Growing Oncidium Orchids in New Zealand

The Oncidium alliance includes numerous related genera such as Aspasia, Brassia, warm-growing Miltonias (often called Brazilian-type), the cool-growing Miltoniopsis, and many of their spectacular hybrids. This diversity means that with proper selection, virtually any New Zealand growing environment can accommodate many of the Oncidium orchids.

1. Light Requirements for Oncidium Orchids

Light requirements vary significantly across the Oncidium group, ranging from bright conditions to nearly full direct sunlight, depending on the specific species and varieties you're growing.

A. General Light Guidelines

Most Oncidium orchids thrive with one to several hours of direct sunlight daily. The key principle is that generally, thicker-leaved plants such as "mule-ear" and "equitant" Oncidiums can tolerate significantly more light than their thin-leaved counterparts.

B. Greenhouse Light Conditions

In greenhouse environments, provide 20-60% shade, equivalent to approximately 2,000-6,000 foot-candles (21,000-65,000 lux), depending on your specific Oncidium varieties.

C. Indoor Light Positioning

For home cultivation in New Zealand, east-facing, south-facing, or west-facing windows work ideally for most Oncidium orchids. The bright filtered sunlight available through these exposures supports healthy growth and flowering.

D. Artificial Lighting Options

Many Oncidium varieties adapt well to artificial lighting setups. Use four fluorescent tubes supplemented with incandescent bulbs, positioned 15-30cm above the plants for proper growth. Metal-halide and sodium-vapour bulbs also provide sufficient illumination without requiring close proximity to plants.

2. Oncidium Temperature Requirements

Oncidium orchids generally require intermediate to warm temperature conditions, making them well-suited to many New Zealand growing environments.

A. Standard Temperature Ranges

• Day Temperatures: 27-29°C
• Night Temperatures: 13-16°C

B. Heat Tolerance

Some of these orchids tolerate temperatures up to 35-38°C provided humidity levels and air movement increase proportionally with rising temperatures. This adaptability makes them excellent choices for New Zealand's occasionally hot summer conditions.

C. Seasonal Temperature Management

During New Zealand's summer months (December-February), ensure adequate ventilation and humidity during heat waves. Winter temperatures rarely present challenges for most Oncidium varieties, though protection from frost remains important for outdoor growing.

3. Water Requirements for Oncidium Orchids

Water requirements vary significantly among different Oncidium types, making it essential to understand your specific variety's needs.

A. General Watering Principles

Plants with large, fleshy roots or thick leaves typically require less frequent watering than thin-leaved or fine-rooted varieties. The media should be kept perpetually lightly moist like a wrung-out sponge for most varieties.

B. Watering Technique

Water thoroughly and allow the growing medium to dry at least halfway through the pot before watering again. This interval may range from every two days to every ten days, depending on New Zealand weather conditions, pot size and material, orchid type, and potting medium characteristics.

C. Seasonal Watering Adjustments

Plants not actively growing require reduced watering frequency. Many Oncidium species experience natural winter rest periods during New Zealand's cooler months (June-August), requiring significantly less water during this dormant phase.

D. Special Requirements for Thick-Leaved Types

Equitant and mule-ear oncidiums, as well as other fleshy-leaved or large-rooted plants, can be grown on slabs of cork bark or tree fern or in pots filled with a coarse, well-drained medium such as charcoal to provide the excellent drainage these types demand.

4. Oncidium Humidity Management

Oncidium orchids typically require moderate humidity levels, often less than many other orchid groups, making them relatively easy to accommodate in New Zealand home conditions.

A. Target Humidity Levels

Humidity should be between 30 to 60 percent. Many Oncidiums require less humidity than other orchids, making them forgiving for home cultivation.

B. Home Humidity Solutions

In the home, placing the plant above moist pebbles in a tray is ideal. This simple method effectively raises local humidity without affecting your entire home environment.

C. Air Circulation Importance

Ensure adequate airflow around your Oncidiums, especially when humidity levels exceed 75 percent or conditions become soggy. Good air movement prevents fungal problems and supports healthy growth.

5. Fertiliser Program for Oncidium Orchids

Regular fertilising proves essential while Oncidium orchids actively grow, supporting the development of strong pseudobulbs that fuel spectacular flowering displays.

Fertiliser Selection Based on Growing Medium

Establish a regular fertilising schedule for optimal Oncidium orchid health. Use a balanced fertiliser formulation such as Superthrive (Dyna-Gro) Orchid-Pro, or Superthrive (Dyna-Gro) GROW or similar fertiliser.

All SuperThrive fertilisers are formulated to contain 16 essential nutrients, including Calcium, which is missing from most store-bought fertilisers.

Use 1 mL to 1.5 litres of water once a week, all year round, and drench the potting mix thoroughly with the fertiliser solution.

6. Potting Oncidium Orchids

A. Optimal Repotting Timing

Repot when new growth reaches approximately half-mature size, typically occurring during New Zealand's spring months (September-November).

B. Potting Medium Selection

Choose a potting media grade based on your Oncidium's root characteristics:

• Fine-grade media: For fine-rooted varieties.
• Medium-grade media: Standard choice for most Oncidiums.
• Coarse-grade media: For large-rooted and thick-leaved varieties

We recommend using Kiwi Orchid Bark or Bio Leaf Orchid Potting Mix. They have been designed to hold a little bit of moisture while maintaining an open and airy structure. Orchid roots like a moist but not wet environment for their roots.

Repotting Technique

Position plants so the newest growth sits farthest from the pot edge, allowing maximum space for future growth before overcrowding occurs. Spread roots over a cone of potting medium, fill around the roots, and firm the medium gently but securely.

Post-Repotting Care

Maintain high humidity levels while keeping the potting medium dry until new roots establish. This period typically lasts 2-4 weeks, depending on growing conditions and season.

7. Oncidium Types and Varieties

A. Thin-Leaved Oncidiums

These varieties typically require more frequent watering, moderate light levels, and consistent moisture during growing seasons. Popular examples include many of the classic yellow "dancing lady" types.

B. Thick-Leaved Types (Mule-Ear and Equitant Oncidiums)

These robust varieties tolerate higher light levels, require excellent drainage, and prefer drying periods between waterings. Many perform excellently mounted on slabs or grown in very coarse media.

C. Miniature Varieties

Compact Oncidiums work beautifully for space-limited growing situations while maintaining the spectacular flowering characteristics of their larger relatives.

D. Intergeneric Hybrids

Modern breeding has created numerous intergeneric hybrids combining Oncidium characteristics with related genera, often resulting in improved vigour, extended flowering seasons, and enhanced adaptability.

8. Oncidium Seasonal Care Calendar for New Zealand

Spring (September-November)

• Ideal repotting period as new growth begins.
• Resume regular watering schedule.
• Begin an intensive fertilising program.
• Move outdoor plants to summer positions.

Summer (December-February)

• Maintain consistent moisture for actively growing varieties.
• Provide adequate shading and ventilation during hot periods.
• Continue regular fertilising schedule.
• Monitor for increased pest activity.

Autumn (March-May)

• Prepare for the flowering season as growth matures.
• Reduce watering frequency for varieties entering dormancy.
• Continue fertilising until growth completion.
• Begin transitioning outdoor plants to winter protection.

Winter (June-August)

• Peak flowering period for many varieties
• Reduce watering for dormant types
• Scale back fertiliser applications during low-light periods
• Maintain consistent temperatures and humidity

9. Common Problems and Solutions

A. Poor Flowering

Insufficient light remains the most common cause of poor flowering in Oncidiums. Gradually increase light levels and ensure adequate pseudobulb maturation before expecting flowers.

B. Accordion-Pleated Leaves

This condition typically results from irregular watering during new growth development. Maintain consistent moisture during active growth periods.

C. Root Problems

Overwatering in poorly draining media causes most root issues. Improve drainage and adjust watering frequency based on your specific variety's requirements.

D. Pest Management

Scale insects, mealybugs, and thrips can affect Oncidiums. Regular inspection and prompt treatment with appropriate controls maintain plant health.

10. Advanced Growing Techniques

A. Slab Culture

Many Oncidiums, particularly thick-leaved varieties, excel when mounted on cork bark or tree fern slabs. This culture method provides perfect drainage while mimicking natural epiphytic growing conditions.

B. Outdoor Summer Growing

Take advantage of New Zealand's mild summers by growing Oncidiums outdoors in protected locations. This provides excellent light, air circulation, and natural temperature fluctuations that promote flowering.

C. Division and Propagation

Divide mature plants with multiple pseudobulbs during repotting, ensuring each division retains at least 3-4 healthy pseudobulbs for reliable establishment.

Oncidium Growing Summary

Successful Oncidium orchid culture in New Zealand centres on understanding the tremendous diversity within this genus and selecting appropriate varieties for your specific growing conditions. These adaptable orchids thrive with bright light conditions (varying by type from moderate to nearly full sun), intermediate to warm temperatures between 13-29°C, careful attention to variety-specific watering requirements, moderate humidity levels of 30-60%, regular fertilising during active growth periods, and appropriate potting media selection based on root and leaf characteristics.

The key to Oncidium success lies in recognising that this diverse genus offers options for virtually every New Zealand growing situation, from windowsill culture to greenhouse cultivation. By matching specific Oncidium types to your available growing conditions and providing consistent care during active growth periods, you'll enjoy the spectacular "dancing lady" flower displays that make these orchids among the most rewarding to cultivate. Their relatively forgiving nature, combined with diverse flowering seasons and spectacular blooms, makes Oncidiums excellent choices for both beginning and experienced orchid enthusiasts throughout New Zealand.

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