Some of the mail order seed and plant outfits are now cottoning on to the popularity of houseplants: Suttons sells a range of interesting begonias, Streptocarpus and African violets which are supplied by the specialist nursery Dibleys, while Crocus sells a good range of plants too. A listener tells us that Thompson and Morgan can sometimes be worth a look.

One of the major players is bakker.co.uk: I have ordered from them in the past and the plants were not bad, but I have heard gripes from other customers about their customer service.

I haven't tried Best4Garden but they seem to have a reasonably big range of houseplants. Hortology has a large range of plants and a stylish website, and sells a large range of pots, too: I haven’t tried this one but I have heard good things about them.

I'd also recommend Shrubland Park Nurseries in Suffolk which has a lovely range of houseplants available via mail order, and Perfectplants.co.uk, an online garden centre in East Sussex which sells an impressive range of houseplants from its hothouse (pictured above).

I have recently discovered the world of vivarium supply shops as a source for interesting houseplants: these may not be your obvious choice, but they are a great way to buy certain plants such as bromeliads, vines and ferns: things that will do well in the high humidity setting of a closed terrarium. They are sometimes sold in pots but also as rooted cuttings which, provided you are confident at potting them up, are a cheap way of getting more plants. I’ve bought from Dartfrog and rainforestvivs (who sell on eBay.co.uk) but there are many more.

Ebay sellers can offer a way of getting hold of rarer plants and seeds, but it’s a bit of a “buyer beware” situation, particularly if you are ordering seeds from outside the UK - I have heard of people getting burned with seed packets containing chaff or something they clearly didn’t order. Postage costs can be high, too. And listener Callym Cooke has alerted us to Arcanopy, which while a small range can include plants not often found elsewhere.