Thursday, July 19, 2018

Spiders in the Garden

Posted by: Jessica Wong, Master Gardener Coordinator, Broomfield County Extension

Spiders may be one of the most important and abundant biological control agents in our gardens. They are generalist predators that feed almost exclusively on arthropods, including many we consider pests. Spiders will kill as many as 50 times the number of prey they actually eat. And, relax, they are not at all interested in biting humans.
This female wolf spider (Tigrosa helluo) was recently brought into our office by a Broomfield employee. She was about 3 inches long! I released her into our Xeriscape Demonstration Garden where, I'm sure, she is providing effective pest control. Photo credit: Jessica Wong 
Dysdera crocata, commonly known as sowbug killer, woodlouse hunter, and “roly-poly killer.” Photo credit:

Spiders provide pest control, day and night, on the ground, on all above-ground parts of a plant, and even in the air. Wolf spiders (Lycosidae) are excellent hunters of pests on the ground, including ants, earwigs, and caterpillars and grubs found at the soil surface. Sowbug killers (Dysdera crocata) are another ground hunting spider that prey on, you guessed it, sowbugs and pillbugs.
This spider is aptly named bold jumper Phidippus audax. Photo credit: Jessica Wong

Jumping spiders (Salticidae) are small hunters can be found in a variety of habitats, from tree trunks to leaves to under rocks. These small spiders hunt for small prey like mosquitoes, aphids, and midges. Crab spiders (Thomisidae) are ambush predators that can be found waiting for prey on flowers. Orbweavers (Araneidae) are the spiders that spin the familiar vertical webs with concentric rings. They catch anything that flies by, such as winged aphids, wasps, and moths.
Goldenrod crab spiders Misumena vatia can change from white to yellow and back to white for better camouflage. Photo credit: Charley Eiseman, Ohio State University Extension
Banded orb weaver Argiope trifasciata. Photo credit: David Cappaert, Michigan State University,

Spiders can provide the most effective pest control when there are many species present in your garden. To support spiders in your garden you will need to provide habitats for them. Apply a layer of mulch or leaf litter for the ground spiders. Reduce tilling to prevent the disturbance of spider nests and burrows. Intercrop varying height plants to create microclimates and web anchor points. Diversifying your landscape can increase the diversity and abundance of spiders in your garden, which will increase the potential for pest control. By creating abundant habitat for spiders in your garden you will also make it more attractive for them to stay outside rather than come inside your house.
Various groups of spiders occupy different parts of a tree. Figure from Patrick Marc & Alain Canard 1997 “Maintaining spider biodiversity in agroecosystems as a tool in pest control.” Agriculture, Ecosystems and Environment 62:229-235.

I love spiders. Spiders are always welcomed in my garden. I don’t even mind them in my house since they are doing a great job of killing flies and ants. I don’t expect you to love spiders now too, but I hope you at least have a greater appreciation for them in your garden.

Tuesday, July 10, 2018

The Plants of Summer

Posted by: Alison O'Connor, Larimer County Extension

Co-workers and friends often joke about my landscape. By now you realize that I adore my lawn, but the landscape plants don't get much attention. My gardening philosophy is that you have to be tough to survive in my landscape. If you need a lot of attention, water or regular pruning, forget it. I've killed A LOT of plants in my tenure in Colorado, but those that have survived have my greatest respect.

And right now, it's tough to be a plant. It's hot, dry and everyone just feels sluggish--including the gardener. But a few are standing up to neglect and thriving. Let's review them:

False indigo (Baptisia australis)
False indigo: Awesome on every level! This has been planted for about six years and this is the first time I really noticed it bloom. Pale lavender flowers on pea-like foliage. The great thing about this plant is it's right where Maple the beagle stalks the squirrels who are trying to eat from the bird feeder, so it gets a lot of paw traffic and abuse. The flowers fade to hardened chocolate brown "pea pods." I cut it back to the ground in the spring.

Sedums: I have many sedums in my garden, but I couldn't tell you any of their names, except for the lime green 'Angelina' (not pictured) and 'Autumn Joy' (not pictured). But ground cover sedums are tough as nails, love it hot and dry and fill in gaps. I call them "gentle creepers" and are not at all invasive. I don't really like the flowers, so sometimes I clip them off.

Above and Beyond rose
Roses: For those who don't grow roses because of the myth they are too much work, you should try them! Roses are one of the easiest garden plants, especially the shrub types--a spring pruning job and occasional clipping in the summer. There are several introductions that you can try. 'Above and Beyond' (pictured) is a climbing rose from the Bailey Nurseries First Editions series. It had incredible blooms just a few weeks ago and is ready for another flush. It also has clean foliage and sparse thorns. Other roses I love are 'Paint the Town' and 'Sunrise Sunset'. Some of the shrub roses have great fragrance, so be sure to stop and smell them!

Hopflower oregano (Origanum libanoticum)
Hopflower oregano: This is a wonderful ornamental that can serve as a ground cover or a trailing plant over a ledge. I love the unique flowers tipped in purple. It's in full bloom right now and the flowers will persist through most of the fall and winter, turning a straw color. The foliage is dainty, held on wiry stems.

Smoketree (Cotinus coggygria)
Smoketree: These large shrubs/small trees are very noticeable when in full bloom (pictured above). The flowers look like plumes of smoke. It's versatile, as it can be left as a multi-stem shrub, pruned to a single-stem tree or cut back to maintain the height you want. The first few seasons it died back almost to the ground in winter. I also love the obovate leaves, which are slightly waxy. The best purple color will occur in full sun. Mine is planted under a honeylocust.

Lavender (Lavendula angustifolia) and threadleaf coreopsis (Coreopsis verticillata)
Lavender and coreopsis: I have seen a lot of lavender in landscapes, which is great, since it's a wonderfully fragrant, bee-attracting perennial. It also does very well in dry, high pH soils. Whack it back to the ground in the spring and watch it re-grow. There's a new introduction called 'Wee One' that is pretty much the cutest lavender you've ever seen. As for the threadleaf coreopsis, also called tickseed, it's a reliable bloomer and I love the purple-yellow combination. Tickseed is a no-brainer. After it blooms, cut it back for a second flush.

A world record prickly lettuce plant?
Check out this record-setting prickly lettuce that was growing up through the lilacs! It was nearly five feet tall. It's amazing how I can wear blinders in the garden and not notice these things...

Maple the beagle is off to investigate other summer-blooming plants for the garden!

Sunday, July 8, 2018

Be Careful with Crabgrass Pre-Emergent Herbicides

Tony Koski, Extension Turf Specialist

Pre-emergent herbicide injury on a Kentucky bluegrass
home lawn. The herbicide was on a fertilizer carrier, thus
the darker appearance where a higher-than-recommended
rate was applied.
Among the mostly widely used lawn weed control products, pre-emergent herbicides (aka “crabgrass preventers") are generally very safe to use on most turf species. Safe, that is, if applied at the correct rate. Using a spreader without adjusting its setting to apply the correct rate, applying the product with a spreader that isn’t operating properly (plugged, skipping, etc.), applying with excessive overlap, or thinking that “more is better” can cause unintended damage to the desirable turf. In the past few weeks we've seen a greater than normal number of pre-emergent herbicide "oops" on home lawns.

New root growth suppressed by a 
misapplication of a pre-emergent herbicide,
displaying the symptomatic root clubbing.
Pre-emergent herbicides “prevent” annual weeds like crabgrass and foxtail from becoming a problem by killing very young, germinating seeds and seedlings; they don’t sterilize the soil, and they don’t kill seeds in the soil. These herbicides kill the young crabgrass, foxtail, and barnyardgrass seedling by stopping root formation – so the tiny plant can’t take up water and dies from drought stress. The crabgrass preventers used most often on home lawns (by lawn care companies, as well as in do-it-yourself products sold to the homeowner) include pendimethalin (Scotts crabgrass prevention products), prodiamine (sold as Barricade; also in Ferti-Lome, Monterey, Bonide, and Pennington home lawn care products), and dithiopyr (sold as Dimension; also in some Ferti-Lome, Hi-Yield, Bonide, and Pennington homeowner products).

Note the root clubbing (red arrows)
on shallower roots: deeper
roots (green oval) are more normal
in appearance because they are
growing beneath the pre-emergent
herbicide layer.
Misapplication due to poor technique (excessive overlap), using a faulty spreader, and intentional or unintentional application at excessive rates can damage desirable turf by stopping or stunting root production in the spring – when these products are typically applied AND when the grass plant is forming its root system. Damaged roots can’t take up water effectively, resulting in turf that is very drought sensitive. Severely damaged plants die – often in spots in the lawn where there was excessive overlap (as in the photos) – leaving brown strips or spots.

Diagnosing this injury can be tricky. Plants on the border of the dead turf will often display stunted root systems – with roots showing little or no branching and a distinctive “clubbing” at the end of the stunted roots. Because pre-emergent herbicides aren’t very water soluble and tend to remain near the surface of the lawn, deeper roots (maybe only an inch or so deeper; see photo) may grow more normally and not display the clubbing seen on roots growing near the surface. Above-ground, the turf may appear dead or severely thinned in stripes that follow application/overlap patterns. As the turf thins, new leaves formed by the surviving grass plants will be wider/more coarse due to the lack of crowding by adjacent plants (the more dense a turf is, the finer the leaf blades will be). The herbicide-stressed turf may also be more susceptible to diseases like leaf spot and dollar spot.

More subtle above-ground symptoms of
pre-emergent herbicide injury on a Kentucky
bluegrass lawn.
Pre-emergent herbicides can last a long time in the soil (4-6 months) – a good thing for providing season-long weed control. That long residual is a bad thing, however, when a pre-emergent causes turf death from over-application – and the residual effect can be even longer because of the very high rates of application that have killed the grass. This makes it difficult to repair areas by overseeding into them – because the herbicide will kill the young seedlings as they germinate. Creeping grasses (bluegrass, the more rhizomatous tall fescue cultivars, bermudagrass) will grow into the killed areas slowly over the summer. Repair by overseeding may have to wait until fall, when the herbicide has been degraded by soil microbes and other degradation forces in the soil. Worth trying, however, is core cultivation/aeration of the affected areas, followed by overseeding with perennial ryegrass. The seed will germinate below the herbicide “layer” on the surface and has a good chance of surviving and masking the damaged turf.

The take-home message? All herbicides have the potential to harm non-target turf, so always follow the label instructions and apply the product using good technique and well-maintained, properly-calibrated equipment.

Thursday, June 28, 2018

Underused dryland native plants

By Irene Shonle, CSU Extension in Gilpin County

Native plants are becoming more and more popular in landscaping, as people seek to reduce water use, increase habitat for pollinators, and create more of a sense of place. Unfortunately, there’s only a limited palette of plants in nurseries to choose from (hint, talk to your favorite nursery and ask them to carry more native species).  The ones that are out there (such as Penstemons, blanket flower, cacti, serviceberry, currants, and more) are great, but there are many deserving plants that I rarely see offered for sale.  This needs to change, people! 😊

Here are some underused (and possibly hard to find) native plants for dry, sunny situations in Colorado.
Cliffrose (Purshia stansburiana)

Cliffrose (Purshia stansburiana) is a shrub native to the western slope.  It has a profusion of creamy yellow flowers, and they smell delightful.  When I was hiking around Grand Junction during bloom (typically May-June), the air was sweet, and pollinators buzzed.  After they are done blooming, they develop a fun fuzzy seed head reminiscent of Apache plume.  They are also very drought-tolerant -- these should be used way more often in our water-limited gardens.  Alas, they do not do well at elevation, but mountain folks like me can make do with a tough (but slightly less showy) relative called Antelope bitterbrush (Purshia tridentata).
Orchid penstemon (Penstemon secundiflorus)

Side bells or Orchid Penstemon (Penstemon secundiflorus): this spring-blooming penstemon has a gorgeous, large flower that is somewhere between purple and pink.  The flowers all bloom from one side of the plant (hence the name side-bells), but the flowers are large and exotic enough that I think the alternate common name, orchid penstemon, captures the essence of them better.  I have seen everything from bumblebees to swallowtails pollinating them. Even out of bloom, the bluish foliage still looks good in the garden.  For a real treat, pair with showy locoweed, (Oxytropis lambertii).
Plains zinnia (Zinnia grandiflora) is a tough ground cover-like flower.  It loves the heat, and will bloom  from mid-late summer in any dry soil, including dry clay.  It covers itself with golden flowers for a long period – and the fact that it blooms in late summer when many other flowers have called it quits give it bonus points.  It looks great with other late summer flowers or grasses.  It prefers full sun but can take some afternoon shade.  There is a Plant Select selection called “Gold on Blue” that has a rhizomatous growth habit and a bluer foliage.
Cushion buckwheat (Eriogonum ovalifolium)

Cushion buckwheat (Eriogonum ovalifolium): I fell in love with this little buckwheat on that same hike I referenced above with the cliffrose.  It is simply stunning – the perfect little puffballs of flowers look like they are out of a Dr. Seuss book – and they often fade from pinkish to pink as they age. This would be awesome in a dry rock garden setting, or in the front of the border. I have my doubts as to how hardy it would be in the higher elevations, but I would grow it now if I could find the right conditions for it.
Pasque flower (Pulsatilla patens)
And can anyone explain why it is so hard to find plants of our native pasque flower (Pulsatilla (Anemone) patens), whereas the European ones are relatively easy to find?  I don’t think they have very different germination protocols, but perhaps I’m wrong on that. It’s such a fantastic early bloomer (early pollinators love it!) and is very tough.

Monday, June 25, 2018

Time for Rust

Posted by Mary Small, Colorado Master Gardener Program Coordinator

Rust on clippers
You’re probably familiar with rust – the kind like you see here on the grass clippers (right) that were left outside all winter!
Plants get rust too, (although not for the same reason as the clippers) and it is appearing on landscape plants now.

Here’s rust on my Zephirine Drouhin rose (below).  I just had to have this plant with the beautiful, fragrant, pink flowers, few thorns and intriguing name. Since Zephrine is a climber, I planted it next to a 4 foot picket fence, imagining how the canes would spread along its length. This antique rose is classified as a “Bourbon” rose and dates from 1868. In spite of all the positives, it has poor rust resistance.
Rust pustules on rose

Rust is a fungal disease that overwinters on fallen leaf debris and canes.  It infects susceptible roses in moist mild weather when the pustules (that form on leaf undersides and canes) release their spores. The disease is tough to control once the symptoms develop. And since you can clearly see the orange pustules as well as yellow spots on the upper leaf surfaces – it is obviously well underway.

Fortunately, it is primarily an aesthetic problem in our climate. Cultural strategies can help manage it – proper siting, keeping the canopy thinned to promote rapid leaf drying and sanitation (removal of diseased leaves and canes.)

While I’ve had moderate success with the cultural strategies I recently learned about a situation in my neighbor’s yard that might be sabotaging my efforts. For some reason, their sprinkler system ran one weekend day when I happened to be looking out a window. One sprinkler head directly targeted poor Zephrine, along with the lawn. I think a conversation and a sprinkler adjustment will help improve the leaf drying situation!

Rust on hawthorn
Here’s a photo of rust on hawthorn (left). I’m not sure which rust this is, but regardless, the rusts that appear on hawthorn (and related species) are more complex than the one on rose.
These rusts have a two- host life cycle, which starts with the maturation of fungal structures on a juniper host. The spores produced by them in the spring blow to alternate hosts, which includes hawthorn, crabapple, apple and others. Years with mild, humid spring weather will produce a large amount of infections.

Tentacle-like reproductive structures
Symptoms appear as yellow-orange spots on leaf surfaces - as soon as flowering is over. Fruiting structures that look like small tentacles develop on the undersides of the spots. When mature, they produce spores that blow to juniper hosts and cause infection. The rust fungus must have both hosts to complete its life cycle. Under the right conditions, the two hosts can be a mile or more apart and still be infected!
Generally, these rust diseases are most obvious on the deciduous hosts because of the colorful spots and premature defoliation of infected leaves. The best way to manage the disease is to select plant species that have rust resistance. You can also remove one of the alternate host plants – three hundred yards up to 3 miles is the standard recommendation. In a landscape setting this is usually impossible.  Generally, the disease is more of an aesthetic than plant health problem in our area.

Rust on mallow - upper surface
Finally, here’s a rust I found on a weedy mallow hiding between a raised bed and fence. It’s the same rust that infects hollyhocks as they are closely related.  Unfortunately it’s not a health issue for the mallow (rats!), but the disease can prematurely defoliate hollyhocks and make them look just plain ugly later in the season. The fungus overwinters on dead leaf and stem tissue of mallow and hollyhock, so sanitation goes a long way to reduce the inoculum for next year. Guess I better get my weed knife out and get rid of this guy.

Rust pustules on mallow - lower surface

Thursday, June 21, 2018

Lilac Ash Borer

Lilac Ash Borer- Cassey Anderson CSU Extension Adams County

Most of us are aware of the looming menace posed by Emerald Ash Borer to our ash trees along the Front Range in Colorado. However, we do have another pest of our ash trees, the lilac ash borer. Lilac ash borer can, like their name, impact both lilacs and ash trees. They are more of a concern in ash trees.  Fortunately they are usually not lethal to the tree.  Adult borers emerge from trees in the spring then lay egg on the bark .  The larva which develop then burrow into the tree where they spend most of their time in heartwood.  They then overwinter in the tree and emerge as adults the next year.

Pupal Skin Left Behind by Lilac Ash Borer (from CSU Extension Lilac Ash Borer fact sheet)

Distinctive round/melon shaped holes can often be found on the main trunk of the tree. During the spring and early summer it may even be possible to find the final pupal skins of the lilac ash borer left in the trunk as the mature insect emerges. The pupal skin may resemble a wasp. They are not related to wasps but rather are a type of clearwing moth which has some resemblance. 
Lilac Ash Borer Exit Holes

We had a severe wind event here in Adams County this spring and saw one of the unfortunate side effects of a tree that had been riddled with the insect.  While the damage caused by the larvae rarely kills trees because it does not feed extensively in sapwood it does weaken and makes them more prone to failure.   

This tree snapped a foot or so off the ground exposing the larval galleries both new and old from the feeding of the lilac ash borer. These trees had been planted in a very narrow strip between road and sidewalk, were not getting sufficient irrigation if you looked at past growth and the grass growing around the trees, several of the trees also had visible girdling roots which likely compounded their stress.
Lilac Ash Borer Galleries 

Generally speaking stressed trees are more susceptible to damage from lilac ash borer. Ensuring that existing trees are planted correctly, do not have girdling roots, and are watered appropriately can reduce infestations of lilac ash borer.  Treatment for this insect is not the same as treatment as for emerald ash borer. For treatment options and more information please see our fact sheet on lilac ash borer:

Monday, June 18, 2018

Growing Strawberries. Vertically!

Adapted from “Vertical Gardening with Strawberries” by Al Myers and Andy Hough
By: Andie Wommack, Douglas County Extension

Vertical gardening greatly increases the amount of plants you can grow in a small space. In a research project done at the Hidden Mesa Research & Demonstration Orchard, they were able to plant 1,500 strawberries in 25 vertical tubes. This took up approximately 13.3% or less of the space that would’ve been needed to plant them in the ground. The methods discussed here can be scaled up or down depending on your production goals! 

When growing strawberries, regardless of method, you need to consider which type of strawberry you want. The three types considered for this project were:
·      June Bearing: produces a major crop but only in spring, usually in June
·      Everbearing: produces a major crop in June and another in late summer
·      Day Neutral: produces a large flush of fruit in June, slows production for approximately six weeks and then produces a more consistent harvest throughout the remainder of the growing season
It’s important to know what your goals are for growing any plant. Knowing when you want, and potentially how much fruit you want, can help you choose which type of plant you want to grow. “Day Neutral” varieties were planted for this project because they produce throughout most of the growing season.

Two different methods were tried, and both have pros and cons. PVC tubes held more plants, hold their shape, and require less potting soil than the fabric tubes. However, the initial cost is higher if using PVC. Also, because they hold less potting soil, the plants run out of fertilizer much quicker. Fabric tubes cost less and can be watered through the sides if needed. These tubs need significantly more potting soil and tended to lose their shape as the soil settled toward the bottom.

If you want to grow strawberries in vertical tubes, the number of plants you will be able to plant depends on the diameter and height of the tube. A 6” diameter, 5’ tall PVC pipe was predrilled to hold up to 100 plants. Spacing for holes in the PVC pipe is 2.5” between each vertical row and 4” between holes in a row. The holes drilled in the PVC pipe were 1.5” in diameter. In the fabric tubes, there is 4” between each vertical row and 8” between the holes in the row. A 2” horizontal slit was cut in the fabric for each hole. A 12” diameter, 5’ tall tube held about 72-75 plants.

Signs of insufficient
nutrient levels
You will need to provide support for your tubes regardless of the type of tube you use. The fabric tubes used in this project were reinforced at the top and bottom of the tubes with high-tensile fence wire then secured to an overhead support structure with bailing wire. The PVC pipes were also attached to the overhead support structure in a similar manner. These were all in a greenhouse, so if you have your tubes outside in an unprotected area, support may have to be stronger to hold up to wind.

Since potting mix is used in these tubes, they should be treated like a house plant container. This means they should be watered frequently and adequately. A micro-sprinkler was installed above each tube and place on an automatic timer so water percolated down through the tube. Fertilizing is also critical and was done on a weekly basis for the fabric tubes because of the high volume of plants and limited soil quantity. Liquid, foliar, or time-release fertilizers can be used and may alter the fertilizing frequency. You will have plants that die for a variety of reasons, however strawberries produce runners that can be used to replace plants lost. If you are growing your strawberries in a climate-controlled environment you can keep them from year to year if you make sure they are watered throughout the winter and don’t freeze. There are other season-extending methods you can use to try and keep your plants from year to year as well, like a mini hoop house or Agribon row cover cloth to hold in heat and moisture.

Initial costs can be high when purchasing the tubes, plants, and planting media, but once this type of system is set up, it requires a very low amount of maintenance. Weeds will be virtually nonexistent, harvest is easy, and since the strawberries are up off of the ground, there is less cleaning and fungal growth on the fruit which can happen if the fruit gets wet. To reduce costs every season, try to overwinter your plants or collect runners that you can plant and grow during winter to plant again in the spring.

The Hidden Mesa Research & Demonstration Orchard in Franktown, CO planted over 500 varieties of fruits and nuts, along with dozens of types of lavender, herbs, and annual vegetables. Their goal is to explore what food crops can be grown in the Front Range Climate and what cultural methods can be used to overcome the extreme climate challenges here. They also provide options for scalable agriculture, edible landscapes, gardening, and community gardens and orchards.

To learn more about the work being done at Hidden Mesa, please visit: