Caring for your new Calathea zebrina

Content: 

• Positioning and light
• Watering
• Why are my Calathea leaves curling
• Feeding
• Do I need to repot my Calathea
• Pests and diseases

Also known as prayer plants as they close their leaves at night, as if in prayer, Calathea originate from the Amazon jungle, so it is best to replicate the conditions they’re happiest growing in. Looked after properly, they’ll get up to roughly a meter tall with a similar spread. 

These plants display ‘nyctinastic movement’, which is in response to changes of light between day and night, hence the stems pulling in together and its leaves closing up when the sun sets. They’re also known for improving air quality in the home as they reduce CO2 levels. 

Positioning and Light

They do best in bright, indirect light. They will tolerate a bit less light but they will be extremely unhappy in very low light..

Avoid direct sunlight and keep out of any drafty areas. They need a minimum indoor temperature of 15°C. Don’t place them too close to windows as temperatures there can fluctuate quite radically between day and night.

Watering

Calathea is a rather thirsty plant so you’ll need to keep its soil moist, not wet, and don’t let the soil dry out between waterings. It is best to water them frequently but not over- zealously!

Why are my Calathea leaves curling?

If you notice the leaves curling, it may not be getting enough water. Rule of thumb (depending on the time of year and your climatic conditions) is to water once or twice a week in summer, and once a week in winter. 

It’s sometimes easier to take your plant and pop it into a sink or bath, and pour water over the surface of the soil until you see water running out of the pots drainage holes.  If there is browning on the margins of the leaf, it’s probably due to lack of humidity. Try and spritz your plant every morning. Or surround it with other indoor potted plants and create a jungle- like microcosm where they keep each other happy. If the leaves roll its leaves in towards its midrib, you have let your watering regime lapse, badly!

One thing to note about using tap water on your house plants – due to the amount of chlorine in the water, you may get brown marks on the leaves. If you haven’t been harvesting rain water, then fill up a bottle or jug with tap water, and leave outside in the sun for a day which will assist with the dechlorination process. Also, don’t use icy cold water on your pot plants, let it stand for a while to get to room temperature.

Feeding

Feed once every 1 – 2 months in summer with a liquid leafy plant fertiliser which has been diluted to half the recommended dose to ensure you don’t burn the plant. You can also use worm compost tea if you have an earthworm bin set up.

Do I need to repot my Calathea?

They like a lot of room, so as they grow bigger they’ll need to be repotted with fresh potting soil, with some perlite and/or coir added which will help with water retention, every couple of years in spring. You can also repot if you notice that your plant is drying out quicker than usual and you’re having to water it more often, or you notice roots popping out of the drainage holes or the surface of the soil. 

If you have leaves that are browning, you can trim off a brown point or edge, but carefully and cleanly. Sterilise scissors before trimming. If a whole leaf is looking unhappy, cut it back at the base near the soil surface. 

Although not grown for their flowers, C. zebrina does produce inflorescences with white and purple outdoors, but that only happens rarely. 

Pests and disease

They’re not bothered too often by pests and diseases, other than mealybugs (look like fluffy residue under the leaves), spider mites (you’ll notice either web-like material or stippled leaves if they’ve taken up residence), or root rot (from overwatering or being left to stand in water). 

Very occasionally a disease such as cCucumber mosaic virus, where you’ll notice jagged yellow patterns on the leaves, or a fungal infection called Helminthosporium leaf spot which causes brown lesions with a yellow halo, may make themselves known. For the former, get rid of the infected specimens to avoid spread to other houseplants, and use neem oil for the fungus in the latter case.