In Isparta, rose harvesting often begins before the surroundings are fully illuminated by daylight. Harvesters enter the rose gardens in the very early morning and carefully pick the fully opened flowers by hand.
This long-established practice is not simply a matter of tradition or working convenience. The cool and humid conditions of the early morning can help protect the volatile compounds found in oil-bearing rose flowers.
However, one common misconception must be corrected:
The essential oil within a rose flower does not suddenly disappear when the sun rises or the clock reaches 10:00 a.m.
Temperature, relative humidity, sunlight, wind, and the time elapsed after harvesting can all affect the flowers. As the day progresses, the loss of certain volatile compounds may increase, but this process occurs gradually and varies according to environmental and post-harvest conditions.
Rose Academy Learning Objectives
By the end of this article, you will understand:
- Why oil-bearing roses are traditionally harvested early in the morning
- How the loss of volatile compounds may occur
- Why dew is considered important during rose harvesting
- How temperature can affect rose flowers
- What the 10:00 a.m. recommendation actually means
- Why harvested flowers should be processed without unnecessary delay
Where Is Essential Oil Found in an Oil-Bearing Rose Flower?
Rosa damascena Mill., commonly associated with the Isparta rose, derives its characteristic fragrance from the volatile compounds present in its flowers. A substantial proportion of these compounds is found in the pink petals.
According to Baydar, petals account for approximately 65% of the fresh weight of an oil-bearing rose flower. However, they contain approximately 80% of the flower’s essential oil (Baydar, n.d.).
The term “volatile” refers to substances that can evaporate relatively easily under suitable conditions. For this reason, harvested oil-bearing rose flowers should not be left in warm environments for extended periods.
Why Are the Early Morning Hours Important?
During the early morning, conditions are generally characterized by:
- Lower air temperatures
- Higher relative humidity
- Weaker solar radiation
- Dew that has not yet fully evaporated
- Petals that are cooler than they would be at midday
These conditions may be more favourable for preserving the volatile compounds in the flowers. As the sun rises, both the air and the flower surface begin to warm. With increasing temperatures, some volatile constituents may evaporate more readily into the surrounding air.
The principal purpose of early harvesting is therefore to collect the flowers under the coolest and most favourable practical conditions available.
Must Roses Always Be Harvested Before Sunrise?
It would be too absolute to state that roses must always be harvested before sunrise.
From a scientific perspective, sunrise alone does not determine the ideal harvesting conditions. Several factors must be considered:
- Air temperature
- Flower temperature
- Relative humidity
- Whether the dew has dried
- Intensity of sunlight
- Wind conditions
- Stage of flower opening
- Time between harvesting and processing
Baydar recommends harvesting rose flowers very early in the morning, before the dew on the flowers has dried, and completing the harvest no later than approximately 10:00 a.m. (Baydar, n.d.).
The expression “before sunrise” is therefore a traditional and effective way of emphasizing how early the harvest begins. A more scientifically precise explanation would be:
Oil-bearing rose flowers should be harvested during the cool morning hours, before the dew has completely dried and before temperatures rise substantially.
Why Is Dew Important?
Dew forms when water vapour in the air condenses into small droplets on flower surfaces that have cooled overnight.
The presence of dew on roses in the morning generally indicates:
- Cool overnight conditions
- High morning relative humidity
- Flower surfaces that have not yet warmed significantly
Baydar reported that flowers harvested before the dew had dried could provide a higher essential oil yield (Baydar, n.d.).
This finding must, however, be interpreted correctly. It does not mean that dew droplets enter the rose and create new essential oil. Instead, dew is primarily a visible indicator of the cool and humid environmental conditions that may help preserve volatile compounds.
Correct Interpretation
Cool, dew-covered morning conditions may be favourable for preserving volatile constituents.
Incorrect Interpretation
Dew enters the rose flower and directly increases or creates essential oil.
The available source does not support the second statement.
How Does Temperature Affect Volatile Compounds?
As their name suggests, essential oil constituents include substances that can evaporate and disperse into the air. Their tendency to evaporate may increase as temperatures rise.
According to Baydar, temperatures of approximately 5–20°C are considered favourable during the flowering season of the oil-bearing rose. Daytime temperatures above 20°C may create less favourable conditions for maintaining essential oil content. Drought and high temperatures may also increase the loss of volatile constituents from the petals (Baydar, n.d.).
This does not mean that the essential oil disappears immediately when the temperature exceeds 20°C. Rather, it means that the probability and rate of volatile-compound loss may increase as temperatures rise.
The extent of this loss may also be affected by:
- How long the flowers remain exposed to high temperatures
- Relative humidity
- Wind speed
- The degree to which the flowers have opened
- How the flowers are transported after harvesting
- Whether harvested flowers are compressed or properly ventilated
What Changes as the Sun Rises?
As the sun rises, several related changes occur in the rose garden:
- Air temperature increases.
- The surface of the petals begins to warm.
- Dew droplets evaporate.
- Relative humidity generally decreases.
- Some volatile compounds may evaporate more readily.
- Flowers may continue to open and gradually begin to lose freshness.
These changes do not occur at the same rate every day. On a cool, cloudy morning, dew may remain on the flowers for a longer period. On a hot, dry, and windy day, warming and volatile-compound loss may begin earlier and proceed more rapidly.
The ideal harvest period should therefore be assessed according to the day’s weather conditions, not solely according to the clock.
What Happens After 10:00 a.m.?
The time of 10:00 a.m. is not a fixed biological threshold at which the essential oil suddenly disappears. It should instead be regarded as a practical upper limit traditionally recommended for harvesting under the conditions of Isparta.
According to the data presented by Baydar:
- Flowers harvested early in the morning may yield approximately 0.04% essential oil.
- Flowers harvested in the afternoon may yield approximately 0.02% essential oil.
- An early-morning harvest may therefore require approximately 2.5 tonnes of flowers to produce one kilogram of rose oil.
- An afternoon harvest may require approximately five tonnes of flowers to produce one kilogram of rose oil (Baydar, n.d.).
In these examples, the difference in essential oil yield is approximately twofold. These figures should not, however, be interpreted as fixed results that apply to every garden and every harvesting day.
Essential oil yield can vary according to:
- The elevation of the rose garden
- Weather conditions
- The stage of the harvesting season
- The degree of flower opening
- Growing conditions
- Post-harvest waiting time
- The distillation method and operating conditions
Rose Academy Note
It is incorrect to say that flowers harvested in the afternoon contain no essential oil. A more scientifically accurate statement is:
Rose flowers harvested in the afternoon still contain essential oil. However, because temperatures rise and environmental conditions change during the day, their obtainable essential oil yield and chemical composition may differ from those of flowers harvested early in the morning.
Are Essential Oil Content, Yield, and Quality the Same?
Although these concepts are related, they do not have the same meaning.
Essential Oil Content
Essential oil content refers to the percentage of oil present in, or measured through the distillation of, a specified quantity of flowers.
Essential Oil Yield
Essential oil yield refers to the total quantity of oil obtained in practice from a specified quantity of rose flowers.
Essential Oil Quality
Essential oil quality concerns more than quantity. It also includes the identities of the chemical constituents and their relative proportions within the oil.
Obtaining less oil from a quantity of flowers is a matter of yield. Changes in the proportions of citronellol, geraniol, nerol, and various hydrocarbons concern the oil’s chemical composition.
For this reason, rose oil is evaluated not only according to how much oil is obtained, but also according to which constituents it contains and in what proportions.
Why Should Harvested Roses Not Be Left Waiting?
Once a rose flower is removed from the plant, it does not immediately become biologically inactive. Biological and enzymatic processes may continue in its tissues for some time.
Overfilling large sacks, compressing the flowers, or leaving them in direct sunlight can lead to:
- Heat accumulation among the flowers
- Crushing and bruising of the petals
- Reduced air circulation
- The beginning of undesirable fermentation
- Loss of volatile compounds
- Changes in the chemical composition of the resulting essential oil
Roses must therefore not only be harvested early but also transported properly and processed as soon as reasonably possible.
What Happens During the First Six Hours?
Baydar recommends distilling harvested flowers without unnecessary delay and within no more than six hours after harvesting.
When flowers are spread over a clean surface and held briefly in a cool, shaded, and well-ventilated environment, significant essential oil loss may not occur during the first six hours. The source also reports that certain enzymatic effects may sometimes produce a modest increase in measurable essential oil content during this period (Baydar, n.d.).
This does not mean that deliberately holding flowers for six hours will always improve the result. The outcome may vary depending on:
- Ambient temperature
- The depth or thickness of the flower layer
- Air circulation
- Humidity
- Whether the flowers have been crushed or damaged
The safest practical approach is to transport freshly harvested roses under suitable conditions and process them without unnecessary delay.
What Happens When Flowers Are Held for More Than 12 Hours?
Baydar reported that the essential oil yield of flowers held for more than 12 hours could decrease by approximately 20%.
The following changes in essential oil composition were also reported:
- An increase in citronellol
- An increase in paraffins
- A decrease in geraniol
- A decrease in nerol
According to the source, the proportions of citronellol and paraffins could increase to approximately twice their initial levels, while geraniol and nerol could decrease to approximately half of their initial levels under the conditions examined (Baydar, n.d.).
These changes are important because post-harvest waiting time may affect not only the total quantity of essential oil obtained but also its aroma profile and chemical composition.
Holding Rose Flowers at Temperatures Above 25°C
Baydar indicated that the loss of essential oil may begin to accelerate when harvested flowers are held at temperatures above 25°C.
Under these conditions:
- Essential oil loss may accelerate.
- The proportion of citronellol may increase.
- The proportions of certain paraffins and stearoptenes may increase.
- The proportions of geraniol and nerol may decrease.
Once again, 25°C should not be interpreted as a precise temperature at which the essential oil disappears. It indicates comparatively unfavourable holding conditions under which volatile-compound loss and compositional changes may occur more rapidly.
How Should Flowers Be Protected If They Cannot Be Processed Immediately?
The best practice is to deliver harvested flowers to the processing facility as soon as possible.
If short-term holding is unavoidable:
- Do not leave the flowers in direct sunlight.
- Select a cool, shaded area.
- Prevent unnecessary heat accumulation.
- Do not compress or crush the flowers.
- Allow adequate air circulation.
- Use clean, production-appropriate surfaces or containers.
- Keep the waiting period as short as possible.
Baydar indicated that fresh flowers may be spread over a clean surface in a cool and shaded environment for up to six hours. In commercial cosmetic, food, or related production, applicable hygiene and processing requirements must also be observed.
Common Myths and Misconceptions
“Rose essential oil disappears completely when the sun rises.”
Incorrect. The essential oil does not disappear suddenly. Rising temperatures and changing humidity conditions may gradually increase the loss of certain volatile compounds as the day progresses.
“No essential oil remains in the flower after 10:00 a.m.”
Incorrect. The 10:00 a.m. recommendation is a practical upper limit for completing the harvest under typical regional conditions. Flowers harvested later in the day still contain essential oil, although the obtainable yield may be lower.
“Dew gives the rose flower additional essential oil.”
Not scientifically established. Dew is primarily an indicator of cool and humid morning conditions. It does not create new essential oil within the flower.
“Harvesting roses early is all that matters.”
Incorrect. Some of the benefits of early harvesting may be lost if the flowers are subsequently left in a warm environment for an extended period.
“Waiting affects only the amount of essential oil.”
Incorrect. Post-harvest waiting time and temperature may affect both essential oil yield and chemical composition.
From Harvest to Distillation
A carefully managed journey from the rose garden to the distillation facility involves the following steps:
- Identify flowers that have reached an appropriate stage of opening.
- Begin harvesting during the cool early-morning hours.
- Collect the flowers before the dew has completely dried.
- Separate damaged, bruised, or unsuitable flowers.
- Transport the harvested flowers without excessive compression.
- Do not leave them in direct sunlight or a warm environment.
- Whenever possible, process them without delay and within a few hours.
- Monitor transportation and holding conditions as carefully as the harvest time itself.
Key Takeaways
The primary purpose of harvesting oil-bearing rose flowers early in the morning is to preserve their volatile compounds under the most favourable practical conditions.
During the morning, the air is generally cooler, relative humidity is higher, and the surface of the flowers has not yet warmed significantly. As the day progresses, temperatures rise, dew evaporates, and the loss of some volatile constituents may accelerate.
The time of 10:00 a.m. does not represent a point at which essential oil suddenly disappears. It is a practical time guideline intended to prevent harvesting from continuing into the warmer part of the day. Actual results may vary according to weather, the rose garden, the developmental stage of the flowers, and post-harvest handling.
Early harvesting alone is not sufficient to support high-quality production. Flowers must also be transported and processed without excessive compression, heat exposure, or unnecessary delay.
Frequently Asked Questions
Should rose flowers be harvested before sunrise?
Beginning the harvest before sunrise is a common and beneficial practice. Scientifically, however, the main objective is to collect the flowers during the cool morning hours before temperatures increase substantially.
Does the essential oil disappear after 10:00 a.m.?
No. Essential oil does not disappear completely after 10:00 a.m. However, as the day progresses, essential oil yield may decline and the relative proportions of certain constituents may change.
Why are dew-covered rose flowers preferred?
Dew is a visible indicator of cool and humid morning conditions. These conditions may help preserve the volatile compounds within the flowers.
How much difference can there be between morning and afternoon harvesting?
According to the values presented by Baydar, flowers harvested early in the morning may yield approximately 0.04% essential oil, while flowers harvested in the afternoon may yield approximately 0.02%. These figures may vary according to growing, environmental, harvesting, and processing conditions.
How long can harvested roses be held before processing?
Whenever possible, the flowers should be processed without delay and within six hours. Brief holding under cool, shaded, clean, and well-ventilated conditions is not equivalent to holding flowers in a hot, compressed, or sun-exposed environment.
What can happen if flowers are held for more than 12 hours?
Essential oil yield may decrease, and the chemical composition of the oil may change. Baydar reported that holding flowers for more than 12 hours could result in an essential oil yield reduction of approximately 20% under the conditions examined.
Is it appropriate to hold harvested flowers in sacks?
Holding flowers for an extended period in tightly packed, warm sacks is not recommended. Such conditions can cause heat accumulation, reduced air circulation, crushing, and undesirable fermentation.
Conclusion
Early-morning rose harvesting represents more than a beautiful regional tradition. It is an important agricultural practice intended to help preserve the quality and volatile composition of oil-bearing rose flowers.
Cool temperatures, higher relative humidity, the presence of dew, and weaker solar radiation create comparatively favourable harvesting conditions. Scientific explanations must nevertheless avoid exaggeration: the essential oil within the flower does not suddenly disappear at sunrise or precisely at 10:00 a.m.
Instead, environmental conditions change progressively throughout the day, and the risk of volatile-compound loss may gradually increase.
The scientifically responsible approach can therefore be summarized as follows:
Oil-bearing roses should be harvested during the cool morning hours and processed as soon as possible without being compressed, overheated, or left in direct sunlight.
Successful production depends not only on when roses are harvested, but also on how they are handled, transported, held, and processed after leaving the garden.
References
Baydar, H. (n.d.). Yağ gülü tarımı ve endüstrisi [Oil-bearing rose cultivation and industry]. Süleyman Demirel University, Faculty of Agriculture, Department of Field Crops.
Baydar, H., & Göktürk Baydar, N. (2001). Yağ gülünde (Rosa damascena Mill.) verim ve kalite üzerine hasat dönemi, distilasyon için bekleme süresi ve distilasyon aşamalarının etkisi [Effects of harvesting period, waiting time before distillation, and distillation stages on yield and quality in oil-bearing rose]. Proceedings of the IV Field Crops Congress, 117–122.
Baydar, H., & Baydar Göktürk, N. (2005). The effects of harvest date, fermentation duration and Tween 20 treatment on essential oil content and composition of industrial oil rose (Rosa damascena Mill.). Industrial Crops and Products, 21, 251–255.
Baydar, H., Kazaz, S., & Erbaş, S. (2013). Yağ gülünde (Rosa damascena Mill.) morfogenetik, ontogenetik ve diurnal varyabiliteler [Morphogenetic, ontogenetic, and diurnal variations in oil-bearing rose]. Süleyman Demirel Üniversitesi Ziraat Fakültesi Dergisi, 8(1), 1–11.
Kazaz, S. (1997). Hasat zamanı ve hasat sonrası bekleme süresinin yağ gülünde (Rosa damascena Mill.) yağ miktarı ve kalitesine etkileri üzerine bir araştırma [A study of the effects of harvest time and post-harvest waiting time on essential oil quantity and quality in oil-bearing rose] [Master’s thesis, Süleyman Demirel University].
Kazaz, S., Erbaş, S., & Baydar, H. (2009). The effects of storage temperature and duration on essential oil content and composition of oil rose (Rosa damascena Mill.). Turkish Journal of Field Crops, 14(2), 89–96.