Hydroponics and hydroculture

an image of a flood and drain bench in my greenhouse when I lived in the Cotswolds - but see note at end of this page.

The classic way of growing orchids is to get them very wet, then let them dry out almost completely, before watering again. And so, when I first started talking about hydroponics (about 1992) with plants standing permanently in water, it did cause a great deal of hilarity amongst those who 'knew better'. At that time, I used to do talks to Orchid Societies, in all parts of UK . I soon learnt to start by showing some results; when people saw giant bulbs, multiple-growths, branched flower-spikes, and the other results of what I must quite immodestly call superb culture, they stopped laughing and sat up and listened.

I did not actually set out to grow hydroponically, but arrived at that point by a series of steps. My starting point was looking for a way of nursing sick plants - meaning those with virtually no live roots - back to health . One idea was to use Perlite as compost. It worked fine, but the problem was in watering every day as it dried out so fast. I tried standing the pots in saucers of water. This worked very well .

One day I had a brainstorm, and said to myself "since these sick plants do so well, what happens if I try this with healthy plants ? So I went to the next show, bought the usual plants I had fallen in love with, and took them home, and put them into this system immediately, and started to get amazing results.

So let's start by looking at some of these results :-

The tape measure shows that this bulb is some 7 inches - 18cm high, and the two new leads just starting are also seen. Big bulbs produce big spikes of big flowers . They are, put simply , an expression of a very happy and healthy plant. This was the first bulb on this plant in hydroculture ( by which I mean permanently standing in shallow water ) and was more than twice the size of any previous bulb on the same plant when grown in conventional fashion.

A very similar story here, with another of the warm growing oncidium related multi-generic hybrids . Again a 7 inch bulb, and again an enormous advance on the best ever achieved in conventional culture.

It is not just with the Oncidiniae, here I show the bulbs of a Coelogyne:-

C.Micholitz (FCC/RHS) - long a favourite of mine, and often available in the form of a three-bulbed propagation from back-bulbs. I bought it several times, but never managed to grow new bulbs much bigger than say a small plum, and naturally, never saw a flower . In hydroculture, the bulbs grew much bigger, easily double the size, and moreover I found that old bulbs threw new growths just as freely as the leading bulb. Note the one on the right hand side in the picture - with two leads, plus the one on the left - so already up to a three lead plant in say a 4 or maybe 5 inch pot.It took a couple of years in hydroculture to get the bulbs up to flowering size.

Here is a plant of this grex in flower :-

The flowers are a good 5 inches across, and last for up to 6 weeks ( in hydroculture )- probably not as long when grown conventionally - if they flower at all.

Encyclia vitellina - (Epidendrum vitellinum in the old books). Fantastic cinnabar red flowers. Not known as a plant producing branched spikes, but here it is. And the flowers last an enormous time in hydroculture - a good three months, but the plant goes on growing all the time. The flowering does not provide any check to growth, or put any strain on the plant when in hydroculture, it seems.

The legend on the picture says it all .

Here is a picture of the whole plant as it was in 2003 - it has since grown bigger, but been divided . (Anyone who has heard my talk on hydroponics given to Orchid Societies, in the last few years will recognise this picture, which is indeed the opening title slide which I use )

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Now for a few Dendrobiums :-

This is a nobile (Yamamoto) hybrid, taken as a keiki (adventitious growth) potted in Perlite ( more anon) and flowering within 12 months. Normally , Dendrobiums need their winter rest - essentially a temperature drop - dryness is unimportant, even counterproductive I believe . I say this from having conducted experiments with nobile dendrobiums for many (14 ? ) years, resting them dry, or cold, or dry and cold, or cold and bright ( a sun lamp) and other combinations. Cold, but wet - in an unheated greenhouse gave excellent results, but if it gets too cold as it did one year when the frost 'stat stopped working - then exit plants. Nowadays I put the plants in the garden in the second half of September, allow them to be rained upon and shined upon, and take them in again when there is a strong risk of frost.

This next plant - D.fimbriatum, var. oculatum, did not get any rest for several years, in the mistaken belief that it did not need any ( based on having grown one in a cool house, very many years ago, where it flowered very well without any further temperature drop.) I now have it in my cattleya house, but naturally it does not get the same cool nights, and did not flower. But last year I put it outside, as mentioned above, and a few weeks after I took it back in the greenhouse, the flower buds started to appear . It had a few flowers out when I went away for several weeks over Christmas and the New Year, and I expected them all to be finished when I got back, as they only used to last 10 days when I flowered it in conventional culture in a cool house, years ago, but no, I was greeted by many flowers, even if some were past their best . There had been, in all , some 14 flower spikes -

D.fimbriatum var.oculatum. By the way, this is in quite a different section of the genus from the nobile types discussed above. The 5 foot (1.5m) canes freely produced, are a direct result of hydroculture - with proper feeding and constant water.

A third Dendrobium from yet another section of the genus -

This is ( ? ) D.Ellen, a cross between D.tetragonum and D.kingianum, and maybe typical of the Australian Dendrobium species and hybrids in its needs. Again, a grand grower in hydroculture, and flowering well after its 6 or 7 weeks in the garden. Incidentally, there are those who say they grow well - as well as rest well - in the garden, and always willing to experiment, I tried a few outside in 2006, but they did not do well . They were not in hydroculture, which seemed a little too difficult to arrange outside.

I could go on with other genera - I have used this system for Cattleyas, Paphs and many others .

Hydroculture - the practicalities -

It's now time to discuss how to do it. Please note, this information relates to the version I have used now for some 10 years - I have recently (late 2006) found a slightly better way- using a "Smart Valve Mk2 " in each tray to control water supply and level ( using virtually permanent water rather than absolutely permanent water discussed below ) ; I shall update these notes when I have been using it for a few months and I am more certain of my facts.

The basis of all hydroponics variants is an inorganic ( i.e. mineral) "compost" which is inert, and which essentially contains and retains no nutrients whatsoever apart from what is in the water, does not dissolve or leach away when kept wet, and is sufficiently lumpy and coarse, so as to create lots of air or water spaces between the lumps. Coarse Perlite, well washed, is ideal. Plants are potted up, fairly high in the pot, and the Perlite topped with a good thick layer of coarse grit with the same kind of specification. Garden Centres sell flint, sea-shore shingle, ( or it looks like that), and granite chips, any of which is fine as the topping which is only to provide a little weight, and stop algae growing on the Perlite. When stood in a tray of water, the water makes it way up through the media by capillary attraction, and evaporates at the surface of the compost.

I theorise that the bottom half inch which is actually in the water is 100% wet, and the top layer exposed to the air feels dry, and at different points in the pot there are different amounts of water, making a moisture gradient, hence creating the possibility of zones which will provide exactly what roots want in this direction.

The "water" is rain water, or Reverse Osmosis water ( same thing, chemically, as near as makes no difference) with nutrient added. I prefer to use a cocktail based on "Optimum Bloom" from Growth Technology. This is a two bottle formulation. I think that any "complete fertiliser" which comes out of one bottle or one packet has almost certainly been formulated for use with tap water, or ground water ( well water, a river or what have you) and not for use with rain. What's the difference ? Ground water, including tap water can be guaranteed to contain enough calcium and magnesium to keep the plants happy, and the fertiliser does not include this, or not enough, when the water is rainwater with no calcium or magnesium in it. Why don't they put them both in a single bottle ? Because something will precipitate out if they do. So a two bottle mix is based on putting much ofl the calcium in one bottle and much of the magnesium in the other, and dividing everything else the plants need between the two. When mixed in the large volume of diluting rain etc., there is no precipitation problem.The cocktail also includes other components from time-to-time; currently it adds Humic Acid (source also Growth Technology - try googling them or contact me ) or Nitrozyme. I don't believe in using cheap tomato etc. fertilisers based on urea; some people get on well with them, so they say, but my correspondence with thinking growers who try to be scientific encourages the view that orchids are not organised to deal with urea ( the explanation is very simple ; urea works with soil based plants, the bacteria inevitably present in the soil can and do break it down. These bacteria are likely to be absent from Perlite in hydroculture even if they are [?] present in say bark mixes). Maybe those who say it's good are using Peat , where I would expect the bacteria to be present.

I don't flush. Think about it, and you will realise that it is unnecessary, and even counterproductive, as well as time-consuming and wasteful, when the media is always wet, and crystallisation of excess fertiliser cannot occur.

The values of the water and fertiliser ( amounts) will later be found by referring to the page on the subject - when it has been prepared and up-loaded; until then , please understand that basically I use pH6.0 and EC 500 - in both cases plus or minus a few percent, i.e. pH 5.8-6.2 , and EC 450-550 .

Here are a few pictures taken from my illustrated lecture on the subject :-

Diagram showing hydroculture - note the 24 hours a day, 7 days a week, and 365 days a year - subject of course to any different ideas for resting to induce flowering.

How capillary action works - a familar image ? Try it out with a lump of sugar and some coffee, and see how quick it is . ( I have never tried growing orchids in sugar lumps, but I expect they would dissolve and not be much use - the sugar, not the orchids. [joke] ).

Showing the various materials I have used . Washing is desirable - just chuck the material in a bucket or larger container of water - the dust settles to the bottom as sludge especially if you give it a good stir - use the larger pieces which float. This improves aeration, and in addition, the dust tends to be rather undesirably reactive, often having a high pH - quite unlike the larger pieces which are broadly neutral.

Another kind of hydroponics uses flood and drain .I have used this very successfully for Vandas but do not use it now, simply because I can grow Vandas in the roof of my greenhouse as well as having plants on the bench - two layers of plants in effect, and I don't want tanks hanging up in the roof . So I am not discussing this here.