PlantRx

Arrowhead plant problems

By Karim DiabatePublished Updated How these guides are built

Most of what goes wrong with an arrowhead plant comes down to a small number of causes, and they produce overlapping symptoms. This is what actually goes wrong with this plant, what separates one cause from another, and where to go for a specific symptom.

A healthy Arrowhead Plant, photographed for reference
A healthy arrowhead plant for comparison. This is a reference photo, not a picture of the problem. Photo by Unknown author (CC BY-SA 3.0), via Wikimedia Commons.

What is specific to this plant

  • Arrowhead plants grow fast and change shape with age, starting compact and becoming a vine. Leggy growth on an older plant is maturity as much as light.
  • It wilts visibly and early when dry, which makes it a useful indicator plant but a poor one to let dry out repeatedly.

What it could be, and how to tell

These look alike in a photograph, so each one below lists what you would ALSO see if that is the cause. Work down the list and stop at the one where the other symptoms match too.

most common

1. Overwatering, and the root rot that follows

What else you would see

  • leaf stalks going soft and translucent close to the base while the blades still look well
  • stems that pull away from the crown with no resistance at all
  • the newest leaves opening smaller and darker than the ones before them
How to confirm it: Slide the plant out of its pot and look at the roots. Healthy ones are firm and white. Brown, soft, or hollow when you press them means rot, and that changes what you do next completely.

What to do

  1. Stop watering and let it dry down this far: the top inch or two.
  2. Check that the pot drains and empty any saucer or decorative outer pot it sits in. Water held out of sight keeps the mix wet whatever you change above it, and it stays invisible until you lift the pot.
  3. If the roots are soft and brown, trim them back to firm tissue with a blade sterilised first and repot into fresh free-draining potting mix.
common

2. A vine outgrowing its compact juvenile shape

What else you would see

  • stems lengthening and trailing over the pot rim rather than standing up
  • newer leaves a different shape from the older ones, often more lobed
  • wider spacing between leaves on the newest growth
  • a plant that has been growing well and quickly rather than struggling
How to confirm it: Compare the newest leaves with the oldest. An arrowhead plant starts compact and becomes a vine as it matures, and the leaf shape changes with it, so legginess on an older plant is partly the plant growing up rather than reaching for light. A plant that is stretching from poor light does it with pale, widely spaced, unchanged leaves; a maturing one changes leaf shape as it goes.

What to do

  1. Cut it back hard if you want the compact shape, which it regrows from readily.
  2. Give it something to climb if you would rather let it mature into a vine.
  3. Rule light in or out by looking at the leaf shape before you move the plant.
common

3. Underwatering

What else you would see

  • leaf edges going papery and thin while the stalks stay firm
  • a pot light enough to shift when you brush against it
  • the plant flat by late afternoon and standing again the morning after a soak
How to confirm it: Dry soil pulled away from the pot wall, with foliage that improves noticeably within a day of a thorough soak. If a thorough watering changes nothing in twenty four hours, stop assuming thirst and check the roots.

What to do

  1. Water thoroughly until it runs freely from the drainage holes, rather than a splash at the surface.
  2. If the mix has gone water-repellent and the water runs straight through, stand the pot in a basin of water for half an hour to rewet it properly.
  3. Water on dryness rather than on a fixed day of the week, and this is how far it should dry: the top inch or two.
less common

4. Not enough light

What else you would see

  • long bare stretches of stem between the leaves
  • each new leaf smaller than the last
  • lower leaves shed while the growing tip carries on
How to confirm it: Stretched growth and shrinking new leaves together, on a plant whose watering is otherwise right. Arrowhead plant wants bright indirect light.

What to do

  1. Move it to bright indirect light.
  2. Cut back the stretched growth. It will not compact again on its own, and cutting back is what triggers branching.
  3. Turn the pot every couple of weeks so it grows evenly.
less common

5. Spider mites

What else you would see

  • fine pale stippling or speckling across the leaf rather than solid patches
  • very fine webbing where the leaf meets the stem
  • a dusty look to the underside of the leaf, worst in warm dry air
How to confirm it: Hold a sheet of white paper under a leaf and tap it sharply. Specks the size of dust that then move are mites. The stippling is what separates this from any watering problem.

What to do

  1. Isolate the plant from your others straight away, before anything else.
  2. Rinse the leaves thoroughly, undersides included, with a strong spray of water, and repeat every few days. Mites breed faster than a single treatment can keep up with.
  3. Raise the humidity around the plant. Mites thrive in warm dry air and struggle in humid air.
  4. If you choose to use a treatment product, follow the label on it exactly. The label is the legal instruction and it overrides anything written here.
uncommon

6. Rootbound, or soil that is worn out

What else you would see

  • roots circling the inside of the pot or escaping the drainage holes
  • water running straight through with almost no absorption
  • two or more years in the same pot, and smaller new growth each season
How to confirm it: Lift the plant out and look. A dense mat of circling roots with very little mix left means the pot can no longer hold what the plant needs.

What to do

  1. Repot one size up in spring into fresh free-draining potting mix, teasing the outer roots loose.
  2. Feed during the growing season, following the instructions on the label of whatever you buy.

Common questions

What is the most common problem with an arrowhead plant?

Too much water, by a distance, and it is common because it looks like thirst: roots that have rotted cannot drink, so the plant wilts while standing in wet mix. Arrowhead plant wants this much to dry between waterings: the top inch or two.

How much light does an arrowhead plant need?

Arrowhead plant wants bright indirect light. Light problems show up in the growth rather than the colour: smaller new leaves, longer gaps between them, and lower leaves shed to fund the tip.

Why does my arrowhead plant look worse after I repotted it?

Some drooping in the week after a repot is ordinary shock and passes. Getting steadily worse over several weeks usually means the new pot is much too large, so the mix nothing is drinking from stays wet, or that the mix itself holds too much water.

Before you act on any of this

This is general plant care guidance for a plant, not advice about people or animals. We never tell you whether a plant is safe to eat or touch, and we never tell you a plant is safe for a child or a pet. If a child or animal may have eaten any part of a plant, contact Poison Control (US 1-800-222-1222) or a vet immediately rather than reading further.

Treatment advice here is deliberately category level. We do not give product names, mixing ratios or application intervals. Whatever the label on the product in your hand says is the instruction that counts, and following it is your responsibility.

Where this comes from

The general horticultural facts behind this differential come from published university extension and Royal Horticultural Society guidance. What is specific to this plant, and the order the causes are ranked in, is ours, and the methodology page says where that reasoning stops being reliable.

Other arrowhead plant problems

Not sure which one it is?

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