editor's note: the dry season

savvy classes: free summer classes

garden hotline: watering wisdom

feature story: a mulch for all seasons

savvy advice: how to water your food crops

It may take a while to arrive but once the dry season begins, many of us turn our attention to watering. The Seattle area has a reputation for being wet, but our 36 inches of annual precipitation is less than Miami, Atlanta or Houston receives, according to NOAA. And our summers are downright dry: less than 5 inches in total falls from June through September. That’s why our water system relies on large reservoirs in our watersheds to get us through the dry spell. Anything you can do to lessen your summer water use helps ensure there is enough water for all. The Savvy Gardener is here to help your garden flourish, without wasting that precious water!

The content in our summer issue was prepared by staff of the Garden Hotline and the Saving Water Partnership. We hope you enjoy it!

These classes are free, and will be held at Woodinville Water District. Please see the Summer Garden Seminars Flyer (pdf) for details and registration information. Co-sponsored by the Saving Water Partnership, Woodinville Water District and the Master Gardeners (WSU/King County Cooperative Extension).

Gardening with Washington Native Plants
Susie Egan, Owner, Cottage Lake Gardens
Saturday, August 7 - 10:00 a.m. to 11:00 a.m.

Natural Yard Care
Ladd Smith, Co-owner, In Harmony
Saturday, September 11 - 10:00 a.m. to 11:00 a.m.

The Garden Hotline Corner is prepared by staff of the Garden Hotline, the experts who answer your gardening questions at (206) 633-0224 or help@gardenhotline.org.

Lawns and Planting Beds: why water them differently?
It may be easier to water everything all at once, but did you know...

• Lawns, trees, shrubs and perennials have different rooting structures, growing wide, shallow, deep or even tap-rooted depending on the species. When you water, the goal is to reach the rooting zone.
• Lawn roots typically reach only 4 to 6 inches deep and need additional summer water to stay green. You can allow them to go dormant in the summer months by not applying water and the grass will green up naturally when cool weather and the rains return.
• Trees, shrubs and perennials have deeper root systems than lawns and can better seek out water from the soil. Most all plants will need additional summer irrigation until they become established. After that time (usually two to three years), if you select and site plants effectively, they will need little supplemental water.
• No matter what watering system you use, your plants will be happier and healthier if you water your lawn areas separately from the garden beds so you can provide each with the water they need, when they need it.

Smart Watering Guide (pdf)
This guide will help you understand the art of watering as it applies to your garden

A Mulch for All Seasons

Our spring Savvy Gardener described mulch as a material placed on the surface of your soil to suppress weeds and maintain soil moisture. In this issue we bring you the lowdown on why mulch is so important and answer some common questions.

Mulch makes the garden grow year-round!

• Fall is an ideal time to mulch, particularly after your fall weeding and after the fall rains have thoroughly moistened the soil.
• During the rainy season, mulch protects the soil from erosion and from losing nutrients that the rain can wash away. Mulch also helps to suppress the germination of annual weed seeds, including many which crop up during early spring.
• The first flush of warm spring weather gives a jump start to weeds; you’ll be glad your mulch is already in place! Mulch will also retain soil moisture and delay the need for supplemental watering. When you do begin watering, mulch will help reduce how often you need to water. Mulch will keep plants’ roots cooler as the weather heats up, benefitting plant health.
• When plants are actively growing, the gradual decomposition of mulch supplies the soil with organic matter and beneficial microbes that enable plants to use soil nutrients.
• Year-round beauty. Mulch can help visually tie your garden together by providing a consistent texture to your beds.

Which mulch to use?

Wood chips are our favorite choice for garden beds featuring shrubs and trees. Of the organic mulches, chips resist weed germination the best and last the longest, gradually feeding the soil.

Wood chips may not be the ideal choice around perennial and annual plants because they use soil nitrogen as they decompose—nitrogen that is also needed by the plants – though this can be addressed by adding supplemental fertilizer. Competition for soil nitrogen is not an issue in tree and shrub beds, since the deeper root systems of woody plants feed below the level of soil affected by the decomposition process.

Wood chips are often available free of charge from local arborists or tree services, which generally have chips in loads of from 5 to 10 cubic yards.

Compost, whether homemade or purchased, can be a good choice in food gardens and in perennial or mixed beds. It’s great for soil that needs a nutritional lift. Water and the action of worms and other soil organisms will move it deeper into the soil, where it will improve soil structure and nourish plants. While it does not work as well as chips for suppressing weeds, it is easy to cultivate and provides an attractive texture.

Leaves can be an ideal mulch. In many cases, you can just leave fallen leaves in place—provided you’ve already weeded! This mimics the natural forest system, where leaves provide organic content to the forest floor. You can rake the leaves and shred them with your lawn mower if you want finer-textured mulch.

You can also add leaves to your compost pile, but put leaves with diseases such as black spot in your curbside yard waste collection, since the heat in commercial compost systems kills disease organisms.

Sawdust/manure blends look attractive initially, and the manure can provide nitrogen. However, the sawdust can become compacted over time, resisting water and reducing air availability at the soil surface. This type of mulch can be successfully used in flower beds where the soil is regularly cultivated.

Grass clippings can be cost-effective if you have a lawn but may be less attractive than other choices.

What about beauty bark? Bark products are readily available and extensively used. Comprised of the bark layer from trees used in the wood products industry, there are several drawbacks to its use.

• Bark has water-repelling qualities. The finer the bark, the more it will repel water. Coarse bark mulch is a better choice if you decide to use this product.
• Bark is low in nutrients, unlike wood chips, which also incorporate leaf matter and other beneficial elements.
• Bark uses up nitrogen in the same way that other wood products do, but offers little additional benefit to soil, such as providing nutrients.
• Some bark products have dye added to them. In addition to raising concerns about how dye may affect the environment as it leaches, as it ages bark turns gray and less attractive.

How much to apply

• Grass clippings: 1 inch deep.
• Compost, leaves, sawdust: 2 to 3 inches deep.
• Wood chips or coarse bark: 2 to 4 inches deep.

Note: One cubic foot of mulch covers 12 square feet to a depth of one inch.

Resources

Wood Chips

• International Society of Arboriculture-Pacific Northwest Chapter (for a listing of local arborists).
• Look for arborists or tree services in the phone book; finding one in your area may help you get chips delivered sooner.
• Asplundh Tree Experts trims trees for Seattle City Light and Puget Sound Energy: (425) 483-9339.

Sawdust and Wood/Manure Blends

• Sawdust Supply
• Sky Nursery
• DeJong's Sawdust and Shavings

Bulk Certified Organic Compost

• Cedar Grove (made from yard waste).
• Bailey Compost (yard waste and dairy manure).
• Yelm Earthworms Farm (earthworm castings).

The Art of Watering the Edible Northwest Garden

We could bemoan the relatively short duration of summer heat in the Pacific Northwest, if all we cared about were tomatoes. Or we could relish the long growing season that allows us to plant and harvest almost year-round! Understanding a little about edible crops and their needs will help make the most of our efforts, water, and other resources, and get more food on our tables.

Basic principles for successful, resource-efficient food gardening.

• Build healthy soil
  Soil that is well amended with compost, and has good structure and proper drainage–which amending with compost supports–will allow plants to grow deep roots and retain water longer.
• Group together plants with similar needs
  Group the plants that have the same water and other needs together to make sure you can provide just what they need to flourish.
• Plant intensively
  Planting leafy plants like lettuces, or roots crops like beets in slightly higher numbers than the seed packets recommend creates a thickly planted bed that shades light from the soil, keeping it cooler, and reduces evaporation. As always, thin seedlings sown in place after they sprout so they are not too crowded to produce.
• Group vegetables with similar water – and other – growing requirements
  Not all veggies need a full day of sun. Did you know that many cool season crops (see below), as well as peas, bush beans, chervil, mint, and cilantro actually prefer a little shade? For best results consult a good, locally-relevant gardening resource when you are planning your garden (see Resources below).
• Check soil moisture before you water
  Learn the water needs of the plants you are growing and use tools like the soil core probe (see favorite gadget) or a trowel to check how moist the soil is below the surface.
• Water deeply, slowly and less often
  Plants will develop deeper root systems in response to deeper watering practices. This makes them more resilient in hot weather. Plants accustomed to frequent shallow watering maintain shallow root systems.

The cast of characters

• Cool weather crops
  These flourish during both spring and fall in the Northwest. We can fill the garden in these seasons with lettuces, radicchio, spinach, chard, kale, mustard greens, collard greens, Brussels sprouts, turnips, cabbage, potatoes, broccoli, peas and radishes. These mostly leafy and root crop plants appreciate evenly moist soils, do not like to dry out and thrive in cooler temperatures. In a mild year, many of these crops can overwinter.
• Heat lovers
  Tomatoes, corn, hot and sweet peppers, eggplants, tomatillos, squash, cucumbers, melon and fresh and drying beans are the flowering plants that need sun and heat. They like deep, consistent watering, dry weather to attract pollinators, and do best with some drying out in between waterings.
• The straddlers
  Some veggies tolerate a broader range of weather conditions but appreciate regular summer irrigation. These include carrots, beets and parsnips.

So is there a best way to water?
There is no 'one size fits all' but here are the basics...

• Drip irrigation
  Drip systems can be useful if your planting patterns are similar year to year. An initial investment in time and materials but convenient to use, drip systems deliver water to the plant roots, where they need it, and can minimize evaporation from surrounding soil. See the drip article in last summer’s Savvy Gardener.
• Soaker hoses
  These can be easily installed and rearranged as needs change. Covering them with mulch reduces evaporation and protects them from sun to increase their useful life.
  See our soaker hose fact sheet (pdf).
• Hand watering
  This can be effective, particularly in a smaller garden and when you want to keep water off plant leaves-such as tomatoes-to reduce the possibility of disease. Watering wands are an excellent tool for hand watering. Useful for all plants in any setting, they are particularly useful for watering pots and hanging planters. Make sure yours has an on/off setting to avoid water waste.
• Overhead sprinkling
  Whether using an in-ground system, or a hose-end sprinkler, overhead watering is the least desirable way to water your edible garden. It is less water-efficient than the other methods above, and also can promote disease by regularly wetting plant leaves. If using this method, make sure you water in the early morning to allow leaves to dry during the day and to limit the evaporation that occurs during the hottest part of the day. Avoid watering on a fixed schedule, and check the soil moisture before watering (see above).

Resources

Growing Vegetables West of the Cascades: The Complete Guide to Organic Gardening, by Steve Solomon; Sasquatch Books, 2007.

Seattle Tilth's Maritime Northwest Garden Guide is available on the Seattle Tilth website and at local bookstores and nurseries. This guide lays out monthly tasks for the food garden, recommends varieties of edible plants that do best in the Northwest, and covers essential information such as how and why to rotate crops.

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