Laburnum
Laburnum x watereri
The pruning window is narrow — cut the moment the flowers fade, and leave it be the rest of the year.
- Type
- Tree · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green · Gold and chartreuse
- Flower color
- Yellow
- Sunlight
- Full sun or partial shade will both do.
- Watering
- Moderate water; established trees ride out dry weather.
- Feeding
- All-purpose balanced
- Frost tolerant
- Yes
- Flowering
- May
- Pruning
- Cut as soon as flowering finishes in early summer.
- Apr–May Bud Break
- May–Oct Flowering
- Oct–Nov Leaf Fall
- Nov–Dec Winter Dormancy
- Jan–Apr Winter Dormancy
- Plant spacing
- 13 ft 1 in
- In-row spacing
- 13 ft 1 in
- Between rows
- 16 ft 5 in
- Square-foot density
- Not suited to SFG
- Root system
- Woody, shallow and far-reaching
- Working depth
- 12–24 in
- Can reach
- 4 ft down where the soil allows
- Spread
- 26–39 ft across, about 2–3× the width of the plant
Almost all of a tree’s roots are in the top two feet of soil, where the air is, and they run out well past the branch tips. The deep taproot most people picture belongs to the seedling; the tree grows out of it and spends the rest of its life spreading sideways instead.
The habit is Laburnum’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Green lacewing Chrysoperla carneaHunts Mealybugs
Its bristly larvae — "aphid lions" — impale aphids, mealybugs, thrips, and mite colonies, eating hundreds a week. Adults feed on nectar and pollen from small open flowers and overwinter in hollow stems left standing.
- Hoverfly SyrphidaeHunts Mealybugs
Bee-mimicking flies whose legless larvae graze aphid colonies clean while the adults pollinate. A ribbon of shallow, nectar-rich flowers kept in bloom all season recruits wave after wave of them.
- Ladybird (lady beetle) CoccinellidaeHunts Mealybugs
The gardener’s favorite ally: adults and their alligator-shaped larvae each eat thousands of aphids, plus scale, mealybugs, and other soft-bodied sap-suckers. Grow flat, open flowers for the adults and never spray a colony that ladybird larvae are already working.
- Parasitic wasps Braconidae & TrichogrammaHunts Leaf miners
Tiny, stingless wasps that lay eggs in or on caterpillars, aphids, and moth eggs — the white cocoons riding a hornworm are their calling card, so leave that caterpillar be. Umbel flowers with shallow nectar keep the adults fuelled.
Alliums, Geraniums, Aquilegia, Foxgloves
Green-leaved trees, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com