Peace Lily (Spathiphyllum)

Last updated: August 3, 2025

The Peace Lily is a classic and elegant houseplant, admired for its glossy, dark green leaves and distinctive white, spoon-shaped flowers (spathes). It's a forgiving plant that is excellent at communicating its needs, famously drooping its leaves when thirsty.

Lighting

Ideal: Peace Lilies thrive in low to medium indirect light. A little direct sun in the early morning is perfectly fine and not strong enough to burn the leaves. The diffuse, indirect light for the rest of the day is exactly what they need to grow and bloom.
Benefits: This type of light encourages consistent growth and flowering.
Avoid: While your current location is great, it's important to remember that direct, harsh midday or afternoon sun will easily scorch the leaves, causing them to turn yellow and brown.

Watering Routine

With a large plant in an 18-20" pot, watering will be less frequent than for a smaller one, but it is still the most critical aspect of care.

Frequency: Water when the top 2-3 inches of soil feel dry to the touch. You can also wait for a key sign: the leaves will begin to slightly droop. This is a very clear signal that the plant is thirsty.
Method: Water thoroughly until you see water draining from the bottom of the pot. A large pot like yours may require several gallons of water to saturate the root ball completely.
Important: Discard any excess water from the saucer. Peace Lilies do not like to sit in standing water.
Seasonality: Since your plant is outdoors, you will likely need to water more frequently during the warmer, drier months than you would if it were indoors. Monitor it more closely during heatwaves. In fall and winter, as temperatures drop and growth slows, reduce watering frequency.

Fertilizer Requirements

A large, mature Peace Lily needs regular feeding to support its size and continuous flowering.

Schedule: Fertilize during its active growing season, from spring through early fall. Once every 2-4 weeks is sufficient.
Type: Use a balanced liquid houseplant fertilizer.
Commercial Recommendation: Miracle-Gro Indoor Plant Food (Liquid) or Schultz Liquid Plant Food are easily available options. Dilute these commercial concentrates to achieve approximately 100-200 ppm N in your final solution. This is often equivalent to using them at "full strength" as directed on the package.
DIY Fertilizer Suggestion:
For robust growth and continuous flowering, use your homemade 1-1-1 liquid fertilizer concentrate (Balanced) or the 1-2-1 liquid fertilizer concentrate (High Phosphorus).
- For 1-1-1 concentrate (10,000 ppm N): Apply at a "Moderate to Heavy Feeding" rate, using 10 ml to 20 ml per 1 liter of water (resulting in ~100-200 ppm N). See recipe details.
- For 1-2-1 concentrate (10,000 ppm N): Apply at a "Moderate to Heavy Feeding" rate, using 10 ml to 20 ml per 1 liter of water (resulting in ~100-200 ppm N, 200-400 P₂O₅, 100-200 K₂O). See recipe details.
Avoid: Do not fertilize in late fall and winter.

Misting Requirements

Peace Lilies are tropical plants that appreciate high humidity.

Recommended: Your outdoor location likely provides adequate humidity for much of the year. However, if you notice the leaf tips turning brown or crispy, it can be a sign of low humidity.
Methods:

Misting the foliage with a spray bottle is a good occasional practice, especially on hot, dry days.
The large pot size and amount of foliage will also help create its own humid microclimate.

Pot Size and Soil Type

Pot Size: Your 18-20" pot is a perfect size for a large, mature Peace Lily. It has plenty of room to grow and thrive. Peace Lilies don't mind being somewhat root-bound, but for a plant of this size, it may benefit from having its soil refreshed every couple of years.
Soil Type: Use a well-draining, all-purpose potting mix that is rich in organic matter. A standard indoor potting mix is suitable.
Repotting/Soil Refresh: Instead of a full repot, which can be challenging with a plant this large, you can "refresh" the soil. Carefully scrape away the top 2-3 inches of old soil and replace it with fresh potting mix. This provides new nutrients and aeration. If you do choose to fully repot, remember to choose a pot only 2 inches larger and ensure it has ample drainage holes.

Other Important Care Notes:

Cleaning: The large, glossy leaves of your Peace Lily will collect dust outdoors. Regularly wipe them gently with a soft, damp cloth to keep them clean and to allow for better light absorption.
Flowering: To encourage more flowers, ensure it receives consistent, bright indirect light and a regular feeding schedule during the growing season.
Toxicity: Keep out of reach of pets and small children, as Peace Lilies are considered toxic if ingested.
Winter: Given your location you will need to bring your Peace Lily indoors before the first frost, as it is not cold hardy.