Which? Gardening magazine said potted Christmas trees can look "dull and lifeless" after just three weeks, with the Norway spruce losing most of its needles in that time.
Researchers warned that potted trees are often planted in containers too small for the tree, making them difficult to water and look after.
But the best container-grown Christmas trees performed best overall in a Which? Gardening trial, although they are an "expensive option" at £30-£50, Which? said.
Which? Gardening found that cut trees, sawn off at ground level and stood in a plastic stand with a water reservoir, performed almost as well as container-grown trees but usually cost less.
It found cut Norway spruce and Nordmann fir stayed looking healthy throughout the trial.
Richard Gianfrancesco, head of research for Which? Gardening, said: "If you only want your tree to last for one Christmas, don't bother spending money on a re-potted or container-grown tree. Instead, pick up a healthy cut tree from a reputable grower. These trees performed almost as well as a container-grown tree and could save you a few pounds."
British Christmas Tree Growers Association (BCTGA) secretary Roger Hay said: "This is some difficulty in some people understanding what is a potted tree and what is a container-grown tree. In the BCTGA we try to differentiate. But I have no reason to believe trees that are potted or container-grown would perform less well than many other trees."
The BCTGA said container-grown trees have been grown for at least one season in their pots.
It added: "It is often possible to lift the whole root system out of the pot and see the closely woven root that has grown in the pot. The trees themselves should look fresh. The trees will be small and seldom more than three foot [90cm]. The trees should be watered and cared for as for any houseplant. After Christmas they can either be planted out with a very good chance of success or they can be left to grow on in their pot, but it is much better in this case to re-pot the tree in a larger pot. It is seldom possible to re-pot trees in this way for more than one season."
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