Rowan and red thread: the Scottish door charm, where it comes from and how to keep it today

Search for rowan and red thread and the same picture comes back over and over: two short twigs lashed into an equal-armed cross with red wool. It is a good-looking object and plenty of people keep one. It is not in the rhyme.

We can give you a name and a year for the couplet. We cannot give you a name and a year for the cross. Until someone can, treat the cross as Modern, or as an old pattern that later hands tidied into a shape. Make one if you like it, then write in your own book what it is and where you got it, so the next person reading your page is not misled the way the internet misled you.

What the record does carry is simpler. Rowan at the house. Rowan in the pocket. A red thread with it. That is enough to work with.

Nothing here needs a hammer. Lay the sprig along the top of the door frame. Tape a loop of the thread inside the frame. Stand it in a small jar on the hall shelf among other greenery. Keep one in the glove box and one in a coat pocket.

The pocket version is the older of the two anyway, and it is the quietest thing on this page. A guard that looks like nothing has a long history behind it: the sealed witch bottle buried under a house was invisible by design too.

If you want the rest of the door, the hearth, the bed and the road in one place, with the source and the year printed on every working and a renter's option beside it, that is The Practical Grimoire of Protection. All four books together are the complete series.

Rowan is Sorbus aucuparia, the European rowan or mountain ash. Check four things together:

• Leaves: pinnate, usually nine to seventeen narrow toothed leaflets in pairs with one on the end, set alternately along the twig.
• Flowers: creamy white, in broad flat-topped clusters in late spring.
• Berries: small, round, orange to scarlet, in heavy bunches from late summer into autumn.
• Bark: smooth and gray on young trees, rougher with age.

The look-alikes are worth knowing. Ash carries pinnate leaves too, but they sit opposite each other on the twig, and the tree makes winged keys rather than berries. Elder has opposite leaves with fewer leaflets and flat heads of dark purple-black fruit. Staghorn sumac has pinnate leaves and red fruit, but its fruit stands upright in a dense cone and the stems are velvety.

In North America the tree planted under the name mountain ash is often a close American relative rather than the European rowan. People use it. Just note in your own pages which tree it actually was.

If you cannot tell, do not pick. Photograph the leaves, the fruit and the bark and ask a local tree group or your extension service. And if trees are not your ground this week, the protective plants already in your kitchen ask nothing of you but the cupboard door.

Nobody is eating anything here. Rowan berries are harshly bitter raw, and that bitterness is the parasorbic acid in them; the rowan jelly people cook on the stove is a food with its own recipes, and this is not that page. A twig at a door is the whole of it.

With a cat or a dog in the house, treat loose berries as windfall to sweep up rather than decoration to leave on the floor. Keep the sprig above a curious nose, or inside a cupboard. If a pet eats the berries, call your vet or a pet poison line instead of searching for an answer. We keep a plain list of which plants are toxic to cats and dogs for exactly this reason.

Keep a dried twig away from open flame. If a candle stands anywhere near it, the candle stands in a jar and is never left burning alone. An LED does the same job.

And the honest line under all of it: this is what people did and what they said it was for. We give you the custom and its date. What you make of it is yours.