Troubleshooting
Chestnut 'Colossal' problems — and how to fix them
Chestnut 'Colossal' (Castanea × 'Colossal') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Chestnut blight
Cryphonectria parasitica is the historic killer of American chestnuts. 'Colossal' shows only moderate resistance, so it performs far better in the blight-light West than the eastern US.
Ink disease (Phytophthora)
Root and collar rot in poorly drained or overwatered soil. Plant on a slope or mound and never let the trunk base sit in standing water.
Chestnut gall wasp
Dryocosmus kuriphilus causes leaf and bud galls that sap vigour and reduce nut yield. Encourage the parasitoid Torymus sinensis and remove heavily galled wood.
Poor pollination
'Colossal' pollen is largely sterile, so a lone tree sets few nuts. Plant a compatible pollenizer (e.g. a chestnut seedling or 'Nevada') within bee range for a full crop.
Prevent chestnut 'colossal' problems before they start
Most chestnut 'colossal' issues are care-mismatch, not bad luck. Dial in the basics:
Looking for chestnut 'colossal' in general rather than its problems? Read the full chestnut 'colossal' care guide — light, water, soil and feeding.
Chestnut 'Colossal' problems — FAQ
Why is my chestnut 'colossal' chestnut blight?
Cryphonectria parasitica is the historic killer of American chestnuts. 'Colossal' shows only moderate resistance, so it performs far better in the blight-light West than the eastern US.
Why is my chestnut 'colossal' ink disease (phytophthora)?
Root and collar rot in poorly drained or overwatered soil. Plant on a slope or mound and never let the trunk base sit in standing water.
Why is my chestnut 'colossal' chestnut gall wasp?
Dryocosmus kuriphilus causes leaf and bud galls that sap vigour and reduce nut yield. Encourage the parasitoid Torymus sinensis and remove heavily galled wood.
Why is my chestnut 'colossal' poor pollination?
'Colossal' pollen is largely sterile, so a lone tree sets few nuts. Plant a compatible pollenizer (e.g. a chestnut seedling or 'Nevada') within bee range for a full crop.