According to the Royal Horticultural Society, indoor plants are on the rise and sales in the second half of last year were up 60% on the previous year.

Some have attributed the trend to green-minded millennials who are keen to bring the outdoors indoors and look after something 'real'. If you are one of these green-fingered individuals, and you've extended your gardening skills to your workplace, maybe it's time to look a little closer at the humble pot-plant.

Whether you've simply plonked a plant on your desk, or surrounded your complete office environment with a selection of green leafy friends, indoor plants are considered to have a positive impact on our well-being and mental health, but just how green are they?Let's dig deeper.

1.Plant Miles

There are a number of online companies that now deliver plants direct to your door. This will contribute to your carbon footprint, particularly if the plants are shipped from outside of the UK. Online ordering could rack up 'plant miles'. Instead, initiatives such as PlantSwap could offer a more eco-friendly alternative. As many plants are brought in from overseas, their transportation represents a significant ecological footprint, many come form Holland, but certain varieties such as orchids can be shipped from as far as Indonesia.

Some people argue that online delivery uses less transportation than numerous trips to the garden centre in the car but either way, considering exchanging unwanted plants, or cuttings and seedlings from your garden is a far more sustainable solution. Another benefit of choosing this option is the avoidance of excess packaging that comes with new plants - including pots.

2. Plastic Pots

Pots can be tricky to recycle. Depending on the materials and plastics used to manufacture them, a very low percentage of local authorities will accept them. This is either because they are contaminated or made from black plastic that can't be detected by some sorting machines.

There are a few alternatives emerging on the market that are made from cardboard, compostables or more sustainable materials, but the general advice is to consider how long you will use the plot for and whether you will use it again. Alternatively opt for a retailer that runs a plant pot recycling or "take back" scheme.

3. Peat

As well as the plant miles and the plastic problem, another issue is the soil in which the plants are grown. Peat is an  earthy material used for planting that has taken thousands of years to form and commercial extraction can remove over 500 years of growth in a single year. The alternative is to opt for varieties who use a substitute or indeed, do not need peat to grow, such as Orchids or cacti.

So, do the positives outweigh the negatives?

Plants absorb CO2 and emit oxygen so are considered useful in combating carbon and cleaning the air. However, the quantity of CO2 they remove depends on the species of plant, how much water is in the soil, how much light they get and how many plants you have.

"The amount the plant is watered affects its ability to function and remove CO2, in the same way as with people - if you're dehydrated or have drunk too much water you will not function as well," says environmental consultant, Curtis Gubb.

Gubb found that Dracaena "Golden Coast" plants and peace lillies performed best in his research at absorbing CO2, but points out that a lot of them would be needed to have a significant impact. He says that even installing a vertical garden or "green wall would require extra lighting to reduce CO2 levels.

Ulitmately if you are shopping for a new plant for your office, try to be as sustainable as possible. Talk to suppliers about the use of peat, avoid buying houseplants that are "designed to die" like Poinsettias, and grow your own from cuttings and seeds if possible.