Sun · Soil · Plants · Water — a native, low-water garden in Denver

Getting Started!

I’m going to assume that you want to replace some lawn grass with low-water plants to reduce consumption of this most precious resource here in the rocky mountain west. When I decided to tear up the lawn on our side parkway, aka city ROW, that is exactly what I was thinking. It’s a medium-large sized area for a Park Hill “hell strip” (about 100ft by 15ft) so I did some research to get my bearings. I’ve been a veggie gardener for years, but this was going to be entirely different! The year after starting this garden in spring 2022, I began volunteering at Denver Botanic Gardens in some native and low water gardens to learn first-hand from experts how to grow and care for water-wise plants.

A Bit of Garden Philosophy

I once read that “every garden needs a gardener.” I found this to be personally meaningful. I interpreted this to mean that your garden should be a reflection of you, not your designer or a copy of someone else’s garden.

If you research “types of gardens,” you’re going to find a number of ways to arrange plants, rocks, sculptures, items of interest, etc. I encourage you to identify what feels right to you for your site. There are many types of gardens, usually arranged by style and or plant types. Don’t let these descriptions of what is “correct” limit your creativity! I believe I have used ideas from at least three major garden styles - Rock & Desert, Pollinator/Wildlife and Cottage. And I have focused on xeric to low-water plants that are native or adapted to our steppe climate.

Some call this a naturalistic garden, as it usually tries to emulate a walk in a specific environment. For our garden, I wanted to focus on native plants found in shortgrass prairies, and the foothills of the front range, as these native habitats are rapidly disappearing, as are many of the species that have evolved in them.

I love walking in nature, and paying attention to the interplay of plants, rocks, and natural debris; so hard to duplicate that perfection! One thing I’ve done is reuse every rock and cool bit of old wood from my property, in lieu of buying and having loads of this decorative hardscaping material trucked to our yard. I figured there was no need to burn more fossil fuel than I felt was necessary, and after tearing down a small water feature in our backyard (which I built and maintained for 20 years) there was plenty of material to reuse. Not something out of Martha Stuart magazine, but meaningful to me.

How would you like people to experience your garden?

I wanted to create a beautiful space that people might wander through, or pause and enjoy for a moment out of their day. As I began learning about the importance of saving biodiversity, I realized that creating a space of native and other plants that can create a micro-ecosystem that feeds and shelters all kinds of life would bring even more purpose to the project. I wanted to allow people a place to see this diversity in their day-to-day city life, in particular the kids. At a certain age they love to run from stone to stone on the paths and stop suddenly to see something; it encourages curiosity. The irregular stones used for my pathways were intentional. Japanese gardens often use this principle that irregular stone paths cause us to pay attention to the present, which brings greater appreciation and contemplation than a nice straight path does.

Why include so many native plants?

As you probably know, the many species that make-up an ecosystem are all INTER-DEPENDENT, and in a healthy ecosystem, wonderfully and amazingly balanced. The plants that evolve over millions of years to a particular climate maintain thousands of other species, all of which are at risk due to habitat loss. Note that the word ‘native‘ depends on a designated area. I’ve included the word to describe plants native from the great plains to CA, and south to Mexico. You may decide to include only plants from the state of CO of course, but I let the climate here drive my decisions.

Four Seasons of Interest

Our site is mostly “full sun,” so that became an important consideration for plant selection. I wanted to design a space that would be interesting even in the winter months. Grasses, shrubs, and evergreen species maintain some visual appeal even when temperatures drop and I wanted to be sure to include some. I have also committed to leaving as many perennials standing as I could until spring to provide food and shelter for animals and insects. What remains is called a winter garden, which can be beautiful with dead seed pods, and empty plant stems.

Four things to consider before the plants:

You may notice that I have placed “Plants” as item #5, instead of #1. Please bear with me on that decision. I believe it would have helped me considerably to have understood the first four points I have listed here before getting caught up in plants. If you just want help picking plants like ones you’ve seen in my garden, feel free to jump ahead, and learn by trial and error as I have often done!

I was too overwhelmed (and ignorant) to create a true garden design with all the plants thoughtfully chosen and positioned when I began, so I decided on some cornerstones and planted them first, with the idea that I would choose others that fit with these trees, grasses, and a few prairie shrubs.

1Sun+

Spend time throughout the day becoming aware of how much sun your site gets. Note the relationship between structures and trees that cast shadows, and the ground that is affected. You will absolutely discover changes from one little area to another that will affect the plants you try to grow. Obviously, as the growing season progresses, these sun angles will change considerably. This does require you to spend a few minutes now and then doing nothing but it is worth it!

2Water+

To irrigate or not; that is a question I’ve been asked many times. Drip systems can be invaluable for establishing even drought tolerant plants. As our summers seem to be getting hotter with less consistent precipitation, it is also a very efficient way to water occasionally when needed. They are relatively cheap, and don’t require a lot of knowledge if you like to DIY, but are usually installed (by you or a contractor) after you have a design for the plants, and before they are planted. A downside of drip systems is that they are made of plastics, break frequently, and will usually water a small area at each dripper. A note on drip systems: I now use mine only as a backup to hand-watering, as the plants need varying amounts of water to thrive.

I had neither a design, nor plants, when I paid a contractor to remove several inches of weeds and grass. I wanted to lower the garden to grade (the level of the sidewalk) and then a few inches more to allow for some kind of growing medium and covering mulch. I ended up having them install a ¾” drip line in a serpentine pattern that extends the length of the site. They also ran it under two sidewalks, which I didn’t want to try myself! Ask them to mark it with blue flags so you can find it. I then added (2) ¼” drip lines with 2 gph drippers myself to each of my plants as I planted.

3Soil+

Park Hill’s soil is largely clay, or loam clay unless it has been improved. I’ve been told there is also sand, but haven’t seen it :-) “Native” plants have evolved to handle the weather of this steppe region, but if they are from what was once shortgrass prairie, for instance, they require a soil that is much sandier and even rocky. Many have evolved thin roots that are able to move through sand but not clay. If you want to grow plants native to Colorado, adding compost and other amendments may not work! My site appears to be mostly clay, compacted like concrete for longer than I’ve been alive. I have found that the best mixture for my plants tends to be like 50% sand, 25% compost, and 25% pea gravel or even better, squeegee (available at places like Bedrock Landscaping Materials.) Since I learned this along the way, I now mix this myself, and replace the dirt with it, that is removed when I plant, mixing it into the hole. When I have grown the same plants or sown the same seed in clay with added compost and in my sandy mix, the ones in sand are much bigger and happier!

4Weed containment and mulch+

Mulch is always recommended for keeping down weeds and keeping in moisture. Most of us think of wood bark as the thing to use. As I am about to explain, this isn’t necessarily true! Most xeric or low-water natives prefer a mulch made of pea gravel or pebbles, squeegee, or expanded shale. Not knowing this fact, I ended up choosing double shredded cedar, aka Gorilla Mulch because it is attractive, and it stays in place better than bark. At the time of this writing, I haven’t needed to replace or replenish it in four years. It is also not dyed or treated with anything, but IS more expensive than chips or bark. It is great at keeping weed seeds from germinating and smothering existing weeds. It also prevents the sometimes unwanted spread of your plants that will often set thousands of seeds each year.

Unfortunately, I have figured out it isn’t the optimal choice for native plants, as it will decompose and add organic matter to the soil. As discussed above under number 3, you really want to be adding sand and gravel, with just a little compost or organic matter. If I was starting over (as you are!) I would use about a 4 inch layer of the gravels mentioned above as the mulch for any planted areas, and simply dig through it into the clay or loam for each plant, so that it mixes into the existing soil providing an ideal way to grow our natives and provide them better soil at the same time. Live and learn!

I made the strategic decision to have weed barrier fabric (heavy gray) installed after the excavation, and under the mulch. The positives are that it has completely kept the remaining weeds/seeds from popping up except around the very edges of the site. It has also prevented seeds (both weed AND desireable) from taking hold below the mulch. It also keeps plants that create a web of underground rhizomes, like Milkweed, or Russian Sage from spreading uncontrolled.

The negatives are that you or your contractors will have to cut through it for each plant or lay it in such a way as to allow the proper space for each plant or grouping. Also, if your plants need more space than they’ve been given in the cutout after a while, the barrier will constrain them and prevent naturalization or reseeding except where you have removed it. Given what I now know, I would not use weed fabric except in areas that have no plants.

5Plants+

“Keystone plants are native species that play a disproportionately important role in supporting local ecosystems.”[1] I’ve tried to include as many as possible now that I’m aware of the concept. Some of these plants literally support hundreds of species. This link to CSU Extension Garden and Landscaping is a great resource to learn about this and to answer many many questions you will have.

This article from the National Wildlife Federation provides a great primer on the importance of maintaining native plants. I read a recommendation to try for 70% native plants when creating a new garden space. This seems about right to me, as long as other plants you choose are adapted to the sun, soil, and low water use. The search feature of this site allows you to see whether or not a plant is native.

Where to buy these plants

The Plants

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