For the hobby gardener, growing hydroponically offers enormous opportunities and sometimes opens unsuspected alternatives. When you start a hydroponic system with the proper nutrients, you are generally struck by the rapidity of growth and the vigor of your plants; not to mention the profusion and generosity of your yields.

During the last 30 years of research on plants and hydroponics and growing plants in our greenhouses, we obviously experienced a large amount of plant varieties.

During this time, one of our goals was to attain unequalled growth allied with excellent crop quality and high active principle content. Another objective was to offer new alternatives to small commercial growers, associating them to successful and economically independent ventures. During this time we came across a large variety of plants, and nearly each time the results were astounding. Plants were plentiful, beautiful, and healthy; they smelled sweet and tasted great.

So quite naturally a section of our studies was directed to culinary and therapeutic plants. But if it was easy to choose the right culinary plants (basil, sage, mint, parsley, chives, etc), it was much more difficult to determine which medicinal varieties would be interesting to cultivate. The idea was to establish a list of high-value cash crops that we could grow in our greenhouse in France, analyze, and eventually suggest to potential small-scale commercial growers.

In order to be sure of our choice, we contacted the faculty of pharmacognosis at the University of Toulouse. The faculty suggested a few plants, from which we chose Hieracium pilosella and Hypericum perforatum, which were both excellent candidates for economical, practical, and medicinal purposes.

Hieracium pilosella

Hieracium pilosella (also called Mouse-Ear Hawkweed) has been used since ancient times for its medicinal qualities, mainly as a “cleaner.” Historically, the sap was used to accelerate the cicatrisation (contraction of fibrous tissue, formed at a wound site) of internal and external wounds and to relieve kidney malfunctions.

Today it is still used. Known as an astringent with strong diuretic, depurative, and antibiotic properties, it is often used to eliminate superfluous water from the body and increase the secretions of the gall bladder. All parts are used. The most common way of preparing it is by infusion of the fresh leaves for internal cleansing.

Hieracium is a soil-cover, rampant (30 cm maximum), colony-forming plant. It is a perennial, stoloniferous herb whose rosettes each produce a single, lemon-yellow flower between May and September. Seeds stay on the plant until the end of winter. Their largely smooth leaves vary in size according to habitat, and their under-surface feature a dense cover of white hairs.

Hieracium easily adapts to all substrates and is quite easy to grow. But it has two characteristics that make it less attractive to traditional soil growers.

One is that it is “allelopathic” which means “invasive.” Hieracium pilosella forms dense, prostrate mats in open space through vegetative development and extend quite rapidly. Its roots emit a substance inhibiting neighboring root growth, which makes it a true intruder in some countries.

It is recorded as a weed and forbidden to import in some countries like Australia or Canada, because when the right conditions are met, it competes with neighboring plants to the point of invading the soil completely and threatening local biodiversity.

It is a native of England and grows well in the rest of Europe, especially in areas like the dry prairies of the Pyrenees. It forms a very pleasant mat to walk upon, and makes an excellent candidate for lawns in poor soil.

Its other less-attractive characteristic is that it is a rampant, which has two disadvantages when harvesting: When in contact with soil, the blades of the harvesting machines become blunt and they have to be regularly sharpened or replaced, and become an economical setback. The harvest is also dirty, full of soil and debris, and has to be cleaned before starting proper processing, which represents another economical burden.

While presenting an obstacle for soil growers, these two disadvantages make Hieracium pilosella a perfect candidate for hydroponics. In this system the plant is cultivated in enclosed growing modules and cannot spread out. There are no need for harvesting machines as in hydro your plants grow on high beds, making harvesting a much more practical process. They grow in clean and easy to wash-off substrate like clay pellets, which eliminates the cost of cleaning and sorting.

Last but most importantly, in hydroponics you increase the quality and quantity of your yields, as well as their content in active principles, especially when you use the right nutrients.

So we began our tests on Hieracium pilosella, with the understanding that the faculty in Toulouse would analyze the harvest and give us its conclusions about the quality of our plants compared to soil-grown, and their content in active principles.

We started our Hieracium from seeds in a tray with a mix of perlite and vermiculite. As soon as they became vigorous young seedlings, we transplanted them into a one square meter hydro Dutch Pot System (DPS), with a mix of small and medium size rocks for best adherence to the root system.

We used Flora Series nutrients and set the nutritive solution around EC = 1.0 and pH = 5.8-6.2. The plants developed quite well and rapidly increased in size. In no time they covered the whole area. Maintenance was next to none: just cleaning the dead leaves from time to time.

To respond to the criteria of the analysis we picked part of the plants before flowering and the other after flowering, dried them as requested and sent them to the laboratory.

The results were quite encouraging. “Batch corresponds to Pharmacopoeia, presenting a high level of tracers (active substances),” was the conclusion of the laboratory’s report.

Indeed, the macroscopic and microscopic identifications, as well as the mineral content of our crop, were consistent with the required norms of the soil-grown control.

The dosage showed that the hydroponically grown Hieracium contained 4.24 per cent of active principles compared to 2.5 per cent for the control.

Needless to say that this first analysis boosted our spirits, and opened a large field of investigation and research for us. Once again we had the confirmation that with our technology and our products we could not only increase the volume of production, but we also got the assertion that those products were appropriate for human consumption, and fit to be used for therapeutic applications.

Hypericum perforatum

Our second test was with Hypericum perforatum (or “St John’s wort”), a long-living plant that spontaneously grows in most uncultivated areas. It is called ‘perforatum’ because the leaves, when held to the light, show little translucent dots that look as if they were perforated.

In reality the dots are not holes, but vesicles of colorless essential plant oils and resin. Hypericum contains many active ingredients with therapeutic virtues, including hypericin and hyperforin. In summer it blooms into bright yellow-orange flowers with petals that are peppered with black dots. These dots, when rubbed between the fingers become red. According to herbalists, the translucent ‘perforations’ and black-red dots contain the most active medicinal qualities.

Healing Hydroponics: Try Growing These Medicinal Plants

Hypericum perforatum is an exceptional plant. In the Middle Ages it was considered a magical plant, capable of chasing malicious spirits away. It was mainly employed to treat nervous diseases. It was also used as “red oil” to cure burns, the preparation of which consists in macerating the flowers with olive oil in a sunny spot for a few weeks. Once the oil becomes red, it is filtered and kept aside to use on all kinds of burns and bruises.

Abandoned for a few decades, Hypericum was rediscovered lately thanks to modern research that put into perspective its numerous curative properties. It is today a highly appreciated plant, and you can find it on the shelves of most organic stores and pharmacies worldwide.

Hypericum is generally used to treat moderate depression, anxiety and sleep disorder. It seems to have several other virtues and research is still being conducted as to the extent of its possible applications. With the rising general interest in the plant, demand is increasing.

We started Hypericum perforatum in a hydro DPS row, using Flora Series nutrients. Again, plants grew very rapidly and bloomed at the end of June. We picked the flowers and fruit in the beginning of summer, a few days after the solstice, dried them, and sent them again to Toulouse.

The results that came back were as impressive as for the Hieracium pilosella: our harvest was separated in two groups, one with only the flowering tops, and one with the fruits. They were compared with a batch of wild Hypericum growing in soil in the region of Toulouse as a control. The analysis concluded that the hydroponically grown batch entirely complied with the list of requirements of the Pharmacopoeia.

The content of active substance in Hyperium perforatum was higher: 0.12 per cent for the soil control, compared to 0.19 per cent for the flowering tops, and 0.13 per cent for the fruits. As the minimum required by the Pharmacopoeia was 0.8 per cent, our plants passed the tests brilliantly.

We could now draw our own conclusions: medicinal plants cultivated in a “Hydro” Dutch Pot System, with Flora-series alone, not only fully complied with therapeutic requirements, but also contained more active principles than usual. This confirmed that we could grow these products for medicinal purposes and suggest their cultivation to potential customers who would like to start small commercial ventures in a field that is still unexploited.

This didn’t end our research with medicinal plants. After such encouraging results, we decided to grow “Chrysanthemum parthenium”, a beautiful plant which flowers are used for migraines and headaches, and have antispasmodic and revulsive properties.

Chrysanthemums were cultivated in an AeroFlo with Flora Series and grew into large plants heavy with huge clusters of white flowers. We unfortunately couldn’t send them for analysis, so we have no numbers for them.

This year we are growing Arnica montana, another plant which is used for ailments from muscle aches and bruising to arthritis, and which cultivation may help keep in the wild the ones that are still there. Arnica, which is at danger of being over-exploited due to devastating “in situ” gathering habits, is protected in Romania, France, Germany, and in some parts of Switzerland, and there is a specific regulation as to its gathering in a European directive of 1997.

Each year, Europeans consume some 50,000 kilograms of dry flowers, which represents 250,000 to 300,000 kg of fresh flowers. Plus hundreds of kilos of roots every year. The selling price for Arnica is relatively high: wholesale is approximately 30 euros a kilo for dried flowers and approximately 60 euros for roots. The Spanish gatherer is paid approximately five euros for a kilo of dried matter.

To summarize, it is important to note that although plants are ‘natural,’ they must not be used without the right knowledge or advice. So when you find them on the shelves, and even more if you grow them, make sure to ask for advice before ingesting them, as some of them can be terribly dangerous.