Chamomile: Methods of Cultivation

Cultivation measures such as sowing time, fertilization, weed control, and harvest have to be arranged in such a way that the yield properties and those of quality fixed in the genotype ensure an optimum development.

Cultivation Procedure

In 1956 Heeger still reported that with respect to cultivation chamomile had been worked on to a small extent only. Over the past 40 years rapid development could be observed. Preference is given to chamomile being cultivated. In most countries extensive field cultivation with mechanized sowing, nursing, harvest, and processing has gained acceptance. In nearly all companies specializing in cultivation, technological innovations have been tested and introduced repeatedly. Often technological solutions are quite specific to the companies and having been adapted to the locations and varieties were developed for the individual sections of production. Therefore, a compilation of a generally applicable sample technology does not seem to be recommended. Some experiences from various countries of cultivation are shown in the paragraphs to follow.

Presently three basic variants — being mostly complementary to each other — are applied: autumn sowing, spring sowing, and cultivation of several years’ duration with self-sowing.

Autumn Sowing

In the Northern Hemisphere graduated autumn sowing is done at the end of the summer at an interval of about 8 to 14 days, from the beginning to the end of September. A precondition is, however, that the anticipated fruit is removed as quickly as possible. If sowing is done too early, this leads to premature formation of shoots. Both plants developed too far as well as those that are too small die in winter. Chamomile should start the winter months at a stage of six to eight leaves. At this stage it is definitely cold resistant. Autumn sowing means that the best yields are achieved with the possibility of a long vegetative developmental and tillering phase within the physiological short day. Being largely independent from the sowing time, the flowering period starts with an achieved day length of about 17 hours (in central Europe at the end of May / beginning of June). Due to the fact that flowering generally starts at the same time, the possible cultivation area is strongly determined by the harvest and drying capacity. Even if chamomile is flowering over a longer period, producing new flowers again and again temporarily, the first harvest process has to take place according to exact timing. Thoroughly ripening flower heads favor plant aging. Overripe flowers strongly tend to fall apart during the drying and preparation process after the harvest. Seeds dropping out mean a burden to the location in the years to follow, changing the spectrum of active principles.

Spring Sowing

The advantage of spring sowing is the possibility of graduated steps of cultivation in order to be able to utilize the harvesting and drying technique to the maximum by temporally graduated harvest dates. In central Europe it is a usual practice to start sowing in March at an interval of about 14 days. It is, however, a fact that the yield and the homogeneity of the populations decrease the later sowing is done. The pressure of contamination by diseases and infestation by parasitic insects in the course of the summer months increases just as well.

Cultivation of Several Years’ Duration by Self-Sowing

With extensive production, a cultivation of several years’ duration is possible on the same field considering that the population is being formed by the chamomile seeds that dropped out. Additional seeds may also be sown. After the last economically justifiable harvesting passage, the population remains on the field for a few more days and the plants are mulched. The next step is a non-turning superficial soil preparation. From September onward the self-sown seeds germinate, which may be compared with a thick carpet. This procedure is similar to broadcast sowing without a drilling machine. The strong competitive capability of chamomile against weed, the possibility of utilizing a harrow and a chain harrow or curry-comb for weed control, and thinning out make the procedure a cheap alternative. Companies particularly in Germany, Argentina, Hungary, and in the Czech Republic have practiced this procedure on the same field for nearly ten years. In the total remaining area the weed is reduced by taking the autumn chamomile from the crop rotation. The yields to be expected and the other peculiarities of this procedure may be compared with those of the sowings done in autumn. This form of cultivation is not recommended for the flower production of breeding lines, especially with the cultivation of defined chemotypes, because of the uncontrolled procedure of the pollination as a germination of wild (i.e., nonbred) chamomile or a segregation with hybrid seeds may occur in the following year.

Especially with autumn sowing slightly humid locations are more favorable than regions with plenty of summer rains where chamomile tends to have a luxurious growth of herb and leaves; consequently it is less suitable for being harvested and shows a lower content of active principles. The development of chamazulene substantially depends on the duration of sunshine and the day temperatures from the time of the formation of flower buds.

It is reported repeatedly that chamomile is self-compatible. Experiences regarding cultivation of several years’ duration and self-sowing point in the same direction. Precise indications concerning the value of different fruit rotations are missing but it is a fact that chamomile grows particularly well in fields free from weed; viz., after root crops such as potatoes and sugar-beet, maize, winter cereals, and leguminosae. Using fields for the production of chamomile for several years has also proved to be a success. Chamomile should generally be cultivated as final crop in the rotation without any N-fertilization. A high content of Nmin in the soil leads to strong vegetative growth, makes the harvest more difficult, and can finally also lead to a lower content of active principles. Weeds cause problems for the cultures to follow. First of all a nonturning superficial soil preparation should in any case take place after the chamomile cultivation to stimulate the germination of chamomile seeds dropped out, to be followed by mechanical weed control in autumn. In course of the following year a culture is started after refertilization, being tolerant against herbicides combating chamomile.

Chamomile particularly absorbs the heavy metal cadmium from the soil, at least it concentrates due to the mobility in the flowers like with other flower drugs, e.g., St. John’s wort and flowering yarrow herb. As long as the maximum value of 0.2 mg Cd / kg of drug — a recommendation of the German Federal Ministry of Health since 1991 — is applicable, the maximum soil values indicated in Table “Maximum Tolerable Content of Cadmium for Soils Planned for the Production of Chamomile in Central Europe (According to Plescher, Cd Maximum Value for Matricariae flos 0.2 mg / kg)” may be used for the choice of the location, depending on the individual pH value and on the method of cultivation. If there are critical soil values a trial cultivation should always be used to determine whether the location is suitable.

Nutrient Supply

Although chamomile is a nitrogen-loving plant species, it is, in view of the harvest mechanization, seen that when cultivating it the soil only contains small amounts of Nmin and mostly it is done without any N-fertilization whatsoever. Otherwise moist and leafy populations with a delayed flower maturity or “endless flowering” develop and with the application of harvest technique the species-typical appearance of foreign matter (percentage of leaves and stems) increases. Table “Recommendations for Fertilization Concerning the Cultivation of Chamomile in kg / ha” gives a general idea of recommendations for fertilization with respect to the cultivation of chamomile.

For the development of active principles, a good flowering, and sufficient firmness of stems, a good potassium supply is necessary. On the other hand chamomile is delicate with regard to excessive quantities of P2O5. According to Franz and Kirsch the nutrient ratio of nitrogen:potas-sium oxide should be 1:2. Fertilization by using potassium and if necessary also nitrogen takes place during the tillering phase, i.e., in October (at the Northern Hemisphere) or April (at the Southern Hemisphere) when sowing in autumn; if sowing is done in spring it takes place at a correspondingly later date. Organic fertilizers should by no means be used for chamomile, as the limits of microbial contamination could easily be exceeded. Organic fertilizers may only be used for the anticipated fruit.

With extensive cultivation the recommendations for fertilization based on Nmin values ascertained are the basis for the determination of fertilizer requirements pertaining to the fields. The deprivation of nutrients has become the basis of fertilization to an increasing extent. ()

Harvest

Even though chamomile is cultivated throughout the world, the collection from wild populations, particularly in central, eastern, and southern Europe, Greece, and Turkey has not lost its importance. There is a difference between “pure wild collection” as in Greece and Turkey and the organized harvest of wild populations, as is the case in Hungary for about 95% of the whole harvested quantity. From such wild collections or small cultivations and in gardens, chamomile is harvested at the period of full flowering, i.e., when most flowers are already open. Today, cultivation areas are mainly harvested automatically, although partly manual harvesting is still being practiced as well. The harvest schedule plays an important role with regard to the quality of the product. Harvest of cultivated chamomile should be realized in the same way as for wild populations, i.e., when the major part of the flowering heads has already opened. The essential oil content of inflorescence increases continuously starting from the creation of flowers and achieves its maximum when the ligulate flowers are in a horizontal position (). As per Röhricht et al. harvest is realized from the starting of the flowering period up to the period of full flowering, whereas two or three pickings are effected. As per Dachler and Pelzmann the optimal time for harvest of the flowers is when a circle of tubular florets has already opened in the second third of the vaulted flowering receptacle.

In order to create an objective base for the determination of the optimal harvest time and not leaving this matter to the cultivators’ intuition, the German Working Committee for Cultivation of Medicinal Plants proposed the following flowering index formula in the years 1971, 1972, 1973, 1977, and 1979. It is a compromise between an increasing yield of flowers, a decreasing content of essential oil, and changes in the composition of the essential oil.

flowering index = (V- Kn) / (Kn + eB+ V)

  • Kn = flower buds not yet flourished
  • eB = flowers ready to be harvested (flourished tubular flowers + ligulate flowers)
  • V = withering flowers

With this formula the point of time for harvest of the flowers is calculated from the relation of the number of withering flowers minus flower buds to the total amount of flowers (flower buds + flowers ready to be harvested + withering flowers). The first picking should take place when the flowering index reaches a value of –0.3 to –0.2. As the flowering period depends on the location, climatic conditions, and the variety of the flower and therefore ranges between several weeks up to 3 months (according to eight to ten manual picking cycles are possible), this formula is a good way to determine the corresponding optimal time for harvest. In practical applications harvest takes place two or in rare cases three times.

In 1985 Franz proposed the following flowering index formula:

Ik= (IV – I) / (I + II + III + IV) = -1 < Ik < +1

  • Ik = Indexchamomile
  • I = flower buds
  • II = flowers ready to be harvested with a 50% open tubular flowers
  • III = flowers ready to be harvested with more than 50% open tubular flowers
  • IV = withered, decomposed flowering heads

The realization of the harvest of the flowering heads can take place in different ways, whereas the most labor-intensive method is manual picking. This manual picking is carried out in most countries only for small cultivation areas; in Egypt, however, it is still very popular and is applied almost exclusively ().

Picking yield of freshly harvested short-stemmed chamomile flowers is about 3 to 5 kg / h. Slightly higher picking amounts can be obtained already with so-called chamomile picking combs. Today they are used (e.g., in Hungary) above all for organized harvest in wild populations, and have a capacity of about 50 to 150 kg fresh per day ().

Such a harvest with chamomile picking combs has already been carried out in Hungary well into the 1970s, as well for harvest on cultivated fields. Due to the higher plant and flower density, the picking yield was about 100 to 180 kg per day. Other procedures were the use of special forks or comb shovels, applied in Hungary, similar to a scythe for harvesting the chamomile crop ().

Finally, such manual methods are not practicable above all due to the labor time requirement of about 25 to 30 working days per ha for the production of larger quantities. This problem had to be solved through construction of mechanized harvesting machines. A first step in this direction was the use of manually pushed picking carts with two wheels ().

Later on these picking carts were drawn by horses or tractors, which above all were applied in Argentina and again increased the yield per area.

Today the large-area industrial cultivation of chamomile worldwide uses automatic harvesting techniques with a picking yield of 200 to 300 kg / h and a capacity of about 3.5 ha per day, whereby (dependent on climate and crop-specific conditions) about 65 to 90% of all flowers are harvested. Since 1962 in Germany and since approximately 1975 as well abroad (e.g., in Argentina and Hungary), chamomile picking machines were used that pick the flowering heads on the field automatically and are self-propelling, as a cutter mounted in the front part of a tractor () or as combined harvesters ().

For a competitive production of flower drugs a decrease of the high labor time requirement for the harvest is essential, whereby particular importance has to be attached to the outer quality of the harvested flowers. The demands on the harvest quality are high. The adherent stalk rests have to be as short as possible and the impurities of herb and other constituents the lowest possible. This can be achieved safely by manual picking. Such important countries of production as Italy, Argentina, Hungary, Russia, former Yugoslavia, former Czechoslovakia, and former GDR have developed and applied high-capacity harvesting machines with different picking systems.

Automatic harvest is to be carried out successfully in the case of a large-flowered chamomile variety, having their flowering heads almost at one level. The major part of the commercial drug originates from this automatic flower harvest, which entails Pharmacopoeia’s monographs of chamomile flowers, describing chamomile to only “sometimes” have stem rests of 10 to 20 mm, are not applicable. If the harvested material is not processed after automatic harvesting, it is impossible to avoid stem rests with a length of 20 to 30 mm. With a corresponding postprocessing however, it is possible to produce chamomile of pharmaceutical quality. These not “sometimes” but almost always existing stem rests of 20 to 30 mm in length in no way disturb the medical benefit, insofar as the flowering head disposes of the required content of ingredients. Consequently this should appear in the Pharmacopoeias monographs as reality and therefore should be allowed.

Flourishing herb for production of Chamomillae herba cum floribus, that can be used for the production of tea in filter bags, mostly is harvested by the help of rotary mowers, forage harvesters, chaff cutters with blower, or combined harvesters. To obtain extraction quality for pharmaceutical use, the whole flowering heads are preferably harvested automatically. In this case, a posterior separation of stem rests is not necessary.

Another harvesting principle represent the machine developed in Argentina. Drums equipped with blades are used here. They run top down against a comb and shear the chamomile flowers. Here as well, industrial chamomile is preferably harvested due to the long flower stems. This principle of the rotating blades primarily has been developed for trailer machines that are drawn sideways behind the tractor. Later on these machines were developed further to self-propelling combined harvesting machines.

A third principle of mechanized harvesting is the picking procedure with picking combs. Here, machine widths of 2 to 6 meters of the width of the cutting unit are achieved. The picking drum is equipped with shifted comb strips, whereby long round tines in a wide distance or shorter sharp-edged tines with a lower interspace are used. The picking drum rotates against the driving direction, whereas the combs pass through the crop from the bottom up and separate the flowers from the plants. Adherent stalk rests are cut off with a cutting machine. For further cutting of the stalk parts the harvest is transported onto a swinging sieve with conveyor belts and then is collected in a silo. This is the basic principle of the machine of Ebert-Schubert, the Hungarian machines type “Szilasmenti” (), the Slovakian machines type “VZR” (), the Russian machines and the machine “Linz III,” developed in the years 1972 to 1978 in the GDR and built until 1988; the Linz proved itself in various countries (including Egypt), the quality and performance of which has not been achieved by other constructions so far. This is due to contra blades operated by cam discs behind the comb strips, that in contrast to other machines with picking combs lead mainly to an exact cutting of the flowering heads and clearly reduce the common tearing effect ().

A fourth principle is the rotation of the picking drum in the driving direction, as realized with the Yugoslavian machine. The chamomile herb is grasped by the tines and then drawn into the machine. There, on the vaulted baffle plate a plant pad is formed that is repeatedly combed due to the high-revolution speed of the threshing drum. The combing effect results from a shifted arrangement of consecutive comb strips. The distance between the tines of the comb strips is wider than the diameter of the flowers and consequently inhibits a clogging of the picking drum.

The principle of immobile combs with appropriate separation of the flowers from the plant, e.g., by means of a modified scraper chain on top of the comb, similar to marigold harvesters has been realized in the Italian Chamaemelum harvester.

Summarizing, it can be noted the best principle is a picking drum with comb strips rotating against the driving direction. Unfortunately, at present there is no new, well-priced, and similarly effective machine on the market ().

For after-harvest treatment there are two possibilities. In countries with high availability of manual work, e.g., Egypt, primarily drying is effected and afterward processing and sorting take place. In this way, drying often is realized in racks, e.g., from palm fronds (in Egypt) or on frames covered with gauze (as was used formerly on a large scale in Argentina). During daytime these racks or frames are placed in the open air; at night they are piled (mostly) under the roof, in order not to take up humidity. In Argentina after 1970, in the mornings workers brought daily 35,000 racks outside for sun drying and back to the stockrooms in the evenings. Temporarily during season more than 5000 persons were occupied with harvesting and processing.

A further increase in production was only possible by use of modern picking machines. In 1974 the Argentine production amounted to 2000 tons. With such a high grade of mechanization of harvesting and processing as in Argentina and Germany, sorting and sieving is effected automatically before drying. If need be, after drying short stem rests are separated in a further step. That way, pure flower material is obtained. During season 60 to 80 tons of fresh plant material are processed per day, running continuously through the sorting machines to the belt dryers or discontinuous flatbed dryers and after drying are sorted by the help of transport conveyors and are freed from weeds.

In Poland, which has become an important country for the production of chamomile drug in recent years, such harvesting procedures are applied that by cutting the flower horizon after drying by threshing, and separation by sieving and sifting, lead to a production of chamomile pollen and industrial pollen.

Cultivation in Specific Countries

Cultivation areas in the different countries vary greatly. In France approximately 100 ha of Roman chamomile are cultivated, mostly used for perfumery. In Italy cultivation of Roman chamomile is about 25 ha, of which 7 ha is organic, and 170 ha Matricaria recutita, of which about 100 ha is organic. From Sweden cultivation of 10 ha, from Austria cultivation of 15 ha, from Bosnia-Herzegovina 40 ha, Bulgaria 100 ha of True chamomile, whereas in the United Kingdom 80 ha Roman chamomile and 120 ha Matricaria recutita are cultivated. In Spain plants are collected rather than cultivated. This is the origin of the diploid bisabolol-rich form “Degumill.” In Brazil the main production is concentrated in the southern region Mandirituba (Parana state).

 

 

Selections from the book: “Chamomile”. Edited by Rolf Franke and Heinz Schilcher. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 2005.