Welcome to the Vineland DLI report for December, 2025!
In December, Vineland received 33% less light than in November, 2025.
Read on for the detailed data report and more information about our DLI data collection project.
Only looking for certain information? Use the table of contents to navigate between sections:
DLI Data for December, 2025
Figure 1: Monthly DLI data for Vineland is presented in 2 two graphs. Graph A) represents the average monthly DLI ± standard deviation. Graph B) represents the median monthly DLI and variability in the data using two ranges: the interquartile range (middle 50%) and the outer range (80% of data).
A)
B)
Table 1: Monthly DLI data for Vineland
| Month and Year (number of days of data) | Average ± standard deviation (mol/m2/day) | Median (mol/m2/day) |
| December, 2025 (30 days) | 8 (±4) | 7 |
| November, 2025 (29 days) | 12 (±5) | 12 |
| October, 2025 (21 days) | 25 (±11) | 27 |
| September, 2025 (17 days) | 44 (±10) | 47 |
| August, 2025 (20 days) | 47 (±16) | 52 |
Figure 2: Daily (24 hr period) DLI data for Vineland for December, 2025
Table 2: Daily (24 hr period) DLI data for Vineland for December, 2025
| Date (day/month/year) | DLI (mol/m2/day) |
| 01-Dec-25 | 12.6 |
| 03-Dec-25 | 3.2 |
| 04-Dec-25 | 12.2 |
| 05-Dec-25 | 14.7 (max. DLI for December) |
| 06-Dec-25 | 4.4 |
| 07-Dec-25 | 7.4 |
| 08-Dec-25 | 12.6 |
| 09-Dec-25 | 5.1 |
| 10-Dec-25 | 3.6 |
| 11-Dec-25 | 13.6 |
| 12-Dec-25 | 12.6 |
| 13-Dec-25 | 8.4 |
| 14-Dec-25 | 13.1 |
| 15-Dec-25 | 7 |
| 16-Dec-25 | 6.6 |
| 17-Dec-25 | 4.6 |
| 18-Dec-25 | 12.8 |
| 19-Dec-25 | 4.2 |
| 20-Dec-25 | 5.4 |
| 21-Dec-25 | 7.4 |
| 22-Dec-25 | 9.4 |
| 23-Dec-25 | 3.7 |
| 24-Dec-25 | 13.8 |
| 25-Dec-25 | 7.3 |
| 26-Dec-25 | 1.8 (min. DLI for December) |
| 27-Dec-25 | 2.1 |
| 28-Dec-25 | 2.6 |
| 29-Dec-25 | 9.4 |
| 30-Dec-25 | 8.3 |
| 31-Dec-25 | 7.2 |
| December, 2025 DLI average ± standard deviation | 8 (±4) |
Project Background
We mounted a daily light integral (DLI) meter on the border of Leamington and Kingsville, Ontario, in 2024, and another DLI meter at the Vineland Research and Innovation Centre (VRIC) in Vineland, Ontario, in 2025 to give greenhouse producers in those areas access to publicly available light data.
The Vineland data is available on this blog. If you are interested in the Leamington-Kingville data, you can download the excel sheet at the bottom of this post or visit the ONGreenhouseVegetables blog for more details.
Daily light integral (DLI) data is important to greenhouse production because it measures the amount of light that is available to the crop. This data can be used to adjust the growing environment, such as irrigation and carbon dioxide levels, to optimize photosynthesis and crop yield.
DLI is the total amount of light within the photosynthetically active radiation (PAR) spectrum (light wavelengths of 400-700 nm) that impacts a surface in a day. It is measured in moles per metre squared per day (mol/m2/day).
The data provided in this blog reflects the amount of outdoor light. The amount of light that greenhouse crops receive inside a greenhouse can be significantly lower (90-50%) and is affected by the cover material (clear glass, diffused glass, single polyethylene, double polyethylene, triple polyethylene, etc.), cover material treatment (whitewash), and curtains (shade, energy, blackout, etc.). The DLI required is different for each crop.
Purpose
The DLI Data section of this blog provides greenhouse producers in the Niagara Region, Ontario with outdoor light levels on a regular basis year-round. It is meant to serve as a record of the amount of light this location received on a daily basis throughout the year.
Each blog post in this section contains tables with the available data for a one-month period and an Excel file with data from previous months.
NOTE: This data is provided for information purposes and does not represent the amount of light at other locations.
Materials and Methods
The data was collected using a DLI-600 sensor from Apogee Instruments. It measures the extended PAR (ePAR) spectrum (400-760 nm), which includes far red light. There are two sensors, both are placed 90 cm off the ground. One sensor is located outside of a greenhouse near the Leamington-Kingsville border in Ontario. The other is located at the Vineland Research and Innovation Center in Vineland, Ontario.
Available DLI data is presented for each month in Figure 1 (A & B) and Table 1, for each day (24 hr period) of the current month in Figure 2 and Table 2, and it is all available to download in the attached Excel sheet below.
DLI and PPFD data Excel sheets
Tell us what YOU want
WE want your feedback!
If we can present or interpret this data in a different way that would be more beneficial to you, please let us know. If you have questions, comments or any feedback at all, please comment on this post or email:
Kathryn Russell, OMAFA Greenhouse Floriculture Specialist: kathryn.russell@ontario.ca
Dr. Fadi Al-Daoud, OMAFA Greenhouse Vegetable Specialist: fadi.al-daoud@ontario.ca