Features: The Gardening Coach • Susan Harris

Winter's a great time to manage your ivy

Photos: Julie Wiatt

Ivy is the probably the plant I get the most questions about -- from Takoma Horticulture Club members, neighbors, and people I coach -- and certainly it's a plant about which people have strong feelings. So let's start with what we all agree on: It's a huge problem in natural areas, and we're all disturbed by the sight of it covering our woodlands and hanging from trees. It's important that we prevent its spread into natural areas or into our neighbors' yards. And there's certainly enough evidence of its destructiveness that I'd never suggest buying the stuff, so this article only addresses ivy that's already on your property.

Preventing ivy's spread

The obvious way that ivy spreads is vegetatively, withrunners, and preventing its spread requires trimming it back at least monthly during the growing season. Experts advise that ivy not be grown in gardens that are adjacent to natural areas and in those situations, removing the ivy may be easier and more effective than keeping it trimmed. Even if your property is surrounded only by other homes, it's still important to keep its runners in check and, in Takoma Park, it's the law. That's right, under our "Noxious Growth" ordinance, it's a violation to allow ivy to spread to adjoining properties.

The other way ivy spreads is less obvious. When it gets high enough in trees it morphs into its mature stage, with larger, heart-shaped leaves that people don't even recognize as ivy. Then it produces berries, which enclose seeds that are then spread all over creation by birds. So it's really important not to let ivy grow up trees.

Preventing destruction of your plants

Ivy doesn't mix well with other low plants like perennials, so keep it away from them, or move the perennials somewhere else and let the ivy grow all by itself. If ivy is growing around or near larger plants -- shrubs and trees -- regularly trim it off them. Left unchecked, ivy can easily kill shrubs and small trees, and even larger trees are weakened by its weight. Also, the space between the ivy and the tree trunk is the perfect habitat for unwanted pests, like gypsy moths. As already mentioned, ivy growing in trees spreads by seed. And again, it's the law. In Takoma Park it's a violation to allow ivy to reach the limbs of trees.

English ivy can be an invasive menace. In Takoma Park it's a violation to allow ivy to reach the limbs of trees.

Preventing destruction of structures

There's plenty of evidence that ivy hurts the mortar around brick and apparently even the brick itself, and can do all sorts of devilish things when it's allowed to grow into the eaves of houses. So if you want to use ivy to hide a wall, grow it on a trellis that's attached to but not touching the wall. For existing ivy on old buildings, however, preservationists warn that yanking it down can actually rip out the mortar in the process, and suggest getting a consultation from an expert. The solution may be to use the same technique that is recommended for removing ivy from trees: cutting it at its base and allowing it to die slowly.

When ivy is useful in the garden and can be managed

•On the Ground. When planted as a mass ground cover all by itself in a clearly defined area, ivy can not only look good but be relatively easy to manage. For all its destructiveness in the wild, groundcover ivy in the garden is effective in reducing weeds and retaining the soil against erosion, looks good, and is easier to manage than most of its invasive brethren. Where your ivy is retaining soil on an incline, it may be more harmful to rip it out and start over with a replacement groundcover. A local gardening writer recently urged his readers to remove all the ivy from their properties but as a replacement on hillsides his only suggestion was to "construct terraces." Unfortunately, such an expensive solution is beyond most homeowners' budgets.

If carefully managed, existing ivy can provide ground cover, or as shown here, cover an ugly chain link fence with living green.

Even as a skirt around trees or shrubs, ivy can still be managed to prevent harm to your plants. Just keep an eye on it, making sure it doesn't grow up into the plants.

•Covering Ugly Fencing. Your ivy can be used to cover a chain link fence. My fence had ivy growing along it, so I wound it in and out of the chain link and within two years the chain was invisible. Twice a year or so I remove the runners creeping along the ground, where they would otherwise soon smother the perennials.

The efficient way to trim ivy: The most efficient way to trim ivy is to grab long pieces that are heading in the wrong direction and remove them at their source, or as close to their source as possible, rather than trimming the ivy neatly following a line.

The Big Picture

In addition to ivy's virtues in soil retention and weed prevention, the ivy on your property is free. Replacing it may be something you can't afford and the ground would stay bare or weedy, with water running off it. (Like John Hartmann often says, "Use what you've got," and John loves to save money for his clients.) Then there's the labor and water it takes to establish a new groundcover over its first season or two. And, on the subject of water, established ivy is very drought-tolerant, more so than most of its potential replacements.

So in deciding what to do with your ivy, keep all this in mind, especially the part about the law, and try to be realistic about your commitment to management. Mike Welsh, the City Gardener, would tell us, "It's called gardening, folks," and he's right. Gardening is about managing our plants, and ivy, in its place, can be managed. But if for any reason you're unable or unwilling to manage it, get rid of it.

Master Gardener Susan Harris writes about gardening for UDC's Cooperative Extension Service and teaches gardening privately; see - thegardeningcoach.com. She also blogs at gardenrant.com and takomagardener.typepad.com.