When to Plant Hydrangeas in London, ON – 2026
Published: April 27, 2026
London is in Canadian Zone 6a (southwestern Ontario temperate). Last spring frost averages May 3; first fall frost October 20; the growing season runs about 170 frost-free days. Plant hydrangeas in London from may (spring) or september (fall)..
Hydrangeas Planting Window for London, ON
Plant hydrangeas in spring or fall. Spring: after last frost. Fall: at least 6 weeks before first frost to establish roots. Avoid midsummer planting in Zones 7–9. Bigleaf hydrangeas bloom on old wood — do not prune in fall.
For London, ON specifically, the recommended planting window is May (spring) or September (fall).. London has 150-170 frost-free days — adequate for most warm-season crops when transplants go in by late May. The region's rich soils support heavy feeders like tomatoes and brassicas with minimal amendment.
Panicle hydrangeas (Hydrangea paniculata) are hardy to Zone 3 and bloom on new wood every year — choose 'Limelight', 'Bobo', or 'Quick Fire' for reliable Canadian gardens. Bigleaf hydrangeas (H. macrophylla) bloom on old wood and are marginal in Ontario — choose only for BC coast (Zone 7+).
Best Hydrangeas Varieties for London, ON
For London, ON (Canadian Zone 6a), choose varieties rated for your zone or one zone colder for reliable winter survival. The Canadian-bred or tested varieties below perform well in Ontario conditions.
The standard Canadian hydrangea. Cone-shaped lime-green blooms aging to pink. Reliable to Saskatoon and Calgary. 1.5-2 m tall.
Compact (60-90 cm) Limelight-style. Container-friendly. Excellent for small Prairie gardens.
Native North American species. Large round white blooms. Tolerates Prairie winters with mulch.
Earliest-blooming panicle hydrangea — flowers in early summer, ages to deep pink by September. Best for short-season Prairie gardens.
Re-blooming bigleaf — blooms on both old AND new wood. The only bigleaf hydrangea reliably worth attempting in Ontario Zone 5. Not for the Prairies.
How to Plant Hydrangeas in London
Sow method: transplant (shrub). The steps below adapt the general planting advice for London, ON's climate and timing.
- →Choose a site with morning sun and afternoon shade in Zone 7+; full sun in Zone 6 and colder.
- →Dig planting hole 2x the rootball width and equal depth — never deeper than the rootball.
- →Amend backfill with compost; avoid heavy peat amendment that holds too much water.
- →Plant the rootball with the top of the soil 1 cm (0.5 inch) above grade, never below.
- →Mulch 5–8 cm (2–3 inches) deep with shredded bark; keep mulch 5 cm (2 inches) from the stem.
- →Water deeply twice weekly the first month, then weekly during the first growing season.
Frequently Asked Questions about Hydrangeas in London, ON
When can I plant hydrangeas in London?
Plant hydrangeas in London from may (spring) or september (fall). based on the city's Canadian Zone 6a. Last spring frost: May 3; first fall frost: October 20; frost-free growing season: 170 days.
What Canadian zone is London?
London is in Canadian Zone 6a (USDA equivalent 5b). The climate is southwestern ontario temperate. London has 150-170 frost-free days — adequate for most warm-season crops when transplants go in by late May. The region's rich soils support heavy feeders like tomatoes and brassicas with minimal amendment.
Are hydrangeas winter-hardy in London?
Panicle hydrangeas (Hydrangea paniculata) are hardy to Zone 3 and bloom on new wood every year — choose 'Limelight', 'Bobo', or 'Quick Fire' for reliable Canadian gardens. Bigleaf hydrangeas (H. macrophylla) bloom on old wood and are marginal in Ontario — choose only for BC coast (Zone 7+).