Light
Bright Indirect Light
Prefers bright, indirect light; can tolerate some direct morning sun.
Reference image 
Reference image Harrisia portoricensis
Puerto Rico Apple Cactus
Overview
Harrisia portoricensis, commonly known as the Puerto Rico apple cactus, is a rare and endangered columnar cactus belonging to the family Cactaceae. It is highly valued for its elegant slender branches and nocturnal blooms 1.
Taxonomy and Naming
Described scientifically by Britton and Rose, this species is named after its native archipelago of Puerto Rico. Locally, it is often referred to as "Higo escuero". It belongs to the genus Harrisia, which comprises several dry-forest cacti native to the Caribbean 2.
Distribution and Habitat
This species is endemic to Puerto Rico, specifically restricted to three small offshore islands: Mona, Monito, and Desecheo. It thrives in seasonally dry tropical forests, growing on limestone substrates and coastal scrubland 1. Due to its restricted range and habitat degradation, it is listed as Endangered on the IUCN Red List 2.
Appearance
Harrisia portoricensis exhibits an erect or sprawling growth habit, with stems reaching up to 2 meters. The slender green branches have 10 to 11 ribs lined with sharp spines. Its nocturnal flowers are funnel-shaped, white to pale yellow, and give way to smooth, round, yellow edible fruits.
Cultivation and Care
In cultivation, it requires conditions that mimic its dry tropical habitat. A highly porous, mineral-rich potting medium with excellent drainage is crucial. Place it in a location with bright, indirect sunlight and water only when the substrate has dried out completely.
Common Mistakes
Overwatering is the most common cause of failure, quickly leading to root rot in poorly drained soils. Insufficient light can cause etiolation (stretching), weakening the plant's structure. Additionally, exposing this tropical cactus to freezing temperatures will cause severe tissue damage 1.
References
Watering
7-21 Days
Allow soil to dry out completely. Water weekly in summer, monthly in winter.
Soil
Well-draining cactus mix with pumice and coarse sand
Mineral-rich, well-draining soil with pumice, coarse sand, and limestone.
Safety
Pet Friendly
Non-toxic to pets, but has sharp spines that can cause physical injury.
Difficulty
Moderate
Moderate. Requires careful watering control and frost protection.
Native Habitat
Puerto Rico, Caribbean
Endemic to the dry limestone forests of Mona, Monito, and Desecheo islands in Puerto Rico.
Frequently Asked Questions
Can Harrisia portoricensis be grown in a pot?
Yes, it can be grown successfully indoors or on patios in deep, well-draining pots filled with a gritty cactus mix.
How often should I water it?
Water about once a week in summer after the soil dries out completely, and reduce to once a month during the winter.
What kind of soil should I use?
Use a highly porous, gritty cactus soil mixed with pumice, coarse sand, and limestone chips.
Does it tolerate direct sunlight?
It prefers bright, indirect or filtered light. Extreme, direct summer afternoon sun can cause sunburn on the stems.
When does it bloom?
It produces large, white flowers that open at night, typically during late spring and summer.
Is it toxic to pets?
It is non-toxic to pets, but its sharp spines pose a physical hazard to curious cats and dogs.
What is its growth rate?
It has a slow to moderate growth rate, adding a few centimeters of height each year under optimal conditions.
What is its cold tolerance?
It requires minimum temperatures of around 10°C (50°F) and must be protected from frost and freezing weather.
Are the fruits edible?
Yes, the round, yellow fruits that develop after successful pollination are edible.
What causes yellowing or softening of the stem?
Softening at the base is a classic sign of root rot due to overwatering. Stop watering immediately and check the roots.