Leafy vegetables — what the family shares
Quick answer. In a leaf crop the harvested organ is the leaf, so nitrogen drives yield directly — this is the one family where the instinct to feed for growth is broadly correct. Two constraints define it instead: bolting, which ends useful production and is caused by heat rather than hunger, and food safety, because the edible part is the part in contact with anything applied.
What unites this family
The vegetative phase is the entire crop. There is no flowering stage to manage toward, no fruit to fill and no storage organ to bulk. That simplifies the nutrient question enormously — even, sustained, nitrogen-led supply with potassium support — and shifts the difficulty elsewhere.
Where it shifts to is timing and temperature. Every member bolts, and bolting is triggered by heat and day length. Since these are cool-season crops in a country with a long hot season, the practical skill in this family is choosing the window and sowing in succession, not designing a feeding programme.
Where its members differ — and why this page is not enough
Cutting patterns differ sharply. Lettuce may be a single head or a cut-and-come-again crop. Swiss chard and parsley are cut repeatedly over months, so removal is repeated and supply must continue. Coriander's window is so short that a heavy programme cannot act within it. Rocket is faster still. Parsley germinates slowly enough that its establishment is a distinct problem the others do not have.
Read the individual crop guide before acting. Two crops in this family can need opposite decisions about how long to keep feeding.
The mistake this family invites
Feeding to prevent bolting. Bolting is a temperature and day-length response; no nutrient delays it, and nitrogen applied to a bolting crop is spent on a stem you will not eat. The correct response is a different sowing date, shade, or accepting the end of the crop.
Crops in this family
- Lettuce
- Spinach
- Rocket
- Swiss chard
- Parsley
- Coriander
Each has its own guide in the crop library, filtered by family.
Food safety, specific to this family. The edible part is the leaf, in direct contact with anything applied to it. Do not use raw manure on leaf crops, and avoid foliar application to leaf destined for the kitchen. General yellowing on the OLDEST leaves suggests nitrogen; on the NEWEST leaves it more often reflects iron availability on calcareous soil. A visual symptom alone is not a confirmed diagnosis.
Sources
FAO — Fertilizer and Plant Nutrition Bulletin 16, Chapters 3, 4, 6 and 7. Accessed 27 August 2026. Family-level synthesis of the crop guides in this library; no rate, planting date or irrigation quantity is stated.
Last reviewed 27 August 2026