CO-Horts Blog

Thursday, March 17, 2022

When Dryish Eyes are Smiling


Posted by: John Murgel, Horticulture and Natural Resources Agent, Douglas County


Looking for some green in your life, but concerned about landscape water use?  Then let me tell you about extremely dry gardens.  Gardens without supplemental water.

 If you’re shuddering now, I don’t blame you.  You’ve probably seen xeriscapes that hardly inspire enthusiasm.  But whether you’re interested in dry gardens for sustainability, economics, aesthetics, or because (like me) you’re just tired of dealing with the sprinkler system, I have some solutions and suggestions that go beyond rocks, a steer skull, and a wagon wheel.

 To succeed with a dry garden, understanding how plants cope with drought is a great way to begin.  Annuals take advantage of favorable conditions to sprout and flower quickly, set copious seed, and then perish as conditions get drier.  Their seeds will rest until conditions are right again.  Bulbs use a similar strategy, but rest as a perennial plant, hidden beneath the soil surface.  Both annuals and bulbs can be extremely showy additions to gardens, filling spaces between perennials—but the display is usually short-lived--maybe a month.  A few annuals will flower for a longer period if conditions remain favorable—California poppies (Eschscholzia californica) and Desert Marigold (Baileya multiradiata) are two examples of plants that can flower all summer if conditions don’t get too harsh.  Both grow easily from seed sown outdoors in spring.

Dry Garden with annuals in Arizona
Desert Marigold (yellow, front) growing happily in Southern Arizona without water.  It can handle Colorado drought, too!

Perennials, shrubs, and trees cope with drought by various methods of tolerance, including morphological adaptations to leaves and roots, by “aestivating,” or going dormant during hot dry periods, and physiological adaptations (like CAM photosynthesis, used by succulents when the growing gets tough).

Choosing plants for your garden should begin with an evaluation of the type of drought you’re dealing with.  A gardener in Castle Rock, for example, will be facing a very different drought than a gardener in Grand Junction or Lamar.  Geography will tell you about your “normal” precipitation patterns.  Then factors like soil (its nature and depth), microclimates, shade, tree roots, wind, and salt will all play in as well.  Once these are known, at least approximately, you can begin choosing plants. 

no-water garden with full flowers
No-water gardens can include native and non-native plants.

In general, the only soil improvement that you should undertake is to reduce compaction by “forking”.  Do everything you can to maintain soil structure--if you're using machinery, don't overdo it!  As a general rule, drought-tolerant plants prefer stony, coarse, well drained soil that is low in organic matter (you know, the stuff that we all like to complain about as "terrible Colorado soil").  Use mineral mulch (like pea gravel or crushed granite) or low berms to ensure that moisture drains away from plant crowns quickly.  Plant perennials in wide, shallow bowls so that they can be watered deeply and infrequently during their establishment year.  After a once a week-ish drink the first summer, you can let the plants fend for themselves.  The bowls can be disguised with the mineral mulch if you don’t want your garden to look too lunar. 

A quick aside—don’t put weed fabric below your mulch, just use deep enough mulch.  4” of gravel will suppress weeds and won’t impede air- and water-flow like weed fabric does.

Perhaps the most counterintuitive principle for starting with plants is to plant small!  Large tender plants straight from the cushy conditions of the nursery will quickly shrivel in the tough conditions of your new drought-tolerant garden.  Start with small plants, or even try planting perennials from seed (check the seed packet for the best planting time).  Plant your plants early to take advantage of spring moisture.  Hardened plants can go out in early April along the Front Range, for example, as long as the soil workable. 

Be patient.  Your plants will grow slowly in their first year, but they’ll reward you each successive season with bigger displays.  Maintenance often includes only cutting back spent flowers (if you like). 

First year xeric garden
This first year xeriscape is small on plants, but be patient

For more information (including design, maintenance, trees, weeds, and fire)—please join the April 1 webinar about no-water gardening! Registration is required, but the webinar will be recorded and posted in the webinars page of this blog.

Third year xeriscape with bigger plants
The same garden in the spring of year 3, having received no watering other than rain for 2 years!

Update: It's true that perennial beds can look shaggy in winter and dry gardens are no exception.  BUT--careful garden design and strategic use of evergreens (including evergreen succulents) can provide season-long interest without looking unkempt.  Just be sure to mow or cut everything back before the bulbs come up!

Yucca plant in winter
The same garden, from a different angle, in winter

Tuesday, March 8, 2022

Snow and Plants

By Yvette Henson, San Miguel Basin Extension

By the end of January, we had close to average snowpack statewide.  This was encouraging after last years (and previous years) droughts!  In February and into this first week in March, we have had quite a bit of snow in my region of the state which I am sure has resulted in above average snowpack for February.   The Colorado Snow Survey & Water Supply News Release for February hasn’t been published at the time I am writing this blog, but when it is released, you can find it here:

Update March 9th-- imagine my surprise to learn when the report come out yesterday afternoon, that even though we received more than 4' of new snow the last week in February at my 8,400' elevation in SW CO, we are still only 95% of average snow pack for 2022.

snow covered landscape

Snow can be like an insulating blanket over plants to protect them from frigid temperatures and desiccating wind.
  Temperatures at ground level under snow can be degrees higher (even above freezing) and fluctuate less than air temperatures. 

soil temperature is lower under snow cover,  protecting the developing crowns on these native goldenrod Solidago sp.

Light can penetrate the snow cover.  It is interesting that light can only penetrates to a depth of 12-20” through snow in the fall but to a depth of more than 6’ in the late winter and spring!  The angle of the sun, the daylength, as well as properties of the snow affect the timing, the amount and the quality of the light that reaches plants under the snow.   In the late winter, the light penetration through the snow triggers some seeds to germinate and some species to develop buds in their crowns in preparation for spring regrowth.  A classic example of a Colorado native plant that develops leaves and floral structures under snow are avalanche lilies.  As the snow melts in the spring, the flowers bloom.

yellow avalanche lilies (Erythronium grandiflorum) and spring beauties (Claytonia lanceolata)
Have you noticed that the plants that have been growing under snow often have a red tint when the snow melts but change to green as the season progresses?  This is due in part to the fact that the red pigments in the plants absorb blue and green light that pass through the snow in winter. 
red foliage on emerging plants, right after snow-melt

We gardeners learn which plants do well under snow cover and which don’t.  We often learn this the hard way.  Not all plants do well with snow cover.  In this case, it is often the wet soil under the snow rather than just the cold that kills these plants during winter.  A general rule is to research the environmental conditions of where a plant is native to.  If it is an area with no snow fall and you typically have snow cover in the winter,  you could site those plants on south facing slopes and/or against structures with south and west exposures where snow melts more quickly.  In a similar way, snow will melt quicker off rock mulch than bark or leaf mulch.  Plants that come from areas that do receive snow can withstand colder temperatures with snow cover than without and don’t mind ‘wet feet’.  

south facing berm and gravel mulch absorb heat and melt snow quicker-- this is a good place for plants that don't overwinter well with snow cover

North facing (same berm) as previous photo has more consistent snow cover-- this is a good place for plants that do well with snow cover.

Snow load can break branches of woody shrubs and trees, especially where it lands after falling off roofs.   If you have this situation in winter, you can plant shrubs that respond well to being cut back to ground level in the spring.  Some examples are elderberries (Sambucus spp.), grown for their foliage, dogwoods (Cornus spp.), grown for their colorful winter branches and butterfly bushes (Buddleja spp.)  It can be done with many multi-stemmed, summer flowering shrubs that form their flower buds on the current season’s growth.  This severe pruning stimulates multiple stems to regrow from the base and may keep your shrubs smaller in stature, depending on their growth rate. 

 I am thankful for the snow this winter.  I can’t wait till spring to see my favorite plants again, after the snow melts.