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I have recently had some potatoes that were said to benefit from being planted at an advantageous time because of the lunar cycle.

I had never heard of such a thing, but apparently "it is quite common on the continent"(European mainland).

My immediate reaction was that it was hoopla, but the potatoes were the best I have tasted.

Are there any studies to show the benefits or otherwise of planting at different phases of the moon? Is it actually used in mainstream agriculture?

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+1 Yes I know a French gardener have that kind of advice. –  ChrisW Jun 16 '11 at 13:30
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It certainly is common over here. I was thinking that was a universal myth around the world. Apparently not ;) Thats what I really like about this site. Makes you see how some universal "truths" are in fact just local fairy tales. –  user288 Jun 16 '11 at 16:24
    
@Sejanus that is why it is interesting, if people are doing it commercially, it may have some use. –  Jeremy French Jun 17 '11 at 13:45
    

2 Answers 2

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Moon Planting philosophy is a Myth in that it does not work for the reason Lunar Planters think it does, but there are several reasons why people swear by it.


How They Think It Works

There are two main ideas behind moon gardening practices. First, lunar gardeners believe the moon's gravitational pull affects the flow of moisture in the soil. Just as the moon has a noticeable effect on the oceans in the tides, the moon may have a subtler effect on smaller bodies of water and thus change the levels of water in the soil. For example, to take advantage of the lunar cycle, a gardener would avoid turning over the soil in his or her garden when there is the most moisture in it (and thus when the soil was hardest to turn over) which lunar gardeners propose is during the new and full moons. Another, less direct, proposed connection between the moon and gardening is that moonlight is thought to have an effect on seed germination because exposure to light can enhance germination. [Ref]

What's Going On

Let’s look at a possible scenario. Gardener I is a moon planter; Gardener II isn’t. Both gardeners wait till spring to plant their beans. (No sensible cool climate gardener will plant beans in winter. It’s too cold for them to germinate, and many seeds will rot or be taken by ants.) But come the first warm spell Gardener II succumbs to one of the great spring urges and plants the beans at the first hint that spring has arrived. Gardener I, on the other hand, waits till the next good moon planting time before planting the seeds. Early warm spells are usually followed by another cold one… and again seed planted too early may rot. Even if it doesn’t, plants that suffer any set-back when they are young usually don’t do as well as plants that have flourished right from the start. (The set-back can be from cold, boggy soil, snail or scale attack — the effect is the same). So counterintuitively, beans that are planted later in spring will probably do better than beans planted too early. [Ref]

The result is essentially that what may seem as an intuitively good time to do gardening is often counter-productive, and anyone adhering to a fixed schedule independent of the weather is likely to do better than the intuitive gardener.

The reverse may happen in autumn — the moon planting gardener will be aware that they only have one good time to plant, so may get their seeds in without delay — and in autumn, earlier planting into warmer soil usually means bigger plants. It’s this tendency to slightly later spring planting and perhaps slightly earlier autumn planting, that I suspect is the reason so many gardeners will swear that they see an effect. (One keen gardener who has been following moon planting for more than 30 years once told me that he finds moon planting more effective for early rather than late spring plants, though he believes it’s because the young spring moon is more powerful.) Which means that generations of gardeners may not be deluded about the efficacy of moon planting. It just works for a different reason than the one they believed.

Furthermore, those enjoying the superior goods of moon planters are likely to find them better for reasons other than moon planting. Confirmation Bias likely plays a role, but even more than that - someone who is attentive enough to their garden to adhere to moon planting folklore is likely to be doing other things to ensure the health of their crops - such as using healthy soil, watering properly, and being generally more attentive. In short, most of the gardening behaviour that goes hand in hand with the superstitious tendencies will have an actual positive effect on the crop.

From this national geographic article Michael Jawson, US Department of Agriculture Systems Laboratory in Beltsville, Maryland said:

The reported benefits of moon-gardening practices are most likely indirect effects that stem from gardener’s attentive care. The indirect effect could be one simply of overall better management because of being careful to do good practices at more optimum times in relation to plant growth cycles.


Research

Few studies have been done to test the veracity of lunar gardening. This due in large part to the fact that such experiments would need to be performed over multiple years, since weather, time of year and other external factors immediately affect plant growth. The few studies that have been done have questionable methods, limited time frame, inconclusive results or conflicting results. [Ref]

There was a study done by the Agricultural Research Service in Iowa where they found a link between weed germination and exposure to light. They determined that tilling the soil (i.e. bringing weeds to the surface) was best done at night by a new moon (when there was as little light as possible). Tilling in the dark led to less weed seed germination and thus to fewer weeds in the garden.

Pubmed - Lowell W. Woodstock and Don F. Grabe. Relationships Between Seed Respiration During Imbibition and Subsequent Seedling Growth in Zea mays L., Plant Physiol. 1967

This would suggest that freshly tilled gardens exposed to the outdoors are less likely to become weedy when it's dark out (obscured moon or cloudy weather), and facilitate false attribution of the outcome to astrological myths.


Biodynamic - Nicholas Kollerstrom and Gerhard Staudenmaier. Lunar-Sidereal Rhythms in Crop Yield, Biological Agriculture and Horticulture, 2001

This article summarizes a large number of older studies, many of which appear to support planting by the moon or other astrological principles. Invariably, the studies are near sighted, providing only a single (anecdotal) data point in time, mistakenly claiming statistical significance due to a large number of sample germinations. Studies that confirm the behaviour fail to account for the majority of independent variables which are known or theorized to affect germination and growth.

In the 1990s, discussions in print of the biodynamic calendar in Europe, America and New Zealand, have alluded to the experiments conducted by Spiess as having tested the Thunhypothesis and failed to replicate it (e.g., N.Z. Biodynamic Association, 1989; Llewellyn, 1993). Enjoying widespread publicity, and published by the Forschungsring of the German biodynamic movement, the Spiess results have worked to discredit biodynamic calendars.


An attempt at a conclusion

So to answer your question precisely, I would say that yes, there is plenty of evidence to support the benefits of lunar planting - but this evidence is often attributed to confirmation bias, improperly conducted experiments, and a failure to account for uncontrolled variables affecting the entire test population. We have yet to produce a long term scientific study which supports lunar planting.

Basically, the time at which you plant something certainly does play a factor in how well it grows, but the thing that makes that time better or worse is not the moon.

What is much easier, is the task of dismissing the proposed mechanisms behind lunar planting. The suggestions that astrological alignment of the moon and constellations, or that lunar gravity impacts the moisture of soil, can be easily dismissed with grassroots skepticism and a basic understanding of physics.

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This... is an awesome answer. Would that I had more than one plus to give. –  erekalper Jun 24 '11 at 15:31
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-1 You mentioned tides and yes, it is just possible (but not likely) that they effect plants. However, the phases of the moon are completely independent of the tides. So scratch that idea. As for the extra light, the sun is 400,000 times brighter than the full moon, so even a little bit of cloud cover has much more effect than the moon. –  hdhondt May 12 at 0:33
    
@hdhondt Both of the myths you're objecting to are clearly labelled as such under the "How they think it works" quoted section of my post. They are not my words, but the words of the superstitious - so it's no surprise that there's no merit to them. I reiterated them only to serve as the notable claim that I would go on to counter. While your comment is a good 'grassroots skepticism' approach to debunking those beliefs, people here tend to appreciate links to peer reviewed studies more, which is why I attempt to appeal to those rather than common sense reasoning such as your own. –  Alain May 12 at 18:41
    
@hdhondt In fact, I just realized that the very last paragraph of my post says exactly that, so it seems as though you're downvoting the superstitious theories that I quoted in my premise (which I then went on to debunk), not my actual answer. –  Alain May 12 at 18:44
    
I agree that your last paragraph states that, and the first paragraph says it's a myth, but the rest of your answer talks only about what "they" believe. I think you should have spent more time explaining why it has to be a myth. Just stating that it "can be easily dismissed with grassroots skepticism and a basic understanding of physics" does not really explain why it is so. –  hdhondt May 13 at 23:25

Unfortunately Alain's approach is not an objective one but seeks to prove his a priori beliefs on this matter. Just one short but conclusive example: from the article on Biodinamic that he quotes above, he selected a short fragment that is taken out of context and seems to support his ideas. The actual conclusion of the article, after reviewing years of experiments by different authors is actually the opposite:

Results published to date suggest that the ‘Thun-effect’ is a testable and verifiable hypothesis. The current analyses endorse Spiess’s general conclusion that ‘lunar factors’ may have a practical significance for agriculture.

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+1 For pointing that out. However its Abstract says, "This paper reviews published confirmations of the ‘Thun effect’ and reanalyses data concerning etc." So perhaps it's drawing from a pre-biassed sample of tests (i.e. only tests which "published confirmations of the ‘Thun effect’")? –  ChrisW Dec 29 '13 at 13:06
    
Regardless of what the biodynamic people claim, it is nothing but a myth. See my comment to Alain's answer. –  hdhondt May 13 at 23:29

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