Marigolds help send pests in the wrong direction and is an ideal 'companion plant'

Marigolds can be a multi-purpose source of colour in the garden as well as being a valuable companion for the veg patch, writes Fiann Ó Nualláin.

I wasn’t much a fan of French or African marigolds (Tagetes spp) when I was growing up — my Dad would send me into town to pick up a few bundles, whenever he decided it was time to refresh the border edge of the path into our house after the spring bulbs had receded. 

Generally, that was the first or second week in May. They, like wallflowers and other bedding, were sometimes wrapped in wet newspaper and elastic bands —and even now I can vividly relive the icky touch of the soggy bundles in the palm of my hands — it’s my ‘nails on the blackboard’ equivalent.

When I got home, I didn’t mind helping to plant them, but as some years they came yellow, other times orange and some years more a bad bronze, I never quite could decide if they were cheap and cheerful, or a bit gaudy. 

We had a long sway of sky blue Campanula portenschlagiana self-seeding along that path, so the orange and blue years were favored over the yellow and blue ‘Wicklow county colour’ years. 

Nothing against Wickla, mind — or Roscommon or Clare for that matter. Just yellow and blue didn’t do it for me — at that age, I would have planted it black and more black.

The golden hues of tagetes are echoed in the name marigold — Mary’s gold — but long before their reassignment to the Christian tradition, Tagetes derived their botanical name from an Etruscan God of divination. 

A hint to some ethnobotany. One variety is still linked with shamanic ritual — Tagetes lucida — smoked or brewed as a psychoactive tea.

In fact the Aztecs referred to it as yauhtli – they used it to ‘sedate’ those who were to be sacrificed, while other cultures kick-started their dream quests with the plant. 

Tomatoes with marigolds planted as companions. Marigolds can be helpful in sending pests in the wrong direction. istockphoto
Tomatoes with marigolds planted as companions. Marigolds can be helpful in sending pests in the wrong direction. istockphoto

Discovering that in my late teens was part of my growing appreciation for the plant. That — and the horticultural benefits of planting tagetes in the garden that I would soon learn.

In Ireland today there are three types of tagetes readily available. All sold as bedding and ornamentals — treated as half-hardy annuals.

The three are; the French marigold (Tagetes patula) which is a small bushy bedding variety around 15-30 cm in height. Dense and vibrantly colored ray florets. They will bloom from late June until October frosts and come in single, semi-doubles and double forms. 

African marigold (Tagetes erecta) are a taller plant (more than double the height) and display larger flowers but with a shorter blooming period than French; more often found in semi-doubles and double forms.

Then, there are the Signet hybrids aka Triploid marigolds (Tagetes signata/pumila/tenufolia) which are sterile hybrids of the two former species. Prized as long blooming. Often sold with ‘gem’ in the name.

So while these guys are sold as bedding and ornamentals, they should not be disqualified from the vegetable garden. In fact I recommend their repeated use each year. 

Ok, yes they are a minor edible — in that their petals, (in strictly adhered-to moderation), supply beautiful vivid colours and a mild citrus flavour for garnish and other culinary purposes.

But it is their ‘companion plant’ potential that offers real promise. They are all excellent as scent deterrents to pests. Inside in the greenhouse, they dissuade white flies.

While outside, tagetes affect a trick of olfactory misdirection with not just cabbage white butterfly but also carrot root fly — so planting them near those crops is most helpful to send pests in the wrong direction.

Now is the best month to plant out any hue of tagetes and just in time to repel the summer influx of cabbage white butterflies

A woman offering marigolds for the gods in Varanasi, India by the banks of the Ganges river. The Portuguese introduced marigolds to India and they’re widely cultivated to make garlands, for marriages and festivals. Particularly, Dussehra where individuals adorn their vehicles and homes with marigold garlands.
A woman offering marigolds for the gods in Varanasi, India by the banks of the Ganges river. The Portuguese introduced marigolds to India and they’re widely cultivated to make garlands, for marriages and festivals. Particularly, Dussehra where individuals adorn their vehicles and homes with marigold garlands.

French Marigolds can have a pungent — dare I say, somewhat ‘pissy’ aroma, while the African and hybrids can have some citrus notes. 

Tagetes oil is utilized in perfumery and also in aromatherapy to treat wounds, infections, and respiratory conditions. 

Collectively their particular fragrance profiles do not deter hoverfly and other beneficial insects; in fact it attracts many — so some extra pest control.

But it is not all about deterring leaf munching pests or attracting pest munching predators. As a companion plant they have it going on underground too. 

What I really like about them is that they exude thiophenes from their roots – a sulphur compound which kills off nematodes; so potato eelworms look out.

There is potential here as a phytoremediation crop, planted in soils where nematodes have built up a strong and persistent presence. It will take the whole summer to do the job — so planting early is great.

In the tradition of a companion plant, it is not advised to plant near legumes, but otherwise their good neighbourliness is regarded highly by organic gardeners to improve the yields and individual vigour of most other garden vegetables, in particular crops of the Solanaceae family which includes potato, tomato, tomatillo, aubergine and capsicums (bell and chili).

Marigolds are so easy to grow, just plant in sun and add some water from time to time. They are easy from seed and come in plug trays and packs from your local garden centre. Long gone is the wrap of soggy newspaper.

And while they come in and out of fashion for baskets, containers and border edging — their use in the veg patch should be constant.

Plus, its nice to see some bright colour amongst the haze of greens on the allotment this month.


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