Measuring the marigolds

Miracle cures abound in the organic gardening world, and the marigold is a top tip for all sorts of duties. However, it’s a bit more complicated than the stories usually suggest and like most people we’ve bought a packet of marigolds at the garden centre and discovered too late that they weren’t the ones we should have bought. So here’s a very quick disambiguation of the minefield.

  • Two kinds of Marigold share a common English name, and even look similar but they belong to two separate ‘tribes’, so let’s look first at the Pot Marigold, Calendula officinalis* which has a country cousin called – unsurprisingly the Field Marigold – Calendula arvensis which is rather uncommon so we needn’t worry too much about it. The Pot Marigold is a lovely plant; easy to grow and it’s a good pollinator attractor. It self-seeds freely so it’s best to harvest the flower heads before they mature unless you want to save the seeds. It’s also the source of the flowers from which calendula cream is made – it’s got to be one of the safest and easiest home medicines to make and it really works. The picture at the top is a part of last year’s crop of flowers that we turned into a wonderfully fragrant ointment last autumn by steeping the flowers in sweet almond oil and then adding beeswax to form a firm cream. It’s great for skin problems – although the price of organic almond oil will make your eyes water – but even using the best ingredients it’s half the price of the commercial product.

The other ‘tribe’ of marigolds are the Tagetes; and these are the ones whose roots are said to exude a chemical that deters or even kills some of the nematodes that can cause problems in the garden. There are three members of the family you’re likely to meet in the UK (the US has at least one additional member that I know nothing at all about).

The first of the three is Tagetes erecta which is very confusingly known as the African Marigold in the UK in spite of originating (as they all do) in South America.

The second is Tagetes patula – the French Marigold – which is a smaller plant and is the one that’s most often interplanted for its suppose effects as a pest deterrent. We use these all the time because, being quite small they’re easy to run in between tomatoes and other crops. As to its effectiveness it’s hard to say, but they’re very pretty and if they deter pests then all the better.

The third is Tagetes minuta the Southern Marigold which – again confusingly – is actually taller than the other two. The minuta in the name refers to its very small flowers. This one hardly appears in the seed catalogues because it’s not much of a looker, but ironically it may be the most potent of the three, because aside from its capacity to see the nematodes off it’s also said to be capable of getting rid of some of the most pernicious weeds like couch grass and bindweed. Anything that can achieve such a miracle is worthy of a mention but apart from a paper published by the HDRA I haven’t found much evidence. It has certainly been widely used in South America as a herbal medicine. My only caveat would be that if it does possess the magical powers that are attributed to it, it might be a very poor companion plant if its secretions attack the very plants you’re trying to grow. However I’m sufficiently interested to try to grow a small patch so I can try out its insecticidal effects against the asparagus beetle that regularly attacks our asparagus bed. This time last year we were cutting our first spears, but after such a cold and wet winter and early spring there was no sign of any spears today when we peeped under the fleece.

So I hope that’s of some interest. This is a short piece because we’re so frantically busy on the allotment. The polytunnel is already showing us new possibilities. Some containers of very early potatoes have needed earthing up twice in the last week, and our seedlings just love the warmth and light- although we’re still covering them at night. Happy days!

  • * Having posted this piece yesterday I was reading John Jeavons’ marvellous book “How to grow more vegetables ..” which I’ve only just been able to get a hard (ie real) copy of, and he unequivocally lists the pot marigold Calendula officinalis as a companion plant to tomatoes.