Cultivation guide Pot chrysanthemum
Pot size
4 standard pot sized are used.

9 cm pot
for one single cutting
 12 cm pot
for three cuttings
 14 cm pot
for 5 cuttings
 23 cm pot
for 7 cuttings
Evidently, the amount of pots per m² depends on the pot size.
On average, this results more or less in the following distribution.
 9 cm pot
50 - 55 plants per m²
 12 cm pot
23 - 25 plants per m²
 14 cm pot
15 - 17 plants per m²
 23 cm dishes
9 - 10 plants per m²
Potting compost
The most commonly used potting compost for pot chrysanthemums is the socalled “fine” 40/60 mixture. This consists of 40 % garden peat and 60 % bog
moss peat.
This potting compost mixture has been passed through an extra fine sieve,
which removes the long fibres.
These days, a small percentage of perlite or coconut fibre is often used as
well. This raises the air containing capacity and speeds up the rooting process.
Especially when using coconut fibre, you should avoid using too high a
percentage of this in the potting compost. This medium has quite an influence
on the intake of nutrients and the binding of certain elements.
The used potting compost always requires a basic fertilizer. For achieving the
correct pH level, around 5 to 7 kg of Dolokal per m³ is needed. In addition, a
basic supplement of trace elements is advisable in the shape of 0.5 to 1 kg
PGmix.
Several nurseries also use 400-700 g calcium nitrate per m³ of potting
compost as slow-release fertilization.
Sticking and rooting
As far as pot chrysanthemums are concerned, the cuttings are immediately
stuck into the final pot.
At the production location, the cuttings are dusted with a rooting hormone. This
promotes faster and better rooting.
Before sticking the cuttings, the potting compost is usually moistened once. In
this case, watering from the bottom is preferable because this way, the potting
compost retains its airy structure.
Depending on the time of year and the cultivar, it is possible to spray 1 to 2
grams of Alar 64% per litre of water, before putting the rooting plastic over the
cuttings. Sometimes, this is supplemented with a product against Botrytis
and/or insects.
Particularly during warmer seasons, it is vital to cover the cuttings with the
rooting plastic as soon as possible after sticking.
The plastic needs to be sufficiently large to cover the entire surface properly,
including the sides. This is the only way to achieve even rooting.
In winter and in early spring, transparent plastic will suffice. However, as spring
progresses, this will have to be replaced with a milky white plastic and the
screen above the rooting cuttings will have to be closed. If there is no screen in
place, the greenhouse will have to be whitewashed. Direct sunlight on the
rooting plastic is fatal to pot chrysanthemums.
After seven to ten days (depending on cultivar and season), rooting needs to
be checked and when this looks in order, the plastic needs to be removed.
This is best done closer to the evening, giving the plants the opportunity to
acclimatize.
Pinching
About 13 to18 days after sticking, the pot chrysanthemums can be pinched
back. This is subject to the season. When pinching back the top, a minimum of
5 to 6 leaves have to remain on the plant. Pinching back needs to be done
very evenly in order to achieve a crop that is as uniform as possible. After
pinching, the plants may stay next to each other and do not have to be spaced
out until a maximum of one to one and a half week. After this, they need to be
spaced out at their final distance; this to prevent stunting of the plant habit.
These days, several companies have started pinching back using an
automated mowing arm. This system does work but does demand a number
of adjustments to the technical aspects of cultivation.
It is advisable to test the technique at one’s own premises before changing
entirely to automated pinching.
Fertilization and watering
Both fertilization and watering are actions that depend on factors such as plant
stage, season, potting compost, growth and climate.
During the cultivation period, there is always a need for extra fertilizer. Subject
to the stage the plant is in and the growth at that time, one waters with an EC
of about 1.5 to 2.
During the first few weeks of cultivation, one generally provides lots of nitrogen
for promoting the forming and growth of shoots. In doing so, one also often
adds some potassium, magnesium, phosphate and iron as well. During the
cultivation period, the emphasis will be more on potassium and magnesium,
although phosphate, nitrogen and iron are still indispensable at that stage.
Depending on the type of irrigation water, it will also be necessary to add trace
elements from time to time. By means of the EC given, it is possible to
influence growth and stretching of the plants. As the EC in the pot increases,
the plant will not as easily stretch and in general, leaf colour will become
somewhat darker.
Please find a schedule with target figures below.
EC
<1.4
pH
5.6
NH4
<0.1
K
2.4
NA
<2.5
CA
1.4
Mg
0.6
NO3
Cl
6.0
<2.5
SO4
1.0
HCO3 P
0.50
Fe
8.0
Mn
2.0
Zn
2.0
B
10
Cu
0.7
Growth regulator
Spraying with growth regulator (PGR) is one of the most important operations
when cultivating pot chrysanthemums. This determines the shape, height and
therefore also the quality of the plants.
Growth regulator spraying is subject to many factors, including:
● cultivar
● greenhouse climate
● season
● EC in the pot
● pot size
● cultivation method (wet or dry)
Under the influence of light and temperature, Alar breaks down relatively
quickly. It is therefore vital that the powder to be sprayed is not dissolved in hot
water but at most in lukewarm water. Furthermore, it is advisable to spray
closer to the evening, just before the blackout screen shuts, so the light can
affect the decomposition of Alar hardly or not at all.
Climate
A day temperature of approximately 19 to 20 C and a night temperature of
20 to 21,5 C needs to be maintained.
Depending on season and outdoor conditions, temperature boosts, moisture
gaps, minimum pipe temperatures and so on are applied.
During a large part of the year, it makes sense to apply CO2 doses. The
objective is a value of 800 to 1200 ppm.
Labour
For pot chrysanthemums, the labour requirements strongly depend on the type
of cultivation system. Therefore, the figures below are the averages of several
growers as registered a few years ago.
The labour requirements are given per 1000 pots of 12 cm with 3 cuttings per
pot.
potting up
pinching back
spacing
sales/transport
Total
2 hrs + 21 minutes
51 minutes
1 hr + 9 minutes
3 hrs + 42 minutes
--------------------------8 hrs + 3 minutes
Lighting
In order to discourage bud formation in pot chrysanthemums, it is necessary to
illuminate during a certain period of the year. Illumination is required in the
period between the 1st of August and the 1st of May. In the period after the 1st
of May, there is sufficient natural day length for discouraging bud formation.
However, one needs to bear in mind that in spite of this, illumination is
necessary during this period because the blackout screen is closed in other
parts of the greenhouse. Illumination only takes place at the start of the culture
during the rooting phase. In doing so, one achieves that the plant develops a
little more growth before it starts forming buds. The result is a slightly heavier
and well developed plant. A cyclic lighting treatment is sufficient for
suppressing bud formation. In that case, one needs to illuminate from 10 pm
until about 4 am. The usual illumination time is 7.5 minutes per half hour.
The number of days that extra light is provided depends on the time of year
and the pot size. In summer, it is even possible to stick cuttings directly during
the short day. In summer, an illumination period of 5 to 7 days is the most
common and in autumn this is increased to 16 days.
When using cyclic lighting it is common practice to have a string of light in
every 3.20 m light fitting and to have a distance of 3 m between lamps. The
lamps are 150 Watts if Super Argenta types are used. This results in a light
capacity of about 90 lux.
Blackout
In order to get a pot chrysanthemum to flower, it is necessary to blackout for a
large part of the year. Chrysanthemums are namely short day plants. This
means that flower bud initiation is only induced by a night length of at least 13
hours. In the period from the 1st of March until the 24th of September, the
greenhouse will need to be blacked out because this period has naturally long
days. The blackout screens will have to be shut for at least 13 hours in this
period; this in addition to the normal time the screen is shut.
When extreme outside temperatures occur in summer, it may be advisable to
extend this blackout time a little, in order to compensate for delayed bud
formation caused by high temperatures.
Pests and diseases
It is vital to spray preventatively against a number of pests and diseases. In
winter, one single spraying every 3 to 4 weeks usually suffices but in summer
this needs to be done once a week.
Animal parasites
Leafminers
In chrysanthemums, we come across two different types of leafminers. Firstly,
the American serpentine leafminer (Liriomyza trifolii) and secondly, the South
American leafminer or pea leafminer (Liriomyza huidobrensis).
These tiny flies mine food from the leaves, resulting in damaged leaves. They
may also lay eggs in the leaves, resulting in larvae that will create tunnels in
the leaves. Leafminers can be recognized by the tiny yellow shield on their
back.
Treatment:
 Trigard;
dosage
100 cc / 100 l water
 Vertimec; dosage
50 cc / 100 l water
 Splendid; dosage 75 -100 cc / 100 l water - works especially against
the flies but does not suffice for controlling the larvae.
Thrips
Most feared is the western flower thrips (Frankliniella occidentalis).
Mainly in the top of the plant this causes deformity and coarsened leaves. One
of the dangers of thrips is that it may transfer the tomato mosaic tobamovirus
(ToMV).
Treatment:
 Mesurol;
 NeemAzal;
 Match;
 Conserve;
dosage
dosage
dosage
dosage
150 cc/100 l water
250 cc/100 l water
150 cc/100 l water
75 cc/100 l water
Aphids
Aphids come in many different types and sizes. They can be yellow, green,
black or red. When plants are colonized by aphids, one often finds the empty
skins in the crop.
Treatment:
 Actara;
 Admire;
 Gazelle;
 Plenum;
 Teppekki;
dosage 10 g/100 l water
dosage 10 g/100 l water
dosage 25 g/100 l water
dosage 20 g/100 l water
dosage 25 g/100 l water
Whitefly
In general, this does not really present any problems in chrysanthemum
cultivation.
Treatment:
 Admire;
 Decis;
 Gazelle;
 Plenum;
dosage
20 g /100 l water
dosage
50 cc/100 l water
dosage 25 - 40 g /100 l water
dosage
60 g /100 l water
Bugs - Heteroptera
This is a very lively little insect. Both the eggs as well as the larvae are difficult
to spot in the crop. Therefore, they are often not discovered until the damage
becomes obvious. Young leaves develop misshapen and as the growing point
further develops, the bud often ends up on the stem at an angle.
Treatment:
 Admire;
dosage 10 g /100 l water
Caterpillar / Florida moth
The caterpillars of the Florida moth (Spodoptera exigua) can cause extensive
damage to crops. The moth is grey-brown and has 2 yellowish kidney-shaped
spots on its wings. The moths can be caught using UV light.
The caterpillars are characterized by their bright green colour and yellow stripe
along the length of the body. They have legs along the entire length of their
body.
At an early stage, catching the caterpillars is often the best method of
Treatment.
Treatment:
 Nomolt;
 Dimilin;
 Runner;
 Spod-X;
 Steward ;
dosage 100 cc/100 l water
dosage 50 g /100 l water
dosage 40 cc/100 l water
dosage 30 cc/100 l water - in particular against Florida moth
dosage 12.5 g /100 l water
Red spider mite
Since the arrival of Vertimec, there seemed to be hardly any red spider mite in
chrysanthemums. However, this has been superseded lately and red spider
mite is a major problem regularly.
It has become a necessity too alternate between well-known phytosanitary
products. Be sure to use high pressure when spraying; the turbulence will help
to include the underside of the leaves.
Treatment:
 Cantack;
 Envidor;
 Floramite;
 Masai;
 Milbeknock
 Nissorun;
dosage 100 cc /100 l water
dosage 40 cc /100 l water
dosage 40cc /100 l water
dosage 12.5 g/100 l water
dosage 50 cc / 100 l water
dosage 50 g/20 cc/100 l water
Fungi
Pythium
The roots turn brown and die back. Growth is (severely) stunted. Leaves turn
yellow and the plants may show signs of deficiency. Pythium is always present
everywhere. It is a parasite that only thrives on weak plants that are not
entirely healthy. The fungus requires relative high humidity levels, which
means that dryer cultivation often helps to control it sufficiently.
Japanese rust (Puccinia horiana)
At the upper side of the leaf, green to yellow, slightly sunken spots appear. At
the underside of the leaves, yellow-white and later dull brown little cushions
with spores appear.
Treatment:
 Kenbyo;

dosage 100 cc /100 l water -

Flint;
Daconil;
dosage 12.5 g /100 l water
dosage 200 cc /100 l water -

Ditane;
dosage 300 g
Do not mix. Watch carefully
in vegetative stage.
The product does leave
some residue.
/100 l water
Rhizoctonia
Where soil and air meet, the stem is constricted. At an early stage, the plant
wilts during the day and restores itself during the night. A warm and humid
climate favours the development of this fungus. Small quantities of water on
relatively warm potting compost do promote the attack. This fungus often
appears in combination with Pythium.
Treatment:
 Rhizolex;
dosage 100 g/100 l water
Botrytis
Grey-brown blemishes appear on leaves and stems. In humid conditions, grey
fluffy spores appear. Small brown spots (blight) appear on the ray florets,
these spots start to rot at a later stage (rot).
As in most fungi, climate is here a determining factor.
Treatment:
 Switch;
 Rovral;
 Teldor;
dosage 80 g /100 l water
dosage 100 cc/100 l water
dosage 100 g /100 l water
Sclerotinia
The plants will droop. On the border of healthy/diseased plant material, a thick
white mould occurs. At a later stage, the sclerotia or "rat droppings" will
develop in this mould. Sick plants will have to be removed very carefully
because any sclerotia that drop off may cause another infection. Crops that
remain very wet for a prolonged period run a higher risk of developing
Sclerotinia.
Treatment:
 Ronilan;
dosage 50cc/100 l water
Mildew
This fungus causes white spots on the leaves. There is a clear preference for
specific cultivars. The susceptibility may strongly depend on the variety.
Contrary to many other fungi, this one does not require high atmospheric
humidity but in fact prefers a low one, which means that any damage is often
noticed first near dryer positions such as along the concrete path.
Treatment:
 Kenbyo;


Baycor;
Flint;
dosage 100 cc /100 l water - Do not mix. Watch carefully in
vegetative stage.
dosage 100 cc /100 l water
dosage 12.5 g /100 l water
Agrobacterium
The bacterium brings about tuberous growths on roots, stems, leaves or
leafstalks. Infection with this bacterium may occur through wounds. After
infection, the bacterium can be found throughout the entire plant (systemic
movement). The best course of action is to remove all infected plants. There is
really no chemical possibility to fight this. The best way to control
Agrobacterium is to keep the crop as dry as possible.
Tomato mosaic tobamovirus (ToMV)
Bronze coloured rings and stains appear on the leaves. The stalk develops
brown lengthways stripes. The virus is transferred by thrips. For that reason,
good thrips control is vital.
Attention
Because of the vast changes in the authorization of phytosanitary products, it
is possible that certain products as mentioned above are no longer allowed in
your country. You should therefore always check which products you are
allowed to use.
If you have no experience which a specific product, we advise you to spray it
by way of a test for assessing the sensitivity of the cultivar.
In conclusion
Royal Van Zanten wishes you every success in the cultivation of Pot
Chrysanthemum.
This cultivation description is only intended for your information. Royal Van
Zanten cannot be held responsible for any problems resulting from said
advice.
More information:
Royal Van Zanten / Van Zanten Cuttings B.V.
Rijshornstraat 205, 1435 HH Rijsenhout
The Netherlands
Telephone
Fax
Email
Website
+31 (0) 297 389 600
+31 (0) 297 389 610
cuttings.nl@royalvanzanten.com
www.royalvanzanten.com