The popcorn plant is a tall shrub, and in its native African habitat it can grow up to 25 feet in height. When grown as a small shrub in colder climates as an annual, it usually doesn't get taller than 3 feet. The plant's common name comes, in part, from its distinctive scent, said to be uncannily like buttered popcorn. The smell comes not from the bright yellow flowers (which also look a bit like popped popcorn), but from the small oval leaves. The leaves grow to about 3 inches long in pairs up and down the stem. The plant is popular with children for its recognizable scent that must be coaxed by touching the leaves. However, since the plant is poisonous if ingested, it's best not to have it in reach of small children or curious pets.
|Botanical Name||Senna didymobotrya|
|Common Name||Popcorn plant, cassia|
|Plant Type||Perennial, annual|
|Mature size||10-25 ft. (perennial), 2-3 ft. (annual)|
|Soil pH||Acidic, neutral|
|Toxicity||Toxic to Humans and Pets|
Popcorn Plant Care
With proper care, plenty of water, and good fertilizer, popcorn plants will bloom all summer long and into the autumn but will be at their most floriferous in the hot humid days of summer. When other plants wilt in the heat, the popcorn plant flourishes. After flowering for a long season, the plant puts out brown seed pods that are a tasty snack for songbirds.
The popcorn plant's vibrant color makes it a dramatic sight in the summertime garden landscape. It is a heat-tolerant species, well suited to hot and humid regions.
Popcorn plants are somewhat invasive in their native Africa. One variety of the Senna genus can be quite weedy in some hot humid regions such as south Florida. Check the label and be sure to get Senna didymobotrya and not Senna pendula var. glabrata.
The popcorn plant likes heat and light, so it's best to place your plants in direct sun. If the plant is getting too hot and dry, its leaves may close up during the day. They also tend to close up at night to conserve moisture.
This plant likes very fertile, rich, and well-drained soils. When grown in pots, potting mix with some sandy loam is a good combination. Potting mix alone may drain quickly and leave this moisture-loving plant too dry.
Water your tropical popcorn plant regularly. Daily is the best bet if it's in a container. If the leaves close up during the day, that means it may be wanting some water. Keep the soil moist but not wet. Misting the leaves with water in a sprayer is advisable if the weather is hot and dry.
Temperature and Humidity
After daily temperatures fall below 80 degrees Fahrenheit, the flowering and growth of your popcorn plants will slow down somewhat. This plant adores high humidity levels.
Popcorn plants respond well to fertilizer throughout the growing season. Fertilize in late spring and again once or twice in middle and/or late summer with a fertilizer designed specifically for tropical plants.
Deadheading spent blooms and trimming any dead or leafless branches will help to keep your popcorn plant looking healthy and full. There's no need for serious pruning.
Propagating Popcorn Plants
This plant can also be propagated from seeds or cuttings but is usually fairly inexpensive at a garden shop when purchased as an annual. Keep in mind that growing it from cuttings can take a long while and is often unsuccessful, which is why propagating via seed is usually the best bet.
How to Grow Popcorn Plants From Seed
The seed pots on popcorn plants are several inches long and contain at least a dozen seeds each. Pull the dried pods from the plant in late fall and collect the seeds. Before planting in the spring, soak the seeds in water for 24 hours. Sow them in containers filled with well-draining yet moist potting soil. Sow them in very early spring with the goal of planting healthy seedlings in the garden after all threat of frost has passed.
Potting and Repotting Popcorn Plants
When growing these plants in containers, make sure the soil is well-draining, and ensure plenty of drainage holes in the bottom of the container. It can also help to add a layer of pebbles to allow the water to drain even further. The container should be at least a few inches wider than the roots of the plant to allow for space to grow, as well as wide enough to handle the height of the growing plant without allowing it to topple over.
Popcorn plants can be overwintered if kept indoors. A greenhouse is preferable, but a garage is fine if the temperature stays above 40 degrees Fahrenheit. They will only need watering occasionally.
If kept in a dark place the plant will go dormant. Bring it back outside once all danger of frost has passed and the nighttime temps stay above 40 degrees Fahrenheit on a regular basis.
If you are in a tropical zone, overwintering plants in the garden should not be an issue.
Common Pests and Plant Diseases
Fortunately, this plant doesn't have much trouble with pests or diseases. Aphids will sometimes sample it; they can be remedied by a strong jet of water to wash them away or horticultural oil to deter them. This plant can also experience fungal diseases if kept too wet. Avoid this by giving it excellent air circulation and keeping the soil moist, but not wet.
How to Get Popcorn Plants to Bloom
Popcorn plants should bloom readily in their proper zone. As a tropical plant, blooms can be severely stunted if the temperatures drop below 40 degrees Fahrenheit. To keep it blooming well, make sure it's inside and protected during the colder months. A popcorn plant that is kept in the garden soil will die back if the winters are too cold and will need to be replaced in the spring.
Where should I place popcorn plants in my house?
These are tropical plants, so give them full sun on the hottest windowsill you can find. They also need good air circulation, so a room with a ceiling fan is ideal. Be sure to mist the plant on a regular basis.
How long does a popcorn plant live?
Though these are often planted as an annual in colder climates, when kept in a tropical climate and given proper care, the popcorn plant can live for up to 10 years.
Why did my popcorn plant suddenly turn brown?
These plants are very susceptible to frost. If there was a sudden dip in temperature overnight, or the plant was covered in frost, the demise can be surprisingly quick.
Witt A, Luke Q, eds. Guide to the Naturalized and Invasive Plants of Eastern Africa. CABI, 2017. doi:10.1079/9781786392145.0000