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March 27th, 2012

Invasion of the Rampant Vines

A new weed appeared in my garden in Raleigh two years ago. This spring I realized it’s seedlings from my sweet autumn clematis. I hate to give up this beautiful vine, but how else can I deal with the aggressive seedlings?

blog-dougSweet autumn clematis (Clematis terniflora) is a perennial vine of Asian origin. It climbs vigorously in a dense tangle of leaves and stems up to 30 feet tall. The blooms appear in August—fragrant masses of tiny white flowers—and are followed by feathery seed heads.

This is where the problem begins. The seeds blow far and wide, and by the following spring, clematis seedlings are popping up by the dozens. Sweet autumn clematis is on the invasive species lists of several states, mostly in the Southeast and mid-Atlantic regions. The Invasive Plant Atlas of the United States has mapped the problem areas on its website.

Prompt deadheading to prevent seed formation is one option. A more practical solution, however, is to replace Clematis terniflora in your garden with Clematis virginiana, a species that is native to the eastern half of North America. The two species are so similar in growth and appearance that they share a common name: virgin’s bower.

Clematis virginiana is also a rampant grower that will self-seed in your garden, although not as aggressively as Clematis terniflora. Most importantly, if any of its seeds blow into natural area, like a stream bank or woods, the resulting seedlings aren’t going to disrupt nature’s balance.  —Doug Hall

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March 20th, 2012

Battling a Sweaty Greenhouse

Last summer my wife and I added an attached greenhouse to the side of our house. When it is cold outside it sweats an awful lot. What can we do to eliminate (or at least minimize) this sweating? We do have a dehumidifier there that we use, but it doesn’t solve the problem.

blog-dougPlants constantly pump moisture into the air through their leaves—a process called transpiration. More moisture evaporates from the soil. For those of us whose homes become dry in winter, the extra humidity given off by a roomful of indoor plants is welcome. But when humid air comes into contact with a cold surface, like window glass, you get condensation.

Greenhouses are humid by nature. You don’t mention what types of plants are growing in your greenhouse, but because most plants prefer a humid environment, the moist air is probably doing more good than harm.

If drippy glass is an annoyance, you could try adding a second layer of glass, plastic film, bubble wrap, or polycarbonate sheeting inside your greenhouse. This added layer of insulation means you’ll get less condensation because the surface won’t be so cold. Add a fan, if you don’t already have one, to keep the air constantly moving. Raising the temperature in your greenhouse slightly will also help reduce condensation (but will increase your energy costs). When you’re watering, take care to not splash water on the benches, foliage, and floor.

These tactics will help somewhat, but in the end, you have to choose between dry glass and an environment that encourages plant growth.  —Doug Hall

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March 13th, 2012

Bricks in an Organic Garden

I want to build an organic herb and vegetable garden and was looking to edge it with brick. Can you please guide me on whether the bricks would leach toxins into the soil.

blog-dougA brick is as clean as the ingredients that went into its manufacture. Like terra-cotta pots, which are used by many organic gardeners, bricks are made from the soil itself—clay, in particular—and fired at extremely high temperatures to make them resist weathering. A typical modern brick is mostly clay with some sand and other minerals mixed in—nothing that would cause harm to an organic garden.

Still, there’s always a chance that a brick maker will introduce something toxic into the formula. If you’re buying new brick for your project, it’s worth calling the manufacturer and asking about its suitability for garden use. If you choose salvaged brick for the edging, make sure it hasn’t been contaminated with anything toxic—traces of lead-based paint, for example.

Personally, I have no qualms about using bricks in my garden.  —Doug Hall

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March 6th, 2012

Wood Ash as a Compost Ingredient

I’m not sure what to do with all my excess wood ash from the fireplace. I need to lower my soil pH, so I can’t add the ash to the garden or compost.

blog-dougThe ash from a wood-burning fireplace contains nutrients that plants need, including potassium, calcium, and trace amounts of zinc, magnesium, and phosphorus. But those nutrients come with a warning: Wood ash is strongly alkaline. If added to soil, it will raise the pH, or the measure of a soil’s acidity or alkalinity. Where the soil is too acidic (pH too low) and a higher pH would be beneficial, wood ash can be applied to lawns or gardens in place of agricultural lime to raise the pH. But if you are dealing with a neutral or alkaline (high pH) soil, adding wood ash would be a mistake.

The same goes for adding wood ash to a compost pile. Consider including wood ash as a compost ingredient only if the pile contains significant quantities of acidic materials, such as shredded oak leaves or pine needles. Even then, apply the ash with restraint, because too much can result in a loss of nitrogen from the compost. At a higher pH, the nitrogen present in the compost pile will escape to the air as ammonium hydroxide; if you smell ammonia near your compost pile, it’s losing nitrogen.

If you decide you shouldn’t use wood ash in your garden or compost, and you can’t find a farmer or gardener who can use it, I suggest you send the ash to a landfill with the rest of your household waste.  —Doug Hall

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