Nasturtiums bloom best in lean, poor-to-average, well-drained soil in full sun
Nasturtiums bloom best in lean, poor-to-average, well-drained soil in full sun. Rich soil or heavy nitrogen feeding pushes the plant into lush leaf growth at the expense of flowers, the familiar 'all leaves, few blooms'. Go easy on feeding, and do not fertilize except on very poor ground.
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
Rich soil and abundant nitrogen bias the plant toward vegetative leaf growth over flowering; lean, low-fertility soil shifts the same balance back toward bloom. It is the foliage-over-flower tradeoff that heavy feeding produces in many plants, here spending the plant on leaves at the cost of the flowers it was grown for.
What to do about it
Plant in average-to-poor, well-drained soil in full sun. Do not fertilize, and avoid nitrogen-rich feeding; reserve any feeding for very poor ground. The planner doesn't guess at fertilizer numbers.
How much it matters: No figure is stated. The penalty is foliage instead of flowers on an otherwise healthy, vigorous plant, which does not fail. Because feeding is the gardener's own choice, the rule only advises.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
Do not fertilize, except on extremely poor soil, as high rates of fertilization promotes leaf growth and reduces flowering.
It grows best in poor to average, well-drained soil in full sun, but with some afternoon shade in hot summers
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. "Nasturtiums bloom best in lean, poor-to-average, well-drained soil in full sun. Rich soil or heavy nitrogen feeding pushes the plant into lush leaf growth at the expense of flowers, the familiar 'all leaves, few blooms'. Go easy on feeding, and do not fertilize except on very poor ground." Evidence grade: Promising. https://milpa.garden/rules/nasturtiums-bloom-best-lean-poor-average-well/
A garden planner built on graded evidence. Every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.
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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.