Sowing Lunacy?

MoonMagazines are full of articles, the Farmer’s Almanac publishes a yearly calendar to guide you, and my niece swears it works. What is it that’s so popular in the garden world? It’s the age-old practice of planting according to the phases of the moon.

I’ve pretty much ignored moon planting charts, at least until now. It’s hard enough to find time to plant my garden without consulting a lunar calendar. With our Colorado weather, odds are that the “correct” planting date will either be too hot, too cold, too wet, or too windy—or I’d be getting pelted with hailstones, dodging lightning bolts, or brushing off snow… or all of the above!

Finally, after listening to yet another gardener tell me that planting by the moon will solve all my gardening woes, I decided to check it out. I had two primary questions.

1. What exactly does the practice entail?

Sowing seeds and planting crops according to the moon’s monthly cycle has its roots in antiquity. The advent of biodynamic gardening in 1924 led to an increase in the practice, and it has grown along with the organic gardening movement. Most gardeners simplify lunar gardening to a simple rule of thumb, summarized here by

Plant above ground crops while the moon is waxing (i.e. growing brighter) and plant below ground crops as the moon wanes (i.e. grows dimmer). That’s Moon Phase gardening in a nutshell!

(Those willing to carry the practice further time their planting according to astrology—specifically the moon’s position in the zodiac. Personally, I fail to see how stars thousands of light years away can affect the growth of the radish seeds I plant—or anything else on earth, for that matter.)

I admit to being a bit confused. Does the plant know that it’s an “above ground crop” or a “below ground crop”? What difference can it possibly make to the plant what part of it we prefer to eat? And what about crops like beets or parsley, where we can eat the both roots and leaves?

Then, what’s with the waxing and waning? True believers explain that lunar tides move water up and down in the soil and in the plants’ stems. The MoonGrow website continues:

The ocean tides are at their highest during the time of the full moon, when the sun and moon are lined up with the earth. The ancients believed that as the moon draws the tides in the seas, it also draws upon all water, causing moisture to swell up in the earth, which promotes growth. This is the best time for planting seeds.

Other moon-gardening websites have conflicting instructions. For instance, some say to sow right after the moon starts to wax (in other words, just after the new moon)! You can’t have it both ways.

Still, the idea that the phase of the moon matters might sound plausible, but think for a moment. Tides occur twice a day as the earth rotates beneath the sun and moon. Any gravitational effect on plants, soil, or seeds also alternates twice a day. Further, while the alignment of the moon and sun causes the highest high tides, it also causes the lowest low tides. Wouldn’t they cancel each other out? Maybe we should be planting at high tide instead of at the full (or new) moon!

Further, the force of gravity is only one factor affecting the movement of moisture in soil or plants. We also need to include the adhesive force of water for soil (which varies according to the soil type), the cohesive force of water to itself, osmotic pressure, and transpiration (for starters). As an example, “Ninety percent of water is taken up by plants as passive absorption caused by the pulling force of water evaporating (transpiring) from the long column of water that leads from the plant’s roots to its leaves.” (Wikipedia) Gravity has nothing to do with that.

2. There’s plenty of anecdotal evidence supporting the practice, but are there any truly scientific studies to back up the claims?

In brief, no. John Teasdale, director of the U.S. Department of Agriculture’s Agricultural Systems Laboratory in Beltsville, Maryland, was quoted in a National Geographic article as saying that “he is not aware of any research on the lunar influences on agriculture.”

But maybe the Brits, those gardeners extraordinaire, have done some studies? I found  just one. According to,

The moon planting theories were thoroughly tested by Which? Gardening in 2003, who followed the instructions given in the lunar sowing calendar published each year by Nicholas Kollerstrom and couldn’t find any difference at all in the yields of vegetables sown on “good” days or “bad” days.

Of course, a lack of evidence doesn’t disprove anything. Maybe the next study will turn up significant results. Meanwhile, proponents continue to insist that moon planting works. Perhaps the best explanation is summarized on one site I visited:

[S]omeone 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. …  [and] 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.

Additional reading: for an excellent article on the topic that includes the results of French’s own garden trials, see Planting by the Moon: Explaining a persistent myth, by Jackie French.

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