CO-Horts Blog

Thursday, August 29, 2019

A Selection of Indian Paintbrush of the Southwest Colorado Mountains by Yvette Henson

Indian paintbrush has always been one of my favorite wildflowers.  When I was living I Louisiana, homesick for summers in the southwest Colorado Mountains, I often dreamed of Indian paintbrush and columbines.  Now, I am fortunate to live in the SW Colorado Mountains again and this summer I have been even more infatuated with our Indian paintbrushes.  I will share the species I have seen this summer in this blog post.  I would love it if those who read this blog will post pictures of the Indian paintbrushes they have seen in the comments. 

Indian paintbrushes are in the genus Castilleja, named for the Spanish botanist, Domingo Castillejo. Without getting into the details, the genus Castilleja has recently been moved from the Scrophulariaceae family to the Orobancaceae family.  One of the reasons is its semi-parasitic nature.  If you want more information, research the work botanists are doing for the Flora of North America, etc. using plant DNA and not just morphological characteristics to classify plants.  For the plants featured in this blog post, I have used the scientific names found in the Flora of Colorado by Jennifer Ackerfield.  

Our native paintbrushes possibly sometimes cross, making them difficult to identify at times.  I will do my best to correctly identify the paintbrush in this blog post.  One thing that helps to identify them is the habitat they are growing in.  There is also often a range of color in plants of each species.  The colored portion that attracts us is actually not the corolla of the flower but are modified leaves called bracts.  This is a photo of an actual corolla with sexual parts inside (Castilleja miniata).   

Castilleja corolla including sexual parts

Indian paint brushes are semi-parasitic on the roots of other plants, which is important if  you would like to try to grow them from seed.  They often need a host plant to germinate and grow on.  

To most of us, the red colored paint brushes, are what come to mind when we ‘picture’ Indian paintbrushes.  In fact the reds are the most common and abundant. 

Castilleja chromosa, desert paintbrush, can be found growing in spring, from desert to montane, often in sage brush habitats.  Sage and blue gramma grass are two of the species it is semi-parasitic on.  It is usually under a foot tall and can grow into a wide clump.  The leaves and bracts are softly hairy.  

Desert Paintbrush, Castilleja chromosa

Castilleja linariifolia, Wyoming paintbrush, can be found blooming in the summer from foothills to montane with sage brush, pinion and juniper and ponderosa pine.  Sometimes it can be found growing with aspen.  It is the most common Indian paintbrush in Utah and is the state flower of Wyoming.  Its stiff stems are 2’ tall (or more), sometimes branched, with narrow, usually entire leaves.  The bracts are orangish-red.  

Wyoming paintbrush, Castilleja linariifolia

Castlleja miniata, scarlet paintbrush, grows in moist montane and subalpine forests and meadows. Its stems are usually unbranched and more ‘pliable, with wider leaves than C. linariifolia.  The upper leaves and lowest bracts are often divided into three lobes, the center lobe being the widest.  The color of its bracts can range from salmon-orange to pinkish-red.

scarlet paintbrush, Castilleja miniata

The next three species may cross and some botanist even think they could be the same species.  But for now I’m going to try to keep them separate.

Castilleja septentrionales, northern or sulphur paintbrush, is found in montane and subalpine forests and meadows and along streams in summer.  It has white to yellow bracts and dark stems.  It is 1.5’ tall on average, taller than the next species, C. occidentalis

Sulphur paintbrush, Castilleja septentrionales

Castilleja occidentalis, western or alpine paintbrush, is abundant all summer in dry to moist subalpine meadows and most often in the alpine tundra, where it often grows with C. rhexifolia.  It has creamy- yellow bracts and dark, smooth stems but is usually only about 6-8” tall. 

western alpine paintbrush, Castilleja occidentalis

Castilleja rhexifolia,  split-leaf or rosy paintbrush, can be found blooming from snow-melt to frost in moist subalpine to alpine tundra, along with C. occidentalis.  The bracts are many shades of fushia-pink.  Not only does it reportedly cross with C.  occidentalis, making some interesting color combinations, but it apparently can cross with C. miniata as well.

Rosy paintbrush, Castilleja rhexifolia, showing variation in color

Castilleja rhexifolia and Castilleja occidentalis  hybrid?
Who knows how botanists will classify these several Indian paintbrushes in the future, whether they are different varieties of the same species or still seen as separate species.  Regardless, they are some of the most abundant and iconic wildflowers of the Southwest Colorado mountains and will remain some of my favorites!   

Friday, August 23, 2019

What are those spots on my aspen?

Posted by: Todd Hagenbuch, Routt County CSU Extension Agriculture Agent

This summer, our office has been flooded with calls about aspen that are looking poorly.  Most often, the first thing a homeowner notices about these trees is that the leaves are starting to get spots on them.  As the condition persists, the spots can cover the majority of the leaf, and leaves become shriveled.  Often times the leaves look dead, and then they fall off. 
As you can imagine, watching the leaves on your tree go through this transformation can be quite alarming.  Most people call the office saying, “My tree is dying!” When I or one of our Master Gardeners take a look at it, we see that the tree is being harmed by Marssonina leaf spot, an all-too-common fungal disease that occurs on aspen and cottonwood.
Marssonina leaf spots are dark brown flecks, often with golden yellow halos.  Immature spots may have a white center. On severely infected leaves several spots may grow together to form large black or brown  patches. 
Marssonina leaf spot on aspen leaves
Photo courtesy of Routt CMG Vicky Barney
Marssonina is a fungus that is always present in our mountain areas. The spores (or 'seeds') the fungus produces survive the winter on fallen leaves that were infected the previous year.  When spring arrives and the temperatures increase, the fungus produces new spores that are carried by the wind and land on new, budding leaves. Wet weather in the spring increases the number of spores present.
Early infections are typically not serious, but if the weather remains damp, spores from the original infection can spread and cause significant secondary infection. These secondary infections are noticed later in the growing season and create the large, dead patches on the leaves mentioned above. As the leaves are overcome by the fungus, they may fall off the tree. I assure people who have Marssonina in their tress that it rarely kills infected trees; its damage is mostly aesthetic.
As you can imagine, the wet weather we’ve had this summer has produced an ideal situation for Marssonina fungus to thrive, meaning we’ve seen more of it this year than usual. I also suspect we may not have a spectacular fall since many aspen leaves are compromised by the fungus.
Because the fungus overwinters on leaf debris on the ground, rake up your fallen aspen leaves every fall to reduce the incidence of the disease. However, this is only effective if you have a solitary stand of aspen in your yard. If your neighborhood has a lot of aspen or if you’re next to a natural stand, raking up the leaves will not significantly reduce the number of spores that could re-infect the tree next year. 
There are fungicides you can apply to the tree at bud break in the spring time that will control Marssonina. We rarely recommend this because the disease is mostly aesthetic and it doesn’t usually harm the tree. To help reduce the spread of the spores, try to keep leaves as dry as possible to reduce the incidence of leaf spots by measures you can control:  water your lawn and garden in early morning so leaves can dry out, and keep sprinkler patterns adjusted so leaves don’t stay wet.
So, what does next year look like? The reality is, if next spring is wet, then Marssonina be back. If we have a drier spring, then we should get through the season with little impact. Either way, the aspen will still turn gold each autumn and provide beautiful displays, even if the colors are muted this year. 

Thursday, August 15, 2019

Planning Ahead

By Andie Wommack, Douglas County Extension

While it’s still too early to be planting bulbs in your garden, it’s never too early to be thinking about what you might like to plant. The growing season this year was much different than ones we’ve seen here on the Front Range in the past few years. Some plants thrived with the cooler temperatures and extra moisture at the beginning of the season, and others struggled. Are you noticing some bare spots in your landscape, or are there areas you’d like to renovate? Bulbs can offer a variety of color and interest to your landscape.

Early September is the best time to buy bulbs to be planted from mid-September through late October. Bulbs need time to root before the ground freezes or they may not bloom uniformly in the spring. Did you know that bulb size has a direct correlation with flower size? That’s why it’s best to be able to choose bulbs from open bins rather than prepackaged bulbs, so you have more control over the product quality. This also allows you to inspect each bulb for any damage or mold.

Have you ever thought about, or wondered where these bulbs come from? They’re grown on farms just like other crops. Bulb farms are popular tourist attractions when the flowers are in bloom. Holland is one of the most famous locations for bulb farms, but there are plenty in the states as well.

Western Washington is home to several different bulb farms. I lived near several during my student teaching. Thankfully I did my student teaching during the spring semester so I had the opportunity to attend one of their festivals. Online resources say that planting solid blocks of color are more impressive from a distance than a mixture of colors and varieties. This is true in a home landscape, and it is immensely impressive on a large-scale bulb farm.

Monday, August 12, 2019

Fall pollinator feast by Irene Shonle

Many of our gardens peter out in the dog days of summer. We go great guns in the spring, snapping up anything that is blooming at the garden center, desperate for the color after a long winter.  But we often forget that summer keeps going, long after we have wilted.
And this can be a problem for pollinators - they need to find nectar and pollen for the entire season, not just the spring.

Here are some suggestions for fall blooming plants that will keep your pollinators happy until frost:

First, some native suggestions:
Showy Goldeneye
Showy goldeneye (Viguera multiflora). These plants cover themselves in small yellow blooms that butterflies and bees visit. Bonus points: they also provide seed for small songbirds later in the season.

Tansy aster
Tansy aster (Machaeranthera bigelovii). Short lived perennials that love dry disturbed areas, and keep out noxious weeds.  Super easy.
Gumweed (Grindelia squarrosa).  Just as easy as useful as the tansy aster for pollinators - and if you plant them together, you have a vivid combination!

Goldenrod (Solidago spp.) This maligned plant is not the allergy culprit that many people believe, and it is one of the top host plants for native bees!  Easy to grow.

Rabbitbrush (Chrysothamnus spp.). These plants are known for their brilliant fall blooms as well as being a butterfly magnet.  Good winter interest to boot!

Spotted gayfeather (Liatris punctata). Beautiful feathery wands of purple also lure in butterflies.

Maximilian sunflower (Helianthus maximiliana). Tall and narrow, this plant is covered with showy yellow sunflowers for pollinators (and later for birds). Very drought tolerant.

And then some non-native suggestions

Russian sage (Perovskia atriplicifolia) is a bit overused, but is good for dry spots and for pollinators. Can spread a little more than you may like.

Coneflowers (Echinacea spp.). Most aren’t native to Colorado, but they are sure to draw lots of butterflies and bees.  Many, many cultivars and colors to choose from.

Catmint (Nepeta spp). I would suggest using a sterile variety such as Six Hills Giant. If you cut them back after their first flush of bloom, they usually rebloom. Bumblebees love them, and deer and rabbits leave them alone. Drought tolerant.
Catmint Six Hills Giant with a happy bumblebee

Fall blooming sedums such as Autumn Joy (Sedum spectabile). These are drought tolerant low-growing plants with clusters of pink flowers beloved by butterflies.

Zinnias - very colorful annuals (grow from seed) to attract butterflies and bees.

Mark your calendars and save the date! The 5th annual Landscaping for Colorado Native Plants will be at the Auraria Campus on Feb 29th! Leap into gardening with native plants!

Thursday, August 8, 2019

When to worry about evergreen needle drop

By: Emily Jack-Scott (Garfield County Colorado Master Gardener)

In late summer and early fall evergreen trees often have needles that dry out and shed. This can be alarming for gardeners, and it can be difficult to tell if early needle drop is cause for concern or just part of the evergreen tree’s annual needle shed. In this blog post we’ll review some signs and symptoms of when summer needle drop in evergreens could be indicative of underlying health problems.

It is typical for all evergreen trees to shed out old needles in the fall. Fall needle drop is usually preceded by yellowing of old (often interior) needles. Sometimes needle drop happens in early summer, especially if a tree has been recently transplanted. Trees can lose up to 90% of their roots when transplanted, which seriously hampers the tree’s ability to provide its needles with vital water and nutrients. Therefore it is common in the first few years after transplant for a new tree to have needles that turn yellow or brown weeks or even months before they typically do in fall.

Premature needle drop in newly transplanted evergreen trees is especially common in interior needles. Evergreen needles often turn a pale sickly shade of green during transplant shock. Once needles discolor, they never recover their original dark green or blue hues. Instead, the tree will retain the weakened discolored needles for several years until the tree has put on enough new healthy growth that it no longer requires the old weak needles for photosynthesis. At this point, the old interior needles will turn yellow or brown and soon after drop off. In spruces and pines, interior needle shed is common August – November. In these instances, summer needle shed is not usually cause for concern.

There are, however, some instances when summer needle shed and discoloration may be symptoms of more concerning health threats such as beetle activity, mites, fungal disease, root damage, or winter burn/injury.

Beetle Activity

When bark beetles such as mountain pine beetle or spruce beetle attack their respective host trees, they first chew through the bark and then tunnel around beneath the bark in the thin layer of the tree’s growing tissue known as the cambium. This can result in sudden red discoloration of needles (in pines), or slow and steady browning and dropping of needles (in spruces). To tell if needle discoloration is caused by beetle activity, look for other symptoms of bark beetles such as small entry holes in the tree’s trunk (with or without sap), fine sawdust (or frass) collecting in the bark or base of the trunk, and/or thin sap streamers dripping down the trunk of the tree.

Once trees have been attacked by bark beetles, there is little that can be done to prevent the decline and death of trees. But there are preventative sprays and pheromone packets available for trees that have not yet been attacked. These can be used in areas where bark beetle activity is high.


Another critter that can cause extensive discoloration of needles is the humble spider mite. Spider mites cause extensive damage and stippling to affected needles as they feed on their host’s sap. Colorado blue spruces are especially prone to spider mites. Webbing may even be visible on heavily infested branches. Improving the general health of affected trees is recommended. Miticide sprays are available to treat heavy infestations.

Fungal Diseases

Spruce and pine trees can be prone to several fungal infections that can lead to needle discoloration and early drop. One of these fungal infections is known as cytospora canker, which primarily affects Colorado blue spruces. Needle discoloration from cytospora is typically purple or rust-colored, primarily on lower branches of mature spruce trees. Cytospora canker also causes resin-covered cankers on affected branches.

Another common fungus in Colorado that can cause needle discoloration and shedding is rhizosphaera needle cast. Rhizosphaera needle cast primarily affects Colorado blue spruce but can also affect lodgepole and ponderosa pines. Needle discoloration caused by rhizosphaera will typically start off yellow in mid-summer, turning to reddish-purple in late summer, before turning brown and shedding out. Spruces and pines affected by rhizosphaera needle cast will lose their interior older needles, leaving only the current year’s growth (which has not yet been infected). Infected needles are often covered in tiny black dots running lengthwise, which are the visible fruiting bodies (pycnidia) of the fungus.

There are preventative fungicide sprays available that can prevent spreading of fungal infection to new growth and unaffected trees in the vicinity. Timing of these sprays is critical, so be sure to carefully follow fungicide directions. Cultural treatments such as removing fallen needles and creating better airflow through tree canopies are also recommended.

Root Damage

If the discoloration and shedding of needles occurs in a spiral pattern up the tree, there is a good chance the premature needle drop is the result of root damage. Trees tend to spiral slightly as they grow (twisting slowly over time in response to prevailing winds). So when a root is damaged, it is unable to provide vital nutrients and water to the living tissue it is connected to running up the length of the tree in a slightly spiraled pattern. This results in the spiral pattern of dieback from damaged roots.

Root damage can be difficult to troubleshoot, since they are not visible below ground. But common causes of root damage include root girdling, root severing/damage from digging (e.g. utility repairs or sidewalk installations), or damage from absorption of salt, chemicals, or pesticides. Needle drop from root damage can be isolated, and the tree will recover in time. The exception to this is when roots have been girdled, in which case the tree will continue to lose needles and will likely need to be removed if the girdling root(s) cannot be isolated and removed.

Winter Injury

Winters in Colorado can often be very cold, with heavy snowfall and strong winds. The thin wax coat on needles is all that protects evergreens from succumbing to harsh winter conditions. It’s no wonder that after particularly bitter winters, some evergreens show signs of winter injury by way of discolored needles. This can be especially true when affected trees endured stressful conditions in the summer growing season before (e.g. transplant, drought), limiting its ability to grow thicker waxy needle coatings. Winter injury can often present itself in a pattern, such as all the needles on the windward side of the tree showing discoloration. Discoloration from winter injury is often reddish-purple in hue.

This has been a review of some of the more common biotic or abiotic causes of premature discoloration and dropping of evergreen needles. There are other causes of needle drop, such as nutrient deficiencies and soil conditions that can also cause problems. If in doubt of the cause of your needle discoloration, contact your local Colorado Extension office or a certified arborist for more information or a site visit. 

Learn more: