Buying plants is one of the most enjoyable parts of gardening. Before you go to the garden centre, have a look through gardening books, to find specimens that are beginner-proof. Mail-order companies online are also good sources of information.

Garden centres are great for introducing you to plants that are in flower at the time of your visit. However, if you are inclined towards impulse buys, beware: the star turns of the season on prominent display may not be suitable for your environment, however beautiful they look.

A visit will help you build up a portfolio of favourite plants. For new gardeners, being able to actually see and smell a viburnum or sweet box (sarcococca), for example, as they flower in early spring, is invaluable.

Where to go: I don’t recommend buying plants at supermarkets and DIY shops. When they arrive at the store they will be in tip-top condition, but after a few weeks, the quality really drops off. It is better to go to a good garden centre or a specialist grower. Don’t be scared to ask questions — gardeners and growers will be more than happy to chat about all things green and gorgeous.

Right plant, right place: If you have a teeny outdoor space, you need to know the plant you have fallen for isn’t going to turn into a green giant. All plants look on the small side when you buy them, but they soon fill out. Check the eventual size of your chosen one and see how much space you have for it to grow and develop.

Refer to your notes about the microclimate of your garden; this is an important factor in determining what you can successfully grow and what you can’t. Take your list along and check out potential purchases. Do they like sun? Will they tolerate thick, clay soils? Are they pollution-tolerant? And don’t buy anything spiky or poisonous if you have got very young children.

Once you have got all this in order, it is time to search for a specimen.

Good-health guide: Look for a bushy, compact plant with the shoots evenly spread out on all sides. Avoid those on which the foliage has wilted or curled and shrivelled. Hungry plants are easy to spot: just look for yellow leaves that are stunted and smaller than those in the rest of the batch.

Check for pests and diseases: lift up the plant and inspect the underside of the leaves. Pests tend to hide from sight, but on close inspection you can usually find them skulking here. Any abrasions, spots, lesions and mottling are a bad sign. And if the leaves are covered in whitefly, bugs or tiny spiders’ webs, look elsewhere. A few holes are nothing to worry about — a passing insect just fancied some lunch. But look carefully to see it hasn’t stayed for dinner and breakfast, too.

Roots: So you’ve examined the leaves; now look at the roots. Most plants are sold in containers but in winter, you will see some “rootballed” plants, box and evergreen trees among them. These have been dug from the field with a ball of soil round the roots, which are then wrapped in sacking. You may also see bare-root deciduous trees, roses and hedging, where the roots are covered with moist compost.

Here are some things to look out for. If a plant is container-grown and the pot feels very light, it needs water. Tap the pot’s sides, too; a dull hollow sound will confirm it.

If possible, slip off the pot and examine the roots. If you can’t see any soil, and the roots have wound themselves round and round, don’t buy it. Also, avoid plants where lots of roots are coming through the drainage holes, or arching over the top. All three mean the plant has been in its pot for too long. In time, the roots will actually strangle the plant or refuse to grow out into your garden soil. Lots of compost with plenty of thin feeder roots showing is a good sign that the plant has recently been potted.

Bare-root plants are cheaper, but you need to check them carefully. A couple of snapped roots are okay, but if half of them have been completely mangled, choose another. Look for a well-developed root system in a radial pattern, too. Most importantly, check they are damp. Pass by any that have their roots exposed to air: they will have dried out and the plant will have died. The same principle applies for rootballed plants.

Sure success: Some plants have been bred to withstand attack from pests and diseases better than others. An RHS Award of Garden Merit, or AGM, is worth looking out for. It tells you that it is a tried and tested plant that performs well in the garden. They will have a gold trophy icon on the label.

A question of scale: Should you buy a huge specimen or a smaller one? Well, that depends on where you want to put it and the effect you are after. Big plants (and I mean “big” — fully grown trees, and so on) are great for instant impact (if expensive), but it can also be satisfying to watch your garden develop slowly.

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