Q. Can you recommend an evergreen ivy for an NYC rooftop location?
Your best bet would probably be Hedera helix ‘Baltica’. It is cold tolerant to zone 5 (about -10 to -20 F), is a medium to fast grower and can reach a height of 50 feet. And while it would prefer partial shade, it can tolerate full sun.
H. hibernica seems to be cold hardy in areas that don’t have severe winters. It can probably take temperatures down to the mid-teens, so a mild-ish winter in the NYC area (zone 7b) would probably be fine but if we have a cold snap or a bad winter it might die or at least suffer greatly. It does seem to be very popular in the UK, but their winters tend to be more mild. Also, it has a reputation of being invasive here in the U.S. Much of the “English” ivy you see vigorously climbing trees is actually Irish ivy (the common name for H. hibernica).
For more information, see the Missouri Botanical Garden's information page on H. hedera ‘Baltica’.
Regardless of what you choose, be sure the containers have good drainage. These plants don't appreciate having wet, cold soil in the winter.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service