Garden columnist Marion Owen answers your questions each Monday in the Kodiak Daily Mirror. Ask your questions at email@example.com.
Q: Can shredded computer paper be used as mulch in the garden or be added to the compost pile?
A: The good news is that many studies have tested the safety and usefulness of shredded paper in the garden. The not-so-good news is that they came up with different answers. Newsprint gets a thumbs-up from almost everybody because the inks are mostly soy-based. But the bright inks on slick paper inserts and magazines can contain dangerous components, and paper bleached with dioxin may be of more concern than the inks used on it.
The main problem with paper mulches is that even then they’re deemed safe, they’re inert, which means they don’t have much going for them. Shredded paper might work great as a barrier against weeds (and heaven forbid, havens for slugs), but not much good as soil improvers. Unless finely shredded, they don’t decompose, and if they DO decompose, they take steal nitrogen from the soil while they’re doing it. All things being equal, it’s better to take your paper to Threshold Recycling and use kelp, grass clippings, or leaves in the garden and compost pile.
Q: Which leaves are best for the garden?
A: Last week I sang high praises for leaves. They’re packed with minerals and provide gourmet meals for earthworms and beneficial microbes. When added to the compost pile, they provide carbon and keep the pile fluffy and oxygenated.
So what are you waiting for? “Don’t pass up the great opportunity to rake some high quality leaves into your compost pile or garden beds,” says Lorne White, of Strawberry Fields Nursery. A 2-inch or 3-inch mulch of leaves stabilizes the soil temperature, reducing the freeze-thaw fluctuations that tear plant roots.
But what kind of leaves are best? The answer might surprise you: “Alder leaves have more nitrogen in them than any other type of tree leaf here in Kodiak,” says White, “and they are all available to be raked in this warm spell we are having.”
Alders are much more than scruffy trees that trip hikers navigating a trail and block roadside views. They deserve a second look, at least below the surface. As a member of the birch family, alders carry on an important symbiotic relationship with a fibrous, nitrogen-fixing bacterium called Frankia alni. Though Frankia can’t be used as a Scrabble word, this bacterium perform a valuable function, developing into fist-sized nodules or lumps on the Alder roots as they do it.
These bacterium quietly go about their business absorbing nitrogen from the air and making it available to the tree. Alders, in turn, provide the bacterium with sugars through photosynthesis. Through this amazing and mutually beneficial relationship, alders improve the fertility of the soil where they grow.
Another local source of leaves is the cottonwood tree. Cottonwood leaves are alkaline, which helps balance the acidity of our native soils.
Q: Can coffee grounds go directly into the garden, or do they need to be composted first?
A: Around Kodiak, there is a gaggle of establishments that serve cappuccinos and lattes. Add to that restaurants and businesses that offer “regular” coffee on the menu, plus households (and let’s not forget galleys aboard fishing boats) that start each day with a mug up. It adds up to a lot of coffee grounds.
Coffee grounds do not need to be composted before being used in the garden. For best results outside of the compost pile, work the nitrogen-rich grounds into the soil. Coffee grounds are on the acidic side, so don’t add more than 5 or 6 pounds per 100 square feet unless you want to change your soil pH.
Q: What is neem oil, and how is it used as a pesticide?
A: Neem is an organic pesticide derived from the bark and fruit of a common Asian evergreen tree (Azadirachta indica). When applied to insects , neem oil causes them to feed less and grow more slowly.
Neem is best used before pests become a serious problem. For example, if your hoophouse or greenhouse is plagued with aphids halfway through the summer, spray the environment early on, says Christy Mathews, who grows and harvests near Ouzinkie. “We spray a neem-water dilution on the soil and on overwintered plants and seedlings in later winter and we rarely have an aphid problem.”
Neem is safe to use, with some limitations. For example, it does not harm birds but if it is used fresh out of the bottle, it will kill fish. So keeping it out of the water is a matter of not pouring it in.
Shake neem products well before using to emulsify the oil. It’s important to shop carefully (read the label) when looking for ready-to-use commercial products. Some formulations are stronger than others.
To mix your own, use lukewarm water to get a good mix. Thoroughly wet both sides of leaves and places where insects may be hiding. If honeybees are expected to visit the plants, exclude them with an old sheet or piece of row cover for 24 hours after applying neem.
To treat your plants, a general dilution is to mix one teaspoon of neem oil with one quart warm water. Add a teaspoon of organic dish soap to help the oil spread evenly. Spray your plants, including the undersides of the leaves and soil.
Neem oil is also effective in reducing an infestation of thrips and aphids on your houseplants, using the same dilution described above. With summer behind us and winter lurking around the corner, now is a good time to look over your long-forgotten houseplants.
Recipes and gardening tips are featured in Marion Owen’s 2014 calendar: “Flavors of Kodiak Island.” Read Marion’s latest blog postings at http://marionowen.wordpress.com. Connect with local gardeners on the Kodiak Growers or the Sustainable Kodiak Facebook page. Archived copies of Marion’s columns are posted at www.kodiakdailymirror.com. Contact Marion at firstname.lastname@example.org.