Repotting guide

When & how to repot Canadian Lousewort (Pedicularis canadensis)

Also called Canadian lousewort, Wood betony, Forest lousewort, Lousewort.

More about canadian lousewort

About Canadian Lousewort

Pedicularis canadensis · also called Canadian lousewort, Wood betony · flowering

Pedicularis canadensis is a spring-blooming hemiparasitic perennial native to open woodlands, prairie edges, and mesic forests from Quebec and Manitoba south through the eastern US to Texas and Florida. Its finely divided, fernlike foliage and tight spikes of hooded yellow to reddish-purple flowers emerge from April through June; it taps the roots of surrounding grasses and forbs for supplemental water and minerals while still photosynthesising its own sugars. Because it is a hemiparasite, it must be grown alongside suitable host plants — native bunchgrasses and prairie forbs are ideal — and it resents transplanting once established. It contains alkaloids and phenylpropanoid glycosides and is classified as mildly toxic to pets.

Mature size: 20–45 cm (8–18 in) tall in flower; basal rosette spreads 15–30 cm (6–12 in).

Watch for — Failure to thrive without a host: Plants grown in sterile, isolated soil without neighbouring grasses or forbs for root attachment are short-lived and produce little flower. Establish a community planting with native bunchgrasses, little bluestem, or prairie sedges before or alongside sowing seed.

How to tell canadian lousewort needs repotting

Repotting on a calendar is less reliable than reading the plant. For canadian lousewort, watch for these signs:

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for canadian lousewort) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot canadian lousewort

Only every 2–4 years, when genuinely crowded. Canadian Lousewort is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. Low clump-forming perennial; produces a basal rosette of deeply pinnate-lobed leaves and an upright flowering stem in spring, dying back to the ground by midsummer..

What size pot to step canadian lousewort up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Canadian Lousewort positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping canadian lousewort into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot canadian lousewort

Early spring, just as new growth restarts, is the ideal window for canadian lousewort. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting canadian lousewort

Confirm it actually needs it. Slide canadian lousewort out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip canadian lousewort out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh loamy, humus-rich, moist, well-drained, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water canadian lousewort again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for canadian lousewort

Canadian Lousewort wants loamy, humus-rich, moist, well-drained. Thrives in the slightly acidic to neutral forest loams of its native habitat; amend heavy clay with leaf mould to improve drainage, or lighten sandy soils with compost to retain adequate moisture. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting canadian lousewort — frequently asked questions

How often should you repot canadian lousewort?

Only every 2–4 years, when genuinely crowded for canadian lousewort. Only repot canadian lousewort every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using loamy, humus-rich, moist, well-drained. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does canadian lousewort need?

When is the best time of year to repot canadian lousewort?

Does canadian lousewort like to be root-bound?

Yes — canadian lousewort genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise canadian lousewort after repotting?

Not immediately. Wait about 4 weeks after repotting canadian lousewort. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.