From my experience mould is only an issue with poor quality teak furniture.

The best quality teak will be kiln dried over at least 21 days to slowly reduce the moisture content of the timber before moulding and assembly. Teak is naturally about 30% water when the tree is felled. The drying process in large industrial ovens slowly reduces the moisture content to around 10 – 14% moisture. This ultimately reduces any chance of warping or cracking once the furniture arrives into the drier air of the British climate compared to the humid tropical climate of Indonesia.

Leaving teak planks in an oven for 3 weeks costs money, which ultimately is passed onto the consumer. However should mean that the furniture will now last many many years longer and probably pays for itself handsomely on a £/years of use basis.

Poorer quality teak tends to be between 18 and 24% moisture and has only been dried natural by being left outside the factory in the tropical humid heat.

The high moisture content of the furniture once packaged and then stored is a breeding ground for mould and an obvious indicator of poorly manufactured furniture.

The simple application of silica gel sachets inside the packaging should solve any natural moisture problems occuring inside the shipping container and any good manufacturer will hang around 8 large moisture absorbing bags inside the container.

So advice would be to avoid any furniture that is mouldy

Look for retailers that source and retail low moisture teak garden furniture such as Chairs and Tables Limited. Companies that sell teak at moisture levels at less than 14%