pest and when should they be applied? Treatments run the gamut from Cultural (reducing nitrogen and continuing to mow in the fall) to Chemical (fungicide applications). We decided the best course of action was to spread his snow from the driveway around instead of mounding it in one place. He agreed to rake the affected area to allow for better air circulation.

As he hung up, I realized I had handled a client’s question (with a little help from my friends), diagnosed his problem and formulated a workable plan for future containment of the disease. The second and third calls were easier and now I feel confident again. Open the gates, I’m ready.

Thursday, March 19, 2015

The Great Heirloom Apple Adventure: Part II of…?

Posted by: Deryn Davidson, Boulder County Extension

The first entry of this adventure blog left us having learned a bit about the history of apples in Colorado and the folks who were instrumental in bringing them here. As I continue down the path of knowledge, I have met some very interesting folks who are instrumental in keeping the memory of these old varieties alive.

At the ProGreen Expo in January 2015, I attended a talk titled, “Heirloom Fruit Trees of Colorado”.  The speaker was Jude Schuenemeyer of Let itGrow Nursery and the Montezuma Orchard Restoration Project (MORP).  Jude gave a great presentation advocating for these old varieties and telling stories from his own orchard and the work he is doing to preserve them.  He asked the audience, “Why don’t you eat Colorado apples?” (Hmmm. An interesting question. Perhaps one that I will get into more in Part III.) If you go to the MORP website, you will see:

“The MORP is working to preserve rare fruit genetics, revive historic orchards, plant new orchards, research the history of heritage orchards, provide orchard education, and foster the blossoming of a new fruit economy in Montezuma County.”

How fantastic! These folks are passionate about heirloom varieties and keeping the history alive. Their interest lies not only with apples, but also peaches, cherries, pears and plums. Their location in southwest Colorado  is great for this project since at one time it was noted as being “the most  favored district in Colorado” for fruit growing potential. 

John Chapman
a.ka. Johnny Appleseed

The next character in this story is Scott Skogerboe. Many of you may know Scott, he is the Head Propagator at Ft. Collins Wholesale Nursery working with all types of landscape plants, including Phellodendron...but that's a story for another time. One of Scott's passions is old apple varieties. Back in February I was lucky enough to spend an afternoon with him walking around looking at some of his trees and listening to his stories. He is a true plantsman and historian. One of the things that amazed me about talking to Scott was how he is able to remember all of the many, many stories that go along with each variety. He has traced the history of the Hung Hai Tung crabapple back to a Buddhist temple in the Yinshan Pagoda Forest near Beijing China and the Goodhue apple to T.E. Perkins in Goodhue County, Minnesota (just to name a few). All of these stories are fascinating to listen to. When you know the history of these trees, it makes your connection to them more personal. Speaking of personal, Scott is responsible for preserving the lineage of one of the trees that Johnny Appleseed himself planted!! How cool!!

One of the properties owned by Masonville Orchards
Finally, I spent some time with Walt Rosenberg, another local apple expert (I don't know if he'd call himself an expert, but I do). Walt owns and operates Masonville Orchards. They have several properties along the Front Range, the first of which was in Masonville, CO (hence the name). I visited their  Ft. Collins nursery out east of the Budweiser Brewery. This orchard is in a pretty idillic setting with incredible views of the mountains. He specializes in "antique, heirloom and unique apple and pear varieties". Walking through the orchard with Walt was a huge lesson in all the different varieties that he grows. As we walked he explained some of the business side of owning an orchard that focuses on heirlooms and how that differs from a grower who only has 5 or 10 more conventional varieties (he has 150!!). His really is a niche market, and one that suits him well. As we passed each variety, he told me about the unique characteristics and why he likes them all. The Pristine has a lemon taste, the Prisilla tastes like licorice. Yellow T makes good sauce and the Scarlet Surprise... well, Walt called it the coolest apple on the planet. Apparently, when you bite into it, it fizzes, as if it were carbonated!! I can't wait to get to the Farmer's Market this year to wait in line for one of those!! Maybe that's the next step in this adventure...finally getting to EAT some of these apples!!

Saturday, March 14, 2015

Put me in coach! I'm ready to play!

Posted by: Alison O'Connor, horticulture agent, Larimer County

Me. As a Smurf. See those skinned knees?
This is my favorite time of year. Yes, it's almost gardening season...but even better is the non-stop sports action that currently inundates our lives. I'm talking March Madness, the Masters and the beginning of the baseball season.

I'm a Minnesota native and I love our (now) terrible sports teams. I still remember when I was 7 years old and the Twins won the World Series for the first time in 1987 (they won again in 1991). Mom let my brother and me stay up late to watch Kirby Puckett, Dan Gladdon and Kent Hrbek bring home the Commissioner's Trophy. Everyone was so excited at school the next day that the teachers had a hard time keeping us on track.

In 2010 the Twins built their new outdoor stadium, Target Field. I was there for the sodding of the field and it was exhilarating. In case you didn't know, Graff's Turf Farms in Fort Morgan, Colorado grew the turf for the field. Just this week, my dad texted me to tell me that Larry DiVito, the sports turf manager for Target Field, had taken off the turf cover. The Twins will open on April 13 against the Royals, who, as you may remember, played last in the World Series. Let's hope that new manager Paul Molitor will bring home a win. Maybe his new cell policy will help.
Target Field for the 2014 All-Star Game (photo from
Other stadiums have made the news this week, like Fenway Park in Boston. The sports turf manager there, David Mellor, was dealing with feet of snow on the field and he enlisted the help of black sand to hasten the snow melt. Unlike Target Field, Fenway doesn't have field heating (though it should be mentioned that field heat isn't used to melt snow, rather to keep the soil from freezing). So while Target Field has the "Cadillac system", Fenway staff had to resort to innovative technology to melt their record 4.5 feet of snowfall to be ready for the Red Sox opening day on April 13.
It's not "dirty snow" but black sand spread over the top to aid in snow melt.
(Photo courtesy of David Mellor)
The outfield fence and Boston's record-breaking snowfall in 2015.
(Photo courtesy of David Mellor)
Also in the news was the U.S. Cellular Field (home of the Chicago White Sox). Their field was frozen solid. This is also a stadium without field heat. So the Chicago field manager, Roger Bossard (AKA The Sodfather), has kept the field tarped while blowing hot air underneath to gently warm the soil. According to Bossard, he says, "Last year I had 30" inches of permafrost. I do have about 15" now. I'm throwing heaters underneath my tarp and then I'm putting heaters in my drainage system, which is something I've never done before." The White Sox will host the Twins on April 10 for their home opener. 
The Sodfather himself, Roger Bossard, standing on his frozen field in 2013.
(Photo from 
Here in Colorado, the Rockies are fortunate to have a newer stadium with field heat and Mark Razum has likely taken a leisurely vacation to spring training in Arizona, simply because Colorado has had a very mild winter.
Mark Razum is grateful he didn't have to deal with permafrost or 4.5' of snow in 2015.
(Photo from
So no matter what baseball team makes you cheer (or hang your head in shame), give the sports turf managers credit for getting the fields green and glorious in early April. And now for a song all Minnesotans should know: "We're gonna win Twins, we're gonna score! We're gonna win Twins, watch that baseball soar! Crack out a homerun, shout a hip-hooray! Cheer for the Minnesota Twins to-day!" (Yes, it's darn catchy. Yes, it will stay in your head.)

Friday, March 13, 2015

Warm soil jump starts spring

Posted by Carol O'Meara, Horticulture Entomologist, CSU Extension Boulder County

For gardeners, seeing the first, green shoots of spring is like hearing the NASCAR announcement “Gentlemen, start your engines.”  Our engines rumble, our minds become sharply focused.  We act like rookies on the line by digging a bit too early, our eagerness to get started getting the better of us.

If you’re itching to plant, get a jump on the season by warming your soil.  With a few simple tricks, you can get your spring salad off to a quick start.  Before you start, a note of caution:  make sure you’re not working wet soil.  Turning it can damage the tilth of soggy ground. 

One of the simplest ways to warm your soil is covering the ground with plastic sheets. Use 6 mil or thicker, UV resistant clear or black plastic and lay it over the soil, weighing down all edges with rocks or soil to prevent winds from whipping it up, up, and away to Kansas.  Alternately, you can anchor it down with wire U-shaped pins.

Check the soil after ten days to see if it’s warmer; for germination of cool season vegetables the minimum temperature needed is 40-degrees F.  Typically, it takes two to three weeks for it to rise, depending on the soil type. Sandy or manufactured "planters mix" soils warm faster than wet, heavy clay. 

If you’d like to speed the process, combine the plastic cover with an insulating layer.  Using only clear plastic, lay a sheet on the ground, anchoring it as described above.  Then drape a second layer of clear plastic slightly above the first, using bricks or other objects to make a small space between the two layers.  Anchor the second layer securely, by tucking its edges under the bricks or by weighing them down on the ground.

To plant, fold back the plastic drape and remove the plastic sheet covering the soil, cleaning, drying, and folding it away for use another time. Plant seeds of lettuce, radish, kale, collards, cabbage, broccoli, spinach, peas, onion and carrots and then replace the plastic drape over the spacers, creating an impromptu cold frame, anchoring the cover securely so it remains to keep the seeds snugly warm in the bed.  There is no need for a plastic sheet on the soil once seeds are planted.

Patience is required when warming the soil as seed take longer to germinate at minimum soil temperatures than they would later in the spring.  Leaving the plastic on until the temperatures have risen higher than 40 degrees won’t take much more time and you’ll be rewarded with better germination if you wait.   Monitor soil moisture and add water as needed.

Watch the weather and your plants closely; once the weather warms, the plastic tenting will trap heat and can reach temperatures hot enough to sizzle your plants.  Open the cover on sunny days, partially folding back the cover and clipping the flap to prevent it from whipping in the breeze and tearing.  Be sure to close the cover in the late afternoon to retain heat.

When the weather has warmed, remove the cover gradually over a week to harden off the seedlings.  Provide wind protection to keep the worst of spring away from them by making a low wall from straw bales or plastic.

Thursday, March 5, 2015

Learn How to Graft Apple Trees

Posted by: Curtis Utley, Jefferson County Extension

One of the most fantastic horticultural tools discovered by man has to be the art of grafting. The ability to attach a piece of one tree to the branch of another is nothing short of magic. Detached scion grafting was discovered sometime during the first millennium B.C. and contributed to the movement of woody tree fruits out of Asia and into Europe along the silk road (Mudge, K. et al 2009). For Centuries now mankind has been able to perpetuate superior clones of tree fruits by removing a twig or bud from a superior mother plant and attach that twig or bud to a seedling of the same tree species. The result is a replicate of the mother tree growing on the root system of a seedling tree of unknown fruit quality.
Macintosh branch grafted onto Crabapple 
 The practice of grafting is not reserved for fruit trees alone however; many horticultural plants are also reproduced by grafting the most common example is the production of hybrid tea roses. Before the development of tissue culture, the fastest way for a horticulturist to rapidly build up the inventory of a newly discovered rose or other woody plant was by bud grafting. The bud grafting technique is great because the grafter can produce a new plant from a single vegetative bud. If the bud is attached to a large and vigorous rootstock, the plant will often be ready for sale following one season of growth. Grafting is not the only way to produce clones, many plants including roses can be cloned by rooting a cutting. The advantage of grafting is the horticulturist can produce much larger clones and many more of them in a shorter length of time.
Hybrid Tea Rose
Chip bud grafting

Other advantages of grafting include size manipulation, avoidance of juvenility, disease and abiotic stress resistance, damage repair, and the creation of unnatural growth forms. Orchardists and home hobbyists alike have found dwarf fruit trees advantageous. Producing full size fruit on a small tree allows an orchardist the opportunity to plant multiple varieties in the same space it would take to grow one full size fruit tree.  Dwarf fruit trees are also much easier to manage and pick than full size trees. Many fruit bearing trees grown from a seed will not begin bearing fruit until they are mature this is called juvenility. Grafting mature wood onto a seedling tree overcomes this natural habit and allows for fruit production a few years after grafting instead of 15 or more years for a seedling tree to come into bearing.
Production orchard dwarf apple

 Starting in the Twentieth Century research scientists began actively selecting under stalk of horticulturally important crops for resistance against, disease, insect pests, drought, and soil issues allowing these crops to be grown more widely. Even annual crops such as tomatoes and watermelons have been grafted onto hearty rootstocks that have been selected for resistance against soil borne pathogens and greater production. 

Dwarf  limber pine
Grafting also allows horticulturists to produce unique unnatural ornamental growth forms, think of weeping mulberries, weeping cherries, tree form roses, and bonsai conifers.  The last reason for grafting I’ll mention is a technique called inarching. Inarching is a rescue operation orchardists use to save trees that have been girdled by rodents or attacked by a root fungus. New resistant root stock trees are planted directly beside the suffering orchard tree the top of the small rootstock tree is cut off, whittled into a chisel point and inserted (by bending the stem) into a slot cut into the trunk of the suffering tree. When the graft union takes the new rootstock serves as a bridge across the damaged lower trunk or disease ridden root system.
Whip graft

Whip graft budding strip
Successful whip graft union
If you are interested in learning how to graft woody plants I will be teaching a hands-on grafting workshop open to the public on March 31. The workshop will be held at the Jefferson County Extension office located at the Jefferson County Fairgrounds. Participants will be producing their own grafted apple tree to take home and plant. Dwarfing rootstock and a variety of apple cultivars to select from will be provided to participants. This workshop will be repeated April 1 and again on April 2. This workshop costs $20.00 per person, space is limited and reservations are required. 

The Jefferson County fairgrounds are located at: 15200 West 6th Ave., Golden, CO 80401

Citation: Mudge, K. et al. 2009; A History of Grafting. Horticultural Reviews, Vol. 35; John Wiley &Sons, Inc.  

Monday, March 2, 2015

Learning about Native Plants with the Native Plant Master® Program

 by Irene Shonle, CSU Extension in Gilpin County

Colorado is known for its colorful wildflowers.  Some of the earliest treasures start blooming as early as February in warm pockets by rocks at lower elevations, and the wave continues upwards throughout the season with fields of flowers in the high country, and back down to the plains again for a fall show featuring sunflowers and grasses.  
WIldflowers in Colorado's High Country
If you want to become more familiar with these beauties, consider taking a Native Plant Master Class this summer. Participants will be involved in field courses discovering the names of trailside wildflowers while learning how to recognize plants, demystify special botanic terms, understand pollinator interactions, use natives in garden settings, and how invasive species impact the landscape.  There are also special classes explore more in depth plant topics in indoor and outdoor settings.
There are programs across the state; go here to find one near you:

For a full list of events in the Denver Metro Ares, go to For questions contact Lisa Vernon, native plant master program assistant at 303-271-6620 or

I’d like to feature some special classes that will be taught in the very near future by Dr. George Beck, Colorado State University weed expert at the Jefferson County Extension Office:

Exploring Herbicides used to Manage Invasive Weeds on March 5, 9 a.m. to 4 p.m.  This class is for weed managers and others that manage small and large acreages that have problems with invasive weeds.

Introduction to Invasive Weed Management on March 26, 9 a.m. to 4 p.m. This special class is an introduction to invasive weeds and is for anyone interested in controlling invasives, especially those with small acreages.

Bull thistle, a noxious weed

If you want to explore plants now, even while the snow is flying, you can browse the Colorado Plant Database at for research-based information on more than 1,000 Colorado plants.