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The palm lily, also known as the yucca palm, is generally robust and easy to care for. Nevertheless, it can also become ill, which manifests itself, among other things, in yellowish discoloration or spots on the leaves. The reasons for this can be very complex. Starting with unfavorable site conditions, through maintenance errors, to weather-related damage. If the cause of leaf spots is found quickly, major damage or even the loss of individual plants can usually be avoided.
Of the approximately 50 species of yucca, there are hardy varieties that can safely be planted in the garden and overwinter there, as well as insufficiently hardy ones that need a frost-free winter quarters. If a yucca shows discoloration or spots on the leaves, it is important not only to eliminate the symptoms, but to find the cause and remedy or combat it. However, stains or discoloration can have different causes that need to be found.
Too much wet
The most common cause is too much moisture. Almost all representatives of the yucca palm come from rather dry regions. As a result, they react very sensitively to a permanently wet root ball but also to high humidity. Root rot occurs, which is evidenced by fungus-like spots on the leaves. The palm lily in question only grows weakly, gradually withers and a musty smell is noticeable near the ground. In specimens that form a trunk, too much wetness can also manifest itself in the trunk base becoming soft and unable to absorb water or nutrients. Then you should act as soon as possible.
- stop watering the yucca immediately and keep the soil dry
- only water again when the soil has dried well and the surface is completely dry
- with potted plants, repotting is usually unavoidable
- cut out old soil and all rotten areas in the root area
- Thoroughly clean and disinfect pot
- Don't forget drainage on the bottom of the pot
- Always remove excess water from the saucer
- the substrate used should be well drained and structurally stable
Ideally, soil pH is between 6.0 and 7.0. Even if the substrate in the pot dries out faster than in the garden, it should only be watered sparingly to avoid waterlogging.
Tip: If the base of the trunk of the yucca palm is affected and muddy, it is usually too late. If there is one, you can cut off the healthy part of the trunk and try to use it to grow a new plant.
Unfavorable site conditions
If the yucca shows one or the other yellow or mottled leaf from time to time, this is completely normal. However, if this phenomenon occurs more frequently, it may be due to unfavorable site conditions, among other things. Locations with too little light are particularly problematic, although there are species that need a lot of light and those that can get by with less.
Many even tolerate the blazing midday sun without any problems. An exception are species of the yucca palm, which are kept exclusively as houseplants.
If a location that is too dark is the cause of leaf discoloration, it is usually sufficient to transplant the yucca to a lighter place. It is even easier with potted plants, which can change their location relatively easily. Houseplants should be in a sunny to semi-shady position and protected from the midday sun.
Mistakes are also often made during hibernation. Above all, if a palm lily is frost-free in a bucket over the winter, maintenance errors can cause yellow leaves and black or brown spots on the leaves, but these are usually not life-threatening for the plants, provided the respective defects are remedied as quickly as possible. The location in the winter quarters is usually too warm or the bale too wet, which means that almost all yucca palms react with discoloration of the leaves. Wintering in a warm living room is particularly disadvantageous.
Specimens that hibernate outside can suffer frost damage, which shows up as light spots (cold spots). Sometimes the trunk of the yucca palm becomes soft, bends and leaves and branches hang limp. This is possible because the trunks of these plants do not become woody. The culprit is usually insufficient frost protection for young and potted plants.
- Provide freshly planted specimens in the garden with light winter protection
- frost-hardy yucca palm in a bucket with appropriate protection overwinter outside
- put it in a place that is protected from rain and direct sun
- Wrap the planter in fleece and bubble wrap
- Place the pot off the ground on a wooden pallet or styrofoam
- This is to prevent the bale from freezing
- overwinter non-hardy potted plants in bright light at about 10 degrees
- water rarely and very sparingly
- Leaf spots usually disappear when temperatures rise again
- Trunk that is only soft and not squishy to raise again with a support
- they tend to recover when the weather warms up, provided the damage is not too severe
Tip: With the finger test you can test in winter whether the leaves are damaged or not. To do this, take an apparently damaged leaf between two fingers until this area has warmed up. If the spots are no longer visible afterwards, the tissue is healthy.
Nutrient deficiency or excess
Leaf spots can also be caused by an excess or deficiency of nutrients. Palm lilies, which you can buy in garden centers, are often in plant pots that are far too small and the yucca palm does not like narrowness in the root area at all. In addition, the nutrients are used up quickly here, resulting in a nutrient deficiency, which in turn causes the leaves to turn yellow. Equally harmful is an oversupply of nutrients, which usually occurs more frequently. As far as the nutrient requirements are concerned, palm lilies are basically very frugal.
A newly purchased palm lily should be repotted in fresh soil and, if necessary, a larger planter as soon as possible. Older potted plants should also be repotted regularly, about every 2-3 years, into larger pots and fresh soil. The best time for this is before the new shoots in early spring. If there is an undersupply, you should fertilize at fortnightly intervals during the growth phase until the plants have recovered.
Later it is sufficient to give potted plants a slow-release fertilizer once in the spring and to work horn shavings or granulated cattle manure into the soil in the garden once a month from March to July. In some cases, the garden does not even have to be fertilized at all. From August, fertilization will be completely stopped. Yellow and mottled leaves can be cut off. If too much fertilizer has been given, which mainly occurs with potted plants, affected plants should not be fertilized at all for a few weeks. In most cases, they recover relatively quickly.
Tip: Liquid fertilizer should always be given with the irrigation water and not on dry soil. Otherwise, the salts contained in the fertilizer could burn the roots.
leaf spot disease
The most threatening trigger for yellow leaves and black or brown spots on the leaves of otherwise problem-free plants is the so-called leaf spot disease. Plants that are already weak are mainly affected, with broad-leaved yucca palms being attacked particularly frequently. Fungal infestation is usually preceded by serious mistakes in care, such as too much moisture in the root area, insufficient drainage, humidity over 85 percent, a location that is too cold and insufficient ventilation. The leaf spots can vary in size, shape and color.
- The best and most effective protection is choosing the right location
- observe species-specific characteristics
- Remove heavily infested leaves and dispose of with household waste or incinerate
- do not throw in the compost
- Trade offers numerous sprays to combat it
- very effective and effective are systemic agents
- they are distributed throughout the plant via the sap stream
To avoid reinfection, copper preparations, e.g. green copper, can be injected as a precaution in October. This is repeated in winter and spring. In contrast to systemic agents, these are not absorbed by the plants. They remain on the surface and thus prevent the fungal spores from penetrating or germinating.