Anyone who grows Phalaenopsis orchids knows that autumn is their critical growth season. During this period, they not only grow new roots and strengthen their leaves, but also store up energy for winter flowering. The big question is: what kind of fertilizer should you give in autumn? Too much risks burning the roots, too little leaves them undernourished.
What Do Orchids Need in Autumn?
In summer, when temperatures are high, Phalaenopsis often enters a semi-dormant state and absorbs very little fertilizer. But once autumn temperatures drop to around 20–25°C (68–77°F), it enters its golden growth phase. If nutrients are lacking now, new leaves will be small and thin, and flower spikes may not emerge in winter. That’s why autumn feeding is all about supplying the right nutrients—not overfeeding.
Fertilizer Choices by Stage
Early Autumn (September–October): Growth Stage
Focus on fertilizers that promote root and leaf growth—so-called “growth fertilizers.” Choose a balanced NPK formula, such as 10-10-10 compound fertilizer, or diluted organic options like fermented soybean solution. Water-soluble fertilizers work well: simply add a little to your watering can, but keep the concentration light (e.g., if the label says 1:1000 dilution, use 1:1500). Always err on the side of caution—Phalaenopsis roots are tender and can burn easily.
Late Autumn (From Late October): Flowering Preparation
Once the plant starts preparing to send up flower spikes, it needs more phosphorus and potassium. Use fertilizers like monopotassium phosphate or blends with an NPK ratio of 1:3:2. Apply weekly, either as a foliar spray or soil drench. If spraying, avoid letting liquid collect in the crown to prevent rot.
Other Key Management Tips
Watering and Fertilizer Go Together
As an epiphytic orchid, Phalaenopsis roots need to breathe. Let moss or bark dry slightly before watering again. Always apply fertilizer with water—never on dry roots—or damage is guaranteed.
Temperature Control
Keep daytime temperatures around 20–25°C and avoid dropping below 15°C at night. Sudden fluctuations stress the plant and reduce nutrient absorption.
Light
Autumn sunlight is milder, so place plants near a window with gentle morning sun (before 10 a.m.). With enough light, photosynthesis turns fertilizer into usable energy. Keep them in the dark, and no amount of fertilizer will help.
Common Mistake to Avoid
More fertilizer does not equal faster growth. Orchids absorb nutrients slowly. Overfeeding in autumn leads to root rot, yellowing leaves, and even plant death. A friend once fertilized daily after National Day, and within two weeks the roots had turned black—beyond rescue.
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