Organic. Inorganic. Rocks, bark, straw, leaves or even – gasp! – poop. Mulch is vital to your garden, but there are a lot of options. Your choice should be based on aesthetics, practicality, and just plain science.
“There are many reasons to mulch,” says Sue Goetz, owner of landscape design company The Creative Gardener. “Weed suppression, finishing the surface of the soil to look nice, and – with some types of mulch – nourishing the soil. It reduces water evaporation, too.”
But which mulch do you choose?
It depends on what you need, says Goetz. Mulch can be divided into organic (bark, compost, anything that was once alive) and inorganic (rocks, gravel, landscape fabric.) Organic mulches, particularly those that break down easily, are best for planting beds that need constant nourishment, Goetz explains.
The more nitrogen a mulch has, the more it feeds the soil and plants – think compost, manure, grass trimmings. The more carbon a mulch has, the slower it will break down and the more nitrogen it will take from the soil to do it – wood chips, straw and coarse bark, for instance.
Other organic mulches like shells also will take a long time to break down because of the minerals in them. Inorganic mulches, on the other hand, will never break down and are good for pathways or plants that have needs other than food.
Other considerations include cost, ease of transportation and appearance.
Here’s a list of local mulches and how to use them. Prices are from River Road Landscaping unless otherwise noted.
ROCKS AND GRAVEL
Cost: $25-$55 per yard
Where: landscaping suppliers, hardware stores
They may be heavy, but they’re permanent, and if you lay them thick enough they’ll keep weeds down and keep moisture in the ground for as long as you like. But how to choose? River Road Landscaping has a dozen types of rock for every situation, says owner Pat Hebert. Salt and pepper granite is more expensive but looks beautiful with its play of grays and whites. Pumice is also dear, but is light to haul and comes in red and white. Big river rocks make visual statements; 2-inch rocks are great for drainage in wet areas. Pea gravel is easy on your feet for a pathway, and crushed rock is good for packing on a driveway.
Rocks make superb mulch for low-nutrition plants such as desert and Mediterranean, and on sites that get hot sun.
Cost: $25/yard whole, $85/yard crushed
Where: Minterbrook Oyster Company in Gig Harbor, other oyster farms
“I use them underneath all my lavender,” says Goetz. “Then it doesn’t get that rotting, miserable winter mess underneath. People don’t know how good it is.” Oyster shells may be tricky to obtain – you have to drive out to the coast or Sound – but with great drainage and a white color to reflect heat, they’re excellent for all kinds of Mediterranean plants such as rosemary, lavender or even yucca.
Like rocks, however, they won’t give any nutrients to the soil, and make sure they’re washed of salt before you dump them down.
Cost: $25/40 lb. bag (covers 6-7 square feet)
Where: Chirp and Co. Nature Store, Tacoma, hazelnut farms, or your own leftovers
Goetz uses these between her raised veggie beds. With their rich cedar color and organic crunch underfoot, they’re not as sterile as gravel and make good pathways, she says. They also don’t break down easily, lasting many years. And if you eat a lot of nuts you can save your own shells for use on container plants: hazelnuts, almonds and pistachios are all good.
WOODCHIPS/BEAUTY BARK/HOG FUEL
Cost: $11/yard for hog fuel, $17.50/yard for nugget bark, $28.50/yard for cedar playchips
Where: landscaping suppliers, hardware stores, supermarkets
One of the easiest mulches to find, woodchips (bark stripped from logs before they’re milled) have their uses: They finish beds with a rich brown look, they make ideal mulches for children’s play equipment, pathways and dog runs, and they’re slow to break down. However, says Goetz, woodchips and bark both rob the soil of nutrients, so if you’re using them near plants make sure to add compost or other fertilizer first. Pat Hebert adds that the larger the chips, the less effective the weed suppression – for pathways, use with landscape fabric. Other than that, it’s a visual decision between the blond playchips or the reddish-brown nuggets.
Cost: $17.50-$22/yard depending on grade
Where: landscaping suppliers, hardware stores, supermarkets
This is bark that’s been milled a bit finer, so it will break down more quickly and look less woody, more foresty than chips. Most homeowners get the medium, says Hebert, but it’s the fine grade that mats up tight in the rain, controlling weeds better. Recycled tree clippings are between a fine and medium grade, and are 100 percent recycled from local tree trimmers. At some suppliers you can choose between dark brown or orangey-brown.
Cost: $12.50-$19.50/yard depending on age
Where: landscape suppliers, or your own if you do carpentry
Sawdust may look brightly blond when it’s fresh, but as the finest grade of wood-based mulch it breaks down quickly, turns darker and adds to soil structure. It suppresses weeds, is good for mixing in home compost bins for texture, and is soft for bare feet. It’s also free if you do your own carpentry.
Cost: around $8/bale
Where: feed stores, farms, or free from Halloween decorations at some businesses
Straw – not to be confused with hay, which has more seeds – is a dried grass. As such, it will break down more quickly than a woody mulch, though not as quickly as compost. Partially-rotted straw is best, as any weed seeds will have already germinated. Tacoma gardener Sass Ruthven layers it over fall leaves to create a mulch that will suppress the weeds and feed the soil over winter, breaking down enough to plant veggies in spring. It also heats the soil a little, making it a great mulch for tomatoes and other heat-loving plants.
Where: your yard, your neighbor’s yard...
This is by far the easiest home-made mulch. You may even find other people have collected it for you in bags during fall. Leaves make an excellent layer mulch with straw (see above) or weighted down with something else, as they break down and create rich humus. You can also pile them in a chicken-wire cylinder, add some compost and leave the whole thing out of sight for a year while it turns into compost. Avoid leaves from black walnut or eucalyptus trees, though, as they hinder plant growth.
Cost: free if home-made, $27.50-$29.50/yard for commercial
Where: landscaping suppliers, hardware stores, supermarkets, your own home
Compost is another easy mulch to make at home: All you need is a container, a blend of green ingredients (grass, food scraps, prunings) and brown (paper, sawdust, leaves), and some patience. Commercial varieties include Cedar Grove, compost from mushroom farms, even Tagro mixes. All of them are perfect for feeding plants and soil, and they’ll conserve water too. But be warned – weeds love to grow in them too, says Hebert. Consider adding a woody mulch on top.
Cost: $14/yard for steer/chicken, or $12.95 for 2 gallon-bucket of Zoo Doo at Woodland Zoo
Where: landscaping suppliers, hardware stores, supermarkets, the zoo, your own chickens
This is the ultimate food mulch for really depleted soil, says Goetz. Dumped, dug in or mixed with straw for a less-intense, longer-lasting mulch, it feeds plants like crazy. It also feeds weeds, and yes, there’s a bit of a smell. Like compost, you can top it with a more attractive mulch if you like. It’s great for veggie beds or struggling plants. Point Defiance Zoo has not sold its elephant poop (aka Zoo Doo) for a couple of years, but Seattle’s Woodland Zoo does. The poop, which includes manure from zebras, gazelles, oryxes and hippos as well as elephants, is a fully-composted mix of poop, straw bedding, grass, leaves and woodchips, and saves the zoo disposal money as well as enriching your garden. Zoo Doo is so popular they award it via biannual lottery: Send your name, address, phone and desired purchase amount on a postcard to the Woodland Zoo between Sept. 1-23 for October pickup. You can also buy smaller buckets and pints at the zoo year-round.
MULCHES YOU SHOULDN’T DO
Cocoa beans or coffee grinds, as both are attractive to and poisonous for dogs. Put them in your compost mix instead.
Rosemary Ponnekanti: 253-597-8568