The last time I read actual 'evidence' beyond anecdote the answer was yes, marigolds have some repellent properties, but it's a specific marigold not commonly found in the retail trade (forget which one, sorry). It wasn't enough to plant a marigold here and there, the crop to be protected had to be surrounded by an ocean of them.

Great. It looks like I bought a flat of marigolds for nothing. They'll look pretty by the vegetables anyway. The gardener dude down the street has them bordering his whole veggie garden. It looks pretty and the [marigold] plants get pretty darn big. I think maybe they come back every year for him, seeing as how they're so big.

Marigolds are annuals so he is either replanting each year or he is allowing the flowers to ripen seeds and they regrow each year from seeds.

Either way they are a great garden companion. Fairly easy to grow, adaptable to a range of conditions, don't require a lot of water or nutrients so they don't compete much with veggies for those things. Plus, they look great.

Maybe they will repel a pest, who knows? Maybe they will attract a pest and the pest will feed on them instead of a veggie. Again, who knows. They will certainly attract a variety of good bugs, including pollinators. Overall I think flowers are a great thing to have in the veggie garden and marigolds are among the best in my opinion.

Do they actually repel pests effectively? I really doubt it, but I don't think your purchase of a flat was 'for nothing'.

Here I planted marigold among my brassica for nothing.

Oh, well. They're pretty, and I like marigolds.

For a long time, when people ask me if I grow flowers I respond, "No, if I can't eat it I don't grow it." But, I've become an absolute fanatic about marigolds. Let me remove all doubt: MARIGOLDS DETER APHIDS. Only yesterday I went to a party where I knew my married children would be. I brought a BIG bag of lettuce for each of them (Ruby and Romaine, on ice, in a cooler). These were HUGE heads, more than 12 inches across, and when I washed them and cut 'em up in the kitchen sink I found not a single aphid. I still remember vividly the kazillion aphids I would have to deal with before I started the marigold thing.

There's nothing special about the marigold seed that I buy. Dwarf marigold is all I ask for. I plant them in pots so that they A)don't take over the garden, and B)so they remain small. At first I used to grow a late summer set of plants, for when the potted ones would run out of gas, but last year I did not. It appears that if the aphids don't show up by late spring/early summer they may not show up anymore.

Remembering how dense aphids used to be in my garden, on the lettuce and tomatoes especially, I feel euphoric over this discovery, and I can only hope it continues.

Besides, they are awful pretty.

> ...the crop to be protected had to be
> surrounded by an ocean of them...

I have read that is the case when marigolds are used to control NEMATODES.

For aphid control, "ligardener" puts marigolds in pots and rotates them around her garden.

Studies have been done on Marigolds and to put it plainly, there is no evidence they deter aphids. I am sure there are many folks who planted marigolds and then had no aphids, but there are more whose aphid problem (or lack thereof) didn't change one bit with marigolds.

That's the problem with anecdote, there are always a bunch of people who can report any outcome. On the net those who got positive results outpost those who had no results.

In controlled studies marigolds don't repel anything except for one species and only then with a ton planted around the plant to protect.

Still, go ahead and plant them. They won't hurt and they look nice.

My brother has 4 roses in the backyard in a line. Two weeks ago the buds were absolutely covered in aphids, and I mean covered. He planted Marigolds in front of the roses, and yesterday there were none. They really do work

Another reason that marigolds help is they attract the green lacewings and other bugs that eat dozens of aphids every day. Limnanthes (poached egg plant) and phacelia are other easy to grow flowers that have really helped with my aphid problem.

Again (and for the last time in this thread) marigolds do not deter pests. There have been large scale studies done on this and they universally fail to find any deterrent effect.

There is one marigold not available in the retail trade (normally) that when planted in large numbers has been found to provide a deterrent affect, but that's it.

All the anecdotal evidence in the world doesn't change the results of controlled studies.

I am inclined to believe Julieherb though. The planting of any plant near another is going to create a more diverse environment which will attract a broader range of insects. The diversity tends to promote a better balance of prey/predator.

Planting nothing but veggies will certainly attract veggie preys. Planting veggies with flowers and other plants will immediately attract a more diverse insect/critter population and thus the over presence of any of them will *tend* to be kept in check.

In this respect marigolds are a great companion plant, but not necessarily any more so than nasturtium, phlox, sunflowers, daisies, wild flowers, morning glories or anything else.

In some areas gardeners actually find their marigolds devoured by insects. Not my area, but in some areas.

A diversely planted garden will attract a diverse group of bugs which will compete with each other and even prey upon each other, but there is nothing special about marigolds other than they tend to form neat, compact plants that aren't very invasive (unless allowed to go to seed over the fall/winter). They also tend to be easy to grow with no special attention.

So make an insecticidal spray out of it:

Entomologia Experimentalis et Applicata
Volume 115 Issue 1 Page 153 - April 2005

To cite this article: Blagovesta S. Tomova, John S. Waterhouse, Julian Doberski (2005)
The effect of fractionated Tagetes oil volatiles on aphid reproduction
Entomologia Experimentalis et Applicata 115 (1), 153Â159.

Abstract
The effect of fractionated Tagetes oil volatiles on aphid reproduction

* Blagovesta S. Tomova*Environmental Sciences Research Centre, Anglia Polytechnic University, East Road, Cambridge, CB1 1PT, UK*Correspondence: E-mail: ,
* John S. Waterhouse &
* Julian Doberski
* Environmental Sciences Research Centre, Anglia Polytechnic University, East Road, Cambridge, CB1 1PT, UK

Key words: Tagetes minuta, insecticidal, Acyrthosiphon pisum, Myzus persicae, Aulacorthum solani, Homoptera, Aphididae

Abstract
The biological activity of essential oil volatiles from Tagetes minuta L. (Mexican marigold) against three aphid species was investigated in a series of laboratory experiments. The aphid species (Homoptera: Aphididae) studied were: Acyrthosiphon pisum (Harris) (pea aphid), Myzus persicae (Sulzer) (peach-potato aphid), and Aulacorthum solani (Kaltenbach) (glasshouse and potato aphid). Tagetes minuta oil volatiles significantly reduced aphid reproduction (up to 100% after 5 days of exposure). The effect depended on the quantity of essential oil used, and varied with the aphid species tested. Pea aphids were the most susceptible. Tagetes minuta oil was fractionated by vacuum distillation. Fractions and three pure compounds (limonene, (Z)-ocimene, and β-caryophyllene) were tested using the same experimental technique. The chemical composition of the volatiles was investigated by headspaceÂsolid phase microextractionÂgas chromatography mass spectrometry (HS-SPME-GCMS), and the main constituents of the oil were identified. Overall, applied in equal quantity, fractions predominantly containing sesquiterpenes and oxygenated monoterpenoids were more effective in restricting aphid population growth than fractions predominantly containing monoterpenes. When tested as a pure compound, the sesquiterpene β-caryophyllene produced a greater effect than the monoterpenes limonene and ocimene. The study demonstrates that T. minuta oil volatiles have potential for aphid control.

Anecdotal evidence. Why do some folks have so much trouble accepting it? Isn't that where discovery and progress begin? If a cancer pill came out that claimed to kill 75% of tumors should that pill be rejected because it failed in 25% of cases. If a "cure" for baldness was discovered that helped 80 folks out of 100 should that cure be abandoned because 20 people weren't helped? If scientific proof is the only thing to guide us in our decision-making, all we have to do is reflect on how many "truths" have fallen throughout the history of the world. Remember when the world was flat? And the sun revolved around the Earth?

I'll say it once again, a little more emphatically this time for the naysayers. I've been gardening for thirty years. I remember the times when my tomato plants and everything else were infested with aphids. INFESTED. I remember when my kitchen sink was littered with aphids as I rinsed the lettuce over and over again. I was reluctant to give some to the neighbors, thinking they would probably throw it away. No more! Two rinses is all they need now, just to get rid of some dirt. I haven't seen a single aphid YET this year. And the tomato plants are coming along, clean as a whistle. That's all the science this guy needs.

One further note (very important). I start my marigolds indoors in early February so that I will have established potted plants by early April when the first lettuce plants are going into the ground. This way the marigolds are in early bloom long before aphid arrival time. By late April, when lettuce is being picked and mid-May, when the tomatoes are making their move in my zone 7, the marigolds are in full bloom, lending great color to the garden and doing their thing, which is to deter aphids.

Try it; you'll like it.

Anecdotal evidence. Why do some folks have so much trouble accepting it? Isn't that where discovery and progress begin?

Often, yes. That's where investigation begins, but it isn't where investigation ends (in the case of a good investigation).

People notice something and form a hypothesis ( a guess based upon observation) and then set up a way to test the guess in a controlled manner.

Do Marigolds deter aphids or any other pests? The research says one species, in large numbers does, and the rest do not.

Does this mean planting marigolds won't deter pests? No, it doesn't. It means there is nothing about marigolds that in and of themselves deters pests (except one species planted in massive numbers).

Some people may still find they reduce pests. It could be the scent confuses some insects in some areas. It could be the plants attract insects which feed on one's local pests? Who knows?

The point is that anecdotal evidence is based upon observations and not tests controlling for variables. It's one of the reasons why one gardener reports marigolds deterred aphids, another reports no control and yet another reports the aphids ate the marigolds.

Whose experience/observation should one value most?

If we go off anecdotal evidence (and sometimes we have no choice) then pretty much anything does anything. It's not difficult to find someone on the net who will claim will work well for .

It's the controlled studies that actually figure out why something does or doesn't work and what conditions it works best in.

I'm sticking to my guns that they do indeed work quite well!!
As said above, my brother put some around his roses. The roses used to be covered in bugs, now none. Went by yesterday and the roses are still bug free, yet the Marigolds are ravished. One is almost completely gone...eaten to all heck by pests

bdobs, your experience would argue that in your area marigolds do not deter pests, they attract them so powerfully they act as trap cops. The marigolds get eaten, the more desirable plants do not.

To quote myself ;-) The point is that anecdotal evidence is based upon observations and not tests controlling for variables. It's one of the reasons why one gardener reports marigolds deterred aphids, another reports no control and yet another reports the aphids ate the marigolds.

Sometimes we gardeners have nothing to go on other than experience and other's anecdotal evidence. This is fine, but sometimes we do have the benefit of well done, properly controlled scientific studies. In the case of Marigolds and their pest repellancy we do have the benefit of quality, controlled studies. They don't repel pests except one species in massive numbers completely impractical for a veggie garden.

Relying upon anecdote in the absence of science is fine. Relying upon it when the science contradicts it is faith based gardening. To each their own.

I believe that "Myzus persicae" is one of the 3-4 aphids that are major pests of lettuce. Grinding up marigolds and extracting the essential oils apparently works, according to the (presumably) controlled study cited by Violet. That study doesn't prove that placing potted marigolds will deter aphids, because potted marigolds are intact and the essential oil vapors are in low concentration.

Perhaps those controlled studies which failed, with intact marigolds, were in windy climates? And the one study that "worked" was in a weakly windy zone? Or in a greenhouse? "Ligardener", how windy is your garden?

I live in very windy climate. I think that it may be worthwhile to grow some marigold, pick the leaves and flowers, soak and gently heat them in diluted Safer Insecticidal Soap or Baby Shampoo (or Bubblebath) to create an enhanced soap spray.

We started from the Soap Spray Thread, and to there we return !!
;-)

Violet,

Have you been hanging around "Agricola" again?

Or do I smell "scholar dot google" on your breath?

Geeze, you make me feel like a lazy bum.

There are many more more sources than "Google" believe it or not. "Agricola"? No... but thanks for pointing me to the source! It's always good to learn.

*wink*

I guess that this is one subject that we are going to have to leave up in the air and have individuals decide on their own. In bdobs case, where the marigolds themselves got all eaten up, we don't know what did the eatin' so no clear conclusion can be drawn. As I explained in my earlier postings, the marigold trick worked so convincingly for me that I will swear by it. I would like to remind others, meanwhile, to keep open minds because there are many theories, tricks and beliefs not only in gardening, but in life in general, that were once written in stone only to be disproven later on. I remember when it was a requirement to use tree wound paint on any tree limb or branch that was pruned off. As I understand it, that is no longer recommended because the cut limb is now said to heal itself. I read once that allowing the surface of the ground in a garden to get bone dry reduces moisture loss in the soil itself because it reduces capillary action. Does anybody believe that? I don't. Other examples abound. Beyond the garden, look at how many "life-saving" drugs get pulled because anecdotal evidence -- there's that phrase again -- shows that they kill too many people.

Anyway, I think this topic has been exhausted, at least for me, but I enjoyed the exchange. I'm a recent entrant to this forum, and I hope to return frequently.

Y’all tripping. I’m dying laughing reading these comments.

This is a multi-year thread! I just bought a bunch of marigold (100+ little plants) and then saw this article: https://www.google.com/amp/s/www.chicagotribune.com/news/ct-xpm-1992-09-13-9203230490-story,amp.html

It says marigold attracts aphids! I am then ready to return all marigold then saw this thread. Which ones are true? LOL