It's no exaggeration to say that I don't know what I would do without my greenhouse. You might think that's because it allows me to grow more crops, produce more plants and save money, but it's rather more than that. My greenhouse is my sanctuary - a place where I can ease myself into the day of a morning, potter among my pelargoniums, removing a dead leaf here and a faded flower there, and generally feel at one with the world. Perhaps you think that's an extravagant claim for a small glass structure that sits in my garden? Not a bit of it.

A greenhouse is more than the sum of its parts and anyone who relishes the freedom of being out in the garden in all weathers, at all times of year, simply cannot do without one. So every other month this spring and summer I'll offer you a deeper insight into the benefits of a mini palace of glass, whether or not you already have one or are contemplating the investment Hopefully you'll come round to my way of thinking and decide that such a facility is a must in your own garden. And when it comes to timing, there's no better month to get started than this one.

What is a greenhouse? It's a simple question but the answer isn't straightforward. Yes, it differs from a garden frame - or a cold frame, as the unheated kinds are called - in that you can walk into it, but it can be almost any shape you like, from rectangular to dome-like, made of timber or metal, glass or plastic, heated or unheated, large or small.

What it will do is give you year-round access to the part of your garden that it covers. And if, like me, you get itchy in winter when the garden is out of bounds due to heavy rain, frost or snow, it allows you to continue gardening in all weathers.