The worst day of your life?

When our first child Polly was a baby, my wife fell down the stairs with her in her arms. She shattered her elbow and Polly fractured her skull, and I found myself in hospital with both of them. I was very worried, but luckily it was all right in the end.

The worst thing anyone could do in a garden?

Block paving on front gardens. You might get an electric car to be kinder to the environment, but if you’re parking it on paving, you’re covering up the earth and stopping plants from growing. Plants are so important for absorbing carbon dioxide and water, and for biodiversity, that the good work of getting an electric car is undone. People also prune things very badly. I’ve seen feathery, light birch tree canopies have their branches butchered.

Your worst modern obsession?

Avocados. They chop down rainforests to plant avocado trees, which need litres and litres of water to grow, and then they’re shipped across the ocean. They’re a no-no for me when I think about what it’s taken to get that smashed avocado on to a piece of toast. I’m not that wild about the flavour anyway.

Your worst pet peeve?

I can’t stand “routemaster bus moments” on television, when the wrong thing is depicted in the wrong place or time. In period dramas, by which I mean anything pre-1960, men should never wear a hat indoors. If you went into somebody’s house back then, the hat came off the moment you went over the threshold. I know it’s pathetic and pedantic, but when I see policemen on the box going into people’s houses with a trilby on, it gets to me.

The worst plants to grow?

There are a few plants I don’t like. Gladioli, those Dame Edna things, are hopeless in a garden because they’re so stiff. They’re all right in church- flower arrangements. And while some grasses are very soft and graceful, I’m not mad on pampas grass. They look like feather dusters on sticks.

The worst thing about public debates concerning the environment?

Too much hot air and not enough action. Governments can have as many conferences as they want, agreeing what they should do, but unless they do it, it’s not going to translate into action. The amount of plastic in the ocean now is shameful. We need to be a lot more assiduous about discouraging it.

The absolute worst

Littering is the most irresponsible thing. I think people who are found to be dropping litter should be given a month’s community service picking it up. They wouldn’t do it again, and it would help to get rid of it. It’s ugly and dangerous to livestock and wildlife.

Alan Titchmarsh’s latest novel The Gift (£20, Hodder & Stoughton) is out now, available to buy from Telegraph Books