Fertilising guide
How to fertilise Butterhead Lettuce (Lactuca sativa var. capitata)— schedule & NPK
Also called Butterhead Lettuce, Boston Lettuce, Bibb Lettuce, Cabbage Lettuce.
More about butterhead lettuce
About Butterhead Lettuce
Lactuca sativa var. capitata · also called Butterhead Lettuce, Boston Lettuce · edible
Butterhead lettuce forms loose, rounded heads of soft, buttery-textured leaves with a mild, sweet flavour. Among the easiest lettuces to grow, tolerating heat better than crisphead types. Quick to mature (45–60 days), ideal for succession sowing in containers and raised beds. Popular varieties include 'Buttercrunch', 'Tom Thumb', and 'Marvel of Four Seasons'. Favoured in both US and UK kitchen gardens.
Growth habit: Low, compact rosette forming a soft, loose head; shallow fibrous root system
Watch for — Tip burn (calcium deficiency / poor translocation): Brown, papery leaf edges, especially on inner leaves, caused by rapid growth in heat or low humidity impairing calcium uptake — not a soil deficiency. Improve airflow, water consistently, avoid high-nitrogen feeds, and harvest promptly when heads are full.
What fertiliser butterhead lettuce actually wants — and why
Butterhead Lettuce feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for butterhead lettuce: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed butterhead lettuce, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For butterhead lettuce:
Apply a balanced liquid fertiliser at half strength every 2–3 weeks. Nitrogen encourages leafy growth but excess causes rapid bolting in heat. In fertile garden soil, no feeding may be necessary. In containers, regular feeding is essential as nutrients leach quickly. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
The dormant-season rule matters more than the exact interval: skip feeding entirely when butterhead lettuce is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for butterhead lettuce
Follow the crop-feed label rate for butterhead lettuce — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
Feeding always goes onto already-damp soil, never dry roots — water butterhead lettuce first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the butterhead lettuce watering schedule.
Signs you are over-feeding butterhead lettuce
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for butterhead lettuce:
- Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen).
- Lush foliage hiding the crop; soft growth prone to pests and disease.
- Salt crust on the soil and scorched leaf edges in containers.
Signs you are under-feeding butterhead lettuce
- Pale, yellowing lower leaves and stunted growth.
- Small fruit, poor set, and a quickly exhausted plant.
- Blossom-end rot and weak cropping from erratic or insufficient feeding.
If the symptoms point at watering, light or roots rather than nutrition, the full butterhead lettuce care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
In containers, fertiliser salts build up fast — water butterhead lettuce thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Organic vs synthetic feeds for butterhead lettuce
Organic options
Garden compost or well-rotted manure dug in before planting, plus a liquid comfrey or seaweed feed once fruiting starts. UK: comfrey feed or organic Tomorite; US: Espoma Tomato-tone or Neptune's Harvest. Builds soil and feeds in one.
Synthetic / liquid feeds
A balanced feed at planting then a high-potash tomato feed in fruiting — UK: Growmore at planting then Tomorite (Levington) or Phostrogen; US: a balanced 10-10-10 then Miracle-Gro Tomato or a bloom booster.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising butterhead lettuce — frequently asked questions
What fertiliser does butterhead lettuce need?
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen. Butterhead Lettuce feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
How often should I feed butterhead lettuce?
Apply a balanced liquid fertiliser at half strength every 2–3 weeks. Nitrogen encourages leafy growth but excess causes rapid bolting in heat. In fertile garden soil, no feeding may be necessary. In containers, regular feeding is essential as nutrients leach quickly. Apply a balanced liquid fertiliser at half strength every 2–3 weeks. Nitrogen encourages leafy growth but excess causes rapid bolting in heat. In fertile garden soil, no feeding may be necessary. In containers, regular feeding is essential as nutrients leach quickly. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
What strength of feed for butterhead lettuce?
Follow the crop-feed label rate for butterhead lettuce — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
What does over-feeding butterhead lettuce look like?
Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen). Lush foliage hiding the crop; soft growth prone to pests and disease. Salt crust on the soil and scorched leaf edges in containers. Staying on a high-nitrogen feed once butterhead lettuce starts flowering is the classic error — you get a huge leafy plant and a disappointing crop. Switch to high-potash the moment flowers appear.
Should I flush the soil of butterhead lettuce?
In containers, fertiliser salts build up fast — water butterhead lettuce thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Keep reading
- Butterhead Lettuce care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water butterhead lettuce — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise turnip 'hakurei'
- How to fertilise turnip 'golden ball'
- How to fertilise turnip 'oasis'
- All 6887 fertilising guides in the Growli library