Gadenin日本語Get the appBright enough to cast a soft shadow
The useful test for bright indirect light is physical rather than numerical. Hold your hand a foot above the plant at midday: you want a shadow with a soft but clearly defined edge. A hard black shadow means direct sun and the leaves will scorch. No visible shadow at all means the plant is in a holding position, not a growing one.
Philodendrons survive in light far below what they want, which is why so many of them limp along for years looking thin. Surviving and growing are different states, and the difference is almost always the position.
- East facing window Soft morning sun for a couple of hours then bright shade. This is the most forgiving position of all for both habits, and usually needs no curtain.
- South or west, behind a sheer curtain One layer of sheer diffuses the sun into roughly the right intensity. In high summer move the plant two or three feet back instead of adding more layers, which flattens the light too much.
- North facing window No scorch risk but often short of light. Put the plant within a foot of the glass and turn it a quarter turn each time you water so it does not lean.
- Interior wall away from any window Not viable long term without a lamp. The plant holds its existing leaves for months and then declines from the bottom up.
How far from the glass changes the plant
Light drops off much faster with distance than your eye suggests, because your pupils adjust as you walk into the room. Moving a plant three feet is a bigger change than it looks.
| Distance from the window | Light level | What the plant does |
|---|---|---|
| Within a foot, diffused | Ample | Short spacing between leaves, full color, steady new growth |
| Three to five feet back | Slightly short | Holds its shape, new leaves come a size smaller |
| Eight feet or more | Poor | Stems stretch, leaves shrink and space out, variegation fades |
| Windowless room with a grow light | Workable | Lamp twelve to twenty inches (30 to 50 cm) above, ten to twelve hours a day |
Pale walls and floors bounce a surprising amount of light back. A plant at a north window in a white room can be better lit than one three feet inside a south window in a dark room.
Direct sun burns within a day
The thin leaves of the trailing types scorch fastest, but even the thick upright ones bleach to a dull gray green and then brown in strong direct sun. The damage shows up within a day or two of the move that caused it, and it does not heal.
If a leaf has one scorched patch, leave it on the plant. It still works. Only remove a leaf when more than half of it is dry, and cut it off at the base of its stalk rather than tearing it.
Variegated philodendrons need more light than plain green ones, because the white areas do no photosynthesis, but they also scorch sooner. Bright shade right at the glass is the narrow band that suits them.
Temperature and drafts
Philodendrons are comfortable in the same range people are. They stop growing below about 59F (15C) and start suffering below 54F (12C), with cold damage showing as blackened patches that appear overnight rather than developing gradually.
| Situation | Effect on the plant | What to do |
|---|---|---|
| Leaf touching cold window glass overnight | A black patch exactly where it touched | Pull the pot back into the room at night in winter |
| Directly above or beside a radiator | Crisp brown edges and rapid drying | Move it several feet away, humidity will not fix this |
| In the path of an air conditioner | Leaves curl inward, growth stops | Redirect the vent or move the plant |
| Beside an outside door in winter | Sudden leaf drop after a cold snap | Relocate before the cold season, not after |
Two moves a year is usually enough
The right spot in midwinter and the right spot in midsummer are rarely the same, because the sun's angle and strength change so much. Rather than fussing constantly, plan on one move into the room for summer and one back to the window for the cold half of the year.
| Season | Where to keep it | Reason |
|---|---|---|
| Spring | Right at the window behind sheer curtain | Growth restarting, it needs everything you can give it |
| Summer | Two or three feet back, out of afternoon sun | Heat and strong light together cause most scorch |
| Autumn | Back towards the glass | The sun weakens and the summer spot is now too dark |
| Winter | At the window by day, pulled back at night | Maximum light, no contact with cold glass |
Note in a record where the plant stood each season and how the leaves that opened there turned out. After one year you will know your own house better than any general guidance can tell you.
Outdoors for the summer
A philodendron does well outside in deep shade once nights are reliably above 59F (15C), and often puts on its best growth of the year there. The transition has to be gradual, though: a plant moved straight from indoors to an open position scorches every leaf in a single afternoon.
Start under a covered porch or beneath a dense tree and increase the light over about two weeks. Bring it back inside before autumn nights fall below 59F (15C), and wash the leaf undersides and the outside of the pot first so you do not carry pests indoors with it.
Wind is the underrated risk outdoors. The large upright types have long leaf stalks that snap at the base, and once a stalk breaks the leaf is lost. Put the plant somewhere sheltered rather than somewhere merely shaded.