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Does the pH of Tap Water Affect your Landscape?

Denver Water customers received news last year that the pH of the water delivered to them by Denver Water would be adjusted from near neutral (pH 7.5) to slightly more alkaline (pH 8.5), which began in Spring 2020.

The motivating reason for this change is for improved human health, which is highly commendable (more alkaline water is less prone to leach lead from pipes into people’s drinking water; lead is toxic to human health).

But, this announcement has many in the Landscape Industry wondering what impacts this may have on irrigating landscape plants, as well as indoor plants, and how it may affect water conveyance equipment (irrigation systems, etc).

A cursory investigation via the internet seems to indicate that the possible impacts from higher pH water on irrigation systems and the plants that receive that more alkaline water are:

  • Increased mineral deposits on irrigation equipment as well as pots, planters, etc. For drip emitters this can be very problematic as the water emits at such a low and slow rate that calcium scale build-up could end up clogging the emitters.
  • Reduced absorption of minerals and nutrients by the plants.

Most of the soil pH in Colorado’s Front Range are alkaline, so it is possible that this increase in pH will have little or no effect on plants that are already suited or adapted to the native soils of our area.  But for plants that don’t do well in alkaline soils, will this more alkaline water be the factor that pushes those plant over the edge? Is this such a bad thing if those plants aren’t suited for our soils (and climate) to begin with?

What are some actions you can take to mitigate the problems of more alkaline water?

  • Water more deeply and less often. Frequent and shallow waterings may cause more build-up of salts and minerals like calcium.
  • Use alkaline adapted plants in your landscape rather than plants that need acidic soils. Generally speaking, most native plants for our region (Colorado’s eastern Front Range) are well adapted to alkaline soils.
  • Check your irrigation equipment for hard water scale build-up. Clean or replace drip emitters that are clogged with scale to ensure proper water flow.
  • Add Acidifying materials to the soil, like granules available from garden stores? Some experts seem skeptical of this method, saying it is very difficult to have much impact on the total alkalinity of our native soils.
  • Add more organic matter such as compost? Aside from most xeric adapted plants as well as plants native to our region, many of the standard landscape plants benefit from added compost for multiple reasons. Adding compost to soil can lower the pH (more acidic) as well as aid in water retention, soil texture and provide nutrients to plants.

You may wonder if softening your water via chemical means is a good option. Several experts say this is not a good way to lower the pH of the water for plants because softened water has higher salt content, which is also problematic for plant health.

Some articles sourced on the internet mention lowering the pH of the water you irrigate your houseplants with, by adding vinegar. This may work for a small watering can used on houseplants, but for landscape plants this is simply impractical. Could an in-line fertigation system be used with an acidifier such as vinegar on landscapes? We here at ODG are uncertain about this option, but it seems like an intriguing, if also risky, option.

Time will tell how our landscapes react to the increased alkalinity of our water supply. We hope the effect is minimal, because gardening in our high altitude semi-arid climate is challenging enough as is!

This is the official blog of Outdoor Design Group, Colorado Landscape Architects.  For more information about our business and our services, click here.

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When the Grass was Greener

Once upon a time, there was a castle guarded by soldiers. Enemies obscured by the trees would sneak close to the castle, so the soldiers reduced the threat by removing the trees. Without the trees, the land filled in with grasses, thyme, and chamomile. Animals began to graze in these new fields, keeping the plants low. The soldiers could see clearly across the land, and the sheep were fat and happy. The castle prospered, and everyone who visited wished their land could be so grand. The other land owners cut down their trees and filled in their land with grasses. The smell from the grazing animals wasn’t ideal, so they brought in men to cut the grasses low instead.

The “green carpet” surrounding the finest castles and estates in the 16th & 17th century became a status symbol, and planted the seed for the sod lawn we’re all familiar with today.

In the United States after WWII, automobile technology and availability took off. With the open road ahead of them, well-to-do folks left the cramped urban conditions of the cities, moving outward to new suburban neighborhoods.

Planners like Frederick Law Olmsted and Abraham Levitt gave the people sprawling neighborhoods, with acres of lush green grass. With the popularity of the 2-day weekend on the rise, homeowners indulged in their green Edens. This ignited a new chapter for the centuries old status symbol of the turf lawn – now repurposed for mini-golf and lawn bowl rather than spying enemy invaders and feeding livestock.

“No single feature of a suburban residential community contributes as much to the charm and beauty of the individual home and the locality as well-kept lawns” – Abraham Levitt

Ingrained into the new vision for the American Dream, well-kept lawns became the golden standard. With an estimated 30 to 40-million acres of the United States serving as an irrigated sod lawn today, this status symbol is butting heads with our resources and priorities.

The cold hard truth about lawns are that they are a water hog, high maintenance (what other non-food-production plants do you cut weekly, fertilize seasonally, and treat with chemicals?!), lawns are a food desert for animals & insects, and they do nothing for our groundwater while the water runoff often pollutes creeks and streams with high nitrogen fertilizers, causing harmful algae blooms. All of that lawn maintenance also creates air pollution and noise pollution from mowers, blowers, and trimmer equipment.

A renovation project where Outdoor Design Group helped our client reduce their turf lawn.

But lawns can be great in the right location!

This is where “active-use” vs. “passive-use” spaces come into play. Lawns can be very durable, and are amazing for active children and pets. Maintaining a lawn to play and entertain on is a lovely idea. Kentucky Bluegrass has been a popular turf choice for decades, but climate suited alternatives like Dog-Tuff Buffalo Grass, Bermuda grass, or “steppable perennial lawns” made up of creeping thyme or clover can serve the same purpose as high-water turf lawns with fewer drawbacks.  While choosing the right type of lawn for your environment is a start, reducing the overall amount of lawn is still the key to a progressive and sustainable landscape. Maintaining any type of lawn on the side or front of your house where no-one ever spends their time is wasteful for you, your wallet, and the environment.

Steppable groundcover used with other perennials, step stones and mulch.

Consider ditching the golf-course-quality front-yard peacocking and save that neighborly competitiveness for the holiday light display. Instead, beef up your shrub beds, add some neat planters, and opt for native seed mixes that include drought-tolerant grasses & wildflowers. Keep your lawn only where you will use it, and plant a nice tree just west or south of it to keep it cooler and healthier during hot sunny days.

A front yard filled with a diversity of ornamental grasses, perennials, shrubs, landscape rock and mulch.

This is the official blog of Outdoor Design Group, Colorado Landscape Architects.  For more information about our business and our services, click here.

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Are All Oak Trees Slow Growing? …No, They’re Not

It seems that the fields of landscaping and gardening are full of many timeworn statements that people like to repeat over and over. Some of these green “rules of thumb” are tried and true, while others may not be so true.

One landscape stereotype regarding tree growth rates that is being challenged is the old adage that “oak trees grow slowly”.  I have heard and read this many times and I have repeated this mantra myself for years. But a study of urban trees in the Denver Metro area, published by the Colorado State Forest Service, got me to rethink that stereotype.

This tree study recorded the growth rates of 19 commonly planted trees planted in public land in the Denver suburb of Westminster, for 24 years. The authors of the study measured the trunk diameters of the trees in 1992, 2000, 2008, and 2016.

The most eye-opening nugget of information in this report is that the white oak group of trees (bur, swamp white and English oak) were the 3rd fastest growing trees in the study! They grew faster than green ash, lindens or honeylocust trees.  They even had the same rate of recorded growth as silver maples, a species often referred to as a “fast grower.”

Data table from the Colorado State Forest Service’s study “Growth Rates of Common Urban Trees in Westminster, Colorado”. Authors: K.A. Wood and A.M. Poulson

One important take-away from this study for me is the fact that we should reevaluate what trees seem to be the best for planting in challenging ecosystems such as the urban/suburban areas of the high plains where Denver sits. It is worth quoting the State Forest Service report to emphasize this point:

“Some tree species revealed to be fast or moderate growers in this study have previously been viewed as slow growers, and they are often passed over at planting time. However, equating growth rates with vigor can be misleading, as some of the slower-growing tree types on this list can be the most adaptable to the area (including hawthorn, hackberry and honeylocust). Adding newly discovered fast-growing species to the planting palette and incorporating hardy, slow-growing species will maximize the success of planting projects and promote species diversity.”

To be clear, it is only one type of oak trees (white oaks) that exhibited fast growth in the study sample. Red oak was also in the study and showed slower growth. The authors note this is possibly due to the low pH of high plains soils.

It very well could be that other types of oak trees grow slowly too, but we don’t have data for that. Or, perhaps another study may come along and challenge that, as well. So, as with many “rule-of-thumb” type statements, don’t believe it until you have seen some data to back it up.

This is the official blog of Outdoor Design Group, Colorado Landscape Architects.  For more information about our business and our services, click here.

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Hail-proof Plants for your Colorado Garden

It’s summer, which means in Colorado and other surrounding states in the Central Plains/Inter-mountain West region of the country, it is Hail Season!

Earlier in the Summer, the Denver area had several sessions of hail that ripped through gardens and landscapes late one June night. Avid gardens who’d been awakened by the cacophony of thunder, torrential rain and hail that night, sleepily rushed out in the morning to find shredded plants and debris scattered everywhere. I myself had many plants I’d been babying from seed and roots all Spring which were severely torn up by the barrage of hail stones.

This horticultural carnage got me wondering what plants are best at surviving the annual severe weather in our region? As I walked around the yard sadly inspecting the damage, it was easy to see that the native and climate adapted plants fared best from the aerial ice-bullet onslaught. So I thought it might be a good idea to create a list of “hail-proof” (or at least “hail-resistant”) plants. The following list of plants is just a cursory look at some possible plant choices that should be better able to handle hail storms:

Ornamental Grasses:

-Many, many varieties. Some of the hardiest, and easiest to grow in our region are Feather Reed (Calamagrostis spp.), Switch grass (Panicum virgatum), Little Bluestem (Schizachyrium scoparium), and Giant Sacaton (Sporobolus wrightii)

Korean Feather Reed Grass

Plants with Grass like leaves:

-Daylilies, Bear Grass (Nolina microcarpa), Desert Sotol (Dasylirion)

Trees and Plants that Leaf out Later:

-Catalpa, Gaura, Datura

Datura

Trees and Plants with Small Leaves:

-Honeylocust (Gleditsia triacanthos), Rabbitbrush (Ericameria nauseosa), some Hysops (Agastache spp.), some Penstemons, California Fuschia (Epilobium canum), Coreopsis

Pineleaf Penstemon

Plants with No or Insignificant Leaves:

– Cacti (many varities), Ephedra, Broom (Cytisus purgans, Cytisus scoparius)

Cylindropuntia cactus

Plants with Tough Leaves:

– Evergreen trees & shrubs (Pine, Spruce, etc.), Agave, Yucca, False Yucca (Hesperaloe)

Agave

Plants that can be moved or sheltered easily:

-Annual/Perennial pots

Pot planted with perennials

This is the official blog of Outdoor Design Group, Colorado Landscape Architects.  For more information about our business and our services, click here.

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What’s That Stench? – The Corpse Flower & Other Fetid Flowers

This past August, the Denver area was captivated by another blooming of a corpse flower (Amorphophallus titanum) at the Denver Botanic Gardens. Large crowds lined up to get their chance to get a whiff of the bloom that emits a fragrance similar to a rotting animal carcass. I was one of the masses of plant geeks who waited in line early on a Friday morning before work, just to get a glimpse and a sniff of the malodorous corpse flower. The first bloom of an Amorphophallus titanum plant doesn’t appear until after 8-20 years of vegetative growth. A second bloom from a corpse flower may not occur until as long as 10 years after the previous bloom. Although this was the Denver Botanic Gardens third bloom of a corpse flower, the rare occurrence for a bloom (along with the plant’s other odd characteristics) leads to a lot of excitement for botanical enthusiasts.

Amorphophallus titanum photographed at the Denver Botanic Gardens on August 31, 2018.

The foul stench of the bloom is not as interesting as the giant size and fascinating form of the flower. This Indonesian rain forest native sports a huge flower (it is actually many flowers, aka an inflorescence, grouped together on one fleshy axis, what botanists call a spadix) that is unlike any flower that grows in North America. In fact, botanists tell us it is the “largest unbranched inflorescence in the world”. The massive size of the flower is the source of another common name for it, the Titan Arum. That common name was bestowed by the British naturalist and TV host Sir David Attenborough for his BBC series “The Secret Life of Plants”. Mr. Attenborough felt that repeatedly calling the plant by its botanical genus name Amorphophallus (Greek for misshapen phallus) was “too rude for television audiences”.

Readers are likely familiar with other plants that bear spadixes such as the common houseplant, the Peace Lily (aka Spathiphyllum, related to the corpse flower, and also in the Arum family of plants). Unlike the inflorescences of the peace lily which are around 6 inches in length, the corpse flower inflorescence can grow as tall as 10 feet, although the one at the Denver Botanic Gardens (nicknamed “Stinky”), was probably closer to 4 or 5 feet tall. In the center of the flower is the large and somewhat crumpled looking spadix. Framing the giant spadix, is a wine colored skirt-like apparatus that appears to be a type of flower petal, but in actuality is called a spathe. The spathe is a modified leaf which helps protect the spadix.

Aside from the fascinating scale and form of the corpse flower, the rank stench it produced was curious as well. While viewing the bloom, I would describe the acrid scent as similar to an infant’s dirty diaper. There are several repulsive chemicals released during its peak bloom period. Scientists have recorded a range of compounds emitted by the corpse flower that are also found in limburger cheese, animal feces, stinky feet, and dead fish, along with some other not so foul compounds. The exact foul fragrant mix emanating from the flower might vary hourly from rotting fish to rancid cheese throughout the blooming time. All of these nauseating notes are released as the plant is able to heat itself up to 90 degrees Farenheit, helping to volatilize the stench and get noticed by pollinating insects that might pass by. The increased heat of the bloom is theorized to also give the illusion of a recently deceased animal carcass.

Before we look at other stinky flowers, it is interesting to note that there are about 170 other species closely related to Amorphophallus titanum. Botanists report that many of these 170 species emit various unpleasant odors that range from rotting meat to rancid cheese. And size of flower does not translate to the power of stench. Some of the smaller species stink the most. However, some of the 170 species actually smell pleasant to humans, such as A. haematospadix, that smells of banana, and A. manta which smells of chocolate.

While the corpse flower may get all the attention for being one of the world’s most unpleasant floral scents, there are many other fetid flowers that are lesser known, but are just as notable for their “disagreeable odors”.  Apparently emitting foul odors has been ecologically successful for several species. And of course, what humans may consider a foul stench, a carrion beetle may interpret as a false “dinner bell”.

Now on to the list of a few of the other unpleasantly scented flowers:

Rafflesia arnoldii – Another so-called “corpse flower”, this one is also native to Sumatra, Indonesia, like the other corpse flower (Amorphophallus titanium) that recently bloomed in the Denver Botanic Gardens greenhouse. This corpse flower is quite rare, and is a parasite on the host Tetrastigma leucostaphylum. It is said to have one of the largest (1m wide) individual flowers in the world, and has no roots or leaves. Most of its life is spent inside the stems and roots of its host. Rafflesia arnoldii only becomes visible when its flower buds break through the bark of the host and form into the large flowers, which like Amorphophallus titanium, also smell like rotting animal flesh. Unlike Amorphophallus titanium, Rafflesia arnoldii is very difficult to grow in cultivation.

Frittillaria agrestis  -This flower from the lily family, commonly referred to as stinkbells, is purported to smell like dog feces. It is endemic to California.

Frittillaria imperialis –This is another flowering plant from the lily family, commonly called  “emperor lily”. It’s native to Iraq, Iran and other parts of Central Asia, and has showy blooms that have endeared it to horticulturalists who’ve brought it into wide cultivation. The flowers are said to smell like skunk. Others say they have a “distinctly foxy odor” which repels mice, moles and other small animals.

Tree of Heaven (Ailanthus altissima) – This weedy tree, originally native to China, but now present in many urban and other disturbed sites in North America, emits a slightly unpleasant scent from its flowers. The smell is akin to rotting garbage. The leaves and green stems of Ailanthus also smell unpleasant when cut. The Chinese name for this tree, chouchun translates to “foul smelling tree”.

Hawthorne trees – (Crataegus, various species) These beautiful trees are a useful ornamental tree to have in a xeriscape garden. They are tough and beautiful drought survivors. However pretty the white flowers are in springtime, they do not, in my opinion, have a pleasant scent. Some observers have likened it to being like ‘power bait’, the fish lure. Luckily, it is not a very strong or long lived odor.

Lysichiton americanus – Western Skunk Cabbage. This North American native is a distant relative of the Amorphophallus titanum, as they are both members of the Araceae family. It is native to wet areas of the Pacific Northwest. As the name suggests, it emits a “skunky” odor.

These are just a few of the many unpleasantly scented plants to be found in our world. Perhaps you have one you would place in this group of foul smelling botanicals?

This is the official blog of Outdoor Design Group, Colorado Landscape Architects.  For more information about our business and our services, click here.

 

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