Gadenin日本語Get the appThe two growth habits want different intervals
Philodendron covers two very different plants in the same pot shape. The trailing heartleaf types have thin stems, small leaves and a shallow, fine root system, so they dry out quickly and show thirst within a day. The upright self-heading types have thick stems, heavy leaves and coarse roots that store water, so they tolerate drying far better and rot far more easily.
If you water both on the same day of the week, one of them is wrong. Work out which habit you have first, then read the intervals below as a starting point rather than a rule.
| Habit | How to recognize it | Drying speed | Main risk |
|---|---|---|---|
| Trailing heartleaf type | Thin stems, leaves under six inches (15 cm), vines over the pot rim | Fast, often dry in three or four days | Going bone dry and crisping the tips |
| Upright self-heading type | Thick central stem, large leaves held out on long stalks | Slow, holds moisture over a week | Staying wet and rotting at the base |
| Climbing type on a pole | Aerial roots gripping a support, leaves enlarging up the pole | Medium, the pole itself dries fast | The pole dry while the pot is soaked |
| Recently repotted, any type | Fresh compost with unrooted space around the ball | Very slow at the outside | Watering to the old interval |
A philodendron that has gone too dry recovers overnight after a thorough soak. One that has been kept wet does not recover at all once the base of the stem has gone soft, so err on the dry side with the upright types.
Rough intervals through the year
These assume a pot around eight inches (20 cm) across in an ordinary living room. Adjust by what the compost is actually doing: a terracotta pot in a bright window can want water twice as often as a plastic pot in the middle of the room.
| Season | Room temperature | Trailing types | Upright types |
|---|---|---|---|
| Spring | 59 to 77F (15 to 25C) | Every four to six days | Every seven to ten days |
| Summer | Above 77F (25C) | Every three to five days | Every five to eight days |
| Autumn | 59 to 68F (15 to 20C) | Every seven to ten days | Every ten to fourteen days |
| Winter | 50 to 61F (10 to 16C) | Every two weeks | Every three to four weeks |
Reduce how often you water in winter, not how much. A half measure wets only the top and leaves the roots at the bottom of the pot permanently dry while the middle stays sour.
How to check without guessing
The surface of the compost dries within hours and tells you almost nothing. Use two of the following together and you will not overwater.
- Finger to the second knuckle Push a finger straight down at the edge of the pot. For a trailing type, water when it is dry at that depth. For an upright type, wait until it is dry and then give it two more days.
- Learn the weight Lift the pot right after a thorough watering and again three days later. The difference is obvious once you have done it twice, and it reads the whole pot rather than one spot.
- Look at the newest leaf On a thirsty philodendron the youngest leaf loses its gloss and the stalk softens before any older leaf reacts. That is the earliest honest signal the plant gives you.
- Check the pole as well On a plant climbing a moss pole, feel the pole itself. A dry pole makes the aerial roots let go, and the plant peels away from the support long before the compost tells you anything is wrong.
Watering thoroughly, then letting it drain
When you do water, water until it runs freely from the drainage holes and keep going for a few seconds after that. A splash that wets the top inch trains the roots to stay near the surface, and those are the first roots to dry out.
Then get rid of the surplus. Water standing under the pot keeps the base of the compost saturated, which is where root rot and fungus gnats both begin.
- Empty the saucer within the hour Tip away anything left after twenty or thirty minutes. This matters most in winter, when the pot may take a fortnight to use what it absorbed in one afternoon.
- Lift it out of any decorative outer pot A cachepot hides the water collecting in its base. Take the plant out, water it at the sink, let it drain completely and only then put it back.
- Use tepid water Cold water straight from the tap chills the roots of a warm plant and checks growth for a week or more. Let it stand in the room, or mix in enough warm to make it feel neutral on your wrist.
Reading the leaves before you decide
Almost every philodendron symptom points in two opposite directions depending on whether the compost is wet or dry. Check the compost first, then read the row.
| What you see | If the compost is wet | If the compost is dry |
|---|---|---|
| Lower leaves yellowing one after another | Overwatered, the roots are failing | Underfed, or the oldest leaf simply retiring |
| Leaves limp and hanging | Root rot, stop watering and unpot to look | Thirsty, soak thoroughly and it stands up by morning |
| Brown crisp edges | Damaged roots cannot move water | Dry air, or the pot went past bone dry |
| New leaf emerges small and deformed | Roots suffocating in dense wet compost | It ran dry while that leaf was forming |
| Black soft patch at the base of the stem | Stem rot, act immediately | Not caused by dryness, look for cold damage |
Write down the date you watered for a month, alongside the room temperature. Once you can see your own interval on paper you stop guessing, and next winter you will already know how far to stretch it.
Humidity is not a substitute for watering
Philodendrons come from humid forest air and they do look better above about fifty per cent humidity, but misting the leaves puts no water into the roots. Treat humidity as a separate job from watering rather than a way of doing less of it.
The measures that actually work are grouping plants together, standing the pot on a wide tray of damp gravel with the pot base clear of the water, and keeping the plant out of the direct blast of a heater or air conditioner. A dry draft does more damage than low humidity on its own ever does.