Castor bean plants are easy to care for, low maintenance, and they grow very quickly. Even beginners can enjoy the large showy foliage in their gardens once you learn how to care for them.
This guide will teach you what your plant needs for water, sun, soil, and fertilizer, plus I’ll share tips on location, temperature, pruning, and much more.
Quick Castor Bean Plant Care Overview
| Scientific name: | Ricinus communis |
| Classification: | Tropical plant |
| Common names: | Castor Bean Plant, Castor Oil Plant, Ricin Plant, Dog Tick Plant |
| Hardiness: | Zones 9-11 |
| Temperature: | 68-80°F (20-26.6°C) |
| Flowers: | Red or pink, blooms summer-fall |
| Light: | Full sun |
| Water: | Keep soil evenly moist, do not overwater |
| Humidity: | Average to high |
| Fertilizer: | General purpose plant food spring-summer |
| Soil: | Rich, fertile, well-draining |
| Common pests: | Spider mites |
What Is A Castor Bean Plant?
Castor bean plants (Ricinus communis) are tropical perennials native to East Africa. This fast-growing plant and can get up to 6-10’ in just one season, reaching heights of 40’ or more in warm climates.
Stunning star-shaped foliage is the main characteristic, and it can be green, red, bronze, or purple. The large serrated-edged leaves range between 2-5” across, and grow at the top of semi-woody stems.
The seeds resemble an engorged tick, which is where the name “Ricinus”, the Latin word for ‘tick,’ came from, and also why it’s two common nicknames are “ricin plant” and “dog tick plant”.
Different Castor Bean Plant Varieties
There are many castor bean cultivars to choose from and each feature different foliage, stem, and seed pod colors. Thankfully, no matter which type you choose, they can all be cared for in the same way. Here are some of the more common ones.
- Ricinus communis ‘Impala’ – A compact cultivar that doesn’t exceed 4’ tall and has purple-red leaves and stems.
- Ricinus communis ‘Zanzibar’ – This tall variety can reach 7-10’ in one season and has vivid green leaves with white ribbing.
- Ricinus communis ‘Gibsonii’ – Expect 4-5’ of height in this type with dark red-hued leaves and pink pods.
- Ricinus communis ‘Carmencita Bright Red’ – This cultivar reaches between 5-6’ with bronze-red glossy leaves and bright red pods.
Flowers
Castor bean plants have male and female flowers that form on a long stem, and both are insignificant in appearance. Depending on the climate, they can bloom year-round, or will appear in mid to late summer.
The female flowers grow in clusters at the end of the spikes and have no petals. The males appear beneath them and have creamy colored ends when they bloom.
Once pollinated the females form striking a pom-pom shaped pods with spiky pink or red outsides, adding to the beauty.
Castor Bean Plant Toxicity
All parts of castor bean plants are extremely poisonous to people and animals, especially the seeds. It’s important to wear hand and eye protection when working with it, and avoid ingesting any part of the plant.
Keep this plant well out of reach of pets and children. You can get more information on toxic plants at the ASPCA website.
How To Grow Castor Beans
Before we get into the details of how to care for castor bean plants, let’s first chat about where to grow them. The right location is key for fast, healthy growth every year.
Ricinus communis Hardiness
Castor bean plants are not very hardy. They are a tender perennial, meaning they’ll come back every year only in the warmest climates, like zones 9-11. So most of us will have to grow them as annuals.
Anything below 32°F (0°C) will kill the plant, but you can move one that’s potted into a bright, warm location to survive the cold.
They can be prolific self-seeders, which means new plants may show up without your help the following spring, even in colder climates.
Where To Grow Castor Bean Plant
Ricinus communis prefers a spot in full sun with well-drained but consistently moist soil where it’s sheltered from strong winds.
They grow well in the ground or in containers, as long as the pot is large and sturdy enough to accommodate the top-heavy plant. Also, make sure the pot has drainage holes to prevent overwatering.
Wherever you choose to grow it, be sure to allow plenty of space for your plant to reach full size and branch out.
Castor Bean Plant Care & Growing Instructions
Now that you know where to grow your dog tick plant, let’s chat about how to provide the best care. Use the tips below to set yours up for a healthy season.
Light
Castor bean plants grow best in full sun. They can tolerate some shade, but the foliage will be sparse, the plant could become leggy, and it probably won’t bloom.
Provide at least 8 hours of direct sunlight exposure a day if possible, with minimal shade.
Water
Once established, Ricinus communis is semi-drought tolerant. However, if you grow it as an annual you’ll need to provide consistent moisture.
Let the soil dry out a few inches deep then water thoroughly, but avoid puddling or completely saturating the area.
If you have trouble getting the levels just right, invest in an inexpensive soil moisture probe. You’ll be looking for the gauge to read between 3-5 before watering again.
Humidity
Castor bean plants thrive best in high humidity, but can tolerate low-average levels too.
In arid regions you can increase levels by grouping plants closer together and making sure the soil stays slightly moist, especially during heat waves and on very sunny days.
Temperature
The optimal temperature range for growing castor bean plants is between 68-80°F (20-26.6°C). Anything cooler than that will slow down growth, or could even stop it.
When temperatures drop below 45°F (7°C) the foliage may begin to show damage, and the plant will die if it gets below 32°F (0°C).
In higher temperatures you may need to water more often to prevent them from drying out.
Fertilizer
Since castor bean plants grow so fast, they do best with regular feedings. Use all-purpose slow release granules once per month, or go with a general liquid fertilizer every other week.
Start fertilizing in early spring when new growth appears, and continue until temperatures begin to drop in the fall.
Soil
A ricin plant will grow best in a well-draining, moist soil that’s rich and fertile. They prefer a neutral to acidic environment with a pH between 6-7.3, which you can check with a probe gauge.
Amend your garden soil with compost before planting to improve drainage and fertility. For containers, amend a general purpose potting soil with compost and perlite.
Transplanting
The best time to move a perennial castor bean plant is in the early spring. Prune it down to just a few inches above the ground in the late fall to make transplanting it more manageable.
When all chance of frost is gone and temperatures remain above 45°F (7°C) at night, carefully dig up the plant and move it to its new location or container.
Spring is also the best time to plant seeds or seedlings. Make sure to wait until the soil is 70°F (21°C), because the cold can stunt their growth or prevent germination. You can check it with a soil thermometer.
Get my full step by step instructions for how to grow castor bean plants from from seed.
Pruning
Pruning is a good way to keep your castor bean plant looking tidy and to control the size and self-seeding habit.
Always wear gloves and eye protection, and use sharp sterile pruners to cut the plant. Trim away any yellowing or damaged foliage throughout the season as needed.
If you’d like to stop it from spreading, trim off the flower stalks before the pods dry out.
In warmer climates, cut the plant back in the fall or winter to control the size. You can prune it to just a few inches above the soil line without worrying about damaging it.
Pest Control Tips
Castor bean plants don’t usually have issues with pests because of their toxicity. But occasionally in dry, hot weather you may encounter spider mites.
Treat them with neem oil or an insecticidal soap. I make my own by mixing 1 teaspoon of mild, liquid soap with 1 liter of water.
Sometimes other bugs, like Japanese beetles, could munch holes in the leaves. But they rarely become a nuisance because they don’t favor the plant.
Castor Bean Plant Propagation Tips
Unfortunately, you cannot propagate castor bean plants by cuttings or division. The best way to multiply them is by seed.
They’re very good at self-sowing and are even considered invasive in some regions because of how quickly they grow and spread.
So it’s easy to collect the castor seeds from your garden after the pods have dried and split open in the fall.
Direct sow them in your garden in the early spring when temperatures are above 60°F (16°C), or start them inside 6-8 weeks beforehand.
Troubleshooting Common Problems
Castor bean plants are very easy to care for and generally have few issues, but no plant is completely problem free. If you run into one of these more common ones, use my tips to get back on track.
Castor Bean Plant Not Growing
The main reasons that a castor bean plant may not grow are temperature issues, lack of light, or inconsistent watering.
They’ll grow best when it’s between 68-80°F (20-26.6°C), where they get 8 or more hours of direct sun a day, and in well-drained soil that’s evenly moist but not wet.
Yellow Leaves
The main causes of yellowing leaves on a castor bean plant are aging, overwatering, lack of nutrients, or bacterial leaf spot.
Don’t water to the point of puddling the soil, and use a moisture gauge to monitor it. Ensure your plant has plenty of nutrients from rich soil or fertilizer, and give it lots of direct sun.
If only the occasional leaf turns yellow and drops off, it’s just a process of aging, and nothing to worry about.
Holes In The Leaves
Holes in the leaves of your castor bean plant are usually caused by insects, but it’s pretty uncommon for them to cause major damage. I’ve seen Japanese beetles munching holes in mine before, but never more than a few at a time.
If you see any bugs eating the leaves, and they become a problem, you can treat the plant with insecticidal soap or neem oil.
FAQs
Castor bean plants grow very quickly. In an ideal environment they can add 6-10’ of height every summer, and can grow as large as 40 feet tall or more in just a few short years.
Yes, you can grow castor bean plants in heavy, large pots that have good drainage. Choose a container that can hold the weight of the tall plant without toppling over, and use a 12-14” pot at minimum.
Castor bean plants are tender perennials that can come back every year in zones 9-11, where the temperatures don’t drop below freezing in the winter. In colder regions, you can grow them as annuals.
Castor bean plants will survive the winter outdoors in zones 9-11. In cold regions that get down to 32°F (0°C) or lower, the freezing temperatures will kill off the plant.
No, castor bean plants are not safe to eat. All parts of the plant, especially the seeds, are extremely poisonous to pets and humans if ingested.
Yes, you can safely touch a castor bean plant. However if your skin is exposed to the oils, they can cause irritation. It’s a good idea to always wear gloves and eye protection when relocating or pruning the plant.
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Share your castor bean plant care tips in the comments section below.
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