I’ve been told that there are some trees that you shouldn’t use for cooking with. Is this true, and which would be best for BBQ skewers?

JONNY CROCKETT replies: You should avoid any poisonous trees like laburnum, yew, rhododendron and elder. You should also avoid conifers unless you want an ‘essence of toilet cleaner’ taste in your food. The best skewer wood is probably dogwood. ‘Dog’ is a derivative of ‘dag’ as in ‘dagger’ and it grows straight and hard. You can tell that you’ve got dogwood because when you pull the leaf apart down the length of the veins, you can see latex strung between the two parts. With a knife, you need to take the bark off so that it is clean and contains no tannins.