Friday, April 16, 2021

Watch Your Woody Plants for Damage Caused by Environmental Stress

By Kristina Hughes, Clear Creek County Master Gardener

In spring of 2020 I noticed my hawthorn, lilacs and roses were struggling. They leafed out much later than usual and were growing very slowly. My neighbors were having the similar issues with their woody plants. There was much more winter dieback than usual, even on native plants.

 

I consulted the Plant Diagnostic Clinic and learned that the damage was a result of the sudden, extreme freeze that had occurred in April 2020, a few months prior. There had been a warm spell and the plants had started to leaf out, then the temperature plunged more than 40F. The first round of growth and buds had frozen. The plants then tried to push out leaves again later in the spring, but by then it was very dry. Plants need water to fill out their expanding leaves and there wasn’t enough water in the soil at that time for the plants to fully expand the second set of leaves. I realized that if the plants were stuck with stunted leaves for an entire growing season they would only generate a fraction of the energy that they would normally make in a season. The entire plant would be weakened the next year.

 

So I followed the advice of the Plant Diagnostic Clinic and watered my woody plants very well. It took a concerted effort to water by hand until the entire root zone down 12”-18” was moist. But I did it quickly and I watched my plants expand their leaves to full size. I knew they would have a fighting chance of recovering from the freeze damage. 

 

Late frost damage. Photo by Dana Ellison.

I bring this up now because stress to woody plants can take a long time to show up. The damage done during the extreme freeze of Easter 2020 can continue to appear during this growing season. This year we’ve had a dry and warm winter which has added more stress to the plants, so I’m going to continue to watch my woody plants closely this year and make sure they have enough water if they look like they’re struggling.

 

For more information on freeze damage:

 

Jeffco Clinic’s Top 10 Plant Problems of 2020

 

Environmental Disorders of Woody Plants (sections on drought and freeze damage)

 

Jefferson County Plant Diagnostic Clinic diagnoses samples for a small fee

Friday, April 2, 2021

High Altitude Natives

By Sandy Hollinsworth, Gilpin County Master Gardener

Increasingly, mountain gardeners and homeowners living above 8,000 feet are interested in landscaping with native plants to increase success and promote sustainable, natural habitats. Native plants are inviting to pollinators, birds, and mammals by providing food, shelter, and nesting material. There are many benefits to using Colorado native plants including biodiversity, beauty, adaptability, plus many are fire-wise plants. They are naturally adapted to Colorado’s climates, soils, and environmental conditions. By choosing native plants, gardeners can work with nature, rather than trying to grow plants that are not suited to our local high-altitude conditions. Native plants are also more resistant to pests and disease when grown in areas where they are found in nature.


The mountain region is characterized by short growing seasons, cool nights, strong sunlight, and high winds. The soils tend to be decomposed granite, low in organic matter, and are usually very well-drained. Many native plants prefer particular soil textures, whether sand or clay or loamy soils. Almost all high mountain natives do not last as long in enriched garden soils; they grow faster and may look fabulous for a few years then die sooner. Because native plants are adapted to native soils they will thrive without fertilizer or soil amendments. A small amount of compost may help work the rocky soil, but gardeners will benefit by using compost sparingly. Species like columbines and Jacobs ladder that grow in moist forests, may benefit from more compost but otherwise, plant natives without fertilizer and other amendments.

Another consideration is microclimates, sections that are hotter and drier, or cooler and wetter than the rest of the property. Every garden and property have microclimates, depending on shade, sun, slope, water, and wind protection. Grouping plants with similar sun, water, soil and protection requirements will add to success and help with supplemental watering as needed. Colorado mountain natives generally require less water unless they naturally grow in riparian areas like Bluebells, Parry’s Primrose, Scouring-rush Horsetail or Blue-Eyed Grass.

Maintenance in your garden may be easier with natives. It is recommended not to rake away all dead leaves and twigs as it helps protect the soil and offers protection to overwintering pollinators. In fall it is best not to cut back plants but instead to leave seed-heads and dead stalks for food, perches and winter homes for native bees, beneficial insects, and wintering songbirds. Wait to cut back dead plant stalks in early spring at the first sign of green-up.

Mulch is critical for starting native plants from seed, and it can be a huge help in establishing nursery-grown plants too. Gravel mulch is best for retaining soil moisture without causing crown or root rot. Next best is locally-sourced shredded bark mulch although it can blow away.

Non-native plants that are adapted to Colorado’s climate, including CSU Plant Select species, may be more readily available. In years with less than normal rainfall and snow these non-native plants may need supplemental water, again pointing out the adaptive advantage of native species. Gardening with native plants also prevents the introduction and spread of noxious weeds. Many noxious weeds were intentionally introduced as garden plants and can crowd out or change the garden’s native characteristics.


In Gilpin County, the following list of native plants are found at 8,500 – 9,500’ on nature hikes and in established natural habitats. Most are available at local native oriented nurseries or through CSU Extension native plant sales. Inquire about sun and water recommendations to make sure to plant the right plant in the right place. Seedlings will take a few years to fully establish. Some reseed freely while others stay put and grow to their mature spread and height over time. Wind, furry critters, birds, and domestic animals may help spread seeds.

Pussytoes Antennaria spp

Kinnikinnick Arctostaphylos uva-ursi

Sulfur Buckwheat Eriogonum umbellatum

Common Yarrow Achillea millefolium (lantana)

Nodding Onion Allium cernuum

Pearly Everlasting  Anaphalis margaritacea

Fringed Sage   Artemisia frigida

Fringed Sage Artemisia frigida

Rocky Mountain Columbine Aquilegia caerulea

Blue Grama grass Bouteloua gracilis

Harebell Campanula rotundifolia

Indian Paintbrush Castilleja spp.

Rocky Mountain Bee Plant Cleome (Peritoma) serrulata

Showy Fleabane Erigeron speciosus

Wallflower  Erysimum capitatum

Blanketflower  Gaillardia aristata

Richardson’s Geranium Geranium richardsonii

Sticky Geranium Geranium viscosissimum

Prairie Smoke Geum triflorum

Sneezeweed Helenium  Hymonoxys hoopesii

Showy Goldeneye Heliomeris (Viguera)

Scarlet Gilia Ipomopsis aggregata

Rocky Mountain Iris Iris missouriensis

Blue Flax Linum lewisii

Silvery Lupine Lupinus argenteus

Bee Balm/Horsemint  Monarda fistulosa

Showy Locoweed Oxytropis lambertii

Rocky Mountain Penstemon Penstemon strictus

Blue Mist Penstemon Penstemon virens

Silky Phacelia  Phacelia sericea

Jacob’s Ladder Polemonium viscosissimum

Pasque Flower Pulsatilla (Anemone)

Black-eyed Susan Rudbeckia hirta

Golden Banner   Thermopsis divaricarpa

Current berries

Wax Currant  Ribes cereum                    

Woods’ Rose  Rosa woodsii

Serviceberry  Amelanchier alnifolia

Chokecherry Prunus virginiana

For more information about native shrubs https://extension.colostate.edu/topic-areas/yard-garden/native-shrubs-for-colorado-landscapes-7-422/

Almost this same list, plant photos, and some garden design ideas are in this CSU Extension booklet:https://extension.colostate.edu/docs/pubs/native/MountainsSm.pdf