Ever wonder why certain plants are used in restoration work and not others?
Many factors are looked at when picking plants for any project; what kind of soil, how wet the soil stays during the year, and what plants are already thriving on the site.
This post will look at how the wetness of a site helps determine what plants are used in restoration.
It is one thing to know how well soil will hold or drain water around a plant, it is another thing to know when to expect the water and how much will come. In the Pacific Northwest we receive a large quantity of our water from the Fall through Spring. Summer can be downright parched. For this reason it is good to know what a restoration site looks like all year round before determining what plants to include.
Some restoration sites may retain water year round and others, like North SeaTac Park, may be moist during the winter but dry during the summer. These differing levels of moisture through the year are caused by a combination of rainfall and soil composition. Knowing the moisture profile of the site allows planners to determine if they need drought resistant or aquatic plants for their restoration. In some cases a mixture of both may be needed.
Another factor to consider is how the tree canopy might affect the amount of rainfall actually hitting the ground. A dense canopy could mean little to no rain reaches the understory. We soon realized this might be the case at some portions of our site at North Seatac Park because even in rain some areas could stay relatively dry. If this is a really big concern, manually watering plantings should be considered. Fortunately, for us in the Pacific Northwest even in the dry years we still get downpours in the winter that get passed the canopy and give our plants a good drink!
Knowing the moisture level of a site all year round also determines the best times to plant. Planting in late Autumn and early Winter, when plants are hibernating and will be exposed to large amounts water, is the best way to give plants the best start at a new location. This keeps the plants from being too damaged from transplanting and also exposes the roots to water for a long time allowing them to establish before the Summer heat arrives. Ideally the plants would be watered through the first, and possibly second, Summer to help further establish the roots and increase the likelihood of survival However sometimes it is not possible to manually water a restoration due to size,location, or resources. This means choosing plants that are best suited to the sites conditions is extremely important to the success of the restoration project.