How to Grow Roses – Rose Greenhouse Guide
Roses are an extremely popular crop. You can find rose gardens and potted roses almost everywhere in the world. They’re also a common consumer crop, sold in various forms, including cut flowers, shrub roses, and bare root roses.
In this guide, our experts detail how to grow roses in a greenhouse, or other controlled environments. They dive into the ideal temperature, humidity, and other climate conditions for successful rose cultivation. Using these tips, you can grow high-quality roses, while minimizing diseases, mold, and crop loss.
The tips detailed in this guide are useful for most types of roses. These include hybrid tea roses, climbing roses, grandiflora roses, miniature roses, and more.
What Are the Ideal Growing Conditions for Roses?
Roses are perennial plants. A single rose bush can live for years. In fact, some varieties have a lifespan reaching several decades.
However, most growers consider springtime the traditional growing season for roses. As in most climates, roses bloom in the spring. This is true outdoors. But roses can bloom year-round in a greenhouse, or other controlled environment, where growers can replicate spring conditions.
It’s also important to note that roses prefer plenty of light. At least 6 hours of full sunlight is ideal, as long as it doesn’t get too hot. You can recreate this artificially as well, using lighting, such as LED grow lamps.
Rose care is also important when it comes to optimizing yields. To promote flowering, many rose growers lightly prune their rose bushes in the late winter and early spring. Pruning roses helps by removing dead organic matter and diseased canes. It triggers new growth and stimulates blooming.
What Is the Ideal Temperature for Rose Greenhouses?
As a perennial plant, roses are quite hardy and can survive in a wide range of temperatures. However, in order to promote growth and flowering, it’s best to maintain an optimal temperature range.
For most rose varieties, the ideal temperature range is around 65-75°F during the day (18-24°C), and 60-70°F overnight (15-21°C).
Lower temperatures may lead to your roses going dormant, as they would during the winter. Higher temperatures, reaching 85°F (29°C) and above, can lead to heat stress. This materializes in leaf scorch, wilting, and leaf loss.
Ideal Temperatures for Rose Cultivation:
- Daytime – 65-75°F (18-24°C)
- Nighttime – 60-70°F (15-21°C)
What Is the Ideal Humidity for Greenhouse Rose Cultivation?
As with most plants, humidity plays a major role in growth, flowering, and disease prevention. As a crop grown for its beauty, it’s important for the flowers to be vibrant, saturated, and blemish-free.
Humidity control is therefore highly important in rose greenhouses. The correct humidity range stimulates growth and optimal flowering and uniformity.
Fortunately, in a controlled environment, such as a greenhouse or glasshouse, you can create and maintain the ideal humidity. This allows growers to produce the highest quality roses possible.
The ideal relative humidity range for roses is around 70-80%. In terms of VPD, that’s 0.4-0.9 kPa during the day, and 0.35-0.75 kPa overnight.
These ranges are optimal for rose growth, development and blooming. However, it also helps in preventing diseases and molds that are common to rose production. Diseases such as powdery mildew can be devastating to rose bushes. Fortunately, you can completely prevent them by maintaining the correct humidity range.
Ideal Relative Humidity & VPD for Rose Cultivation:
- Relative Humidity – 70-80% RH
- Daytime VPD – 0.4-0.9 kPa
- Nighttime VPD – 0.35-0.75 kPa
How to Create Ideal Humidity in a Rose Greenhouse
Rose greenhouses are naturally humid. Like all plants, they transpire constantly, evaporating water into the air. This inevitably leads to high humidity, reaching 100% relative humidity, in any closed space. Of course, high humidity slows growth, reduces flower quality, and leads to various diseases and molds.
Most traditional rose greenhouses reduce humidity by ventilating and heating. The ventilation removes the humid air, while the heating maintains an ideal temperature range.
However, heating and venting is highly inefficient. Removing humid air from the greenhouse also removes large amounts of heat. Growers then need to compensate for this heat loss, through more and more heating. Naturally, constant heating leads to high energy costs.
In addition to being inefficient, heating and venting may also be completely ineffective, in certain circumstances. Humid, rainy, or cold weather, as well as dark and cloudy days, often make ventilation redundant. If it’s not much drier outside than inside, ventilating won’t help reduce moisture in the greenhouse.
Using Dehumidifiers to Control Humidity
So, fully controlling humidity, at all times, at a high efficiency level, requires active dehumidification. Dehumidifiers like DryGair remove large amounts of moisture, specifically in a greenhouse space, by design. They do so actively, using patented circulation fans, combined with a condensation-based dehumidification system. This makes them incredibly efficient and effective at controlling humidity in commercial greenhouses and grow rooms.
Keeping your rose greenhouse closed and using dehumidifiers to control humidity, ensures ideal growing conditions, regardless of weather conditions. It also ensures a low energy input to achieve this task. Trials and grower experiences show energy savings of 50% on average, compared to traditional heating and venting.
Rose growers, Van der Hulst, in the Netherlands, save 35% on gas, for example. The company uses 24 DG-12 units in their advanced rose greenhouses.
Using Air Circulation to Improve Rose Production
Another important aspect of humidity control is air circulation. Proper airflow between the plants helps to disperse any pockets of humidity that may build up. This is a crucial factor in preventing mildew development, while also stimulating the plants and promoting optimal development.
All DryGair models include a patented air circulation module. DG units utilize powerful fans, with a unique 360° dispersal, that ensures uniform conditions throughout the greenhouse. Uniform growing conditions increases flower uniformity as well as quality, helping growing produce consistently beautiful roses.
