[Garden] Marigolds

[gcmichal]

I think the best approach to "companion planting" is to first examine  
what you are trying to achieve.

The basic question is "Does our garden have a nematode problem? If  
yes, is it significant, or can we live with it?"  No one has  
mentioned to me that there is a nematode problem, and I haven't seen  
any mention in the emails that circulate, so maybe there isn't a  
nematode problem, and therefore there is no need to try to combat them.

If there is a nematode problem, then the first round of enquiry is to  
see what opportunities exist to cope with them.  One way is simply  
not to grow the plants that are damaged to a degree beyond what the  
next critter up the food chain (i.e., us) will tolerate.  A second  
approach is to plant nematode-resistant varieties - information on  
such is available for many garden crops. (Are the vegetable varieties  
we planted already nematode-resistant?) Another approach is to switch  
the garden site.

Then there are different approaches to combatting nematodes, of which  
companion planting is one.  If we were to go to companion planting,  
it is best to first check  on how the companion planting works.  For  
instance, if the companion plant works on the principle of giving off  
an aroma or fumes that repel flying insect pests arriving from off- 
site, then you would do the planting in an interceptive fashion, and  
also have to ensure that you had enough of the plants to assure a  
vapor concentration sufficient to cause the insects enough  
aggravation that they will happily go elsewhere.   If you are dealing  
with pests within the soil, and something that is already there and  
not trekking in from elsewhere, then your planting strategy would  
have to be quite different. Presumably you would have to plant the  
protective plant all over the place because the pest is all over in  
the soil.  In some cases too, the substance of interest is in the  
above-ground growth and you would have to plow it into the soil in  
sufficient quantity to do its job.  Other companion plants are used  
as lures  or decoys, and the strategy is to provide the pests with an  
alternative plant that they really like, but doesn't interest you for  
food, and those pests can happily savage your companion plants all  
they want because you won't be interested in eating them, but rather  
the tasty carrots and onions that the pest has so foolishly abandoned  
when presented with the treat you have provided.

Let's presume that there is a nematode problem and marigolds are the  
way to go.  What crops are we trying to protect? When is the damage  
likely to occur?  How should the marigolds be planted, and how dense  
do they need to be to be effective?  It may be too late to plant  
marigolds by seed - and too expensive to buy sufficient quantities of  
marigold bedding plants.  I checked a couple of internet sites  and  
the recommended density for protection of vegetable plants is 3  
marigold plants per square foot. That's quite a lot, and it may be  
turning the marigolds into the equivalent of weeds that begin  
competing with the garden crop for space, nutrients, and water.   
There is a logistical problem if using marigold seed.  The vegetable  
seeds have now mostly germinated and will be growing rapidly.  If  
marigold seeds are now planted, they might not have a chance of  
competing against this head start.  One report says that it takes 4  
months before there are noticeable effects on the nematode population.

Additionally, the plots are already designed and planted, and it   
might be a big sacrifice to have to tear up portions of it to put the  
marigolds into the desired protective configuration.

There is another crucial question: what varieties of marigold are  
proven effective against marigolds?  Some work and some don't.  If  
the varieties you bought don't have proven nematocidal virtues, then  
you should take the seeds back, unless, of course, their main value  
is to please the gardener's eye and magnify the Lord rather than to  
confound the detested wiggly worm, in which case, the more marigolds  
the marier, whatever variety they might be.

- Greg Michalenko


On May 14, 2007, at 12:46 PM, J. Rochon wrote:

> Gardeners,
>                         I have just picked up a large number of  
> marigold
> seeds. Marigolds are good companion plants, since they work to reduce
> nematode damage. So here are the questions. Where do we want them
> planted? Do some plants benefit from marigolds more than others?  
> Should
> I sprout the marigolds before planting, or just sow seeds?
>                                                          -Jason
>
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