Fertilising guide
How to fertilise Prairie Dock (Silphium terebinthinaceum)— schedule & NPK
Also called Prairie dock, Prairie rosinweed, Basal-leaved rosinweed.
More about prairie dock
About Prairie Dock
Silphium terebinthinaceum · also called Prairie dock, Prairie rosinweed · flowering
Silphium terebinthinaceum is a bold North American prairie native distinguished by enormous sandpaper-rough basal leaves (up to 60 cm / 24 in long) that remain near the ground while leafless, wiry flowering stems rise dramatically to 2-3 m (6-10 ft) in midsummer, bearing clusters of small yellow daisy flowers. Like all Silphium species it develops a deep taproot and is strikingly drought-tolerant but resents disturbance once established. The most important care fact is to site it where the impressive foliage can be appreciated and where its height will not shade shorter neighbours. Silphium species are not listed by the ASPCA as toxic to cats or dogs.
Growth habit: Clump-forming herbaceous perennial with very large basal leaves and tall, nearly leafless wiry flowering scapes rising well above the foliage.
Watch for — Wind rock and stem collapse: The tall, slender flowering scapes can be toppled by strong winds, especially in exposed sites or on overly fertile soils. Site in a sheltered position or use discreet staking; avoid rich soil that promotes weak, oversized stems.
What fertiliser prairie dock actually wants — and why
Prairie Dock is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.
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 prairie dock: 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 prairie dock, 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 prairie dock:
No routine fertilising needed; prairie-adapted plants grown in lean soil produce the most wind-resistant, upright stems. Rich soils cause excess height and floppy growth. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
The dormant-season rule matters more than the exact interval: skip feeding entirely when prairie dock 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 prairie dock
Half strength is the safe default for prairie dock — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
Feeding always goes onto already-damp soil, never dry roots — water prairie dock first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the prairie dock watering schedule.
Signs you are over-feeding prairie dock
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for prairie dock:
- Brown, crispy leaf tips and edges with no sign of underwatering.
- A white, crusty salt deposit on the soil surface or pot rim.
- Weak, pale, stretched new growth that flops.
- Lower leaves yellow and drop while the soil is correctly watered.
Signs you are under-feeding prairie dock
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full prairie dock care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of prairie dock with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Organic vs synthetic feeds for prairie dock
Organic options
A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.
Synthetic / liquid feeds
A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.
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 prairie dock — frequently asked questions
What fertiliser does prairie dock need?
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Prairie Dock is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
How often should I feed prairie dock?
No routine fertilising needed; prairie-adapted plants grown in lean soil produce the most wind-resistant, upright stems. Rich soils cause excess height and floppy growth. No routine fertilising needed; prairie-adapted plants grown in lean soil produce the most wind-resistant, upright stems. Rich soils cause excess height and floppy growth. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
What strength of feed for prairie dock?
Half strength is the safe default for prairie dock — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding prairie dock look like?
Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding prairie dock year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.
Should I flush the soil of prairie dock?
Flush the pot of prairie dock with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Keep reading
- Prairie Dock care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water prairie dock — 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 pheasant's tail grass
- How to fertilise blue hair grass
- How to fertilise prairie june grass
- All 10153 fertilising guides in the Growli library