CO-Horts Blog

Monday, July 29, 2019

A Good Time To Deadhead

Posted by Carol O’Meara, Boulder County Extension

  This summer has been glorious for flowers, thanks to wet, cooler weather for the first part of the summer.  Gardens are showing off, and with a little help from those who tend them, the flowers should have a spectacular second show.

Keep the bloom going with a simple, but necessary practice. Deadheading, as it applies to gardening, is the removal of flowers from plants when the flowers are fading or dead. If you’ve never done it, here are a few tips to keep it from being a long, strange trip through the garden.

The purpose of a flower is reproduction: attract pollinators by flaunting yourself, either with alluring scent or bodacious color. It isn’t an empty promise; usually, this is a win-win situation for pollinators, who collect pollen, nectar, or fiber from the proffered bloom. Once a flower has been pollinated, the plant produces fruit and seeds.

Deadheading redirects the plant’s energy from fruit swelling, ripening, and seed production into extended flowering. It cleans up the appearance of the plant, and in turn, the garden.

You can use a variety of methods to deadhead: snapping or pinching flowers off by hand, shearing, or clipping with pruners.  In all cases, it’s important to get a clean cut to prevent leaving an open ragged wound for diseases or pests to enter the plant.

Roses are a plant that responds well to deadheading. The American Rose Society recommends deadheading roses just before they drop their petals, cutting the canes at a 45 degree angle just above a 5-leaf set.

Plants such as lilacs and peonies won’t bloom again this season, but deadheading immediately after blooming cleans them up and keeps the plant healthy. Marigolds, verbena, nicotiana, petunias, columbines, and pansies also benefit from deadheading.

Bulbs should have flowers – but not leaves – deadheaded to keep them from expending energy on producing seed instead of storing it in the bulb for blooming next year. Cut back tulips, hyacinths, and daffodils before they begin to drop their petals or look faded and cut individual blooms off of the flower stems of flag iris and lilies as they whither, removing the entire flower stalk only after the last bloom is finished.

Get to know which plants have decorative seed heads after the flower is spent, like echinacea, alliums, and native grasses. The stalks and seed heads provide winter interest as well as important nooks for beneficial spiders to live within.  Leave flowers on fruiting shrubs so that the berries can provide winter interest and attract birds.

If you want some flowers to reseed, leave the flowers on the plant.  Poppies, foxglove, columbine, flax, and lupine reseed.  Their offspring might not hold the colors of the parent plant, though, so you won’t get an exact copy. 

Other plants can be thugs if allowed to reseed, such as some salvia, obedient plant, or cosmos.  To limit their spread, deadhead these plants. Compost the flowers unless they’re diseased. 

Wednesday, July 24, 2019

Roses are all the rage!

Posted by: Alison O'Connor, Larimer County Extension

I feel that roses tend to polarize people--some think they are amazing and wonderful garden plants (me!) and others feel they are too "needy" and hard to grow. I've had a love of roses my entire life, primarily because my Grandpa Stoven was an avid rose grower, and my dad has followed in his steps. Growing up in Minnesota, roses were not for the faint of heart. And to top it off--Grandpa Stoven grew hybrid teas, which are the ultimate Prima Donna of plants. His favorite was 'Peace', a tribute to the end of World War II and a beautiful bloom.
Peace hybrid tea rose (photo courtesy of Jackson and Perkins Roses)
Most of you know that my patience to baby plants is thin, so hybrid tea roses don't grow in my garden. My philosophy is that if you can't thrive on neglect, you're not a plant for me. But I do have several shrub roses, which I find to be easy to maintain, bloom profusely, and have little (if any) insect and disease problems. They really are easy to grow!

And yes, I know that Japanese beetles are munching their way across Colorado's Front Range, as far south as Pueblo. Roses are one of their favorite hosts, but our state entomologist, Dr. Whitney Cranshaw is evaluating roses to determine if there are cultivars that are less tasty to the hungry beetles. He's been studying this for a few years and has some promising results. For those in infested areas, I realize roses are not going to be at the top of your list, but hand picking can be very effective. Or pick and feed to chickens--they love to munch Japanese beetles and will eat them faster than you can pick them.
Chickens adore Japanese beetles (photo courtesy of New England Habitat Gardening Blog)
Larimer County Master Gardener, Roger Heins, is our rose expert, so I consulted him to see what he would recommend if someone wanted to plant roses. His own garden has dozens of specimens, plus he's been active in the rose demonstration garden at Treasure Island in Windsor. Here's our top recommendations:

Above and Beyond climbing rose (Rosa 'ZLEEltonStrack' PP24,463)
I absolutely adore this rose. And yes, it's a climber, so it needs some support. But what I've found after three years in the garden is that it just needs a little training in the spring and mid-summer. My dad is growing this in his Zone 3B garden north of the Twin Cities. This past winter it had very little dieback and had a magnificent bloom set in early summer.
Above and Beyond in full bloom in June
I have seen zero disease and zero insects, and it's super cold hardy. Height can reach 10 feet, so make sure you give it space! The apricot-flowers bloom in clusters and look like a double flower. It will bloom again later this summer, but the foliage is so clean that's it's just a beautiful plant any time of year. I did quickly snip off the spent blooms, not paying attention to the "rule" of pruning back to five-leaflets.
Above and Beyond in mid-July
Paint the Town shrub rose (Rosa 'BAItown' PP18,060)
Paint the Town is cute as a button, since it's a petite shrub rose that doesn't know when to stop blooming. I have this in my front, west-facing yard, and it gets very little (if any) irrigation. The red blooms cover the shrub all summer and stay a good red, even with the intense sunlight. Topping out in height at four feet (and about the same width), this rose can fit in small spaces if you need some color. The foliage is very dark green and I have seen zero disease issues. My brother has propagated this plant for years at Bailey's and it's on the top of his list too, since he doesn't see any disease issues in the greenhouse. In the photo below, it's planted next to hummingbird carpet, a 'Blonde Ambition' grass, and hopflower oregano. As you can see, it's just a bit taller than each of those. You can remove the spent flowers, if you wish.
Paint the Town shrub rose
Paint the Town flower bloom (just past peak)
Strike it Rich grandiflora rose (Rosa 'Strike it Rich')
Roger said this rose is performing amazingly well in multiple locations, so it's on the list. A grandiflora rose, the blooms are larger (about 4" tall) and have a spicy-sweet fragrance. The blooms are a beautiful orange with hints of pink. Introduced back in 2007, this rose has been a garden favorite for over a decade. Don't shy away from grandifloras...they can replace those high-maintenance hybrid teas with less work. And this rose is very cold hardy too.
Strike it Rich rose (photo courtesy of Destinations, Detours, and Dreams)
Golden flowers make this rose a must for your garden (photo courtesy of Edmunds Roses)
Sunrise Sunset shrub rose (Rosa 'BAIset' PP16,770)
There must be something in the water at Roger's house, because his Sunrise Sunset roses are breathtaking...and big! (Roger tends to both fertilize and water, which might be why his are superior to mine.) This non-stop summer bloomer has bright pink blooms that fade to a paler pink as the blooms age. This plant is truly a show stopper. Cold hardy, disease resistant, clean foliage--what more can you ask for in a rose? 
Sunrise Sunset rose (photo courtesy of Easy Elegance)
Bloom for Sunrise Sunset rose (photo courtesy of Easy Elegance)
Drop Dead Red floribunda rose (Rosa 'WEKcharlie' PP22571)
Described on one of the grower's websites as "jaw-droppingly delicious red", you can envision the bloom before you see the photo. Roger states that this is a fantastic red, especially with the dark green foliage. And it's a red that stays red throughout the entire bloom life. As a floribunda, it will produce clusters of flowers. But if you lust for a good red (like finding the perfect nail polish red), try Drop Dead Red.
Drop Dead Red floribunda rose (photo courtesy of Spring Hill Nurseries)
Obviously there are many roses out there that do well in Colorado gardens. What are some others you love? 

Thursday, July 11, 2019

Who's That Larva?

Posted by Sarah Schweig, Broomfield County Extension

Insects that undergo complete metamorphosis will go through a larval stage or stages in which they are unrecognizable from their future (adult) selves. It can be tough to identify larvae, but it’s important for a few reasons. While adults may be more familiar to us, larvae can make their mark on their environment, whether positive or negative, because they’re such voracious eaters. Larval and adult stages often have different roles in the environment as well. Some adult lacewings, for example, prey on garden pests as adults, but many subsist mainly on pollen and nectar. Green lacewing larvae, however, are sometimes called “aphid lions” for the quick work they make on the pests, and in fact they’re generalists and will prey on plenty of other unwanted garden guests as well. We've seen lots of interesting larvae lately - here are some highlights!

Carpet beetle larvae found in a camper van

Dermestid beetles are found throughout the state. While some like those of the genus Dermestes feed on meat-based materials, others like Anthrenus species can feed on wool-based furnishings, thus their common name, carpet beetles. They can be a pest in homes but are beneficial to natural ecosystems where they recycle nutrients by feeding on decaying matter.

Elm leafminer larvae in Siberian Elm

Elm leafminers (Kaliofenusa ulmicreate blotchy leafmines as the larvae eat and develop in elm leaves. Once the larvae are fully grown, they drop from the leaf to the ground where they pupate until they emerge as adults the following season. Some seasons are worse than others, but there is only one generation per season, and the damage is usually just an aesthetic concern.
Corn earworm pupa found under soil in vegetable garden

So no, this is not a larva, but this pupa steals the show for July. Corn earworms (Heliothis zea), are also called tomato fruitworms or cotton bollworms, depending on who they're bothering. The larvae are an important pest of all of these crops, and they pupate beneath the soil before emerging as adults. A closely related pest, which looks very similar at this stage, is the geranium budworm (Helicoverpa virescens). Both have multiple generations in a season, and the pupae can overwinter in mild climates or years.


Tuesday, July 9, 2019

Best of the 2018-2019 CSU Cool Season Trial

Posted by Jim Klett

Growers, landscape contractors and homeowners will want to plant some of these winners in their gardens in the fall of 2019 from our 2018-2019 Cool Season Trials.  These trials included 121 different varieties of cool season plants.  These plants were planted on October 30, 2018 and grown through the fall, winter and early spring of 2019.  Additional water was added to these trial a total of ten times from October 30 through early April.  Watering was done when temperatures were above 40 degrees Fahrenheit and soil was dry.  Our lowest temperature recorded during the period was -8 F in early March.  We recorded frost damage, flowering data and overall appearance on a weekly basis when not covered in snow.  We had below average snow cover during the winter months which resulted in some  damage to the plants but provided a still provided a good trial as the winners that follow are truly the "toughest of the tough".

The Flower Trial Garden Committee evaluated these Cool Season Trial in May 2019 and picked the following six top performers.  The six winners include:

Cheiranthus 'Sugar Rush Orange' from Floranova

Plants were noted for superior cold hardiness and good uniformity. Would make a good companion plant for pansies. Provides color for both fall and early spring. Flowers are attractive with shades of orange and yellow. Plants had an attractive busy growth habit and dark green foliage.

Dianthus 'I.Q. Blueberry Picotee' from Floranova
Great uniformity even after a very harsh winter made this the best Dianthus in the trial. Plants had abundant bud count and excellent vigor with attractive green foliage.

Viola 'Admire® Deep Purple Face' from Benary

The rich, velvet purple flower color was very impressive. Prolific blooming and a mounded growth habit made a great looking plant. Plants were a little more upright and very uniform overall.

Viola 'Fuseabes® Sunny Skies' from PanAmerican Seed

Flowers were noted for their attractive blend of blue and yellow flowers that can't help but "create a happy feeling". Plants were very uniform with excellent vigor and great flower coverage. Nice mix of flowers also produce labor savings for growers that don't have to combine other plants to create the same effect.

Pansy 'Joker Mahogany-Gold' from Benary

Vibrant flowers had an impressive contrast for a very bold appearance. Blooms were noted for standing up with their face held upward to create maximum flower power. Plants had excellent winter survival and were very uniform overall.

Viola 'Admire® Deep Purple Face' from Benary
The rich, velvet purple flower color was very impressive. Prolific blooming and a mounded growth habit made a great looking plant. Plants were a little more upright and very uniform overall.

A wet, cool year isn't always good news for gardens

A wet, cool year isn't always good news for gardens

Darrin Parmenter

If you live in the southwest corner of the state and still read a newspaper, you may have noticed that our climate and/or environment tend to be pretty common topics (as does my use of parenthesis). But really, as gardeners, or farmers, or landowners, so much of our success is based off of: a) if Mother Nature is nice or naughty; or b) how we adjust for her naughtiness without making her more upset. 

2019 is one of those years – nice and well, the consequences of that kindness. Yes, snowpack was amazing this past winter and spring. Snow is still melting, rivers and creeks are still running high, and reservoirs are continuing to fill at a very quick rate (and it’s the first week of July! And I’m using more parenthesis!). 

But along with all that moisture came a relatively cool and wet spring and early summer. The high temperatures in May were 7 degrees cooler than normal; in June, they were 4 degrees cooler. Many of you experienced a frost (or even a freeze) on June 23rd. During the last week of June we had an average daily temperature difference of 36 degrees. So after a couple cold nights, our tender annuals and vegetable that survived the frost have had a tough time getting going again.

You know what else came with the all this winter and spring moisture, cooler than normal temperatures, and higher than normal relative humidity? Telephone calls, emails, samples, site visits, and photos. 

If you like plant diseases, insects (and I do) and weeds (I don’t), well, 2019 is your year. We started with carpets of purple mustard (Chorispora tenella) that blankets our fields and then moved onto that relatively rare, and eventually annoying, mountain cicada (Okanagana bella).

They do little or no harm to your plants (although we have witnessed some wounding by females laying eggs in soft-wooded trees and shrubs) even though they are one of the larger insects you will find in Colorado. Apparently, they emerge every 3-5 years, however this is the first time I remember seeing them, and I’m old. What we are hearing are males trying to attract females.

Aphids and thrips have also been impressive this year, and while aphids are not uncommon in our annuals, perennials, and trees, thrips in the garden 
(and not just in the annuals that come from greenhouses) are relatively rare and unfortunately tough to control. Try insecticidal soaps – or a jet stream of water from the hose – to keep numbers down. Just know that both insects lay a lot of eggs and can also utilize a form of asexual reproduction called parthenogenesis in which an adult female can lay an unfertilized egg to develop into a genetically identical female offspring.

Because of our low relative humidity and the fact that we have a cold winter, fungus and bacteria are typically not an issue. But guess what? Not this year! I’ve seen bacterial issues on tomatoes, peppers, and even landscape ornamentals. Cedar-apple rust is showed up as orange globs in the junipers this spring and can potentially harm our apples, pears, hawthorns and other plants in the rose family. When you see those gelatinous masses in the trees, prune them out and stop the cycle. 


And lastly, and probably most impressively, I just got a photo of slime mold which was awesome! Also known as “Dog Vomit Fungus”, this mass (about 1 foot wide and 1 foot tall) probably formed where there was a lot of moisture. They don’t cause any problems, but sure are attractive to kids with sticks or fingers or adults with weed whackers (or sticks or fingers). Or so I’m told…