Over-feeding a tomato with nitrogen grows a tall, dark-green, leafy plant that flowers late and sets little fruit
Over-feeding a tomato with nitrogen grows a tall, dark-green, leafy plant that flowers late and sets little fruit. The plant pours its resources into vines and foliage instead of blossoms, so flowering is delayed or sparse and yield drops. It's an imbalance between vegetative growth (leaves and stems) and reproductive growth (flowers and fruit), and it comes from how you fertilize. It is a different problem from the heat that makes already-open flowers fail to hold, so keep the two apart.
Promising A person has checked it against its sources. If you skip this, it still grows, just less well. The planner suggests it.
How it works
High available nitrogen biases the plant toward vegetative growth. Abundant nitrogen keeps it building leaves and stems, and that leaf-and-stem growth takes priority over the switch into flowering, so flower initiation is delayed and fewer flowers form. The visible result is lush dark foliage with reduced and later fruit set, with the growth spent on leaves and stems.
What to do about it
Go easy on nitrogen, especially before fruit set; do not feed a tomato a nitrogen-heavy fertilizer at planting and hold off feeding again until flowers and small fruit have appeared. Let a soil test say what the bed actually needs. The planner doesn't guess at NPK numbers.
How much it matters: No figure is stated. The penalty is delayed and reduced fruiting on an otherwise vigorous, healthy plant; because how much nitrogen goes on is entirely the gardener's to control, the rule only advises.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
Too much nitrogen is also a common problem, and can be identified when the plant is tall and dark green, with excessive growth and no blooming.
Too much nitrogen creates excessive vine growth, twisted foliage, delayed flowering and lower yield.
Plants it applies to
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Wording made clearer
- Wording made clearer
- Added to the rules
Cite this page
Milpa Gardens. "Over-feeding a tomato with nitrogen grows a tall, dark-green, leafy plant that flowers late and sets little fruit. The plant pours its resources into vines and foliage instead of blossoms, so flowering is delayed or sparse and yield drops. It's an imbalance between vegetative growth (leaves and stems) and reproductive growth (flowers and fruit), and it comes from how you fertilize. It is a different problem from the heat that makes already-open flowers fail to hold, so keep the two apart." Evidence grade: Promising. https://milpa.garden/rules/over-feeding-tomato-nitrogen-grows-tall-dark/
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.