a)Purpose:
The objective of the obscured cultivation is to make plants flower artificially outside of their normal flowering time. This is possible by shortening the amount of daylight by obscuring the plants i.e. taking away the natural sunlight from the plants (=obscuration).

b)Obscuration:
In principal chrysanthemums change from the vegetative phase (growing phase) to the generative phase (flowering) as soon as the nights start outlasting the days. This varies greatly according to the different varieties. Some varieties already change phase from 11 and a half hours of obscuration (darkness), while others easily need 12 and a half hours. Therefore 13 hours of obscuration is advisable to be able to produce uniform flowering. Flower induction is achieved by artificially shortening the long day. It is possible to place the plants under obscured conditions from the beginning of April till the beginning of September in order to achieve bud formation and flowering. Between the 1st of September and the 1st of April the nights are naturally long enough to obtain flowering.

Obscuration is possible outdoors as well as in greenhouses. Plastic (>0,007 mm) or canvas (e.g. PH-1) can be used as materials for obscuring. Depending on the type of canvas or plastic, there are several different methods of obscuring. A frame can be mounted over the plants over which the canvas can slide without touching the plants. Apart from this method a suitable canvas can also be used, which is placed over the plants. Make sure when using the latter method that the outside rows are fully protected against being knocked over when opening and closing the canvas. Obscuration can also be obtained by installing a fully automatic screen in the greenhouse itself.

c) Reaction Time:
The time calculated from the start of the obscuration until the plant starts flowering is called the reaction time (RT). The RT is dependent on the variety and varies between 5 to 9 weeks. Extremely high or low temperatures during obscuration can influence the reaction time. Too high night temperatures (28-32°C) or too low night temperatures (around 0-5°C) decelerate the development of flowers considerably. Under normal weather conditions (night temperature 12°C-25°C) the development of flowers will proceed normally.
In theory obscuration is carried out daily from day 1 onwards until the flowering stage. After the buds "sprout" (i.e. the bud cluster opens up, mostly +/- 28 days) the obscuration procedure can be discontinued, without the plant turning to the flowering stage again. It is important to perform obscuration without (long) interruption; otherwise this has a negative impact on the shape, the flowering time and the quality of the plant. We must emphatically stress that obscuration be performed particularly during the first fortnight (without interruption). From the 3rd week onwards, it is permissible to skip 1 night per week without detrimental results. It is recommended that these nights are used for spraying or inhibiting.

d) Planning:
Before establishing the growing plan the following must be taken into account. The criteria to be used in determining an effective plan are the final diameter, the flowering period, the pot size, the location and the RT.

When obscuration is initiated, ideally the plant needs to have reached approximately 60% of its final diameter. For example, if you want a plant with a diameter in the region of 50 cm, it is best that obscuration is initiated when the plant is about 30 cm in size. Beware: it is by no means a certainty that the plant will grow by precisely 20 cm under obscured conditions. The larger a plant is at the start of obscuration, the more it will grow in the same number of weeks compared with a small plant put under obscuration.