Arbours, pergolas and gazebos add space, interest and depth to a garden - plus an invitation to meander.

Spring is the perfect time to freshen up the yard and garden surrounding your home or cottage. As endless possibilities and projects fill your mind, consider adding a new structure to enhance your space: an arbour, a pergola or a gazebo.

Once you've decided to go ahead, of course, those of you with non-gardening spouses will be faced with one small problem: the blank stare you'll get when you announce your latest heart's desire and the invariable response-"what the heck is an arbour?" (or pergola or gazebo?)

Don't panic. Here's a primer on garden structures, their role on your property and what to do before you pick up a hammer, or the phone.

In his delightfully informative and practical book Small Buildings Small Gardens, author Gordon Hayward writes that garden structures such as arbours and gazebos are people-focused components of a garden's design. A pergola is a place to walk while enjoying the garden vista; a gazebo gives us a destination to walk to, where we can relax and enjoy our garden's tranquility; arbours make great yard boundaries and focal points to look at or through.

Because the terms "arbour" and "pergola" are sometimes used interchangeably, it can be difficult to distinguish one from the other. These structures have similar features and purposes, but there is a difference.

Both garden structures can support vertically grown vines and other garden plants, greatly enhancing your gardening space. Both can also be constructed of a number of materials, including weatherproofed beams and lumber, naturally preserved logs or poles, iron or other metal.

An arbour can be freestanding or attached to a house, perhaps as part of a fence or deck structure. Arbours range in size. They can be small, arch-like structures to walk through before heading up a path to a door or into a garden. They can also be larger framed expanses that extend over a deck, terrace or other sitting area.

Arbours are commonly used as a threshold or entrance to a home or part of a yard, perhaps a garden room. They're often used to frame a particular view, whether of some special aspect of a garden such as a nook or theme garden, or of a wider landscape view such as ocean or lake frontage. For those with more urban living situations, a larger, attached arbour works very well to either create a spot of privacy in a yard or to screen unsightly views beyond a homeowner's property.

Pergolas are like arbours, but tend to be larger, longer and more extensive. They're often designed to be a major focal point in a garden. Large pergolas laden with wisteria, clematis or roses are a common sight in public gardens-these are popular sites for wedding, graduation or anniversary photos.

Pergolas are for walking, rather than for sitting and relaxing, although there are no fixed rules that say you can't have a bench at the side or end of such a structure. They also do a good job linking two sections of one particular site. For instance, this could be between two different garden "rooms," or a transition from planted garden to wilderness area (in the case of rural properties). It can even be as simple as going from the backyard to the front.

The best definition of a gazebo is "an arbour on its way to becoming a garden shed or studio." More complex and substantial in structure and design, gazebos provide shelter from the weather with their solid roofs. If screened-in, they also protect from biting insects. Because of the nature of their structure, they lend themselves to a variety of ornate detailing, such as patterned floor designs and cupolas. Lighting, furniture and other accents can be added for extra comfort.

You'll normally find a gazebo at the end of a path, as it's meant to be a focal point in a yard, park or other area. At the same time, gazebos are places to relax and enjoy the scenery, so they're best placed in a location with a great view.

When we build our gazebo (when, not if) we've already decided on the location-at the end of the backyard, where we can see parts of our garden as well as enjoy our view of the upper Bay of Fundy-fog permitting, of course.

When planning to add a garden structure to your property, first ask yourself what you want to accomplish. Is this to be a focal point that draws the eye to it, or will it be more utilitarian, obscuring a view beyond your yard? Do you want an overall view of parts of your property or would you prefer a secret, private nook where you can read, doze, or dream away a warm summer's afternoon?

Choosing a structure design hinges on the type of garden you have. Is it formal, or a more relaxed cottage-type with joyful mixed borders? Those who prefer a formal garden will likely want a traditional design using traditional materials. A cottager, on the other hand, may opt to build a rustic arbour using driftwood.

Remember to take the rest of the garden's design into consideration and make your new structure work with that. It looks odd to see an arbour sitting in the middle of a lawn, with no visible path or focal point to explain its purpose. We have two arbours built by my dearly beloved: one is swathed in clematis and frames a walkway leading up to the house, while the other forms a gateway between two parts of the backyard and a bridge between two garden beds.

If you live in a subdivision or other urban locale, you may need to check with local building regulations to see if there's a restriction on backyard constructions. For those who are rural dwellers, this generally isn't an issue, but as more residential areas with building covenants spring up, it's a good idea to check this out.

Just as we always say "plan before you plant," remember to plan before you build or hire a contractor. Decide on your budget, the location of your structure-a level site is essential-and what style of structure you want. Remember to think about drainage needs. A gazebo that becomes twisted from yearly frost heaving due to improper sitting or inadequate frost footings, or a pergola that sinks on one end from overly wet ground is not something you'll relish dealing with.

Talk to landscape designers and contractors about options, or search on the Internet to find designs that appeal to you. You may well design your own, but the most important thing to remember is to have solid supporting beams for the upright parts of your structure. Otherwise, you'll find yourself with a mess in a few years.

No matter what you're building-or having built for you-you'll want these structures to last a long time, so be sure to use top-quality materials. Cedar, though beautiful and very weather resistant, can be prohibitively expensive for construction of more than a simple trellis or obelisk.

Many people opt for pine, spruce or other woods and then paint, stain or otherwise treat them with water repellent products to keep them looking great. If you're designing and/or building your own arbour or pergola, choose lumber for its supporting columns that is heavy enough to support the weight of both the structure and any plants that will be growing up and across it.

Climbing Plants

Another matter to consider is the climbing or vining plants for your new garden structure. If you want to experiment with a different look each season, go with annual flowering vines such as morning glories, hyacinth beans, thunbergia and hummingbird vine, which you can either plant into a bed flanking your structure or in containers near each upright pillar.

Perennial vines such as clematis, Virginia creeper, bittersweet and other ivies need to be sited according to their growing needs. A clematis won't flower well on a northern exposure of a structure, for example, while some wisteria cultivars do best in warmer parts of the region (zone 6 and warmer). Rambling and climbing roses are beloved all-stars of vertical structures, and you'll find hardy cultivars that will thrive in all but the coldest areas.