Defensive Gardening 101

Protecting Your Garden From Flood & Fire

As climate change affects weather patterns, gardeners need to think about gardening in new ways, including plant protection. Though Maritime Northwest winters have typically been wet and cool, this year we’ve experienced the warmest and driest first half of January on record. That represents a major swing from recent years, when the usual daily drizzle was often replaced by epic downpours that caused widespread flooding. That stretch of super rains caused many gardeners with seasonally soggy lawns to evaluate the need for a rain garden, and offered those who had already built one excellent opportunities to assess its effectiveness.

Despite the current under-par rainfall, it’s a good idea to be on the watch for places where drainage is less than optimal. One of the best ways to do this is to capture images and/or videos of heavy runoff, along with enough context to let you and a drainage professional recognize where the action is. Take pictures of areas that puddle after rain as well, especially where the puddles are persistent. If water laps around your home during rainstorms, plan to have new curtain drains installed this summer to protect your house for years to come. New or larger side drains will help keep driveways dry as well as other areas that get swamped when heavy rains arrive.

Where Water Flows, Soil Follows

Heavy rains can wash away inches of topsoil very quickly. To prevent this, we can stabilize sloping areas that tend to erode with plantings of natives with sturdy, resilient root systems. Where erosion has already occurred, start the restorative process by installing sheets of jute netting, which comes in various widths. If you have help with this athletic process, make sure everyone knows that the top edge (4-6 inches) of the netting gets buried and the netting sheets run down the slope, not across it.

Fasten each sheet every few feet on both running sides with metal anchor pins that are at least 10 inches long. When new sheets are added, always overlap old and new by 4-5 inches. Netting can be used between existing plants as well as on washed out areas by spreading the jute netting wide above and below each plant, then bundling it around the plant’s base. Plant youngsters by tucking their roots into the pockets of the netting, cutting the jute as little as possible (preferably not at all).

Natives With Clinging Roots

Good trees for slope stabilizing include natives with spreading root systems, such as red alder, vine maple, native willows, and cascara. Shrubby redtwig dogwood, salmonberry, and ninebark are also recommended, as are evergreen wax myrtle, huckleberry, and salal. Helpful deciduous native shrubs include Douglas spirea, ocean spray, and Indian plum. Wet season planting is best because the roots get a chance to establish before hot, dry weather arrives. Summer watering on damaged slopes without eroding them further can be tricky and is best provided with temporary soaker hoses and/or drip irrigation for the first few years.

Defending Against Wildfire

Terrifying wildfires raging all along the West Coast have sensible gardeners wondering how to make home landscapes more fire resistant. Here in Washington, we can learn a few basics from Eastsiders, which include clearing all vegetation away from the home. This is a hard sell for Westsiders, but home inspectors would certainly agree that anytime plants touch wood, the potential for problems with ants, termites, rats, squirrels, molds and mildews increases. An 18-inch strip of crushed gravel along the walls of any structure will help keep them drier in wet seasons and reduce the likelihood of pest damage as well.

No plants, especially trees or shrubs, should touch the house walls or overhang the roof. A professional arborist can recommend ways to prune such trees without destroying their natural shape. You may also be advised that some trees should be removed altogether, a painful choice that nonetheless must be made, even where fires haven’t yet ravaged the area. That very fact makes it more likely that such fires will occur, especially since recent hot summers have created more deadfall than usual in wooded neighborhoods. To reduce the risk of local fires, clear nearby woodlands of blown down branches and selectively thin dense underbrush.

Defending Against Wildfire

Where wildfires are more common, homeowners are urged to create a “defensible zone” of about 30 feet around buildings. This doesn’t have to be a barren sweep of gravel and boulders, but should be planted with lower growers that are not especially flammable. Canopy trees should be regularly thinned and pruned to make wooded stands less dense, and the understory should be kept clear of deadwood. Thin trees so that their crowns are at least 15 feet apart, and remove dead lower branches to a height of at least 15 feet as well.

Sadly, such rigorous editing destroys the natural character of wooded properties where nurse logs and ancient stumps host carpets of sword ferns, huckleberries and wild roses. Happily, it applies most to the areas immediately surrounding the home, which will remain in better shape without overhanging trees and shrubs. Also happily, quite a few handsome native plants are naturally fire resistant, including rhododendrons, Oregon grape, and Oregon boxwood (Paxistema myrtifolia) as well as redtwig dogwoods, serviceberry, bigleaf maples and vine maples. Ocean spray, Western mock orange, native willows, wild roses, Douglas spirea, and snowberry also make the list (notice some overlap with slope holders?) as do achillea, columbine, penstemon. So does fireweed (!), often the first plant to appear after fires.

Who Can Help?

If you’re wondering if your home might be in danger should wildfires arrive, and how to make it safer, a home inspection and a consultation with an arborist can help you develop a working list. The usual recommendations include removing any and all vines from the home and any outbuildings, especially those with a buildup of old, dried out stems. Besides the tree and shrub pruning or removal already discussed, you will also be told to keep all areas within 30 feet of the home clear of deadwood and old leaves. If a jumble of junk has accumulated anywhere near a building, that will have to go as well. Clear a wide space (at least 10 feet) around any propane or oil tanks, including the barbecue grill, which should be covered with quarter-inch wire mesh screening when not in use to keep wind blown sparks from igniting it. Onward!

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