(Published in Biological Agriculture and Horticulture, 2001, Vol. 19 pp.247-259).
Nicholas Kollerstrom & Gerhard Staudenmaier.

*Tables, graphs and figures can be seen on Nick Kollerstroms website at

In 1956, Thun developed a procedure of sowing according to the position of the Moon in front of the twelve zodiacal constellations. These constellations were classified into four groups according to the element (Earth, Water, Air and Fire) astrologically associated with them. Root, leaf, flower and fruit crops were found to show increased yields if sown when the Moon stood before Earth, Water, Air and Fire constellations, respectively. Thun's philosophy of sowing by this sidereal rhythm has become a major component of biodynamic planting calendars, even though the founder of biodynamic agriculture, Rudolf Steiner, had only mentioned positive effects of the Full Moon in an agricultural context. In 1990, Spiess published a three-year study claiming to find effects of other lunar rhythms but not those of the 27-day sidereal month. This paper reviews published confirmations of the 'Thun effect' and reanalyses data concerning planting times and crop yields from Spiess's study with radish and carrots, by computing yield values as deviations from a moving average rather than as deviations from seasonal trends estimated by quadratic functions. The re-analysis showed an increase (ca +7%) in the yield of radishes which were sown in Earth constellations for his 1982 trial, with a comparable result demonstrated on re-analysing data from three years of carrot trials.

The suggestion that crops should be sown at different times during the lunar cycle, to test traditional lore on the subject, may first have been made by Francis Bacon (Bacon, 1627). He was concerned with the lunar phase ('synodic') cycle, of 29.5 days. Twentieth-century experiments along the lines suggested by Bacon have generally been equivocal (Kolisko, 1936; Mather, 1942; Beeson, 1946). While there is evidence that parameters such as germination rate (Maw, 1967), water absorption (Brown & Chow, 1973) and metabolism (Brown, 1960) respond to this cycle, it does not in general seem to affect crop yield (Kollerstrom, 1980). Researchers at the Sorbonne University found that the volume of plant DNA in cell nuclei tended to alter in relation to the synodic cycle (Rossignol et al., 1990), indicating a possible link between seed fertility and the lunar month. There is also evidence that tree bud morphology is responsive to fortnightly lunar rhythms (Edwards, 1993).

The Biodynamic movement was founded by Steiner in 1924 as a form of organic farming whose approach would cognise the condition of the heavens (Koepf, 1989; Sattler & Wistinghausen, 1992). Steiner affirmed that the Moon, especially in its synodic cycle, was of great importance for the growth of crops (Steiner, 1993). In another context he advised that attention should be given to ecliptic constellations, rather than the tropical zodiac of astrologers.

Time-trial sowing experiments began in the 1930s within the Anthroposophical movement (founded by Steiner), whereby twelve batches of one type of crop were sown under similar conditions through a sidereal month, one per Moon-constellation, comparing their growth (Hachez, 1935). This month has 27 days, so one sowing was made per 2-3 days. In 1956 Thun developed what may be called the 'Thun theory', whereby crops were differentiated into the four categories of root (e.g., potatoes, radish), leaf (lettuce, spinach, etc), flower and fruit/seed (Thun 1991, Thun 1999). This emerged initially from her Moon-constellation sowing trials using radish. She linked each of these four crop types to the four elements, and thereby to the elements of the constellation-zodiac in which the Moon stood at the time of sowing. Whereas Hachez had studied possible effects of individual constellations, Thun viewed an underlying four-element-rhythm as primary.

There were, Steiner had claimed, four types of 'formative force' that worked in the realm of nature. These, he said, did not work centrically as the forces known to modern physics, but rather worked via form, and he called these forces, 'etheric' (Wachsmuth, 1932). This was a reformulation of the ancient doctrine of the four elements, conceiving them as process rather than as substance. Within the Anthroposophical movement, botanical studies of plant morphology by Bockemühl have supported the view that the stages of plant growth may be seen in terms of such 'formative forces' that are linked with the traditional four elements. He has related the stages of leaf, flower and seed formation with water, air and warmth (Bockemühl, 1985).

The Thun theory used the tradition of the four elements embedded in the zodiac, linked to Steiner's notion of four types of formative force working in nature, by the lunar motion against the constellations, but using unequal constellation-boundaries, allocating for example 45° of the ecliptic to the large Virgo constellation and only 18° to the adjacent constellation of the Balance. Biodynamic calendars nowadays refer to these Moon-constellation elements as root days, leaf days, flower days and fruit or seed days, as linked respectively to the traditional elements earth, water, air and fire. This sequence recurs every nine days, thrice per lunar orbit, and forms the backbone of modern biodynamic calendars. Especially in Germany, biodynamic experts have expressed unease about these sidereal element-rhythms in the calendars, viewing them as inappropriate and lacking endorsement from Steiner (Koepf et al., 1996).

Crop yield experiments were conducted by Thun in collaboration with the statistician Heinze over the eight years 1964-71, mainly with potatoes, but also with carrots and radishes, and beans as a seed-crop (Thun & Heinze, 1979). In these experiments, twelve rows of a crop were sown over one sidereal month, one row per 2-3 days, while the Moon traversed a particular constellation. Final crop yield weights were compared, measuring the total yield per row of potatoes or of beans. The weight ratio of the crop/total plant was also evaluated.

Such ‘constellation' experiments for radish involve each row being grown for the same duration, by harvesting them over a similar 27-day schedule as was used for their sowing; for beans, several harvests were taken per plant and cumulative weight yield totals thereby obtained per row; while for potato sowing trials, harvesting and weighing were done for the twelve rows on the same day at the end of the growing season. Results from these trials, as published by Thun and Heinze, seemed uniformly positive, with yield maxima appearing in the predicted 'trigon' or Moon-constellation-element of sowing dates. The term 'trigon' refers to the three constellations of similar 'element' as form a triangle in the zodiac.

In 1962, the Thun theory became embodied into a biodynamic gardening calendar which has appeared yearly ever since (Thun, 2001) and is presently translated into 21 languages. This calendar incorporates various lunar cycles and events, for example it recommends no sowing over eclipses, evidence for which remains scant. Only for the 'Thun effect' does repeatable and statistically significant evidence exist. In the U.S.A., the 'Kimberton Hills' agricultural calendar more or less duplicates the Thun calendar in its recommendations, presently selling 6000 per annum. Its editor Wildfeuer began it after her participation in a Swiss experiment on carrot-growing trials as a test of the Thun-effect (Wildfeuer, 1986).


Ulf Abele

Four years of sowing trials were performed by Abele, three as part of his doctorate at Giessen, depicted in Figures 1-4. Each has a linear regression line through the data representing the seasonal trend (Abele 1973,1975). He grew grain crops (barley and oats) in 1970-1971, and root crops (carrots and radish) in 1972 and 1974. Abele designed the trials to give the predicted yield-maxima in rows 4,8 and 12: the 'fruit-days' for 1970 and 1971, and 'root-days' for 1972 and 1974.

This data was reanalysed by subtracting from each set of twelve weight yields the corresponding values on its regression line, then separating the difference values into two groups: the three with predicted yield maxima, and the remaining nine. The results are shown in Table 1. Each of Abele's four trials showed yield maxima where predicted, and yield deviations from the seasonal trend are positive for the trigons predicted and negative for others. The differences of these means are statistically significant except for the 1971 trial. Significance was investigated by a t-test such that the hypothesis of zero difference between the group means was rejected with a probability of (1-p)% for a degree of freedom v = N1 + n2-2, if the experimental t-value >tv,p. Hence for Abele's trials, the group means differ with a high probability of 95% - 99%. It is preferable to use groups of more than three for statistical treatment, as a t-test requires that the two groups being compared are normally distributed, and one cannot ascertain this from merely three values. These trials were therefore combined with those for grain yields (1970 and 1971) and those for root crop yields (1972 and 1974).

Tables, graphs and figures can be seen on Nick Kollerstroms website at

Four years' trials of the 'Thun effect' by Abele
Crop Date Mean Y Trigon predicted (t ha-1) Other rows (t ha-1) t-value
Mean yields and yield deviations:
Barley 1970 3.67 0.29 ± 0.15 -0.10 ± 0.21 2.6 >t10, 0.05
Oats 1971 5.46 0.22 ± 0.45 -0.07 ± 0.15 1.6 >t10, 0.1
Carrot 1972 9.62 1.29 ± 0.60 -0.43 ± 0.61 3.9 >t10, 0.005
Radish 1974 26.25 4.81 ± 1.05 -1.61 ± 2.1 4.7 >t10, 0.001
Combined data, with yield deviations normalised to a mean of 100:
Barley+oats 1970,'71 (100) 5.7 ± 6.5 (n=6) -1.9 ± 4.4 (n=18) 3.1 >t22, 0.01
Carrot+radish 1972,'74 (100) 15.9 ± 5.8 (n=6) -5.3 ± 7.3 (n=18) 6.2 >t22, 10-4

To do this, the yield-values were first transformed to the same mean of 100, enabling the data-sets to be combined. They were then corrected for seasonal-trends by subtracting out the linear regression lines as before. These combined sets gave the yield data as shown in Table 1.

Statistically, the grain yield excess was significant at p = 0.01, while the root-crop yield over Abele's two trials was significant at p = 0.0001. Expressing the mean yield excess in the predicted trigon as a percentage, for Abele's two grain crop trials, the 'fruit-day' trigons showed a mean yield excess of 7% over the others (5.7+1.9 %), while his two root crop trials averaged an excess of 21% (15.9+5.3%), from sowings in the predicted trigon as compared with sowings at other times. Spiess viewed these results as positive (Spiess 1994).

English data

Figure 5 reproduces a British result from a 1976 sowing trial (Kollerstrom, 1977; Kollerstrom 1993; Kollerstrom & Staudenmaier, 1998). Twenty four rows of potatoes were sown over 2 months by a grower in Sussex, and showed yield maxima for the root-day sowings: their mean yields were 30% in excess of sowings on other days. The crop yields per row were expressed by the ratio, weight yield of potatoes grown divided by weight of potatoes sown, where 4.6 was its mean value. The seasonal trend was modelled by a five point moving average. After subtracting this out, grouping the data by root-day sowings versus all the others gave 1.5±0.9 (n=5) for root-days and -0.5±1.1 (n=15) for other sowings. This excess was significant at 3.5 >t18, p = 0.002, a highly significant result. Another U.K. report from the 1970s described an experiment from sowing 36 rows of lettuce over three sidereal months, by a different investigator, and again a highly significant positive result was obtained, from yield excesses in leaf-day sowings as predicted (Bishop, 1977).


Two years of trials 1979-80 were conducted by Lücke, as part of his doctorate thesis (Lücke, 1982). Figure 6 shows his 1980 potato trial yields, where the predicted maxima (root-day trigons) occur at positions 1, 5 and 9. Four sets of 12 rows were sown over one month, three of them receiving treatment with sprays (Figure 6). As can be seen from the graph, the mean yields per set were very similar. Spiess regarded the results obtained as non-significant (Spiess, 1994).

Lücke obtained 48 potato row yields from his 1980 field trial, then used a single linear regression line to model their seasonal trend. In this analysis residuals (Y1) were obtained by subtracting this trendline from the individual row-yields. Their mean yield was 3.85 tonnes per hectare. Separating the data-points into the two groups, root-trigon versus the others, gave a yield increase of 0.53±0.49 t ha-1 (n=12) for the root-day sowings and a yield decrease of -0.18±0.61 t ha-1 (n=36) for all other rows, corresponding to a total excess yield of 18%. The t-value was 3.6 >t46, so that the predicted effect was significant at p = 0.001. Lücke's earlier 1979 trial using oats had one of its three fruit-day sowings omitted, preventing statistical treatment.


Three years of potato trials by Graf for her doctorate thesis at the Zurich ETH, investigating the sidereal trigons, obtained equivocal results. Graf & Keller commented that Graf's 1975 growth chamber experiment with radishes on biodynamically treated soil gave a yield excess of 20%, significant at p < 0.001, for yields from root-day sowings as compared with the others, for a total of 264 radish grown (Graf & Keller, 1979). A review of the evidence by Dubrov alluded to "very strict standardised experiments..." as having shown how lunar influence worked in plant growth and development (Dubrov, 1996). He referred to Kolisko, but also to the Thun-Heinze and Graf-Keller reports, both published in 1979.


Since 1984, reports of the negative results obtained in an experimental investigation of the lunar-sidereal 'trigons' in crop yield by Spiess have obtained widespread publicity and a major biodynamic textbook discussed the Spiess conclusions as having refuted the 'Thun-effect' (Koepf et al., 1996). It seems, however, that the negative nature of these results (Spiess, 1994) has been exaggerated. The effect present in the Spiess data appears as of relatively small amplitude, though in the case of his carrot data it achieved a high level of statistical significance if the three years of his trial were pooled together. For one year of his radish trials (1982), two sets of radish were sown sequentially, one with added fertilizer and the other without, where the sidereal rhythm was more strongly present in the data-set without added fertilizer.

Spiess developed a distinctive two stage method of data transformation, here applied to results of his 1982 radish sowing trial and his three years of carrot trials, 1978-80. The discussion here is thus confined to his radish and carrot yields (Spiess, 1990b). His winter rye sowing trials (Spiess 1990a) have not been analysed because seeds sown in winter-time could fail to germinate within a day of being sown. It is crucial to the theory of these experiments, that germination occurs on the day of sowing.

Radish trials, 1982

To compare the yields (Y) of two or more trials, normalized yield values Y1= 100Y/Ymean were used. For investigating whether lunar-monthly rhythms are present in crop yield data, it is, in general, necessary to allow for the seasonal or year trend, as this may be larger in magnitude than rhythms of a monthly nature. To do this, one can put second-order regression lines through the data, i.e. best-fit parabolae, as did Spiess, or one can apply a moving average. Such a moving average here includes two sowings before a given date and two after, taking the mean of these five values. The latter method was used here (Kollerstrom & Staudenmaier, 2001). Both techniques, a regression line, plus a five-point moving average, are illustrated in Figure 7, applied to the Y1 data of the 1982 radish experiment.

The trend line values (T) are then subtracted out from the Y1 data-points. That subtraction gives a new data-set, which is called Y2 (i.e., Y2=Y1-T). These Y2 data points are used to test for lunar-sidereal rhythms present in final crop yield. We used this methodology as applied by Spiess, but modelling the seasonal trend differently as described, to go from Y1 to Y2. As Figure 7 indicates, the way one allows for seasonal trend can affect final values considerably. The 1982 experiment involved one lot of sowings per Moon-constellation (i.e. 12 per sidereal month) over a 39-day period, so that 19 rows were sown in all. Two separate sets were conducted in parallel, one with added fertilizer and one without. The experiment had randomized, complete block designs with four replications' at each sowing (Koepf et al., 1996).

The next step involved making a separation within the Y2 data-set. The hypothesis tested was that one 'trigon', in this case root-day sowings, gives a better yield than do the others. The data was therefore separated into two groups, root-day sowings and the rest. Spiess separated the data into four groups, by the four trigons, performing a four-way analysis of variance. These two approaches are both valid, but the former may have simpler statistics. Separating the Y2 yield values into these two groups gave the results shown in Table 2. These Y2 mean values are percentages, because the Y1 groups have means of 100. Thus the no-fertilizer group had 7.6% excess for the root-day yields, while the other rows had 2.4% deficit, so that, overall, the root-day sowings achieved 10% more in weight yield than did the other sowings.


Mean yield-deviations (Y2) normalised to a mean of 100 for Spiess's two 1982 radish trials, root-trigon sowings vs. others.
Root-days Other rows t-value
Trial I (no fert.) 7.6 ± 17 (n=3) -2.4 ± 10 (n=12) 1.7 > t13,0.1
Trial II (+ fert.) 4.7± 17 (n=3) -0.4 ± 7 (n=12) 0.8 > t13,0.5

Owing to the large scatter in the data (Figure 7) the effect was not statistically significant (t=1.7, p = 0.1). It is preferable that mean yields should not increase so sharply during the course of an experiment. Even with a 10% excess as predicted, this increase prevented the data from attaining significance. Trial II with fertilizer did not show a statistically relevant yield distribution.

Thun has claimed that the sidereal trigons show up best if crops are not treated with fertilizer (Thun 1964), which Graf in her PhD at Zurich claimed to have confirmed (Graf 1977). Though of smaller magnitude than others have found earlier from investigations of the 'Thun effect', this yield excess may nonetheless be large enough to be of interest to commercial growers, as the result of a well-designed and carefully performed test of the 'Thun-effect'.

Carrot trials, 1978-80

This same technique of data analysis was applied to the three years of carrot sowing data, which Spiess performed in 1978-80 (Spiess, 1993, 1994). For these three years of trials the same experimental procedure was used, sowing approximately once per Moon-zodiac constellation as for the 1982 radish trial. The trials extended over a month, which meant that 14-15 rows were sown each year. However, the last six rows sown in 1979 had to be omitted, owing to a two-week discontinuity in the data.

The carrot trials achieved a more uniform growth than did Spiess's radish trials. An indicator of how well trials have been conducted is the standard deviation of the yields expressed as a percentage of the mean. This is shown Table 3, where the variance of the carrot-yields is compared with that of the radish-trial discussed above. For whatever reason, these are a mere one-third the value for the carrot trials, so that better results might be expected from analysing his carrot-data. Five-point 'moving average' trendlines were put through these groups as before, subtracting which gave the Y2 values.


Standard deviations in the Y1 and Y2 data groups of Spiess trials here analysed
Crop Date Y1 group Y2 group
Carrot 1978 100 ± 11.8 (n=14) -0.3 ± 2.8 (n=10)
Carrot 1979 100 ± 8.9 (n=10) 0.4 ± 6.8 (n=6)
Carrot 1980 100 ± 10.7 (n=15) -0.3 ± 4.3 (n=11)
Radish 1982 100 ± 40.0 (n=38) 0.1 ±10.2 (n=30)

The Table shows how two-thirds of the variance is removed by subtracting out the seasonal trend line, passing from Y1 to Y2, also how the number of rows per group was reduced in passing from Y1 to Y2 values, by use of the moving average.

The transformed carrot data 1978-80 were separated as before into two groups, root-day sowings and others. Over the three years of these trials, the Y22 root-day values averaged 6.3 ± 4.1 (n=5) while other sowings averaged -1.6 ± 2.9 (n=22), an 8% excess, with a t-value of 5.4, as was highly significant (p = 0.001).


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 Thun-hypothesis 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.

It appears, however, that although the experiments were well designed, this was not matched by a corresponding care in the data analysis. There were two other radish trials, which Spiess performed in 1979 and 1980, over 30-day periods, where in the first case yields increased by a factor of seven from start to finish of the experiment, and in the second case they more than doubled. But, in experiments conducted over only one month, containing such large seasonal trends within the data, it is unrealistic to expect low-amplitude sidereal rhythms to be detectable. The Dottenfelderhof farm near Frankfurt, where the trials were performed, is in a quite highly industrialized area of Germany, as could here be relevant.

While the Spiess sowing trials and methodology had commendable features, use of parabolic curves to model the seasonal trend was inappropriate, and the alternative here used of moving averages to model the seasonal trend gave Y2 element-means of considerably smaller standard deviations. 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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