How to Grow Gardenias in a Greenhouse

Gardenias can make impressive additions to a greenhouse collection.

Gardenias, a favorite among home gardeners, produce large blooms and a strong, sweet scent. Gardenias are best adapted to a hot outdoor climate, but they can also be grown successfully in a greenhouse. Although gardenias tend to wilt or rot under the wrong conditions, it is possible to produce healthy blooms, if the time is taken to create the particular growing conditions that gardenias need to thrive. With the right preparation and materials, you can grow healthy gardenias in a greenhouse.

Things You'll Need

• Well-draining potting soil
• Organic lime-free compost
• Draining tray
• Gravel
• Rainwater collection barrel
• Acidic Fertilizer (for lime-sensitive plants)

Instructions

1. Plant your gardenias in a mixture of well-draining potting soil and organic compost. Gardenia roots are sensitive to lime, so make sure that the compost is lime-free.

2. Place potted gardenias on a draining tray filled with gravel, and soak the gravel. Gardenias do best with frequent watering, but they need to drain well. Situate the gardenias so that they receive eastern exposure.

3. Water your gardenias every day or every other day, making sure that the draining gravel is kept moist. Because gardenia roots are sensitive to additives in water, use rainwater from a collection barrel to water gardenias. Alternatively, water gardenias with boiled or filtered water.

4. Fertilize gardenias once monthly from spring to autumn, using acidic fertilizer for lime-sensitive plants. Mix fertilizer with water in the proportion recommended by the fertilizer manufacturer, or use slightly less to prevent overfeeding. Over-fertilizing can result in the accumulation of excessive salts in the soil, damaging the gardenias. Since gardenias are related to azaleas, azalea food can be used as fertilizer.

5. Pinch off the dead tips after the gardenia plant has finished blooming. The removal of the tips promotes improved flowering during the following season.

6. Maintain the greenhouse climate at a high humidity level, with good ventilation--the most common cause of dropped buds in gardenias is insufficient humidity. However, avoid misting the leaves directly, as gardenias are prone to leaf spot fungi. Keep the greenhouse temperature between 68 and 74 degrees Fahrenheit during the day, and at 60 degrees overnight.

References

• Greenhouse Gardening: Gardenia
• University of Rhode Island Landscape Horticulture Program: Gardenia Care