Sourwood
Oxydendrum arboreum
also called sorrel tree, lily-of-the-valley tree
The Appalachian honey tree: drooping sprays of lily-of-the-valley flowers in July when little else blooms, then fall color that goes from crimson to burgundy while the seed sprays hang on like a second flowering.
- Type
- Tree · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Flower color
- White
- Sunlight
- Full sun for the best color and bloom
- Watering
- Moderate; mulch the roots and do not let it bake
- Soil
- Acidic, well-drained, humus-rich; no lime, no salt, no compaction
- Feeding
- Gentle all-organic
- USDA zones
- 5a–9a
- Frost tolerant
- Yes
- Plant out
- 14 days before the last spring frost
- Plant spacing
- 16 ft 5 in
- In-row spacing
- 13 ft 1 in
- Between rows
- 19 ft 8 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
- 39–59 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 Sourwood’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.
- When
- Not harvested, unless a neighbor keeps bees, in which case the harvest is theirs in July.
- What to look for
- The drooping flower sprays open white in high summer; the seed sprays that follow hold the same shape all fall.
- How to harvest
- No pruning beyond deadwood; the crooked, leaning way it grows is its character. Mulch the root zone and keep string trimmers away from the thin bark.
- How often
- Nothing on a schedule.
- Storing the crop
- Nothing to store. If bees do work it, sourwood honey is extracted in late July and never blended by anyone who knows what they have.
- Generally trouble-free No notable pest or disease problems when grown in the right conditions — one of the easy ones.
Sourwood honey, from bees working these July flowers in the southern mountains, is one of the most sought-after varietal honeys in the country. The leaves taste sour (hence the name) and are safe to nibble.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com