Oncidium orchids, often called “dancing lady orchids” for their distinctive flower shape, are celebrated for their vibrant, often fragrant, and abundant blooms. These captivating flowers emerge from a specialized structure known as a flower spike. Understanding how to identify and encourage the development of this spike is key to enjoying the full display of these rewarding plants.
Identifying an Oncidium Flower Spike
Distinguishing a developing flower spike from new vegetative growth is important. A new Oncidium flower spike typically emerges from the base of a mature pseudobulb, often nestled between the pseudobulb and a leaf. Initially, it may resemble a new root, appearing as a small, rounded tip. However, a spike grows upwards, appearing more pointed and spear-shaped, sometimes with a reddish tinge. New roots, in contrast, are usually rounded, white or silver (sometimes with green or red tips), and grow downwards or along the pot’s edge. While roots maintain consistent thickness, a developing flower spike elongates and often flattens slightly, indicating its potential to branch and form buds. Observing its growth direction and shape over a few days helps confirm its identity.
Promoting Oncidium Flower Spike Formation
Encouraging an Oncidium to produce a flower spike involves providing optimal environmental conditions.
Light
Light is a primary factor, with Oncidiums generally requiring bright, indirect light. An east, south, or west-facing window is often suitable, though south-facing windows may require sheer curtains to diffuse intense light and prevent leaf scorching. Adequate light intensity, typically 2,000-4,000 foot-candles or 4-6 hours of quality light daily, drives photosynthesis and influences blooming.
Temperature
Temperature plays a significant role in initiating spikes for many Oncidium varieties. A temperature differential between day and night, specifically cooler night temperatures, can trigger blooming. Ideal daytime temperatures range from 70-85°F (21-30°C), with nighttime temperatures dropping to 55-65°F (13-18°C). A consistent drop of about 10°F (5°C) at night is often sufficient to stimulate flowering.
Watering
Watering practices also influence spike formation. Oncidiums possess pseudobulbs that store water, but consistent watering is important during active growth. After a new pseudobulb has matured, slightly reducing watering by allowing the potting mix to dry out more can encourage spiking. However, complete drought stress should be avoided, as wrinkled pseudobulbs indicate insufficient water.
Fertilization
Fertilization supports overall plant health, which aids blooming. During active growth, a balanced fertilizer, like a 20-20-20, is often recommended. As flower spikes begin to form, switching to a bloom-booster formulation, such as a 10-30-20, can be beneficial. Dilute fertilizers to half or quarter strength and apply regularly during the growing season, avoiding winter dormancy. The plant must also reach maturity before consistently producing flower spikes.
Caring for a Developing Oncidium Flower Spike
Once a flower spike emerges, proper care ensures healthy development. Oncidium flower spikes can grow long and branch extensively, often requiring support. Staking is usually recommended when the spike reaches 6 to 12 inches, before buds form. Insert a slender bamboo stake into the potting medium, avoiding roots, for stability.
Gently secure the spike to the stake using orchid clips or soft twist ties, starting near its base and adding more clips as it grows. Avoid tightening ties too much, allowing movement and preventing damage. Positioning the orchid consistently in relation to its light source during spike development can encourage blooms to face a desired direction.
Maintaining consistent watering and fertilization is important as the spike develops and buds swell, as the plant needs energy for numerous flowers. Avoid overwatering, which can lead to root rot. Stable environmental conditions are important; sudden temperature fluctuations, cold drafts, or low humidity can cause developing buds to shrivel and drop, known as bud blast.
Post-Bloom Oncidium Flower Spike Management
After the vibrant display of flowers fades and blooms wither, manage the spent flower spike. Most Oncidium varieties will not re-bloom from the same spike; new spikes emerge from new pseudobulbs. Once all flowers have faded and the spike has dried and browned, remove it.
Using a sterilized cutting tool, such as pruning shears or a razor blade, cut the spent spike as close to the pseudobulb base as possible without damage. Sterilize tools before and after use to prevent disease. After removal, resume regular care, including watering and fertilization, to allow the plant to store energy for the next blooming cycle.
Troubleshooting Oncidium Flower Spike Issues
Oncidium orchids can encounter several issues related to their flower spikes, but many have straightforward solutions.
No Spike
If an Oncidium fails to produce a spike despite appearing healthy, common reasons are insufficient light or lack of day-to-night temperature differential. Ensure the plant receives enough bright, indirect light (4-6 hours daily) and experiences a temperature drop of about 10°F (5°C) at night. Maturity is also required for blooming.
Bud Blast
Bud blast, where buds dry up and fall off before opening, is common. It often results from sudden environmental changes like drafts, rapid temperature shifts, or low humidity. Inconsistent watering (too much or too little) can also lead to bud blast, as can exposure to ethylene gas from ripening fruit or certain chemical fumes. Maintaining stable conditions and consistent moisture helps.
Short Spikes or Limited Flowers
Short spikes or a limited number of flowers can indicate insufficient light intensity, preventing enough energy accumulation for robust blooming. Reviewing light and gradually increasing exposure can help. Nutrient deficiencies, especially phosphorus, might also contribute to poor blooming. A balanced fertilization regimen, with a bloom-booster fertilizer when spikes are forming, can address this.
Rotting Flower Spike
A rotting flower spike signals overwatering or fungal issues. Oncidiums are susceptible to root rot if potting medium remains soggy. Allowing the medium to dry slightly between waterings and good air circulation prevent excessive moisture. If rot is observed, cut out the affected portion with sterilized tools and adjust watering.