My life here December through March is one of slogging through mud of varying viscosity, and as I work upon the few ongoing projects that I can when the ground is saturated, I realize how restrictive my environment can be.
My island paradise is built upon a mound of glacial till, dumped here during the Pleistocene glaciation that carved out Puget Sound. A rubble pile is essentially what it is that includes alternating layers of hard clay ‘hardpan’ and unconsolidated gravels. Years ago my mother found a few choice remnants of life from Northern Canada, from which the island partially originated: these included a chunk of sandy rock full of fossil shells and an agate the size of an adult fist.
Alas, the gardening opportunities here are much more limited. My father bought this property cheap – $800 an acre in 1971 – for a reason. Its biggest feature is a central wetland that drains a substantial area of land around it. A series of seeps, intermittent streams, and small wetlands surrounds the larger basin and in winter, everything flows. The partial schematic shows the major drainages in blue, dark green areas are forests, and light green areas are open and generally represent civilized territories. Excised at the bottom is another wetland complex that flows towards the lake (large blue area) from neighboring properties.
In summer, I can convince myself that lots of things will grow here, but winter inundation quickly changes my mind. Heavy rainfall (18 inches since December 21 with a 5.1 inch ‘surplus’) has turned even what I’d perceived as solid ground into slick mud. It has also allowed me to delineate all of the partially inundated areas where I cannot plant anything not tolerant of flooded, anaerobic conditions.
What then, do I plant?
Willows, rushes, reeds, and iris top the list of course. While my goal is native wetland restoration in the hinterlands, I would like to see a wider variety of plants with color and interest closer to the house and driveway.
Soil will play a large role in this determination. In most of the wet areas on the property, the soils are comprised of heavy clay. In other areas, the soil composition is more of a sandy loam. Often I can dig below a layer of compacted clay to encounter many feet of sandy gravel and reddish mineral soil. These areas drain rapidly, unlike the others that may continue to remain moist all year.
The heavy clay rules out many plant choices, such as the quaking aspen that I recently purchased from my local conservation districts. Wet and well-drained are terms that apply to many plant species, so I have to probe the soil around the wettest areas to find the edges of the more well-drained soils. Sun is another condition that many wetland species prefer, yet I must deal with shade in many areas.
Expanding the local native plant diversity on the property, expanding regional native plant diversity, and introducing wetland-tolerant ornamentals are the goals that I used to generate the following list:
Quaking aspen – I got these for color, but found out after the fact that they need full sun, and moist, well-drained soils and generally prefer higher altitudes. I chose to put them in a woodland opening in a sandy, loamy forest soil at the edge of a wetland where facultative upland species such as alder and willow suggested a higher water table. I think they may end up needing a lot of supplemental water.
Blue elderberry – Sambucus cerulea; This is a regional native plant choice as they seem to occur more often in the drier areas of the state. I know them well from drainage ditches in Central California. Here we have mostly red elderberry, but I wanted to make jam from the blue fruits. These can take a drier soil than the red species, which I have found growing at the edge of the lake. I will likely put them along the drier edges of a wetland adjacent to the garden where the soil stays moist most of the year.
Bald cypress – Taxodium distichum ; This deciduous conifer can take continuous moisture and periodic flooding, plus it provides beautiful fall color in shades of gold. I will put three along the boggy edge of the wetland where the gold will contrast with the Douglas fir forest backdrop.
Douglas spirea - Spirea douglasi; These take inundation well, and I am scavenging them from other areas of the property. They have lovely, pink foamy flower clusters that smell wonderful and spread vegetatively.
Red Chokeberry – Aronia arbutifolia; tolerates moist soils but not wet; may be on the property already, but I’m still trying to identify it. Has beautiful orange-red fall foliage and red berries.
Buttonbush – Cephalanthus occidentalis; a Southeastern US native used here as an ornamental; purportedly can tolerate heavy clay soils which would make it a good candidate. Very attractive.
Summersweet - Clethra alnifolia; a Southeastern US nativethat purportedly prefers organic, acidic soils such as found in bogs; may only do well on the loamy soil surrounding the wetlands. Also very attractive. I’d plant this and buttonbush closer to landscaped areas for effect.
Highbush cranberry – Viburnum opulus; I’ve planted lots of these around the garden and found that they prefer moist, organic soil. Otherwise, they take forever to grow and the deer just mow them down to nubs. I plan to move some of those languishing in drier areas to moister places along the edge.
I want to keep most of the wetland open, and will fill in with soft-stemmed bulrush and maybe skunk cabbage already present in abundance elsewhere on the property. I’m also introducing various sedges to replace the ragged field grasses currently present. Ultimately, I want an area with no blackberry, a pleasing succession of color scheme from spring through fall, and a consistent texture throughout the lowest, wettest areas.
Sedges (Carex spp.) grow naturally in large clumps on either side of the lake