North America Non-native Plant

Gum

Botanical name: Eucalyptus ×mortoniana

USDA symbol: EUMO5

Life cycle: perennial

Habit: tree

Native status: Non-native, reproduces and persists in the wild in the lower 48 states  

Eucalyptus ×mortoniana: A Mysterious Gum Tree Hybrid If you’ve stumbled upon the name Eucalyptus ×mortoniana, you’ve discovered one of the more enigmatic members of the gum tree family. This hybrid eucalyptus presents an interesting case study in plant identification and the challenges of documenting the vast world of botanical hybrids. ...

Eucalyptus ×mortoniana: A Mysterious Gum Tree Hybrid

If you’ve stumbled upon the name Eucalyptus ×mortoniana, you’ve discovered one of the more enigmatic members of the gum tree family. This hybrid eucalyptus presents an interesting case study in plant identification and the challenges of documenting the vast world of botanical hybrids.

What’s in a Name?

Known simply as gum (along with its many eucalyptus relatives), Eucalyptus ×mortoniana is a perennial tree that falls into the classic eucalyptus growth pattern. Like its cousins, this species develops as a woody plant with a single trunk, typically reaching heights greater than 13-16 feet. Under certain environmental conditions, it might develop a shorter, multi-stemmed growth form, but it’s generally going to be a substantial tree in your landscape.

Where Does It Call Home?

This gum tree is not native to North America – it’s an introduced species that has established itself and reproduces naturally without human intervention. Currently, it’s documented as growing in California, where it has found conditions suitable for naturalization.

The Mystery Factor

Here’s where things get interesting (and a bit frustrating for plant enthusiasts): Eucalyptus ×mortoniana is somewhat of a botanical mystery. Limited information exists about this particular hybrid, including specifics about its growing requirements, appearance, and ecological impact. This isn’t uncommon with eucalyptus hybrids, as there are hundreds of species and countless natural crosses that occur.

Should You Plant It?

Given the lack of detailed information about this specific hybrid, making a solid recommendation becomes challenging. Here’s what we can consider:

  • It’s a non-native species, so it won’t support local ecosystems the way indigenous plants would
  • Its invasive potential is unknown, which means we can’t be certain about its environmental impact
  • Growing requirements are unclear, making successful cultivation uncertain
  • Like most eucalyptus species, it’s likely to be a large tree that needs significant space

Native Alternatives Worth Considering

If you’re drawn to the idea of a stately tree with distinctive foliage, consider exploring native alternatives that will better support your local ecosystem:

  • Coast Live Oak (Quercus agrifolia) for California gardens
  • California Sycamore (Platanus racemosa) for riparian areas
  • Fremont Cottonwood (Populus fremontii) for larger landscapes

The Bottom Line

Eucalyptus ×mortoniana represents one of those fascinating botanical puzzles – a plant that exists and has established itself in the wild, yet remains largely undocumented in terms of its specific characteristics and requirements. While this doesn’t necessarily make it a bad choice, it does make it an uncertain one.

If you’re committed to growing eucalyptus species, you might have better luck with well-documented varieties that have known growing requirements and established track records in cultivation. And if you’re looking to create habitat and support local wildlife, native species will always be your best bet for creating a thriving, ecologically beneficial garden.

Gum

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Rosidae

Order

Myrtales

Family

Myrtaceae Juss. - Myrtle family

Genus

Eucalyptus L'Hér. - gum

Species

Eucalyptus ×mortoniana Kinney (pro sp.) [globulus × viminalis] - gum

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA