Excerpted from: Latour-Marliac, Bory. "Hardy Hybrid Water Lilies", Journal of the Royal Horticultural Society, vol. XXII. 9 August 1898.
The cultivation of hardy Water lilies is of the simplest, and in no way differs from that of the common indigenous N.alba. Nevertheless, to carry it out under the best conditions, it is as well to use certain precautions which are easily observed
Most of the Nymphaeas called « out-door », although nearly all equally hardy, frequently differ among themselves in their early or late blooming, in their standing up above the water or floating on it, in their flowers being many or few, or in their general structure and growth being compact or wide-spending. Some of them form strong clumps which constantly increase in strength, but do not spread about, whilst others are of a roaming nature, their stolons and interlacing rhizomes wandering over a large space, and quickly spreading across the roots of other varieties. In natural lakes and ponds it is impossible to prevent this undesirable confusion, but this irregular growth should not be permitted in artificial basins and aquaria, where each object in the collection should remain distinct and thrive independently; besides it would not only produce inextricable confusion amongst the plants, but the weaker ones would be infallibly smothered by the stronger-growing ones. In order to obviate this difficulty it is indispensable that the Water lilies should be planted separately and at proper distances, or else in pots or in stonework basins of which the sides and bottom have been carefully cemented.
The form and extent of the basins of water matter little: it is optional, according to the taste of the individual grower. Still a diameter of ever thirty feet will be detrimental to perspective as it will be too far for a clear view.
It is very important that the basins should be divided into several compartments by partitions, which should not be higher than three-fourths of the depth of the water, in such a way that they only prevent the roots and rhizomes from meeting, without preventing the leaves from intermingling on the surface. Two feet down from the bottom of the kerb-stone is enough for the depth of the basins. The outside walls ought to be decidedly slanted outward, so as to run less risk of their being damaged by hard frost and the pressure of the ice, which would certainly happen if their were built straight up.
A bed of earth six inches deep on the bottom of the basins will be amply sufficient for the culture of Water-lilies and for most other aquatic plants: it ought to be as free as possible from gravel and stones. The best king of earth is heavyish loam from the garden or meadow, but earth composed of leaf-mould and alluvial soil is also very suitable. One can also make a mixture of them, but it is better not to put with them any fresh manure which is still undergoing fermentation.
As regards the choice of water, that which comes from a stream or river is to be preferred, though that from wells will do. When the water is taken from running springs it ought in summer to be turned off from the basins, so as to keep the temperature of the water the same as that of the air ; for it is essential to remember that Nymphaeas thrive best in stagnant water, or at least in a very gentle current.
In stocking a basin with Water-lilies the object should be to obtain by a harmonious combination and sequence of shades and colours a generally dazzling effect, and for that purpose plants with high stalks should be avoided, as that would destroy the general view. It is necessary also to suppress Confervae and those Mosses which are too compact, and certain under-water plants which are clogging and clinging, such as Chara,Cabomba, Vallisneria, Elodes, Potamogeton, &c , which live at the expense of the Water-lilies without adding anything to the ornament of the picture. Nevertheless it is as well to except from this proscription Tropas natans and T.verbanensis, Stratiotes aloides, and Aponogeton, which are quite worthy of being admitted into the society of Water lilies.
The Tropas display gracefully upon the surface of the water their triangular leaves, with swollen petioles, disposed in rosette like form, those of T,verbanensis being larger and particularly distinguishable by the stalks and veins of the leaves being of a pretty red colour. The fruits of these two annual kinds, known by the name of Water chestnuts, are eatable. It is sufficient to throw them into the water in spring, when they will make a good display without further trouble. Stratiotes aloides also forms very graceful groups of rosettes, which are like real Aloes. The Aponogeton, with their oblong floating leaves, furnish throughout the year a constant succession of lovely waxen and sweet-smelling flowers, and they are the more worthy of taking a place beside the Water lilies, and of being particularly recommended to aquaticulturists, as they have produced some splendid varieties , with flowers and leaves brightly tinged with pink and carmine, and much larger than those of the original type. These charming varieties, not yet in commerce, are the object of the greatest car at Temple-sur-Lot, and are destined by their hardiness, which will allow them to grow without protection in England to play a prominent part amongst water plants from the double point of view of the decoration of aquaria and for a trade in cut flowers.
It is to be noted that the Aponogeton is the plant of all others for growing in the running water of springs, where it prospers to advantage, and flowers most freely and without ceasing.
The propagation of hybrid Water lilies does not differ from that of the original species, and is effected of the greater number of varieties by the pulling of pieces of their stumps and by the detachment of their tubers. Some individual plants, such as N. Laydekeri rosea, do not give any offshoots, but this case is a rare exception. Others bear seed, but the resulting plants have always a tendency to degenerate and to revert to the original type. To be certain of keeping the exact peculiarities of each variety it is much better to have recourse to increasing them by the division of their stumps. The planting of them can be carried on all through the spring and summer, and presents no difficulty, as it only consists in fixing them in the earth at the bottom of the basins. At the same time it is as well to notice that when it is necessary to alter entirely the planting of aquaria, it is better to undertake it in good time, i.e., in April or May, so as not to keep back the time of flowering too much. If you wish to obtain new varieties you must have recourse to seed and hybridisation. The method of sowing is quite simple. It is only necessary to place the seeds in shallow vessels in the spring, and carefully keep them full of water. The work of hybridisation is more complicated, as it is necessary to entirely cut away, at the very first moment of expansion, all the stamens of those flowers which you wish to artificially fertilise, and on the second day to dust their stigmas with a brush, covered with pollen from those kinds chosen for the crossing of them. It s worthy of remark that success in hybridisation depends principally on the care of the operator in only employing subjects of a vigorous growth, well chosen, and fitted to produce types that will be very free blooming and of perfect forms and shades. The flowers generally sink after the third day of blooming, and the pods which they produce, which are like those of the Poppy, come to maturity at the bottom of the water. They come half open, when thy are ripe, and allow a multitude of seeds about the size of small pearls to drop out, and these immediately rise to surface surrounded by a gelatinous substance. They must then be collected at once, with the aid of a small strainer, as they only float for hardly a single day, and then sick straight to the bottom, from which the sticky substance prevents them from moving. After their capture they should be kept in water, so as to keep them more safely until they grow. People who are unprovided with basins of water, and who wish to start on the culture of Water-lilies, can very well make shift with casks sawn through the middle and firmly surrounded by iron bands round their edges. In temperate countries it is unnecessary to protect these tubs against the frost, but in cold countries they must be protected. To do this a trench is made of a depth of about one third the height of the tubs, which are then places in it and banked up to their edges with the earth dug out. One would hardly believe what a charming effect can be produced by tubs arranged in this style, with art and symmetry, and clothed with Ivy.
Water lilies are blessed with a surprising vitality, which allows them to live for quite a long out of the water, and, in consequence, to survive very long voyages without being any the worse. For example, in 1889 I sent to the Universal Exhibition at Paris a collection of my hybrids in a case which was a lot on the railway, and which could not be found for over a month. I was then obliged to replace this first instalment. Some time afterwards I received a memorandum informing me hat the package had been found, and asking me what should be done with it. Feeling certain that the plants would be dead, T ordered them to be sent back by slow train; but on their arrival I was utterly astonished to see them in good order and covered with shoots, and very little the worse for being so long boxed up. To show the advantage of the endurance of Water-lilies I ought to add that I have thrown waste plants on to the earth surrounding the ponds, and have found their roots still quite sound after having lain six months on the open ground.
Cultivators of aquatic plants have often shown great anxiety about the supposed havoc caused by water rats and mussels; also by different kinds of insects, fish, &c. I think that their fears have been exaggerated, because for my part I have only had to complain seriously of the ravages committed by two kinds of larvae, the one black and the other while, produced by certain small yellowish-white butterflies which deposit their eggs on the floating leaves. These larvae, at first almost invisible, grow to about the thickness of a wheat straw, and devour the leaves of the Lilies during the night, also those of the Aponogeton, Limnocharis,&c. They are very clever in hiding themselves during the day laying fragments of the leaves on their bodies and covering themselves up with pieces of Lemna palustris or Azolla. Their devastation would be serious if it could not be easily stopped by pouring on the surface of the water some drops of a mixture of three quarters colza oil to one-quarter of paraffin, a sufficient dose to poison and destroy them without hurling the plants. The climatic conditions of England are without doubt inimical to the existence of these voracious larvae; but, in any case, I have pointed out the infallible means of suppressing them.
I should not bring this dissertation of Water lilies to an end without bestowing a few words on the splendid section of the Cyanea, or blue Water lilies. It is greatly to be regretted that hitherto all attempts to cross them with their hardy congeners of the northern hemisphere have so far failed. It would be a great triumph to add to the already sumptuous collection some hardy hybrids of a sky-blue colour with a delightful perfume. They are very variable, as from the seed of N.Zanzibarensis one can obtain the most beautiful colouring of deep blue, tender blue, intense violet, clear violet, violet-red, pink, &c., that it is possible to imagine. But, alas! These charming varieties, which have also the advantage of being day flowering, will only thrive with a considerable amount of heat. At Temple-sur-Lot, which has a great number of running springs, they are grown all the year round in the open by the following means. From the end of October to April 15 we pass through their basins a constant current of water from the running springs to preserve them from the cold, and as soon as the cold is less intense we turn off the springs, so that the temperature of the water in the basins becomes the same as that of the air. By these simple means it is possible to enjoy for five months the flowering of these grand plants, which like some of the Nelumbiums, have a decided tendency to acclimatise themselves in the south of Europe. As regards the Nelumbiums their position is too important amongst decorative aquatic flowers to pass them by in silence, and I have not yet given up all hope of obtaining in time varieties sufficiently hardy to live without protection in England; for it must be remembered that they are nearly as hardy against the frost as the indigenous Water-lilies, and that the only obstacle against the realisation of this hope is the fact that they require, in July and August, a greater degree of heat than the Water-lilies for the ripening of their rhizomes, which renovate themselves in the heat of midsummer. It is in April that the Nelumbiums begin the growth, and when their first floating leaves appear, followed shortly by larger ones, which stand up 2 ft. or so above the water. They display themselves majestically like vast air bubbles hanging from a very slender stalk, and the drops of rain or from the waterpot roll off them sparkling like diamonds from their concave and velvety surface. The flowers have an exquisite perfume, and are of the size of large Paeonies, appearing in July, August, and September. They are of many very rich shades of pink, white, red, yellow, carmine, and lilac. Some double varieties have been obtained lately, with about twenty-four petals, which will no doubt still further augment the already great fame of the charming Nelumbiums, whose temperature it is so desirable should acclimatise itself to the climate of England.