Whether a potted plant grows well or badly is first and foremost
a question of the habitat and the care it receives during its
growth period, that is, during the summer months. It is well-known
that light and temperature influence the well-being of plants.
However, humidity, wind, and rain also affect growth.
The most important measures to take during the summer months
in caring for your potted plants are watering, fertilizing, and
pruning. You should remove any wilted flowers from blooming potted
plants daily, if possible, in order to prevent energy loss through
fructification. There are no universally valid instructions for
how often to water and fertilize these plants.
When and how often you should water basically depends on two
factors:
The individual water requirements of the respective plant
The weather conditions of the habitat (sun, rain, wind)
High Water Requirements:
From May to September (main growth period)
In very sunny and windy habitats
During conditions of great heat and not much rain
Plants that need water and nutrients
Plants in small pots
Almost all potted plants need a relatively large amount of water
in the summer. During very hot days, they need to be watered quite
a bit. Plants with high water requirements, such as oleanders,
can even benefit from a footbath. On the contrary, citruses respond
downright negatively to moisture retention. If plants are unable
to revive themselves after watering, they have probably been damaged
by moisture retention. Moisture retention occurs due to excessive
watering, bad drainage, lacking drain holes in the pot, or soil
compaction. The water displaces the oxygen in the soil, creating
oxygen deficiency in the root area and causing the roots to begin
to rot. If this occurs, the plant can no longer be saved. As long
as the roots are not brownish in appearance (discoloration) and
rotting, the plant may be watered and fertilized until it dries
out and has outwardly revived itself. To prevent moisture retention,
ensure that there are drain holes in the pot, a sufficient drainage
layer, and a structurally stable substrate when repotting. Do
not place troughs and pots directly onto the soil, but ensure
that there is a small gap in between. During conditions of continuous
rain, it is better to place the plants under a roof. Some potted
plants, such as the agave, Erythrina crista-galli (coral tree),
Lantana camara, and Olea europaea (olive tree), have relatively
low water requirements even during very hot conditions.
Average Water Requirements:
In shady and wind-protected habitats
During cool and rainy weather conditions
Plants that are bedded out in the garden
Plants in large pots
Do not water plants in the blazing midday sun; the best time
to water is in the late morning or late afternoon. If possible,
do not wet leaves and blooms. Always use temperate water to water
plants. Cold tap water leads to root damage in the long run. Therefore,
always let the water sit for several hours before watering plants.
The quality of tap water is usually good and can be used for watering
without concern. Lime-sensitive plants, such as bog plants, Callistemon
(bottlebrush), camellias, and gardenias must always be watered
with rainwater. If these plants are watered using lime-containing
tap water, they will eventually be damaged. But a high lime content
is disadvantageous for other plants as well, because lime in the
soil also determines the phosphorus that is necessary for bloom
formation.
Like all living organisms, potted plants need nutrients to grow.
The better a plant grows, the more resistant it is against disease
and pests. Therefore, when caring for plants you not only have
to ensure that they have the right habitat and temperature and
sufficient water. During the growth period, you also have to fertilize.
In plant nourishment, we differentiate between main nutrients
(nitrogen (N), phosphate (P), sulfur (S), calcium (Ca), magnesium
(Mg), potassium (K)) and trace nutrients (copper (Cu), zinc (Zn),
boron (B), molybdenum (Mo), manganese (Mn), iron (Fe)). In contrast
to main nutrients, trace nutrients are only used in small quantities.
Fertilizing Correctly
Recently repotted plants are not fertilized in the first
six weeks. The potting soil contains sufficient fertilizer.
Always follow the dosage instructions of the fertilizer and
do not act according to the motto “the more the better.”
Most plants undergo a resting phase during the winter during
which they only grow a little and thus hardly need any nutrients.
These plants are fertilized in the period between the end of
April and August. The plants use the last weeks outdoors to
mature for the winter months, and their growth is strongly restricted.
If they are fertilized up until late fall, then they do not
overwinter well and are more susceptible to disease and pests.
Do not let fertilized plants dry out.
Do not encourage diseased plants to grow through fertilizer.
Do not fertilize plants until they have revived themselves.
In contrast to plants in the garden, potted plants have at their
disposal a very restricted root area. Because the plants do not
only grow above ground but continuously develop new roots, the
substrate in the pot becomes marbled and sapped after a certain
time. The plants need a larger pot and new substrate.
Substrate
High demands should be placed on the substrate. It not only gives
the plants footing, but it also supplies them with water, nutrients,
and oxygen through the roots. A qualitatively good substrate has
a balanced proportion of small cavities that store water and larger
cavities that drain excessive water and ensure air supply to the
roots. This loose, porous structure of the substrate must be retained
over a long period of time.
The Correct Time
The time when a plant needs to be repotted depends on various factors.
The best time is after the end of the rest period (March to May).
With increasing light, plants begin to grow again and start sprouting.
The biggest problems occur during overwintering of potted plants.
When selecting a plant, you should consider what wintering grounds
exist. Some potted plants can overwinter outdoors with the appropriate
precautions; others can overwinter in a cool room. But the wintering
grounds are not the only decisive factor for plant survival; correct
care of plants in the winter is also important. Correct care focuses
on the type of plant as well as on the habitat conditions that
the wintering grounds impose.
Putting Plants Away
In principle, the longer you wait to put plants away and the earlier
you take them out again, the shorter the time period that the plants
are exposed to unfavorable conditions. Many plants tolerate temperatures
at the frost line, especially when placed against a protective building
wall or under a roof.
The following are put away before the
first frost:
Botanical Name
English Name
Brugmansia
Angel’s Trumpet
Bougainvillea
Bougainvillea
Ensete
Banana Tree
Erythrina
Coral Tree
Tibouchina
Glory Tree
Starting at around - 5°C, the following are put away:
Botanical Name
English Name
Abutilon
Flowering Maple
Callistemon
Bottlebrush
Citrus
Citruses
Plumbago
Skyflower
At dry temperatures under about -10°C, the following are
put away:
Botanical Name
English Name
Aucuba
Gold Dust Plant
Eriobotrya
Medlar
Ficus carica
Fig Tree
Laurus
Laurel
Nandina
Heavenly Bamboo
Olea
Olive
Punica
Pomegranate
Before putting plants away:
The plants should not be too wet, because they need very little
water in the wintering grounds. A wet pot ball leads to root rot
and has cost many a potted plant its life. Moreover, wet plants
make transportation difficult.
Wintering Grounds
With the exception of plants that can overwinter outdoors with
the appropriate protection, all other potted plants require wintering
grounds that are ideally frost-free, bright, well-ventilated,
and equipped with temperature control (if possible) and protected
from direct sunlight. A greenhouse equipped with temperature control
is ideal, but typically not available. The winter garden is only
ideal as wintering grounds for potted plants if it is not heated
like a living space and has the appropriate ventilation and shade
facilities. Otherwise, on sunny winter days the room warms up
due to strong sunlight, and at night the temperature decreases
sharply. However, potted plants do not tolerate continuously changing
temperatures.
Most potted plants are first pruned after winter rest, starting
around February, mainly to rejuvenate them and achieve rich arborization.
With maintenance pruning, you remove dried out and dead branches
and shorten long branches. This encourages the plants to sprout
new shoots and grow in a more compact manner. For plants that
have a tendency to bald from the inside and with many deciduous
plants, you cut out the branches that are growing inwards
With increasing light intensity, longer days, and higher temperatures,
plants begin to sprout in the wintering grounds. That means you
have to water more frequently. If possible, place potted plants
in a bright but not too warm a location so that placing them outdoors
does not shock them. When the winter frost is over, you can place
the potted plants outdoors in reverse order of when you put them
away for the winter. First you put out the less frost-sensitive
plants. The correct acclimatization is important. The still delicate
leaves of the newly sprouted shoots are very sensitive to sun
and wind. Therefore, you should place the plants in a partially
shaded, wind-protected, and warm place. The same applies to newly
bought plants, which are suddenly placed outdoors from the optimal
habitat of the greenhouse.
Plants cannot live without light. But light requirements of potted
plants vary greatly. Information about the plants’ home
are important for orientation. In principle, you can divide plants
into three groups as regard their light requirements:
For example, these plants come from desert areas, from the Mediterranean,
and from the dry areas of Africa, Asia, and South and Latin America.
They need a very sunny habitat. In most cases, the darker the
habitat, the fewer blooms the plant has. In order to prevent damage
caused by direct and strong sunlight, you should place plants
with high light requirements in a partially shaded habitat when
they have just emerged from the wintering grounds or were recently
bought.
Plants with high light requirements are the following:
Botanical Name
English Name
Bougainvillea
Bougainvillea
Brugmansia
Angel’s Trumpet
Callistemon
Bottlebrush
Chrysanthemum
Chrysanthemum
Erythrina
Coral Tree
Lantana
Sage
Nerium
Oleander
Plumbago
Skyflower
Punica
Pomegranate
Plants with Average Light Requirements:
These plants live in slightly shaded areas of forests or at forest’s
edge. They thrive in partially shaded habitats that are not affected
by the blazing midday sun. This applies especially to plants with
large, soft leaves that evaporate much water in the midday sun and
would quickly wilt due to the limited water supply in the plant
vessel.
Plants with average light requirements are the following:
Botanical Name
English Name
Abutilon
Flowering Maple
Agapanthus
African Lily
Cestrum
Jasmine
Passiflora
Passion Flower
Pittosporum
Mock Orange
Solanum
Nightshade, among others
Tibuchina
Glory Tree
Plants with Low Light Requirements
These are very rarely found in the potted plant assortment. However,
some types of these plants do grow satisfactorily in partially shaded
areas.
Plants with low light requirements are the following:
The temperature is a decisive growth factor, but this can hardly
be regulated outdoors. In the natural habitat of our potted plants,
the average annual temperature is higher than the temperature
in our regions, thus here the temperature is a significant limiting
factor for growth. If temperatures in spring and early summer
are low, for example, and sunlight is not abundant, blooming is
delayed for summer and fall bloomers. Some plants don’t
bloom until they are in the wintering grounds, if they receive
enough light there (e.g., cassia). Others, such as the oleander,
don’t bloom at all under a certain temperature and don’t
bloom until the following season. The temperature is also decisive
for leaf and branch growth.
Potted Plants for Cool Summers
Botanical Name
English Name
Abutilon
Flowering Maple
Agapanthus
African Lily
Cestrum
Jasmine
Chamaerops
Fan Palm
Erythrina
Coral Tree
Fuchsia
Fuchsia
Laurus
Laurel
Nandina
Heavenly Bamboo
Plumbago
Skyflower
Solanum
Nightshade
Washingtonia
Desert Palm
Other plants only grow in high temperatures. They need hot summers
or very protected habitats in order to grow satisfactorily. Often
they only bloom in a winegrowing climate or in the city, which
stands out from rural areas by its favorable microclimate.
Potted Plants for Hot Summers
Botanical Name
English Name
Bougainvillea
ougainvillea
Callistemon
Bottlebrush
Citrus
Citruses
Nerium
Oleander
Strelitzia
Bird of Paradise
Often enough, a bad summer is followed by a fall with relatively
high temperatures. The consequence of relatively high temperatures
in the fall is undesired shoot growth. This is not good for potted
plants, because they need continuously decreasing temperatures
for their shoots to sprout and thus for their overwintering. The
result of the above-mentioned weather conditions is the drying
of the entire annual shoot, and sometimes additional fungal attacks
can cause problems in the wintering grounds.
In addition to sunlight, the wind affects the temperatures in
the respective habitat. The cooling effect of wind is unfavorable
for warmth-loving potted plants. Moreover, plants that are exposed
to wind evaporate significantly more water. Even abundant watering
cannot compensate for the disadvantages of a windy habitat. Plants
with large, soft leaves such as Angel’s Trumpet and the
banana plant suffer from dehydration and also become unsightly
because the leaves are damaged. Often, a strong wind gust is enough
to break off entire branches from plants with long, brittle branches,
such as the Skyflower. Large plants can be knocked down by the
wind when the plant pot has no corresponding weight.
The beauty of many potted plants cannot be displayed in rainy
summers. Skyflower, blooming oleanders, and other plants whose
blooms do not fall off by themselves become unsightly because
the blooms become brown and rot. However, what is worse is an
attack by various fungal infections after longer periods of rain
with relatively high temperatures.
