VPD Targets for Each Tomato Stage
VPD and Calcium Uptake in Tomatoes
One of the most practical reasons to manage VPD precisely in tomato cultivation is calcium transport. Calcium moves through the plant via the xylem stream — the same flow driven by transpiration. When VPD is too low, transpiration slows, calcium delivery to rapidly growing fruit tips is reduced, and blossom end rot (BER) appears.
Maintaining VPD above 0.7 kPa during fruiting ensures enough transpirational pull to move calcium into developing fruit. This is especially critical in fast-growing cherry tomato varieties where the fruit-to-leaf ratio is very high.
Frequently Asked Questions
What is the ideal VPD for tomatoes?
Tomatoes perform best at VPD 0.7–1.1 kPa during vegetative growth and 1.0–1.4 kPa during fruiting. Unlike some crops, tomatoes tolerate a wider VPD range and can still produce well at up to 1.5 kPa if irrigation is consistent and temperatures are not excessive.
What temperature and humidity should I use for indoor tomatoes?
Target 22–26°C (72–79°F) during the day with 60–70% relative humidity for vegetative growth. During fruiting, reduce humidity slightly to 55–65% to encourage fruit set and reduce botrytis risk. Night temperatures 4–6°C lower than day temperatures improve fruit sugar content.
What causes blossom drop in tomatoes — is VPD a factor?
Yes. Very high VPD (above 1.8 kPa) combined with high temperatures is a leading cause of blossom drop in tomatoes. Pollen becomes non-viable above 35°C or when VPD is extreme. Maintaining VPD below 1.5 kPa during flowering significantly reduces blossom drop.
Does VPD affect tomato fruit size and quality?
VPD directly influences calcium uptake in tomatoes, which affects fruit quality. Low VPD reduces transpiration, which reduces calcium movement to growing fruit, causing blossom end rot. Maintaining VPD above 0.7 kPa during fruit development ensures adequate calcium transport.
How does VPD differ for cherry tomatoes vs. beefsteak tomatoes?
Cherry tomatoes generally tolerate slightly higher VPD (up to 1.5 kPa) and are more drought-tolerant than large-fruited varieties. Beefsteak and heirloom varieties benefit from more conservative VPD management (0.8–1.2 kPa) to prevent cracking and maintain fruit size.