Jefferson County CSU Extension Colorado Master Gardeners

09/07/2026

09/04/2026

Wasps in Your Garden: Friend or Foe? 🐝🌿
Wasps may not be everyone’s favorite garden visitor, but they can play an important role in a healthy Colorado garden.

The advantages:
* 🐛 Natural pest control: Many wasps hunt caterpillars, aphids, and other insects that can damage vegetables and ornamental plants. Some parasitoid wasps specifically attack garden pests.
* 🌸 Pollination: Wasps visit flowers for nectar and can transfer pollen between plants. Colorado State University notes that wasps are important pollinators for some plant species.
* 🌱 Less reliance on pesticides: By naturally suppressing pest insects, beneficial wasps can help limit garden pest problems.

The disadvantages:
* ⚠️ Stings: Some social wasps can sting, particularly when their nests are disturbed. European paper wasps commonly nest around yards and gardens.
* 🍔 Yellowjackets can be a nuisance: Late in summer, yellowjackets may become attracted to outdoor food, garbage, sugars, and meats. They can aggressively defend their nests.
* 🏡 Nests near people can be problematic: A nest near a doorway, patio, play area, or other frequently used space may create a safety concern.

The bottom line: Not every wasp needs to be removed. Many are beneficial garden predators or relatively docile solitary species. If a nest is in a location where people are unlikely to disturb it, leaving the wasps alone can allow them to provide natural pest control. But nests in high-traffic areas deserve extra caution.

In other words: Wasps can be valuable garden helpers—just give them some space! 🌿🐝

Sources: Colorado State University and CSU Extension resources listed below.

* Wasps — Colorado State University Agricultural Biology�https://agsci.colostate.edu/agbio/ipm-pests/wasps/ �

* Beneficial Insects and Other Arthropods — Colorado State University Extension�https://extension.colostate.edu/resource/beneficial-insects-and-other-arthropods/ �

* European Paper Wasp — Colorado State University Extension�https://extension.colostate.edu/resource/european-paper-wasp/ �

* Nuisance Bees & Wasps — PlantTalk Colorado, Colorado State University�https://planttalk.colostate.edu/topics/insects-diseases/1400-1-nuisance-bees-wasps/ �

* Creating Pollinator Habitat — Colorado State University Extension�https://extension.colostate.edu/resource/creating-pollinator-habitat/ �

* Simple Ecology: The Family of Vespidae: Wasps — CSU Extension, Gilpin County�https://gilpin.extension.colostate.edu/wp-content/uploads/sites/29/2020/09/Vespidae-nests.pdf



Photo: CMG Jeffrey Blake
Image Description: wasps on hive

Jefferson County CSU Extension Colorado Master Gardeners are here to help answer your gardening, lawn, and diagnostic questions! Email [email protected] to send us a message or ask a question.

08/30/2026

Heads up gardeners! CSU Extension - Arapahoe County and the Cheyenne-Arapaho Park Community Garden Master Gardeners are hosting “Fall Gardening and Putting Your Garden to Bed” on Saturday, Sept. 12 from 10 to 11 a.m. at Cheyenne Arapaho Park Community Garden in Denver.
Master Gardeners Elaine Davis and Jessie Asimus will share what to plant in fall, how to prep soil, and the steps to tuck your garden in for winter so it’s ready to thrive in spring. It will be great opportunity for gardeners looking to make the most of the season’s end.

https://www.eventbrite.com/e/fall-gardening-tips-and-tasks-9122026-1000am-cheyenne-arapaho-park-tickets-1985609395152?aff=oddtdtcreator&keep_tld=true&fbclid=IwY2xjawUAOUlwZG9mAWV4dG4DYWVtAjEwAGJyaWQRMWZ0RWZvaVV3MGhZRW51b1BzcnRjBmFwcF9pZBAyMjIwMzkxNzg4MjAwODkyAAEeAclN6-zLl3XNHWzWhklLRGHQXUO5qDLit8vkYRZs8pcc35idr3sata8NUU0_aem_oIf6UXp_eWu97olc7TpY6w

08/28/2026

🌿 Growing Rosemary in Jefferson County, Colorado: Love the Herb, Respect the Winter! 🌿

Rosemary seems like it should be right at home in Colorado. It loves sunshine, tolerates relatively dry conditions, and comes from the Mediterranean. So why does it sometimes thrive all summer and then disappear after winter?

The biggest challenge is cold. Colorado State University Extension describes rosemary as a tender perennial and notes that it generally doesn't thrive in Colorado's cold conditions. In Colorado, rosemary is often grown as an annual, with container growing recommended as the best approach.

☀️ Challenge #1: Finding the right location
Rosemary needs plenty of sunshine. Choose a location with full sun and good air circulation. A sunny patio, south- or west-facing location, or container near the house can work particularly well.

💧 Challenge #2: Too much water
This is where Colorado gardeners can get into trouble. Rosemary is a Mediterranean herb and requires less moisture than many other garden herbs.

Give it well-drained soil and avoid keeping the roots constantly wet. Overwatering can contribute to root rot and bacterial leaf problems.

If your garden soil is heavy clay—a common challenge for Front Range gardeners—consider growing rosemary in a container or improving drainage. CSU Extension notes that adding organic material to clay soil can improve drainage and aeration.

🪴 Challenge #3: Colorado's winter
This is the big one. Rosemary isn't reliably hardy through Colorado winters. CSU Extension specifically recommends growing rosemary in pots and bringing it indoors for winter.

That makes a container an excellent strategy for Jefferson County gardeners:
➡️ Grow it outdoors during the warm season.
➡️ Before hard frost, move the pot indoors.
➡️ Put it in the brightest location possible.
➡️ Reduce watering while it's indoors, but don't let it remain constantly wet.
➡️ Return it outdoors once the danger of damaging frost has passed.

🌱 Challenge #4: Keeping it healthy indoors
Indoor rosemary still needs lots of light. CSU's PlantTalk Colorado recommends maximum sunlight for
indoor herbs and suggests a south- or west-facing window or supplemental grow lighting.

And watch the watering! Indoor containers can be particularly vulnerable to overwatering, which can
encourage root problems and diseases.

✂️ A few more CSU tips
• Rosemary can be propagated from cuttings.
• Avoid overwatering.
• Light pruning after flowering can be beneficial.
• CSU recommends waiting to fertilize until after flowering.
• Harvest leaves and flower tops in spring and early summer.

🌿 The Jefferson County rosemary strategy
If your goal is a huge rosemary shrub that stays outdoors year after year, Colorado winters can make that a challenge.

If your goal is fresh rosemary for cooking, however, you have a much easier option:
Grow it in a container, give it lots of sun, keep the soil well drained, water carefully, and bring it indoors before winter.

In Colorado, success with rosemary isn't necessarily about finding the perfect spot to leave it outside—it's about managing its environment through our very different seasons.

🌿 Grow it like a Mediterranean herb… but garden like a Colorado gardener!

1081 – Growing Herbs in Containers — PlantTalk Colorado�https://planttalk.colostate.edu/topics/annuals-perennials/1081-growing-herbs-containers/

1056 – Indoor Herb Garden — PlantTalk Colorado�https://planttalk.colostate.edu/topics/annuals-perennials/1056-indoor-herb-garden/

1003 – Planning & Plants for an Herb Garden — PlantTalk Colorado�https://planttalk.colostate.edu/topics/annuals-perennials/1003-planning-plants-herb-garden/

Vegetables — CMG GardenNotes #731, Colorado State University Extension
�https://sam.extension.colostate.edu/wp-content/uploads/sites/59/2020/01/GN-710-Vegetables.pdf
Growing Herbs at High Altitude — CSU Extension, Gilpin County
�https://extension.colostate.edu/gilpin/resource/growing-herbs-at-high-altitude/

Vegetable Gardening in the Mountains — Colorado State University Extension�https://extension.colostate.edu/resource/vegetable-gardening-in-the-mountains/

Container Gardens — Colorado State University Extension�https://extension.colostate.edu/resource/container-gardens/



Photo: CMG Jeffrey Blake
Image Description: Winter tolerant Rosemary

Jefferson County CSU Extension Colorado Master Gardeners are here to help answer your gardening, lawn, and diagnostic questions! Email [email protected] to send us a message or ask a question.

08/21/2026

🌿🐝 Why Bees LOVE Oregano! 🐝🌿
If you grow oregano mainly for your kitchen, you may be overlooking one of its best garden benefits: its
flowers are a great resource for pollinators!

🌸 Let oregano bloom!
Colorado State University Extension specifically lists oregano (Origanum vulgare) among bee-friendly
pollinator plants. Oregano produces small white flowers, typically from June through August, giving bees
another source of food during the growing season.

🐝 What do bees get from oregano?
Bees visit flowers to collect nectar and pollen. Nectar provides an important energy source, while pollen
supplies nutrients needed for bee development and reproduction. By allowing oregano to flower, you're
providing food that can help support the bees visiting your garden.

🌱 Oregano can feed more than just bees.
CSU Extension notes that many herbs—including oregano—attract a variety of pollinators and beneficial
insects. So that patch of oregano can become a surprisingly busy little pollinator garden!

✂️ One important gardening tip:
If your goal is to harvest oregano for culinary use, CSU Extension recommends cutting off the flowers
before they bloom. But if you're trying to help pollinators, consider leaving at least some plants—or
portions of the plants—to flower.

🌿🐝 A simple win for the garden:
Grow oregano. Let it flower. Enjoy the bees.
Sometimes helping pollinators doesn't require planting something exotic. A common culinary herb can
become an important source of food when we simply let it bloom!

Sources:
1. Pollinators in Vegetable and Herb Gardens — CSU Extension�https://extension.colostate.edu/arapahoe/2026/06/15/pollinators-in-vegetable-and-herb-gardens/

2. Attracting Native Bees to Your Landscape — Colorado State University Extension�https://extension.colostate.edu/resource/attracting-native-bees-to-your-landscape/

3. Bee Friendly Pollinator Plants — CSU Extension�https://fremont.extension.colostate.edu/wp-content/uploads/sites/44/2018/05/August-19-2017-Bee-Pollinators-Web.pdf

4. Growing Herbs at High Altitude — CSU Extension�https://extension.colostate.edu/gilpin/resource/growing-herbs-at-high-altitude/

5. Oregano Hopflower — CSU Extension�https://adams.extension.colostate.edu/horticulture/oregano-hopflower/





Photo: CMG Jeffrey Blake
Image Description: Bee on Oregano

Jefferson County CSU Extension Colorado Master Gardeners are here to help answer your gardening, lawn, and diagnostic questions! Email [email protected] to send us a message or ask a question.

08/17/2026

🦋 Don’t Forget the Moths! Why These Nighttime Garden Visitors Matter 🌙🌼

When we think about pollinators, bees, butterflies and hummingbirds usually get all the attention. But there’s another group working in our gardens—often after dark—that deserves some appreciation: moths! 🦋🌙

Colorado is home to more than 5,000 species of moths, and they play important roles in our ecosystems. Some moths are pollinators, while their caterpillars and adults provide food for birds and other wildlife.

🌸 Moths can be important pollinators.�The White-lined Sphinx moth, for example, visits flowers for nectar and transfers pollen from flower to flower. In Colorado, these moths are associated with plants such as columbine, and some plants benefit significantly from their visits.

🌙 Pollination doesn’t stop when the sun goes down!�Moths are among the most important groups of nocturnal pollinators. Colorado State University Extension notes that miller moths feed on flower nectar from late spring through early fall as they migrate toward higher elevations.

🐦 Moths are also part of the food web.�Moth caterpillars are an important food source for birds and other wildlife. Colorado State University Extension points out that insects—including moths and their caterpillars—help support birds and other animals. In fact, birds can require thousands of caterpillars to raise a single brood.

🌿 So how can you help moths in your garden?
✅ Plant a variety of native plants that provide nectar for adult moths and food for caterpillars.

✅ Keep something blooming from spring through fall to provide a steady supply of nectar.

✅ Reduce pesticide use. Pesticides can harm pollinators and other beneficial insects.

✅ Accept a little leaf damage. Remember: caterpillars are baby moths! A few chewed leaves can be a sign that your garden is supporting wildlife.

✅ Turn off unnecessary outdoor lights at night. A darker garden can be friendlier to nocturnal insects.
Colorado's University of Colorado Museum of Natural History recommends increasing the diversity of native plants, providing nectar-producing flowers, limiting pesticides and avoiding bug zappers when trying to support moths.

🌙 The next time you see a moth fluttering around your garden, don't automatically think “pest.” Think pollinator, caterpillar, bird food and an important piece of Colorado's ecosystem.

A healthy garden isn't just a garden with perfect leaves—it’s a garden full of life! 🌱🦋🌼

Sources

1. Creating Pollinator Habitat — Colorado State University Extension�https://extension.colostate.edu/resource/creating-pollinator-habitat/

2. Miller Moths — Colorado State University Extension�https://extension.colostate.edu/resource/miller-moths/

3. Hornworms and “Hummingbird” Moths — Colorado State University Extension�https://extension.colostate.edu/resource/hornworms-and-hummingbird-moths/

4. Butterfly Larval – Host Plants — Colorado State University Extension�https://extension.colostate.edu/resource/butterfly-larval-host-plants/

5. Moth Matters: Attracting Moths to Your Backyard — University of Colorado Boulder Museum of Natural History�https://cumuseum-archive.colorado.edu/Exhibits/MothMatters/attracting.html

6. Moth Matters: Viewing Moths in Your Backyard — University of Colorado Boulder Museum of Natural History�https://cumuseum-archive.colorado.edu/Exhibits/MothMatters/viewing.html



Photo: CMG Jeffrey Blake
Image Description: Sphinx moth on screen door

Jefferson County CSU Extension Colorado Master Gardeners are here yto help answer your gardening, lawn, and diagnostic questions! Email [email protected] to send us a message or ask a question.

08/14/2026

Now Accepting Applications for the Jefferson County Master Gardener Program

In 1995, I read about an incredible horticulture volunteer program through Colorado State University Extension Services that turned 20 years old. I loved gardening, and I applied. Much to my delight, the program accepted me as an apprentice, and after completing all the requirements, I became a Colorado Master Gardener (CMG) in 1996 for Adams County. I volunteered for seven years for Adams County CMG, working info tables, answering garden questions via phone and in person, and helping in the one garden the program had. Then work and life became too much, and I stepped back.

Fast forward to 2024, I still had that botany and gardening bug. So, I applied to become a Colorado Master Gardener apprentice, this time with Jefferson County, since we moved. Again, the CMG accepted me as an apprentice. In October 2025, I earned the title of Colorado Master Gardener! And I love it.

The CMG matured and changed in many good ways in the 2-ish decades I was away. My first time, the training was in person and was all classroom- no hands-on labs. Now training is online, with several in-person labs, allowing me to do the classes on my schedule. There was a weekly scheduled review session that supported learning from the week’s topic. The hands-on labs provided the opportunity to meet other CMGs and apprentices, practice identifying soil, use a key to identify trees, and learn about the wonderful world of beneficial insects. Gardening Science has advanced. The right way to plant trees has changed; more fact sheets and video information are available to the public, and CMGs can now answer inquiries via email.

So many reasons why I loved being a CMG are still there. I get to volunteer alongside many dedicated and more knowledgeable CMGs, who freely share ideas and information. Jefferson County MG has multiple gardens to work in, such as the Plant Select, Horticulture, Courage, Orchard, Native Plains Garden, Mountain Native Garden, and Low‑Flammability Gardens. There are continual training opportunities. I can work at an info table, be on the help desk answering emails and calls, contribute to the social media team, learn beekeeping, and work towards being part of the diagnostic team. I get to help the public, sharing knowledge and ideas. The opportunities for learning and helping are endless. Plus, Colorado has over 3200 native plants and 100 native tree species, plus all the non-native, introduced, and invasive species; I doubt I will volunteer long enough to know them all!

CSU Master Gardener Volunteer Program is accepting applications now until August 31 for their new cohort of Colorado Master Gardeners. This includes Jefferson County, along with many other Colorado counties, because you volunteer in the county where you live. Here is the link:
https://extension.colostate.edu/colorado-master-gardener/become-a-colorado-master-gardener/

If you love flora, botany, soil, and landscaping, and want to contribute to your community, I urge you to consider this exceptional program!!

Photo: Pat Greer
Image Description: Master Garden apron on a maple tree with certificate.



Jefferson County CSU Extension Colorado Master Gardeners are here to help answer your gardening, lawn, and diagnostic questions! Email [email protected] to send us a message or ask a question.

08/13/2026

08/12/2026

08/11/2026

🌿 **Garden Like a Master Gardener!** 🌿

You don't have to be a certified Master Gardener to use the same research-based practices that help Colorado gardens thrive. Here are a few simple habits that can make a big difference in your own landscape:

🌱 **Plant the right plant in the right place.** Match plants to your site's sunlight, soil type, moisture, and hardiness zone. Plants that are well-suited to their location are healthier, require less maintenance, and use water more efficiently.

💧 **Water deeply, but only when needed.** Frequent, shallow watering encourages shallow roots. Water thoroughly so moisture reaches the root zone, then allow the soil to dry slightly before watering again.

🌾 **Mulch is your garden's best friend.** A 2–4 inch layer of organic mulch helps conserve soil moisture, reduces weeds, moderates soil temperatures, and adds organic matter as it breaks down.

🔍 **Know your pest before you act.** Not every insect is harmful! Many insects are beneficial pollinators or natural predators. Correctly identify a pest and the extent of the damage before deciding if any control is necessary. This is the foundation of Integrated Pest Management (IPM).

🌼 **Build healthy soil.** Incorporate compost or other organic matter when appropriate, and consider a soil test before applying fertilizer. Healthy soil supports healthier plants and reduces unnecessary fertilizer use.

✂️ **Inspect your garden often.** Spend a few minutes each week looking for changes in your plants. Catching diseases, insect problems, or watering issues early often means they can be managed with simple, non-chemical solutions.

📚 The best Master Gardeners know that successful gardening isn't about having all the answers—it's about using reliable, research-based information and continuing to learn. By following these simple best practices, every home gardener can grow a healthier, more beautiful, and more sustainable Colorado garden.

Happy gardening! 🌻

Colorado .edu Sources
1. Colorado State University Extension – GardenNotes (research-based gardening information)
* https://extension.colostate.edu/topic-areas/yard-garden/gardennotes/

2. Colorado State University Extension – Integrated Pest Management (IPM)
* https://extension.colostate.edu/topic-areas/insects/integrated-pest-management/

3. Colorado State University Extension – Mulches for Home Grounds
* https://extension.colostate.edu/topic-areas/yard-garden/mulches-for-home-grounds-7-214/

4. Colorado State University Extension – Irrigation of Home Lawns
* https://extension.colostate.edu/topic-areas/yard-garden/irrigation-scheduling-the-smart-way-7-239/

5. Colorado State University Extension – Choosing a Soil Amendment
* https://extension.colostate.edu/topic-areas/yard-garden/choosing-a-soil-amendment/

6. Colorado State University Extension – Soil Testing
* https://extension.colostate.edu/topic-areas/agriculture/soil-testing-0-501/

7. Colorado State University Extension – Colorado Master Gardener Program
* https://extension.colostate.edu/colorado-master-gardener/



Photo: Colorado State University
Image Description: woman in her garden

Jefferson County CSU Extension Colorado Master Gardeners are here to help answer your gardening, lawn, and diagnostic questions! Email [email protected] to send us a message or ask a question.