Repotting guide

When & how to repot Philodendron Martianum (Philodendron martianum)

Also called Fat Boy Philodendron, Martianum.

More about philodendron martianum

About Philodendron Martianum

Philodendron martianum · also called Fat Boy Philodendron, Martianum · houseplant

Philodendron martianum, the Fat Boy, is a self-heading epiphyte famous for thick, swollen petioles that store water and starch. Broad, glossy dark-green leaves radiate from a low rosette. Being semi-succulent, it tolerates drying out and prefers a chunky, fast-draining mix. Striking and forgiving, but toxic to cats and dogs like all philodendrons.

Mature size: Roughly 50-90 cm tall and wide indoors, with leaves up to about 40 cm long.

Watch for — Yellow leaves: Usually waterlogged roots in too-dense soil; switch to a chunky orchid-bark mix and improve drainage.

How to tell philodendron martianum needs repotting

Repotting on a calendar is less reliable than reading the plant. For philodendron martianum, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot philodendron martianum

Every 2–3 years, into bone-dry mix. Philodendron Martianum's growth habit — self-heading epiphyte forming a low, spreading rosette of thick-petioled leaves rather than climbing. — sets the pace. Philodendron martianum, the Fat Boy, is a self-heading epiphyte famous for thick, swollen petioles that store water and starch. Broad, glossy dark-green leaves radiate from a low rosette. Being semi-succulent, it tolerates drying out and prefers a chunky, fast-draining mix. Striking and forgiving, but toxic to cats and dogs like all philodendrons.

What size pot to step philodendron martianum up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Philodendron Martianum stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot philodendron martianum

Spring or summer, while philodendron martianum is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting philodendron martianum

Repot dry. Do not water philodendron martianum for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty very chunky, epiphytic mix ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set philodendron martianum at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep philodendron martianum completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for philodendron martianum

Philodendron Martianum wants very chunky, epiphytic mix. Use mostly orchid bark, charcoal, perlite and a little peat or coco coir. Even when grown terrestrially it wants epiphytic conditions: little fine soil, high aeration, sharp drainage. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting philodendron martianum — frequently asked questions

How often should you repot philodendron martianum?

Every 2–3 years, into bone-dry mix for philodendron martianum. Repot philodendron martianum every 2–3 years into a snug pot of very chunky, epiphytic mix, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does philodendron martianum need?

When is the best time of year to repot philodendron martianum?

Should you water philodendron martianum after repotting?

No — not straight away. Repot philodendron martianum into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise philodendron martianum after repotting?

Not immediately. Wait about 3 weeks after repotting philodendron martianum. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.