Aglaonema Red Siam is the aglaonema for people who want colour without flowers. Its glossy green leaves are flushed with red and pink, especially along the edges and midrib, and the colour holds well indoors — a rare thing for a plant that tolerates low light. It is compact, slow-growing and undemanding, which makes it an easy statement plant for a desk or shelf. This guide covers light, water, humidity, soil, feeding and the common problems that show up when something is off.
The red colour is the thing to protect. In too little light the new leaves come out greener and the pink fades, and in harsh direct sun the leaves scorch. The sweet spot is medium indirect light — bright enough to keep the colour vivid, gentle enough to leave the leaves unmarked. Get the light right and the rest of its care is straightforward.
Aglaonema Red Siam at a glance
| Care factor | What this plant needs |
|---|---|
| Botanical name | Aglaonema 'Red Siam' |
| Light | low to medium indirect |
| Water | every 1–2 weeks; let top soil dry |
| Humidity | moderate |
| Temperature | 65–80°F (18–27°C) |
| Repotting | every 2–3 years |
| Pet safety | toxic to cats and dogs |
Light
Low to medium indirect light suits it, but for the best red colour give it medium indirect light rather than the dimmest corner — a spot near an east-facing window or a few feet from a brighter window is ideal. Too little light and the red fades to green; too much direct sun and the leaves scorch. If the new leaves are coming out mostly green, move the plant a little closer to the light.
Too little light is the more common mistake with this plant than too much. Growth slows, stems stretch towards the window, and new leaves come out smaller and less distinctive than they should be. If the plant leans hard in one direction, rotate the pot a quarter turn every couple of weeks so it grows evenly. Our grow-light calculator can help work out how much light your spot actually provides, and the houseplants hub has more plants that suit the same light levels.
Watering
Water every 1–2 weeks; let top soil dry. Push a finger into the soil and only water when the top has dried to the depth the guidance suggests. When you do water, water thoroughly — soak the soil until water runs out of the drainage holes — then empty the saucer so the plant never sits in standing water. Soggy soil is the fastest way to kill most houseplants, and it is far more common than underwatering.
Water less in winter, when growth slows and the soil stays wet longer, and more in summer, when the plant is actively growing. If you are unsure how much water your pot needs, our watering calculator gives a starting point, and our watering schedule generator can help you build a routine. Signs of overwatering include yellowing lower leaves and soft, dark stems; signs of underwatering include drooping leaves and dry, crispy edges.
Humidity and temperature
Aglaonema Red Siam prefers moderate humidity and temperatures of 65–80°F (18–27°C). Most homes sit within that temperature range for most of the year, so temperature is rarely a problem indoors — the things to watch are cold draughts in winter, radiators that dry the air, and cold windows that chill the leaves overnight. Keep the plant away from all three.
Humidity is the factor most people underestimate. In a heated home in winter the air can be much drier than this plant likes, and the first sign is usually brown, crispy leaf edges. A pebble tray under the pot, grouping plants together, or a small humidifier all raise the humidity around the plant. Misting does very little — the water evaporates in minutes. Our humidity and temperature checker can tell you whether your room suits this plant.
Soil and potting
Indoors, this plant needs a free-draining potting mix. Standard potting soil on its own holds too much water and compacts over time, so mix it with perlite and bark to keep air around the roots — the roots need oxygen as much as they need water. A pot with drainage holes is not optional; without one, water has nowhere to go and root rot follows. Our potting-mix calculator can work out the parts for a homemade mix for your pot size.
Choose a pot that fits the root ball with a little room to grow, not a much bigger one. A pot that is too big holds wet soil the roots cannot use, which is one of the most common causes of root rot in houseplants. If you are reusing a pot, wash it first so no old salts or pests carry over.
Repotting
Repot every 2–3 years, or sooner if roots are circling the drainage holes or pushing out of the top of the pot. Move up only one pot size — a pot that is too big holds wet soil the roots cannot use. Spring is the best time to repot, when the plant is about to grow, and fresh mix gives the roots a new supply of air and nutrients. Our repotting calculator can help you work out the next pot size and how much fresh mix you will need.
Feeding
Feed during the growing season, in spring and summer, with a balanced liquid houseplant fertiliser, and do not feed in autumn and winter when the plant is barely growing. Always follow the directions on the label — more fertiliser is not better, and excess salts build up in the soil and burn the roots, which often shows up as brown leaf tips. If you have been feeding heavily, flush the soil with plain water every few months to wash out the salts.
Propagation
Aglaonema Red Siam is propagated from stem cuttings or by division. In spring, cut a stem with a few leaves and root it in water or moist mix in a warm, bright spot, or divide a mature clump when you repot, making sure each section keeps its own roots. Rooting is slow, so be patient — several weeks is normal.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Root Rot | soggy soil | See below |
| Yellow Leaves | overwatering | See below |
| Brown Leaf Tips | low humidity or over-fertilising | See below |
Root Rot
Likely cause: soggy soil. Take the plant out of its pot, trim away any black, mushy roots with clean scissors, and repot in fresh, free-draining mix in a pot with drainage holes. Water less going forward and let the top soil dry between waterings.
Yellow Leaves
Likely cause: overwatering. Let the soil dry more between waterings, check the pot drains freely, and remove the leaf once fully yellow. One yellow old lower leaf is normal ageing; several at once points to watering.
Brown Leaf Tips
Likely cause: low humidity or over-fertilising. Raise the humidity around the plant, switch to filtered, distilled or rainwater if your tap water is hard or fluoridated, and flush the soil with plain water occasionally to wash out salts. Trim the brown tips with clean scissors, following the natural shape of the leaf — damaged tips will not heal, but new leaves should come out clean.
Is aglaonema red siam safe for pets?
According to the data used for this guide, aglaonema red siam is toxic to cats and dogs. Keep the plant out of reach of curious pets, especially if it trails where a cat can reach it, and contact a vet if your pet has eaten any of it.
Frequently asked questions
How often should I water aglaonema red siam?
Water every 1–2 weeks; let top soil dry. Check the soil rather than watering on a calendar: if the top of the soil is still damp, wait. Water thoroughly when it is time, let the excess drain away completely, and never let the plant sit in standing water.
What light does aglaonema red siam need?
It needs low to medium indirect light. Too little light and the red fades to green; too much direct sun and the leaves scorch. If the new leaves are coming out mostly green, move the plant a little closer to the light. Harsh direct sun can scorch the leaves, while too little light leads to slow, stretched growth and a loss of colour or pattern.
Is aglaonema red siam safe for cats and dogs?
According to the data used for this guide, aglaonema red siam is toxic to cats and dogs. Keep it out of reach of pets that chew plants, and if a pet eats any of it, contact your vet.
When should I repot aglaonema red siam?
Repot every 2–3 years, in spring, or sooner if roots are circling the drainage holes. Move up one pot size only and use a fresh, free-draining mix. Our repotting calculator can help with the next pot size.
Why is my Red Siam losing its red colour?
The red fades when the light is too low. Move the plant to medium indirect light — brighter, but still out of direct sun — and new leaves should come out with stronger colour. Old leaves will not regain their colour, so judge the change on new growth.
Is Aglaonema Red Siam safe around pets?
No — like all aglaonemas it is toxic to cats and dogs. Keep it out of reach of pets that chew plants, and contact a vet if a pet eats any of it.
Related guides
Browse the full houseplants hub for more species care guides, or explore the tools hub for calculators that help with watering, light and repotting.