CO-Horts Blog

Monday, June 19, 2023

Low Flammability Landscape Plants


Low-Flammability Landscape Plants

Hot off the press is a fact sheet with efforts of a combined team of Colorado State University Extension- and Colorado Forest Service. The Low-Flammability Landscape Plants Fact Sheet 6.305 is part of a Wildlife Mitigation Series, Landscaping and Planting. To begin to understand how to help mitigate a fire to the home, this fact sheet gives you the basics of plant characteristics that create high-flammability in plants or low-flammability. Keep in mind that there are no fully fireproof plants. Low-flammability plants placed in the appropriate zone can help mitigate a fire around the home. 


The low-flammability fact sheet covers plants in zones 1 at 0-5 feet and 2 at 5-30 feet. There is also a zone 3 at 30-100 feet which is found in the Fire-Resistant Landscaping Fact Sheet. These zones are called defensible spaces. Defensible space is about increasing space, both horizontal and vertical between plants and reducing plant volume. As a homeowner, if you need a defensible space plan for your property, please contact the Colorado State Forest Service field office or your local CSU Extension office nearest you for advice.

We created this fact sheet with the highest degree of protection for structures. The recommendations on the plant list in the Low-Flammability Plants were based on the methodology developed by Idaho Firewise in Boise, Idaho. Plants are ranked on the scale from 0-10. Zero is the most flammable and 10 is least flammable. For zones 1 and 2 which are closer to the house, we recommend only plants rated 8, 9 and 10.

When we talk about flammability, we need to consider plant maintenance which is ongoing for the life of the plant. Proper cultural care is necessary to maintain low-flammability characteristics. Keeping plants hydrated is key. Native stay hydrated with less water and hold onto their hydration.

Here are some examples of what can be included in the landscape with low-flammability

in mind:

Oenothera speciosa is rated an 8

Photo Credit: Wikipedia

Oriental Poppy is rated a 9

Photo Credit: Wikipedia

Delosperma species rated at 10

Photo Credit: Linda Langelo

If you would like to learn more please click on the following link and read further to help mitigate a fire on your property:

The team who worked on this fact sheet were Susan Carter, CSU Extension Chaffee
County Director Horticulture, Natural Resource and Ag Specialist, Nathaniel Goeckner,
Natural Resource Specialist, Chad Julian, Wildfire Mitigation Program Specialist,
Colorado State Forest Service, Irene Shonle, PhD.,Extension Horticulture Specialist, 
El Paso County, Extension Professor, Colorado State University

Thursday, June 15, 2023

Squash Bugs in the Garden

By David Fuller, Colorado Master Gardener, Tri-River Area

Squash bugs (Anasa tristis) are a common pest in gardens that attack various types of cucurbits, including all types of squashes, zucchini, pumpkins, gourds, melons and cucumbers. Squash bugs cause significant damage to plants by sucking the sap from within leading to wilting and death.

Squash bug adult, Whitney Cranshaw,
Colorado State University, 

The adult squash bugs are a flat, oval shape roughly half an inch long and have a brown or grayish-black appearance. They also have distinctive orange-yellow markings on their legs and antennae. Some also have an inverted V or diamond shape in the middle of their backs with white dots around the perimeter. While mainly seen walking on plants, squash bugs can also fly.

Squash bug nymphs, Gerald Holmes, Strawberry Center,
Cal Poly San Luis Obispo, 

Adults hibernate under debris in the garden and surrounding areas through the winter. Adults become active and first appear in June when they start feeding on young plants. Once they wake and begin to feed, they then begin to look for mates. An adult female squash bug can lay up to 200 eggs in clusters primarily found on the underside of leaves. Eggs hatch in one to two weeks. After hatching the nymphs have green bodies that change to gray after a few weeks. The nymphs usually feed together in groups on the underside of plants. Nymph to adulthood takes 4 to 6 weeks depending on temperature, relative humidity, and availability of food. Pest populations grow quickly during hot and dry conditions and depending on the location there can be one, two or three generations per season. Adults that develop late in the season do not lay eggs.

Squash bug eggs on the underside of a leaf, 
Whitney Cranshaw, Colorado State

Using some of the following methods of control will help reduce the population.

Maintaining healthy plants is the best defense against pest in the garden. Crop rotation, removing plant debris, and covering crops with floating row covers are some effective ways to prevent a buildup of squash bug populations. Good weed control is also crucial to reducing squash bug habitat in the garden.

Another solution is planting nasturtium, natural companion plants that work to repel squash bugs, between plants that are affected by the pests. The parasitic fly Trichopoda pennipes is a predator of squash bugs. The larva will burrow into the body of the host, where it will live for approximately two weeks, at which point it will emerge from the host, killing the squash bug.

Handpicking and destroying squash bugs, as well as their eggs, is an effective way to control them. You can also capture them by using a piece of duct tape. Eggs are usually laid in clusters on the undersides of leaves and are yellow to bronze in color. Once you catch them simply drop them into a bucket of soapy water or step on them.

Neem oil is a natural pesticide that can be used to control squash bugs. It works by interfering with the bug’s feeding and reproductive abilities.

Insecticidal soap is a contact insecticide that works by suffocating the bugs on contact. It is effective against all stages of the bug’s life cycle and is safe for use in gardens. You can also mix your own homemade spray using tsp mild liquid soap to a liter of water (always spot-test sprays before using them on any plant).

Chemical insecticides, such as carbaryl (Seven XLR), permethrin (Permethrin SFR 36.8%) and lambda cyhalothrin (Warrior, Matador) can also be used to control squash bugs. However, it's important to follow the label instructions carefully and to rotate insecticides to prevent the development of resistance.

Squash bug damage, Whitney Cranshaw,
Colorado State University, 

I have learned that the best time to control squash bugs in the summer heat is after a rain or an irrigation because the bugs will come to the surface, where they can be easier to spray or hand pick. During the summer they will bury down into the soil to get away from the heat, which is why after a rain is the best time to remove the pest.

In conclusion, controlling squash bugs requires a combination of cultural, mechanical, and chemical control methods. Early detection and control are crucial to minimize damage to plants and to prevent the buildup of populations.

Learn more about squash bugs and  from the CSU Extension factsheet: Squash Bug: Management in Home Gardens and find out more about growing squash at this CSU Extension fact sheet Cucumbers, Pumpkins, Squash, and Melons


Thursday, June 1, 2023

San Miguel Basin High and Dry Research Garden Best Performing Plants

By Yvette Henson, San Miguel Basin Extension

I first heard about High and Dry Gardens in Colorado in 2003 or 2004 when I was in graduate school at CSU in Fort Collins.  It piqued my interest because my own graduate research was a drought study.  The concept behind High and Dry gardens is to trial plants to see how they perform on little to no supplemental irrigation. 

I got my graduate degree and moved to Norwood, CO in 2006 to work for CSU Extension.  After I discovered that there were several other Extension Offices in the state that had High and Dry Gardens, we planted a High and Dry demonstration garden outside our Extension Office. 

Planting Norwood High and Dry Garden, August 2006

Norwood is a small town on Wrights Mesa, elevation 7020’.  We are in Zone 5.  Our average annual snowfall is 59.6”. Our average annual rainfall is 15.10” and mostly falls in our ‘monsoon’ period of mid-July through August. Norwood, like the rest of semi-arid Colorado, experiences regular drought and subsequent water shortages and restrictions.  It is not uncommon for residents who live outside of the city limits to need to haul water to their homes for household use. 

I cross-referenced the plant lists for High and Dry gardens at Extension Offices in Gilpin, Boulder, El Paso and Custer counties and selected only the plants that were on all plants lists.  Even though High and Dry Gardens do not typically plant only natives, ours did because those were the plants in common on the other plant lists.

Our original site was a large rectangular bed on flat ground.  Our soil was sandy clay loam soil with a pH of 8.4.  We fenced it to keep our deer.  Each year, we timed our planting to coincide with the annual summer monsoon.  Once the plants were planted, they were watered in and never watered again.  In drought years, I did consider applying the average annual rainfall amount but never did.

Norwood High and Dry Garden in June 2009

The original Norwood High and Dry Garden was there until 2019 (13 years) when the area was leveled to build a new sheriff’s annex.  

Norwood High and Dry Garden in Fall 2017 (note there is no fence)

The plants that survived and performed best were mostly shrubs. Following is a list of the best performers.

Golden currants, Ribes aureum.  All varieties of golden currants require little to no supplemental irrigation.  Golden currants are my favorite of the High and Dry shrubs.  They have beautiful golden flowers in spring (some varieties flowers are more fragrant than others), followed by edible yellow, orange or black fruit.  The shrubs end the growing season with deep-red fall color before the leaves drop for winter.

Golden currants 

Mountain mahoganies: Cercocarpus montanus, C. ledifolius and C. inticatus.  Although the all did well, our favorite of the mountain mahagonies was Cercocarpus ledifolius, curl-leaf mountain mahogany.  We had a 6' x 3’ specimen that kept most of its leaves through the winter. 

Curl-leaf mountain mahogany(photo credit Plant Select, Gary Epstein)

‘Baby Blue’ dwarf rabbitbrush, Chrysothamnus nauseosus var. nauceosus, a Plant Select Introduction was my 3rd favorite shrub in our High and Dry Garden.  It grew to a tidy low mound, 12-18” x 3’.  The yellow blooms were welcome late summer color.

Plant Select 'Baby Blue' rabbitbrush (photo credit Plant Select)

Both ‘Kannah Creek’ sulphur buckwheat, Eriogonum umbellatum (a Plant Select introduction) and James buckwheat, Eriogonum jamesii, performed exceptionally well in our garden.  The deer were not able to eat the blooms like in our Plant Select Demonstration Garden because of the fence.  Both buckwheats form a low mat of semi-evergreen leaves that get good fall and winter color.  In spring and summer, the yellow or cream bracts of the flowers grow about a foot above the foliage.

'Kannah Creek' Buckwheat (photo credit Plant Select)

James Buckwheat (photo credit Al Schneider, SW Colorado Wildflowers)

Rocky mountain penstemon, Penstemon strictus, almost ate the garden.  The showy and reliable early- summer blue flowers reseeded prolifically in our gravel mulch!  So, we learned to cut the blooms off to prevent reseeding.   I found this ironic because most gardening books list this plant as short-lived.  Perhaps they are in watered gardens.

Rocky mountain penstemon in Norwood High and Dry Garden (blue flowers)

Other plants worth a mention are pussytoes, Antennaria parvifolia; blanket flower, Gaillarida aristata; and bluemist penstemon,  Penstemon virens.

blanket flower in background, pussytoes in mid ground
 at Norwood High and Dry Garden

The county gave us a new border for a High and Dry Garden in 2022.

Master Gardeners planting our new High and Dry Garden Berms in 2022