The genus of the screw trees (Pandanus) comprises over 600 species. They are sometimes referred to as pandans or screw palms, although they have nothing in common with other palm trees. These species belong to the screw tree family and originally come from warmer regions of the eastern hemisphere. They are native to numerous islands in the Indian Ocean and the Mascarene Islands. Here the plants colonize coastal areas and develop impenetrable vegetation.
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Pandans are evergreen plants with a tree or shrub shape. They grow persistently and form single or multi-branched trunks that partially lignify with age. When the humidity is very high, screw trees develop aerial roots. With the help of these roots growing freely to the ground, the plants absorb moisture from the air. They make the actual trunk appear broad. The plants reach heights of growth of more than 100 centimeters.
Over time, small side shoots develop on the trunk, which you can cut off with a sharp knife and use as offshoots. In some species, the shoots develop tiny roots on the trunk. To support wound healing, you can dust the cut on the trunk with a little charcoal. The dust absorbs moisture and has a disinfectant effect at the same time, so that the development of diseases is prevented.
The leaves of the screw trees are in a dense forest at the end of the trunk. The leaf blade goes directly into a leaf sheath. Both central ribs and leaf margins are occupied by thorns. The large leaves are simply structured and drawn out in a ruler shape. They hang over so that screw trees look like palm trees. Due to their triple spiral arrangement, the upper part looks twisted, which is why the plants got their German name.
Pandans develop male and female flowers that differ in shape. While the male cobs are multi-branched, female cobs appear simple. In indoor culture there is very seldom flower development. Birds and insects are responsible for pollination. Mainly screw trees are pollinated by the wind.
After successful fertilization, screw trees develop stone fruits, which consist of several chambers. There are numerous tiny seeds in each chamber. There are a few species like Pandanus utilis that develop edible fruits.
With their picturesque growth, screw trees are used for interior greening. Because of their demands, they are only suitable for planting in pots. Pandans decorate pot gardens and tropical warm houses. The plants line artificially created waterfalls and grottos in tropical baths.
Perfect neighbors for screw trees:
- Antler fern
- Flamingo flowers
- Elephant ear
Which location is suitable?
Screw trees prefer a hot and humid climate. They thrive in a bright place with several hours of sunshine every day. Pandans are able to grow well when they get sun during the morning and afternoon hours. The plants cannot tolerate the blazing midday sun. If you cannot meet these conditions, you should use a plant lamp (€ 28.43 on Amazon *). Screw trees require a minimum illuminance between 900 and 1,000 lux.
What soil does the plant need?
Screw palms thrive in a slightly acidic substrate with a pH between 5.5 and 6.5. If you use commercially available compost-based potting soil, the pH value should be in this range. Deviating values lead to unhealthy growth. Mix the soil with peat or coconut fiber, sand or perlite to ensure optimal water and nutrient regulation.
With a self-made mixture you prevent rapid substrate compaction. This saves you time as there is no annual repotting. Mix all ingredients together thoroughly and check the pH with indicator strips or a pH meter. If the value is too low, you can increase it by adding soil. A value above 6.5 can be lowered with acidic peat or humus substrate.
This is what goes into the substrate mix:
- three to five parts conventional potting soil
- 1.5 to three parts clayey soil
- a part of quartz sand (14.90 € at Amazon *) or perlite
Screw tree in the pot
Screw trees can be grown hydroponically or planted in pots. Since the plants become top-heavy over time and tend to tip over, you should choose a heavy pot. You can also place the planter in a larger planter and cover it with stones. Planters with an irrigation system (€ 69.29 at Amazon *) are ideal alternatives to conventional pots.
If the thermometer does not drop below 15 degrees Celsius at night, you can put the screw tree on the balcony. Gradually get the crop used to the outside conditions by moving it to more shady spots first. After a few days it can move to its final place in the light penumbra. The more light the tree receives, the more intense the leaf markings become. In dark locations the leaves remain dark green.
Increase screw tree
The simplest method of propagation is the cutting off and potting of the Kindel, with which screw trees reproduce vegetatively. The offshoots are put into the ground or placed in a water-filled vase. Use a blue colored glass, because this supports the root formation. When growing in soil, the humidity is crucial for successful rooting. Use it in a mini greenhouse or put a foil over the container. It takes between four and six weeks for the offshoot to form roots.
- Get young plants used to the indoor air over the next two weeks
- remove the foil a little longer every day
- Water moderately over the next two months
Water screw tree
When screw trees are in the growth phase, they need to be watered regularly. The ball of the pot should be constantly moist. The exotic plants tolerate neither drought nor waterlogging. Let the substrate dry on the surface before each casting unit. Watering is more economical in winter so that the roots do not fall dry. Use soft water at room temperature. Stale tap water is just as suitable as clean rainwater. As the leaves dry up quickly and turn brown if the humidity is too low, you should spray the plant daily.
Fertilize the screw tree properly
Between spring and summer, the screw tree enjoys fertilization every two weeks. Use a liquid complete fertilizer for green plants in low concentration. An excessive supply of nutrients leads to faster growth. You can keep your pandans small with a sparing dosage.
Cut the screw tree correctly
You can cut off the tuft of leaves from the screw tree if branching is desired. Unsightly and out-of-shape plants are cut down by half. Screw trees can be pruned into the old wood. Use a sharp knife for non-woody shoots. Woody parts of the plant are cut off with secateurs. If the shoot is very thick, you can use pruning shears.
Regularly remove dead leaves and be careful not to damage the aerial roots. You can regularly remove the secondary shoots that develop on the trunk and use them to multiply. If the Kindel stay on the trunk and grow there, the plant increases significantly in size.
How do I transplant properly?
When the supporting aerial roots grow irregularly and the plants lean towards one direction, it is time to repot. The plant needs a larger container, which provides more stability. Like all green plants, screw trees are repotted in spring. Once the plants have reached their final size, they are no longer repotted. It is enough if you cover the roots on the surface with fresh substrate.
Between October and March, growth stagnates, so there is less watering and fertilizing the plant. Watering is necessary when the upper layer of soil has dried. One to two fertilizations are sufficient during the winter. You can put the bucket in a cool bedroom. The temperature should not drop below 16 degrees Celsius.
Sucking pests occur on screw trees that are improperly cared for or cultivated under suboptimal site conditions. Rapid control is necessary so that the plant is not damaged too much.
Occasionally, fine cobwebs can be seen in the leaf axils and between the thorns on the leaf margin. They indicate an infestation by spider mites, which prefer to spread when the room air is too dry. The infected leaves show yellowish-white to silver-colored spots with a slight pest infestation. Severely damaged leaves turn gray-brown in color until they dry up completely.
Shower off infected plants and rub the undersides of affected leaves with a cloth. Put a large sack or a transparent box over the plant so that the humidity is very high for the next three to four days. The spider mites are killed by the moist microclimate.
Mealybugs and mealybugs
These pests are more common on screw trees. Small white webs, reminiscent of cotton balls, indicate an infestation. The leaves turn yellow and become wrinkled. They are covered by a sticky film that provides fungal spores with optimal growth conditions. Neem oil supplements have been shown to be effective control agents.
Pandanus species unfold their full effect in tall vessels, because here the leaves can hang far down. Also place the vessel on a shelf. If the plant is on the ground, the leaves lie on top and look unsightly.
- Pandanus veitchii: leaves dark green with light vertical stripes, up to 100 centimeters long. The most commonly cultivated pandanus species.
- Compacta : Pandanus veitchii variety with 50 to 60 centimeter long leaves, whitish marginal strips and clear vertical stripes.
- Aureus : Pandanus baptistii variety with a short stem. Leaves striped yellow-green, reminiscent of grass lilies.