Gadenin日本語Get the appIt droops early, and that is useful
An arrowhead plant has thin, soft leaf blades on long stalks, and when the compost dries out the whole plant flops within a few hours. It looks alarming. It is not. Water it properly and it stands back up overnight with no lasting damage, and if you catch it in the first day you will not even lose a leaf.
This makes it one of the easiest houseplants to read, and it means you should never water on a fixed day of the week. Let the plant and the pot tell you. The mistake that actually kills arrowhead plants is the opposite one: compost that never fully dries, week after week, until the roots suffocate and the lower leaves start yellowing from the base of the plant upwards.
How fast your pot dries
The interval depends far more on the pot and the position than on the plant. A plant in a small terracotta pot on a bright sill may need water twice a week in summer, while the same plant in a large plastic pot in a dim corner may go two weeks. Work out which end of that range you are on before you fix any habit.
| Setup | Drying speed | What to watch |
|---|---|---|
| Terracotta, pot under 5 inches (13 cm) | Fast | Sides of the pot go pale and the pot feels light |
| Plastic or glazed, pot over 7 inches (18 cm) | Slow | Surface dries while the bottom third stays wet |
| Bright room with air moving | Fast | Leaf stalks soften at the tip of the day |
| Still corner, low light | Very slow | Compost smells sour, gnats appear |
| Climbing up a moss pole | Faster than it looks | The pole dries out before the pot does |
Three checks that beat a schedule
Pick two of these and use them every time. Once you have done it for a month you will know your own interval without thinking about it, and you can stop checking so often.
- Finger to the second knuckle Push a finger straight down into the compost as far as the second knuckle. Dry and crumbly all the way means water now. Cool and damp means wait, even if the surface looks bone dry.
- Learn the weight Lift the pot right after a full watering and again a week later. The difference is obvious once you have felt it, and in a pot bigger than 6 inches (15 cm) weight is far more reliable than any finger test.
- Water until it runs out When you do water, pour slowly until water comes freely from the drainage holes, then stop. Small splashes every day wet only the top inch and keep the roots shallow and weak.
- Empty the saucer within the hour Tip away anything standing in the saucer or the outer pot. Roots sitting in water are the single most common cause of the rot that follows.
If water runs straight through in seconds and the pot is still light, the compost has shrunk away from the sides. Stand the pot in a bowl of water for twenty minutes to rewet it properly, then drain it.
Change the interval as the room changes
The plant drinks in proportion to how fast it is growing, and growth stops when the room drops below about 59F (15C). Carrying a summer interval into winter is how most arrowhead plants are lost, because the compost never dries and the roots have no air.
| Season | When to water | The signal |
|---|---|---|
| Spring | When the top inch (2.5 cm) is dry | New leaves unfurl every couple of weeks |
| Summer | As soon as the top inch is dry | Stalks soften slightly by late afternoon |
| Autumn | Two days after the top inch dries | Room falling below 68F (20C) |
| Winter | When the pot is light through and through | Often only every 10 to 14 days |
Telling thirst from rot when the leaves droop
Both problems look like wilting, and treating the wrong one makes it worse. The difference is in the compost and in which leaves go first.
Thirst: the compost is dry, the pot is light, the whole plant flops at once, and every leaf is still a good color. Water it and it recovers in a few hours. Rot: the compost is damp, the pot is heavy, the lower leaves yellow and go limp one at a time while the top still looks fine, and the base of the stems feels soft. Watering makes that worse. Stop watering, move it somewhere brighter and warmer, and if it does not firm up within a week take it out of the pot and look at the roots.
Brown, crisp leaf edges are usually not a watering fault. They come from dry air, especially near a radiator or a vent, or from letting the plant go bone dry repeatedly. Move it away from the heat source before you change the watering.