Choosing new plants is a huge decision for gardeners. With enough space and time, it’s always more rewarding and cheaper to grow many plants from seed, but with shrubs and a lot of other perennials you should let nurseries do the hard graft for you.

You could take full advantage of these labours and simply wheel a trolley round a garden centre and fill it with pretty flowers. You’d then plonk them in a vacant space in the garden, as if you were finding space in the fridge for the week’s shopping. But this page is for gardeners, not shoppers.

Start with a clear idea of the plant you want and how it will perform in the space you have for it. Will its eventual height be OK? How far will it spread? Will it smother its neighbours or end up surrounded by an earthy moat? If it’s a perennial, is it hardy enough to cope with a Scottish winter?

Then look for healthy, robust specimens and avoid sad ones that are leggy and straggly with yellowing or diseased leaves. A struggling plant, whose growth has been checked, never fully recovers.

When you go to a garden centre you’ll see what you’re getting and if it’s up to the mark. If it’s an impulse buy, check whether it’s suitable for your garden, asking a sales assistant, if necessary.

The downside is that garden centres inevitably carry a more restricted selection than a specialist nursery. If possible, visit the nursery, but you’ll have to rely on website photos and descriptions if it’s in the south of England.

Nurseries vary hugely in the service they offer and the quality of plants. With luck, you or a friend may know of a good place, and Which? Gardening runs helpful surveys from time to time. And you may find useful online reviews.

Otherwise, try a new supplier by placing a small order. Without spending a lot of money, you’ll quickly see if the plants are healthy and whether they’re well packed and arrive undamaged. You’ll find out if they come when you expect or have been promised. I’ve had new asparagus crowns arrive just before Christmas instead of March and a packet of quick-growing De Monica broad beans several weeks late, thereby destroying the point of growing them in the first place. Also, if there are any problems, how helpful is the nursery?

Unsurprisingly, the larger the plant, the more you pay, making plug plants the cheapest. Bedding plants and many other annuals are generally sold singly in strips of cells. They’re unlikely to be more than 5cm tall, so need potting on to let them grow large enough to handle life in a bed or even container. Soak for an hour before moving into a 5cm diameter pot containing a 50:50 general-purpose compost and perlite or grit. You may need to pot on to a 9cm one.

Plug plants of annuals can be a good investment. But, during the first year, perennials won’t flower as well as larger potted ones, though they’ll catch up the following year.

Normally sweet peas, vegetable and herb plants are multiple sown in plug cells. Check them carefully before purchase as they become hopelessly stressed if kept too long in cells. Separate the seedlings as quickly as possible after thoroughly soaking in water. Loosen the roots gently and tease them apart, holding by the base of the stems.

Be sure of what you’re getting. The nursery Mr Fothergill's has launched a useful collection of extra early brassicas with named varieties of calabrese, cabbages and cauliflowers. The nursery has overwintered them and will despatch in March so you’ll get a June harvest.

On the other hand, a well-known seed supplier is promoting a collection of 150 plants which it declines to identify. A cynic might wonder if these are the plants they’re finding hard to shift.