New Castle County, DE Invasive Plant Rules: Tree-of-Heaven Removal (2026)
Key Facts
- Invasive rating
- Rated 'I' - invasive tendency
- Mowing deadline
- Mow by September 30 yearly
- Pollinator/rain gardens
- Tree of Heaven prohibited there
- Applies to
- Unincorporated New Castle County only
- Governing chapter
- UDC Appendix 3; Ch. 7 § 302.4.5
Summary
New Castle County's development code lists Ailanthus altissima (Tree of Heaven) as an invasive tree to avoid, and its property maintenance code forces owners to mow down any harmful population by September 30 each year.
Ailanthus altissima / Tree of Heaven / Invasive Tendency: I / Note: Plant where it cannot escape cultivation.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 5).
Full Breakdown
The Unified Development Code's Appendix 3 plant guidance rates Ailanthus altissima / Tree of Heaven an 'I' for invasive tendency and directs planters to 'plant where it cannot escape cultivation.' That listing carries real weight: Property Maintenance Code § 7.01.002 (adopting IPMC § 302.4.5) requires an owner to mow a parcel at least once a year, by September 30, if it holds an Appendix III invasive-plant population large enough to harm neighboring properties. The same Appendix 3 list also bars Tree of Heaven from qualifying pollinator or rain gardens under § 302.4.10.4, and it applies only in unincorporated New Castle County. Wilmington and Newark run their own codes.
Violations & Fines
Skipping the required annual mow-down on an invasive-choked parcel is a Property Maintenance Code violation, enforced through inspection and civil penalty; a Tree of Heaven planted in a pollinator or rain garden forfeits that garden's protected status.
Frequently Asked Questions
Is Tree of Heaven illegal to own in New Castle County?
Does this rule cover Wilmington or Newark?
Sources & Official References
Other rules in New Castle County
Compare New Castle County to another location·View the Delaware invasive plant rules overview
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