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Potting up

This is done at 16 weeks after sowing, in 11-15cm pots of terracotta or plastic (depending on the consumers’ preference) in aerated and free-draining compost based on young peat which encourages root development.

Initial fertiliser at 1kg/c.m. of a general mix is sufficient.

As for pricking out, it is important to place the tuber properly in the upper layer of the medium.

For the first four weeks, watering is done from above, in good quantities, and light intensity should be kept to a maximum of 40,000 lux.

The plants must be spaced soon enough apart so that their leaves do not touch.

The night-time temperature in the glasshouse should be kept down to 15ºC (59ºF), and some form of whitewash should be used to keep daytime temperature down.

Supplementary fertiliser in the irrigation water is given as soon as the roots appear at the edge of the pot, with a balance of 1:0.7:2 at an electrical conductivity of 1.2 mS/cm, rising to 1.8 mS/cm as the plant grows.

In the heat of the summer the conductivity (soil salts concentration) should be kept down, and the nitrate supply reduced.

Good ventilation, especially horizontal breezes, help the cyclamen plants to better withstand heat. 

> Size of pot

Gardening practice varies from country to country. In northern Europe growers use 10cm or 12cm pots, while in Southern Europe we frequently find larger pots used, with diameters up to 17cm. The consumer’s preferences govern this choice, so far as cyclamen are concerned.

> Plant staging

We use ventilated staging of the grid type. It is also possible to cover the staging with coarse gravel, so that no water remains stagnant on the surface under the pots which the plants’ roots may get to. Other systems of the fill-and-drain or the trough type also give good results.

> Timing of potting up

We pot up at 15 to 17 weeks after sowing. It should not be done too late, or the leaf stalks may become elongated; the plant is becoming ‘leggy’: if this happens, there is a considerable risk that the plant will continue this kind of growth. We need to be sure to pot up while the plant is good and compact.

 

We recommend the use of 14cm pots (the European standard). These are in terracotta or plastic, and have good drainage (5 holes and stubs to help water to drain away). If you choose terracotta pots, this will add to the plant’s value on sale.

 

In the case of terracotta it is a good idea to use pots that have been treated against moss and algae. Not only are these growths on the pot’s surface rather unsightly; but also they can affect the porosity of some pots, resulting in plants that grow at different rates.

> Potting-up medium

The quality of the compost used is supremely important: the elements it is made from must be the very best. We recommend going to specialist firms which produce and market growing medium for cyclamen. Suitable, high-quality compost is an essential part of the struggle against disease.

Never use anything but new compost.

 

Our potting up is done in very free-draining compost from company EGO, based on a different grade of young peat and perlite (10%).

The medium has a pH of 5.6 to 5.8.

 

This medium contains no clay. Clay is quite unnecessary and when it is included in composts it is never more than 5% or 10% of the mix, which is not enough for the clay to play any buffering role for the fertiliser.

 

A free-draining medium is very important for the structure of the plant at the start of its life in the new pot. In such a medium the cyclamen’s relatively fragile root system will find it can spread out well; the tuber will grow, and the flowering process can get under way. The general health of the plant makes it less liable to succumb to a disease.

 

To keep the medium open and aired it is better to use perlite, an inert product, rather than fresh pine bark which will eventually break down and in so doing will lock up some of the available nitrogen in the medium. As the temperature rises, some of this nitrogen will be released, just when it is advisable to keep the nitrate content low (see the § on “Growing conditions in warm spells”).

 

If the compost is not free-draining, the root system will not develop so well and will be more open to bacterial attack and to the fungi Cylindrocarpon and Thielavopsis.

 

What is more, the medium must have a considerable water retention capacity; the compost we use must not lose its moisture too quickly, nor should it keep it too long, for if it does harm may follow, especially if the temperature swings violently up and down. It is easier to make watering a function of the temperature. Obviously, though, there will be other considerations in the choice of a growing medium as well, such as climate, the type of glasshouse and its fittings, and the knowledge, skill and habits of the grower.

> Initial fertiliser

The initial store of fertiliser is provided with an NP2O5K2O mix of 15:11:21; but the quantity supplied will vary depending on the size of the plant aimed at:

 

“Standard” cyclamen

Compact cyclamen

Mini cyclamen

1 kg / c.m. of medium

0.5 kg / c.m. of medium

0.5 kg / c.m. of medium

 

> Potting-up method

It is easier to remove the young plants from their polystyrene trays if their root ball is slightly dry. We first make a central hole in the potting-up compost, which should be moist and not compressed. As we position the tuber properly in the centre of the pot, it is important to watch out for damaging the roots which are extremely fragile. At this stage it is vital that the tuber should be completely covered with medium, though it should not be buried too deep or it will lose the advantage of unchecked growth.

The mini cyclamen may be potted up with the tuber half out in the open.

> Watering

At the start of the potting-up stage, watering is done from above. As with the pricking out, a rain of extremely fine droplets is the most suitable way of watering, and this should be done immediately the plant has been potted up. For a period of 15 days to 3 weeks the plant should have nothing but water.

The root ball must be well wetted so that when the earthenware absorbs water the upper part of the medium does not dry out. If that happens, then the anchor roots find it hard to get established, and the balance of the plant will suffer.

> Irrigation

The irrigation system we use is one of local water supply, and works in such a way that the roots and compost become soaked through without any water running out of the pot.

With a localised water supply system, a telltale pot can be chosen and made to tip a scale to work each electric gate valve, so that the water needs of each sector can be met automatically.

Watering is done little and often.

If the medium becomes too dry, the cyclamen deals with this form of stress by going into a resting state; it is not easy to notice this state, or bring the plant out of it. It is better to keep the roots moist at all times and be in a position to control development with precision by choice of times and quantities of fertiliser. The supply of water is the fundamental factor to be considered, and the fertiliser factor should then be adjusted as a function of this.

Equally, it is essential to watch that the medium does not become too full of water, or the plant will tend to drink too much (become over-turgid) and produce huge leaves.

> Light

The cyclamen does not react to changes in day-length as such; but the growth of the plant and flowering are governed by the amount of light that reaches the heart of the plant (light intensity and hours of sunlight in the day).

Cyclamen require a light intensity of around 40,000 lux. If they are getting more than 50,000 then it is better to shade them in order to diminish the amount they receive. For that, we recommend a partial whitewashing of the glasshouse by means of droplets, which will tend to diffract the light. This is better than a systematic use of shading screens, which cut down the light too much as well as lowering the quality of the radiation that falls on the plants so that the leaves become soft and wilt. Shading generally reduces the number of flowers and should not be done permanently or it will do harm.

 

The hours of sunlight increase until 21 June, and then start to get less; if the covering is not removed until too late, the cyclamen will miss some of the light intensity they should have.

> Temperature

To bring about a lowering of temperature when it is too high, some growers go in for the practice known as “misting”. This is not advisable. It lowers the temperature only momentarily, and leads to a softening of the plant tissues as they become full of water: combined with too much nitrogen and warmth, this is a fertile breeding-ground for disease bacteria.

 

It is best to have completed potting up before the heat of the summer; and we also have to remember that summer temperatures of up to 30ºC (86ºF) are borne more easily by plants in the middle stages of development, while older plants will not stand the heat so well.

 

Once flowering has begun, the night-time temperature in the glasshouse should be kept to 15ºC (59ºF) for the flowers to develop properly.

From early January the night-time temperature can fall to 12ºC (54ºF) if there is winter sun.

> Supplementary fertiliser

A plant that has been grown with just a little nitrogen will have a longer life after it has been sold.

Premature cutting of fertiliser may lead to an exhausting of the plant’s reserves and this will show as a lightening in leaf colour.

 

The consequences of mistakes in fertiliser application are hard to put right. It is the tuber that suffers first, and it is some while before symptoms appear in the foliage.

1 > Irrigation + fertiliser

This begins 15 days to 3 weeks after potting up. At the start the solution is one of 1:0.7:2 at a strength (conductivity) of 1.2.  As the plant grows this is brought up gradually to 1.8.

This fertiliser is given through the same localised system as for irrigation, at each watering.

 

By adjusting the nutrient solution it is possible to alter the plant’s behaviour. A balanced solution will allow the plant to grow into an ordinary sized plant with a normal habit, while extra potassium at the start of potting up, or less nitrogen, will favour more tuber and root system development.

The same condition will encourage all the flower buds to form at the same time, and lead to most of them opening together later on. Giving a balanced fertiliser as the plant grows will stagger bud formation and flowering is then spread over a longer period as well.

In our glasshouses we ran fertiliser trials on the Halios variety Bright Scarlet in 1994.

The aim of the trials was to investigate the best N:K mix for advanced and synchronised flowering in the conditions that obtain at Fréjus in high summer.

We tested different fertiliser proportions from the first spacing stage until the end of the cycle.

From our observations it appeared that a 1:0.7:2 mix of fertiliser throughout the period was not the best choice in order to get the flowering pattern aimed at.

At first we tried reducing the nitrogen content to 0.5:0.7:2. With this relative lack of nitrogen and excess of potassium we got a great number of buds and of flowers.

The number of leaves however stayed low; and the leaves were smaller and lighter in colour, with shorter stalks.

 

In the end it became apparent that we could have a large number of buds and flowers, and in addition the ideal amount of foliage growth, by giving a 0.5:0.7:2 mix at first, to encourage bud formation (for 9 weeks after first spacing), and then going back to the usual 1:0.7:2.

2 > Slow release fertiliser

This form of fertiliser is not recommended; the reason is that their release is governed by temperature: as temperatures rise this stimulates nitrogen release in the very conditions under which it ought to be kept low.

 

NB : Fertiliser with equal proportions (10:10:10 for instance, or 20:20:20) is not recommended, since it leads to plants with few leaves which take a long time to come to flower.

 

It is a good idea to arrange for regular analysis of the conductivity of the nutrient solution, in order to be able to make comparisons from year to year.

> The influence of heat and light levels on supplementary fertiliser supply

During the summer season fertiliser application should be rationed in accordance with the temperature and, also, with the level of light that filters through whatever shading is used”

 

When the temperature is high, cyclamen take up nitrogen more readily, and plant growth is encouraged but the leaves are soft and floppy and more open to bacterial attack.

 

In the glasshouse in summer there comes a time when the intensity of light must be controlled because the sunshine is too strong for cyclamen plants and also makes for too much heat. As glasshouse temperature rises, we respond with a set of successive measures. Shading arrangements are put into operation to make the temperature fall, and the combination of lower temperature and less light makes for a reduction in the plants’ capacity for nitrogen uptake; we must then reduce the quantity of nitrate in the nutrient solution. We also need, however, to make sure that the light received is always adequate, or photosynthetic activity will be hampered.

A deficit of nitrogen in the summer is not really a disadvantage in terms of the grower’s marketing needs. What results is smallish plants with a great number of leaves, a well developed tuber and a very early onset of flowering, with a fine development of the root system.

By contrast, an excess of nitrogen in summer produces plants with large leaves and too many of them; the growing period before flowering is longer, and there is more risk of Botrytis attack.

During hot spells the amount of fertiliser given should be cut back as a whole. We recommend decreasing the nutrient concentration, or conditions in the pot may become too saline. Because the plants transpire more, they take up more water to compensate for this loss, and unused nutrients build up in the pot. Too great a concentration of salts is not good for the plant, for it can lead to scorching on the edges of leaves and on roots, as well as greater susceptibility to fusarium and bacterial attack. What is more, when faced with this stress, the plant goes into a resting state.

 

Keeping the nutrient solution balanced also plays an important part in keeping the plant fit enough to face the hot spells. A plant that has properly balanced nutritive supplements in the quantities it needs will be so much the better at coping with conditions of strong sunlight.

> Growth regulators

We do not recommend the use of gibberellic acid to accelerate flowering, for it softens stalks and distorts the flowers and spoils the cyclamen for the consumer.

> Glasshouse ventilation

Glasshouses are to be as well ventilated as possible. If it is very hot, just opening ventilators in the roof is not enough: there must be some moderate side ventilation at the level of the glasshouse walls, so that there is a good circulation of air at plant level and the plant tissues are not softened.

> Spacing the plants

The plants are grown under a “pot to pot” system for the first four weeks after potting up: this system produces a better micro-climate.

Spacing the plants out in good time improves the quality of the plant, keeps it compact, brings on early flowering and improves resistance to disease.

If the plants are not spaced out then the leaves they have will become large and coarse and they will not form many more.

 

The plants are spaced out twice, before finally being set at their full distance.

It is a good idea to organise the plants so that the spacing out stage will not be hampered by shortage of labour (holidays, ....) or lack of time. This can be done so that just one spacing out will be needed before the plants are set at their final distances.

> Flowering

We recommend removing the first 3 or 4 flowers that open, which otherwise would tire the plant. When they are gone, the other buds will be encouraged to develop and bloom.

 

All these operations, apart from spacing out, are to be done as the plants are coming into flower. During the flowering season temperature and ventilation must be carefully watched to prevent Botrytis attack which causes Grey Rot on the flowers.

Caution

This advice sheet is based on the methods used at the SCEA at Montourey (Fréjus, France). These procedures may need some modification to adapt them to other climatic situations. Before starting to grow cyclamen there needs to be a review of precautions against pests and diseases.   We must point out that our advice and suggestions are offered for information purposes and therefore cannot include any guarantee of specific results; it is a good idea to carry out trials beforehand.

 

Culture factsheet :

S.A.S Morel Diffusion

2565, rue de Montourey
83600 Fréjus - France

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