Leaf splitting (fenestration) is a sign of leaf maturity. Monstera plants’ upper leaves usually split when the plant is 2 or 3 years old.
The upper, older leaves split as an evolutionary adaptation, allowing more sunlight to get through to the lower part of the plant where the younger leaves are just starting.
Fenestration May Also Promote Good Air Circulation
Monstera deliciosa is commonly called “Swiss Cheese Plant” because of its holey leaves.
This climbing vine has deep green leathery leaves that can grow to be three feet wide under the right circumstances.
In mature leaves, natural fenestrations begin to form near the central rib of the leaf. From here, they radiate out, increasing in size and number as the leaf grows larger.
Although the purpose of these splits is apparently to enable more light to get to young leaves below, it’s worth noting that immature, understory plants in the wild tend to grow away from the light these splits let in.
It is speculated that the reason for this is that the young vines want to ramble toward the base of a large tree to climb up and into the light. [source]
For this reason, it has also been speculated that the splits in Monstera leaves help to promote good air circulation around the plants.
This helps prevent the development of fungal and bacterial infections.
The holes in the leaves also allow rain water to pass through, thereby watering the immature understory plants below and preventing the pooling of water in the leaves.
When water pools up in large, mature plant leaves, it encourages fungal and bacterial growth and provides breeding grounds for a wide variety of insect pests and potentially undesirable critters.
How Can You Get A Monstera Plant’s Leaves To Split?
There is no magical incantation to force leaf splitting in Swiss Cheese plants.
Your plant must be 2 or 3 years old before even considering developing split leaves.
Additionally, it must be in good health. If you want your Monstera to develop split leaves, the best thing you can do is take good care of it in a regular, ongoing, patient manner.
To do this, you must provide:
- Support by giving the plant a moss pole, stake, or trellis to climb. Moss poles are best because they are most like the trees these plants naturally climb in the jungles of Mexico and Panama. When your mature plant is well cared for and securely supported, it will begin to develop fenestrated leaves.
- Consistently warm temperatures that never fall below 45 degrees Fahrenheit. Keep in mind that Monstera is only winter hardy in tropical and semi-tropical settings (e.g., USDA hardiness zones 10a-12b).
- Regular, soak-and-dry watering. Allow the top 3” inches of soil to dry before providing your plant with a thorough watering. Never allow your plant to stand in water.
- Bright, indirect sunlight for 3 to 6 hours daily. Too much sun or harsh sun exposure will burn the plants’ large leaves.
- Light monthly fertilizing during the spring and summer months. Do not fertilize during the autumn and winter.
- Well draining potting soil with a high percentage of natural, organic matter.
What If Your Plant Is Mature & Healthy, But Its Leaves Still Don’t Split?
When you purchase or receive your Monstera, be sure to identify it right away so that you will have realistic expectations. If your plant is either Monstera deliciosa or Monstera adansonii, it should develop leaf fenestrations as it matures.
In fact, many types of Monstera develop split leaves, such as:
- Monstera acacoyaguensis
- Monstera epipremnoides
- Monstera punctulata
- Monstera borsigiana
- Monstera acuminata
- Monstera variegata
- Monstera sublimate
- Monstera esqueleto
- Monstera obliqua
However, quite a few of these will not develop fenestrations if they are grown indoors!
Some types of Monsteras do not develop split leaves at all. Among these are:
- Monstera pinnatipartita
- Monstera karstenianum
- Monstera standleyana
- Monstera siltepecana
- Monstera dubia
It’s easy to see that adequately identifying your Monstera right from the start is an essential part of growing a Swiss Cheese plant with truly holey leaves!