Last fall, Robert set up some rainbarrels to collect runoff from our roof during the rainy season. We had thought to use this water to keep our garden growing during the dry summer months, but after some investigation, discovered that roofs are often covered with toxic chemicals, which might make using the rainwater on edible plants a bad idea. Seattle Pacific University offers the following advice:

When NOT to use a rain barrel for watering

If you have certain kinds of roofing material you shouldn’t use rain barrels for watering plants. If your roof is made of wood shingles or shakes that have been treated with any chemical (usually chromated copper arsenate—CCA) to make them resistant to rot and moss, lichen and algae growth, don’t water your plants from a rain barrel. Water collected from copper roofs or copper gutters also should not be used. Zinc (galvanized metal) anti-moss strips—usually mounted at the roof peak— also produce toxic chemicals you don’t want in your garden. Don’t use rain barrels if you have these strips (you may want to remove them), or if you have had your roof treated with moss-, lichen or algae-killing chemicals within the last several years. Note that nowadays there are asphalt shingles on the market which have zinc particles imbedded in the surface. Check your shingle specifications if you have recently re-roofed.

In addition, general practice is to avoid watering vegetables and other edible plants, such as herbs you plan to use in cooking, with rain barrel water collected from asphalt-shingle roofs. These kinds of roofs may leach various complex hydrocarbon compounds, so most people avoid using water from asphalt-shingle roofs or flat tar roofs on plants meant for human consumption. To date there is no definitive research on the amounts and types of hydrocarbon compounds which may leach from such roofs, though it is common practice to use water collected from asphalt-shingle roofs for watering ornamental plants and shrubs. Enameled steel and glazed tile roofs generate little or no contamination and rainwater harvested from them is commonly used to water vegetables.

Here are a couple of links to pages that discuss water quality and roofing materials:

• Stormwater Center (PDF)
• Colorado State (PDF)

The water we saved will still come in handy. We’ll be watering our ornamentals with it. This will help keep our water bill down and place less demand on the local salmon runs. We’ll also be saving our pennies to purchase a metal or tile roof, which will keep the runoff much cleaner.

There’s no way I can recount all we did this past weekend. Robert and I worked our tails off. Since his sister, Robin, was visiting, we had the rare luxury of a babysitter and were able to run some errands we’ve been meaning to take care of for a long time. First thing Saturday morning, we drove over to Ballard to visit Walt’s, an organic gardening shop recommended by Seattle Tilth. It’s a small locally owned business specializing in fertilizers. It’s also known as one of the few places that carries bales of organic straw, which I really wanted to try out as a mulch in the veggie beds. We bought that and picked up a maidenhair fern and a mason bee house on impulse.

Afterwards, we headed back north, stopping for a short time at Skye Nursery, where we bought a trellis for my clematis and then walked over to the lumber store for an armfull of wood, which Robert wanted for his ingenious cloche design (see photo below).

With the wind blowing and the skies threatening rain, it was too cold out to encourage an extended shopping excursion, so we returned home. Almost like magic, it seemed to warm up once we climbed out of the truck and started unloading our supplies. Robert set up the trellis and I untangled the clematis vines and wove them up and over it.
Once that was taken care of, I sowed a generous amount of a Real Shady floral mix in the bed surrounding the clematis. I hope they take off! The bed is located in a spot that was once covered with an invasive ivy, which we have been steadily removing as time and energy allows. It will be nice to have something pretty growing there.

I planted the herb and strawberry starts I had purchased last weekend. My son, Sam, enthusiastically helped me mulch the strawberries with the straw. I was a little surprised at just how enthusiastic he was to be involved. I’m going to have to dream up some other gardening projects for him.

What else? Let’s see…I repotted the tomato and broccoli seedlings, planted nasturtiums and lettuce starts in the garden beds, and sowed a beneficial insect mix in one area of the veggie beds. Robert cleaned out the gardening shed and built some shelves. The kids chased a squirrel and tossed straw all over the back yard. It was an eventful and pleasant weekend, to say the least!

Note to self: One likely reason my sweet peas did not germinate is they require “scarification,” i.e. a process that helps to break the hard seed coat. Next time, I’ll soak them overnight before planting or roll them on sandpaper to slightly nick the outer surface.