Lovage (Levisticum officinale) is a perennial culinary herb in the Apiaceae family, related to celery, parsley and dill.
It can develop into a very large plant, with strongly aromatic leaves and stems, and this robust appearance can make lovage seem like a crop that simply benefits from more light and stronger environmental inputs.
Research does not support such a simple conclusion.
There is currently no scientifically established stage-by-stage PAR, DLI, CO₂ and VPD recipe for greenhouse lovage.
What researchers have studied directly is more useful: how lovage responds to different light intensities and spectra, how those treatments affect fresh and dry biomass, and how light treatments can change compounds such as rutin.
That gives growers a scientific basis for measurement without pretending that one precise environmental table applies to every greenhouse.
What Do We Actually Know About Lovage Light?
One of the most useful modern studies on Levisticum officinale was conducted in a controlled indoor production system.
Lovage was grown for 50 days under a baseline PPFD of approximately:
245 ± 12.5 µmol/m²/s
with a:
16-hour photoperiod
The corresponding DLI is approximately:
14.1 mol/m²/day
The chamber environment was maintained at approximately:
23°C during the day
18°C at night
with relative humidity around:
78% during the day
68% at night
and CO₂ around:
460 ± 60 ppm.
These are particularly valuable numbers because they come directly from a lovage experiment.
But they must be interpreted correctly.
They describe experimental growing conditions, not universal optimum settings for commercial lovage production.
Direct PPFD Testing in Lovage
The same research compared lovage under two PPFD levels:
135 µmol/m²/s
and:
223 µmol/m²/s
while also changing the proportion of green light in the spectrum.
With a 16-hour photoperiod, these PPFD levels correspond to approximately:
7.8 mol/m²/day
and:
12.8 mol/m²/day
respectively.
The results were more complicated than “more PAR equals more fresh weight.”
Total PPFD alone did not significantly affect fresh weight across the experiment.
At one spectral treatment, plants under the lower PPFD actually had greater fresh weight, but the researchers found that much of this difference was associated with higher tissue water content rather than greater dry biomass.
Under another spectral treatment, increasing PPFD increased dry weight.
That distinction is important for greenhouse growers:
Fresh weight, dry matter and visual plant size are not always measuring the same crop response.
A plant can appear heavier simply because its tissues contain more water.
Why “More Light = Better Lovage” Is Too Simple
The researchers also observed elongated growth under lower PPFD.
This is consistent with a plant adjusting its morphology to improve light interception.
At higher PPFD, the relationship between biomass and spectrum changed, showing that lovage response depended on both photon quantity and spectral composition, not simply one PAR number.
The researchers ultimately suggested approximately:
220 µmol/m²/s
under their particular spectrum as a useful treatment for balancing biomass and rutin production.
This is one of the strongest lovage-specific light reference points currently available.
But it should still be described as:
a result from a controlled experiment
rather than:
the universal optimum PPFD for lovage.
Earlier Lovage Research Used Much Lower Light
Another lovage experiment used only:
90 µmol/m²/s PPFD
with a:
16-hour photoperiod
That corresponds to a DLI of approximately:
5.2 mol/m²/day.
Plants were maintained at approximately:
23°C during the day
18°C at night
and:
70% relative humidity.
Lovage successfully grew under those conditions.
However, that study was focused on rutin analysis and LED treatments, not on determining maximum commercial yield.
So 90 µmol/m²/s should not be converted into a recommendation that lovage “only needs low light.”
What it does show is that lovage has been successfully cultivated across substantially different controlled-light environments.
Other Studies Used Much Higher PPFD
An additional series of experiments with lovage cultivar ‘Elsbetha’ used:
500–700 µmol/m²/s
for:
16 hours per day
with approximately:
25°C day / 18°C night
and:
75% relative humidity.
That corresponds to a very large DLI of approximately:
28.8–40.3 mol/m²/day.
But these experiments were designed to study elicitation, phenolic compounds and essential-oil-related quality characteristics.
They were not trials comparing 500–700 µmol/m²/s against lower PPFD to determine the optimum commercial light level.
This difference is critical.
If one paper successfully grows lovage at 90 µmol/m²/s and another successfully grows it at 500–700 µmol/m²/s, it would be incorrect to conclude that every number between them is an acceptable “recommended range.”
The experiments asked different questions.
What This Means for PAR Recommendations
The scientific literature therefore does not justify the original type of table that says:
- seedlings need 80–150 µmol/m²/s,
- young plants need 150–250,
- mature plants need 250–400,
- regrowth needs 220–350.
Those values may look practical, but they are not established lovage growth-stage requirements.
A more defensible interpretation is:
Around 135–245 µmol/m²/s has been studied directly in controlled lovage lighting experiments, while substantially higher PPFD has also been used in biochemical studies.
Growers should therefore use PAR measurement to compare their own canopy conditions and use crop response and DLI to determine whether light is limiting.
DLI Is Especially Useful in a Greenhouse
A greenhouse differs from a closed growth chamber because sunlight changes throughout the day.
Suppose the canopy measures:
220 µmol/m²/s
at noon on two different days.
One day may remain sunny for many hours.
Another may become cloudy shortly afterward.
The noon PPFD readings are similar, but the daily photon exposure can be very different.
That is why DLI is useful.
DLI integrates PAR over time and allows growers to compare:
- sunny and cloudy days,
- different greenhouse positions,
- different seasons,
- supplemental-light treatments,
- and conditions before and after harvest.
For a perennial herb such as lovage, long-term light monitoring can be more informative than chasing one instantaneous PPFD number.
What Does the Research Say About CO₂?
This is another area where the old article gives more precision than the research supports.
The current lovage-specific literature does not establish an optimum CO₂ enrichment concentration for different growth stages.
In the 50-day controlled-light experiment, lovage was grown at approximately:
460 ± 60 ppm CO₂.
The plants were therefore successfully cultivated without the 700–1,000 ppm concentrations previously presented as desirable for mature lovage.
However, this experiment was not designed to compare different CO₂ treatments.
So it would also be incorrect to conclude that 460 ppm is the optimum.
The scientifically accurate conclusion is:
Lovage-specific research currently provides very little evidence for an exact CO₂ enrichment target.
Should Lovage Be Enriched to 800 or 1,000 ppm CO₂?
There is currently insufficient lovage-specific evidence to say that it should.
CO₂ enrichment can enhance photosynthesis in many C3 crops when sufficient light and other resources are available, but the magnitude of the response depends on the crop and environment.
For lovage, the first practical question should therefore be:
Is CO₂ actually becoming depleted around the active canopy?
If greenhouse CO₂ remains near outdoor ambient concentration, simply increasing it to an arbitrary target is not automatically justified.
If a dense canopy in a relatively closed greenhouse causes CO₂ to fall significantly during bright periods, measurement can reveal that limitation.
That is a much better basis for deciding whether enrichment is useful.
What About VPD?
There is currently no strong body of research establishing an optimum VPD range specifically for lovage.
The 50-day controlled-environment study provides a useful reference condition.
Using its reported air temperatures and relative humidity, the approximate air VPD was around:
0.6–0.7 kPa
assuming leaf temperature was close to air temperature.
Again, this is a derived description of the experiment, not a demonstrated optimum.
The researchers did not compare lovage under 0.6, 1.0 and 1.3 kPa to identify the best VPD.
Therefore claims such as:
“0.8–1.2 kPa produces ideal mature lovage”
or:
“high VPD makes lovage aroma harsh”
are not supported by current lovage-specific evidence.
VPD Is Still Useful
Removing an unsupported VPD target does not mean VPD is irrelevant.
VPD helps describe atmospheric drying demand.
As temperature rises or relative humidity falls, VPD usually increases, which can increase potential water loss from leaves.
For growers, VPD is therefore useful when interpreted together with:
- root-zone moisture,
- irrigation frequency,
- leaf temperature,
- air movement,
- radiation,
- and plant size.
A large mature lovage canopy may use much more water than a small seedling even when the greenhouse VPD is identical.
So VPD should be used as a plant-water-balance measurement, not as a direct indicator of aroma quality.
Does VPD Control Lovage Aroma?
There is currently insufficient evidence to support that claim.
Lovage is strongly aromatic because its tissues contain volatile compounds and essential oils.
Research has shown that the composition of lovage essential oils changes between different plant organs and can also change with harvest timing.
Studies have identified major volatile constituents including compounds such as α-terpinyl acetate, β-phellandrene and phthalides, with composition varying between leaves, stems, flowers and seeds.
That supports the idea that lovage aroma chemistry is biologically variable.
But it does not establish:
high VPD → harsh aroma
or:
moderate VPD → cleaner aroma.
Those claims should therefore be removed.
Light Can Affect Secondary Metabolism
There is, however, real evidence that light treatment can influence lovage phytochemistry.
Rutin is an important flavonoid found in lovage.
In the controlled lighting research, PPFD and spectrum interacted with rutin accumulation.
The researchers observed that approximately 223 µmol/m²/s combined with a higher proportion of green light produced useful biomass and rutin results.
They also tested supplementary UV-B.
A short treatment of:
1 W/m² UV-B for 5 hours
increased rutin content by approximately:
80% compared with the control
under that experimental protocol, while longer exposure did not produce the same response.
This is an excellent example of why environmental responses should not be simplified.
More radiation is not necessarily better, and treatment duration matters.
UV-B Did Not Increase Lovage Fresh Weight
The same research found no significant fresh-weight increase from supplementary UV-B treatment.
Its major effect was on secondary metabolism rather than general biomass production.
That distinction is useful for controlled-environment growers.
A lighting treatment can influence:
- fresh weight,
- dry weight,
- morphology,
- or secondary metabolites,
and these responses do not necessarily move in the same direction.
So “better growth” must always be defined.
Lovage Can Tolerate Sun and Partial Shade
Outside controlled-environment research, horticultural references generally describe lovage as capable of growing in full sun to partial shade and preferring moist, well-drained soil.
It is a large perennial that can ultimately reach around 1.5–2.5 m in height.
This again fits the research evidence:
Lovage is not a plant with one narrow instantaneous PAR requirement.
It can adapt to different light environments, but its morphology and biochemical composition may change as those conditions change.
A Better Research Reference Table
Instead of presenting invented growth-stage targets, use actual lovage experiments as reference points.
| Lovage research condition | Light | Environment | What it actually tells us |
|---|---|---|---|
| Controlled LED cultivation | 245 ± 12.5 µmol/m²/s, 16 h; ~14.1 DLI | 23/18°C, RH ~78/68%, CO₂ 460 ± 60 ppm | Successful 50-day controlled cultivation |
| Light-intensity experiment | 135 vs 223 µmol/m²/s | Controlled environment | PPFD and spectrum interacted; fresh and dry biomass responses differed |
| Earlier LED study | 90 µmol/m²/s, 16 h; ~5.2 DLI | 23/18°C, RH 70% | Lovage can grow at substantially lower PPFD |
| Elicitation / phytochemical study | 500–700 µmol/m²/s, 16 h | 25/18°C, RH 75% | High PPFD was used successfully, but was not tested as the commercial optimum |
| UV-B experiment | Supplemental UV-B before harvest | Controlled environment | Short UV-B treatment changed rutin but not fresh weight |
These studies should not be merged into one numerical “perfect lovage recipe.”
Their research objectives were different.
What About Repeated Harvest?
Lovage is commonly harvested for its leaves and can regrow after cutting.
However, current research does not provide a scientifically validated post-cut formula such as:
PAR 220–350 + CO₂ 600–900 + VPD 0.9–1.3 kPa.
That degree of precision is not supported.
Instead, post-harvest regrowth should be monitored using the same principles as the main crop:
- measure canopy PPFD,
- track DLI,
- maintain adequate root-zone moisture,
- monitor temperature and humidity,
- watch CO₂ during active photosynthesis,
- and observe the rate and quality of new leaf production.
If regrowth becomes weak, the measurements can help determine whether light, water or greenhouse climate changed after cutting.
Sensor Position Matters as Lovage Grows
Lovage can develop a tall, spreading canopy.
A PAR sensor left permanently below or above the active leaf layer may no longer describe the light the crop is actually receiving.
For useful comparisons:
measure PPFD near the active canopy and adjust sensor height as plants grow.
Temperature and humidity sensors should also represent the crop zone rather than only the greenhouse roof environment.
CO₂ can vary with air movement and canopy density, so measurements near the crop can reveal conditions that a distant controller may miss.
A Practical Greenhouse Lovage Monitoring Workflow
A scientifically defensible lovage strategy does not require complicated environmental recipes.
1. Measure canopy PAR
Use PPFD measurements to determine whether one location receives substantially more light than another.
2. Track DLI
Compare total light between days instead of judging the crop from one noon measurement.
3. Record temperature and humidity
Calculate or monitor VPD to understand changes in atmospheric water demand.
4. Monitor root-zone moisture
Lovage generally performs best with consistent moisture, so interpretation of VPD should include water availability.
5. Check CO₂ during strong photosynthesis
Determine whether CO₂ becomes depleted before deciding whether enrichment is necessary.
6. Compare crop response with environmental records
If leaf size, biomass or regrowth changes, compare the change with recorded PAR, DLI, temperature, humidity and CO₂ rather than attributing it immediately to one variable.
What Should Growers Actually Optimize?
Current lovage research supports a few clear principles.
Do not assume stronger light always produces better fresh biomass.
Fresh weight and dry weight can respond differently because tissue water content changes.
Treat approximately 220–245 µmol/m²/s as a useful research reference, not a universal optimum.
Direct lovage experiments have produced useful biomass and phytochemical results around this level.
Do not prescribe high CO₂ without evidence.
Modern lovage experiments have successfully grown plants close to ambient CO₂, and lovage-specific CO₂ optimization studies are limited.
Use VPD as a measure of atmospheric water demand rather than an aroma-control setting.
There is no strong evidence that a precise VPD determines whether lovage tastes or smells “harsh.”
Recognize that crop quality includes more than biomass.
Light spectrum and short stress treatments can affect compounds such as rutin even when fresh weight does not increase.
Key Takeaway
Lovage is a good example of why precise-looking greenhouse recipes can be misleading.
The current research does not show that seedlings, mature plants and regrowth each require one exact PAR, CO₂ and VPD range.
Instead, direct Levisticum officinale research shows that plants have been successfully grown under very different PPFD levels.
A modern controlled study grew lovage at approximately 245 µmol/m²/s for 16 hours, equivalent to about 14.1 mol/m²/day, with CO₂ close to ambient concentration.
Direct comparison of 135 and 223 µmol/m²/s showed that fresh weight, dry weight, water content and spectrum interacted — demonstrating that “more PAR” does not translate into one simple growth response.
Research also shows that light treatment can change rutin accumulation without necessarily increasing fresh biomass.
For greenhouse growers, the stronger approach is therefore to:
measure canopy PAR, track DLI, monitor temperature, humidity and CO₂, maintain adequate root-zone water, and evaluate biomass and quality separately.
That produces a much more defensible picture of lovage growth than a fixed four-stage environmental recipe.
References
Thoma, F., Schlehuber, D., Somborn, A., Keuter, V. et al. (2023). How does supplementary green light and UV-radiation affect biomass and rutin content in Levisticum officinale? Frontiers in Sustainable Food Systems.
Wack, M. et al. (2022). Cultivation of Lovage under Exposure of Light-Emitting Diode Illumination and Analysis of Rutin Produced by HPLC and UV-Vis.
Złotek, U. et al. (2019). Antioxidative and potentially anti-inflammatory activity of phenolics from lovage leaves elicited with jasmonic acid and yeast extract.
Effect of Jasmonic Acid, Yeast Extract Elicitation, and Drying Methods on the Main Bioactive Compounds and Consumer Quality of Lovage. (2020).
Influence of Harvesting Time on the Composition of Volatile Components in Different Anatomical Parts of Lovage. (1998). Journal of Agricultural and Food Chemistry.