Sun · Soil · Plants · Water

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!

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.

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 40% sand, 25% compost, and 35% pea-sized gravel or even better, squeegee (available at places like Bedrock Landscaping Materials.) Since I learned this along the way, I now mix this myself (roughly by volume,) and replace the dirt 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!

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 Hair 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 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. Another benefit is that it prevents seeds (both weed AND desirable) from rooting. 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.

“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