Native Plant Propagation

When carrying out restoration, it is important to use native plants for re-vegetation. Luckily in Alberta there are a number of large commercial plant nurseries that supply native species of shrubs and trees suitable for this. However, the best results for restoration success come when plants are sourced as locally as possible. While these nurseries offer the right species, they are often sourced from places like Calgary and Lethbridge, which have very different conditions to those of the SEAWA watershed. Additionally, these plants are often bred for horticultural use, and can be more delicate than wild plants. It is no doubt that nursery plants are convenient, but for optimal restoration results it is best to use the stock of plants growing wild in the region.

Propagating Wild Plants

To utilize wild plants for restoration, SEAWA uses plant propagation to grow copies or offspring of trees and shrubs that grow within the watershed. This is done either by growing plants from seed collected in the fall, growing cuttings taken during the winter, or occasionally through direct transplantation. To date, SEAWA staff have had success growing the following species:

  • Plains Cottonwood (Populus deltoides)
  • Silver Sagebrush (Artemisia cana)

We encourage our members to propagate any native plants that interest them! If you are new to plant propagation and would like to give it a try, click here for an excellent resource to help get started! Additionally, you can choose to donate propagated plants to SEAWA, and we will transplant them at our restoration sites. Learn more about donations here.

How to Grow Your Own Cottonwoods

SEAWA staff and volunteers in recent years have tried growing native cottonwoods for use in restoration, as the local populations of these trees are most likely to be successful. Winter 2020/2021 was the first time SEAWA tried plant propagation on a larger scale than just a few plants at a time. With the COVID-19 pandemic limiting staff use of the SEAWA office, the space was turned into a greenhouse for tree cuttings. Plants were also cared for in the homes of staff and volunteers. From this endeavor, we have developed some tips for others who would be interested in propagation.

Tips for cottonwood propagation:

  • Choose the trees you would like to harvest stems from before fall. In late summer you can check the donor trees for obvious signs of disease or pests. Ideal trees for stem harvesting are naturally growing along a body of water.
  • For restoration purposes in Southeast Alberta, Populus deltoides var. occidentalis is the best suited. There however are several different poplar and willow species and subspecies that grow in the area, as well as hybrids. For landscaping and aesthetic purposes many different options can work well.
  • Harvest stems during chinook periods in late January and into February. Early March is also a good time to harvest. Harvesting in late March and early April can also work well. In this case the plants can be grown entirely outdoors, and should be able to withstand any late snowfall and low temperatures.
  • For best results, choose stems that are healthy, 1-2 years old, 50-80 cm in length, and less than 1 cm in diameter. The stem must retain the terminal bud(s) (the tip of the stem/branch). Stems like this should root rather quickly, with no added rooting hormone necessary. Older, larger stems take much longer to root.
  • Place stems in a bucket or vase with water 10-12 cm deep until the soaked ends show the beginning of new roots (tiny bulging white spots); change the water weekly.
  • Prepare a soil mixture of 2 parts garden soil (ex. black earth/top soil), 1 part potting soil, and a small amount of sand (play sand or weighted sand bags work for this). These should all be available at a farm or garden supply store.
  • Fill some pots with soil (pots must have drainage holes). The depth and volume of soil will depend on what allows the stems to stand up stable.
  • To plant the stems, make a hole in the soil and place the stem gently inside, such that the emerging root points aren't rubbed off or damaged (they are soft and fragile). The bottom of the stem be approximately 2.5-3 cm from the bottom of the pot. Pack the soil around the stem and water.
  • Place the planted stems near a sunny window (may also supplement with grow lights), away from heating vents and fans (these will dry the plants out quickly). Water when soil surface is dry.
  • Pests may be an issue throughout the growth process. Fungus gnats from contaminated potting soil can be managed by spraying a light soap solution, or insecticidal oil (ex. neem oil) on the soil surface periodically, as well as by using sticky insect traps. As the leaves begin to emerge, aphids may become a problem as well. They should be dealt with by killing any adults and gently wiping away eggs and larvae with soap solution or oil. Other pests may make appearances depending on what lived in the parent tree (SEAWA staff found a tent caterpillar). Many poplar varieties are susceptible to fungal infestations as well. A simple fungicide of baking soda, water, vegetable oil, and dish soap can be used to keep this at bay.
  • When risk of frost and sudden cold weather is gone (late April-May), plants can be placed outdoors. It is a good idea to protect young plants from deer.
  • When the plants have developed a strong root system (roots emerging from pot drainage holes is an obvious sign), they are ready to be transplanted by August or earlier. Avoid transplanting during periods of extreme heat (30+ degrees C). Protection from deer is recommended.
  • Ensure plants have enough water until first frost hits. Build a basin around each tree that holds 7-10 litres of water, and water twice a week. In Southeast Alberta regular watering is recommended, though plants in wetter climates may fare well without additional water.

How to Grow Silver Sagebrush

Recently, SEAWA has been exploring the use of silver sagebrush (Artemisia cana) to aid in restoration. Silver sagebrush is known to have exceptionally deep roots, and grows very well in dry conditions, making it an ideal shrub for Southeast Alberta. SEAWA is using the shrub's deep roots to help control erosion on the high banks of some restoration sites, as well as A. cana's allelopathic properties to hopefully control some invasive species such as leafy spurge (learn more here).

Tips for propagating silver sagebrush:

  • At the second or third chinook in early winter (November or December), collect the seeds by stripping the flowerheads of mature shrubs into a large paper bag
  • Store the seeds in a dry place with the bag partially open to facilitate drying
  • In March or April, strip the seeds from the stalks
  • Have a commercial tray of pre-prepared peat plugs; water to make them moist
  • Press seeds on top of each moist plug; put the tray lid on somewhat tilted for ventilation
  • Place seeded plugs by a sunny window and watch the seedlings grow; water as needed; keep the plugs moist to prevent the seedlings from drying out
  • When a lot of roots are growing out of the plugs, transfer them to bigger pots
  • When risk of frost is over; move the pots outdoors
  • When roots begin to come out of the bigger pots, plant them in the field (approximately mid-late June)
  • Water the plants in the field during the entire first season. They develop drought tolerance later once their taproots have grown enough to reach deeper soil moisture.