Gardens: Discover the secrets of your favourite gardens by looking at them in a new way

If there's one thing most gardeners enjoy almost as much as working in their own garden, it's taking a closer look at someone else's.

That might mean peering over the fence to see what your neighbour's been planting, visiting some of the private gardens that open for Scotland's Gardens Scheme, or going on a day trip to explore one of the country's grander historic gardens. And in the same way as a trip to an art gallery is enhanced by knowing a bit about art history, garden visits can be even more rewarding if you do a bit of research in advance.

"There's absolutely nothing wrong with just enjoying a casual stroll around a lovely garden, enjoying the views and the atmosphere," says Lorraine Harrison. "But just like looking at a painting or hearing a piece of music, the more you understand the more you get out of it." Harrison is the author of a new book, the pocket-sized How To Read Gardens (9.99, Herbert Press). Subtitled "a crash course in garden appreciation", it's a sourcebook which provides easy-to-digest information about all the different factors that go into making a garden. She encourages us to ask lots of questions when we visit a garden - is it an original landscape or a recreation, for example? Is the planting material authentic or composed of modern hybrids? Are the steps and terracing in the Italianate style or Arts and Crafts? She explains that although most gardens have been changed and adapted over time, there are still plenty of clues that can tell us about a garden's past.

As well as looking at the history of gardens, Harrison explores the history of garden visiting. Back in 1640, for instance, Louis XIII opened the gates of his Jardin Royal des Plantes Medicinales in Paris to the public, and lemonade was sold to thirsty visitors. The Grand Tourists of the 18th century could draw upon a wealth of guides to the Italian Renaissance gardens they'd be visiting and during the same period, Britain's aristocrats were opening up their homes and gardens to the public. Today access to other's people's gardens has never been wider, although Harrison points out that you might not get quite the experience that the original designer had in mind. "One of my particular bugbears when visiting quite large-scale gardens attached to an interesting or important house is the route the visitor now has to take through the garden," she says.

"Invariably the first thing one encounters is the shop, followed by the cafe and toilets. I appreciate that visitors have to be managed, and their needs catered for, but it mostly destroys the way a garden and its house was originally planned to be seen."

Even if we might not get the authentic experience, there are always plenty of clues which will help us learn more about the garden we're visiting. How To Read Gardens acts as a sort of field guide, describing historical influences, origins and styles and pointing us on the right road towards interpreting the landscape around us. The first obvious question to ask (but one which is easy to overlook) is "what is it for?" Harrison says that gardens can fulfil many different functions: they can display wealth and status; express theological ideas or scientific knowledge; produce food or medicine; and, of course, many gardens are designed just to look and smell beautiful. She uses Versailles as an example of a garden whose scale and formality leave the visitor in no doubt that its owners were powerful people. In contrast, Munstead Wood in Surrey is the epitome of the English country garden, filled with informal planting and exuding a relaxed atmosphere.

Don't be surprised if the garden you're visiting seems to be sending out mixed messages. "Gardens that are very unified and have a single theme, such as the classic Islamic courtyard garden or a Japanese Zen garden, are easier to grasp, even though the concepts they express are complex," says Harrison. "But lots of gardens fulfill many needs. This is especially true of gardens attached to domestic dwellings. Such gardens may have formal space, areas for playing games, for the production of fruit and vegetables, each fulfilling very different needs."

From looking at the purpose of a garden, we might then want to move on to its style. Is the garden very ordered, relying on symmetry and strong lines to give a formal impression? Is it filled with the grottoes, terraces, fountains and other features that were popular in Italian Renaissance gardens? "I think it's only natural that if, say, you are really keen on growing vegetables that you'll be most interested in looking around a well-maintained kitchen garden," says Harrison. "But I hope the book will open people's eyes to some of the wider things that are going on in a garden. Gardens encompass such a wide range of disciplines and influences; architecture, horticulture, history, design and I think it's much more fun and rewarding if you have a little understanding of what you are seeing and why it is there."

The book examines landscaping, buildings, garden features and, of course, plants, providing insight as to why particular choices might have been made by the garden's owner or designer. There's also a useful glossary, ranging from "arboretum" to "winter garden" and covering terms you may well be unfamiliar with (including "ha-ha": a steep ditch that keeps grazing animals out of a garden without the need of a visual boundary). But how much can we really tell about the owner of a garden by looking around their plot? It depends on the type of garden, says Harrison. "I always really enjoy going around privately owned gardens, the ones that just open for a few days a year," she says. "These are owned and made by very passionate gardeners who are often highly skilled plantspeople and designers, even though few have formal training. It is a privilege to be invited in to look around their private space and get a real feel for how much their gardens mean to them."

• This article first appeared in The Scotsman, Saturday September 11, 2010