Tall Pencil Cactus growing in a greenhouse in Richmond, VA

What do you think of when you think of a cactus? For most of us, the image is probably a rotund, spiny plant that may not be very large. Do you picture a plant that resembles a quirky tree? If not (or if that description is something that intrigues you), then the Pencil Cactus is certainly a cactus variety to check out with its pencil-esque, fast-growing branches. 

Pencil Cactus Characteristics

The Pencil Cactus is one of the more unique varieties of cacti that you will find. The following are some characteristics and fun facts about Pencil Cacti:

  • Also known as Firesticks, Sticks of Fire or Pencil Tree 
  • Grows about 2-3 feet tall and can reach nearly ceiling height inside the home
  • The branches are thin, green, and pencil-like in thickness, thus the name, with thicker, brown stems near the base 
  • Blooms from May to July with small, yellow flowers 
  • Does not have spines like other cacti 

Light & Temperature Requirements

The Pencil Cactus likes to have full sun

Full sun does not, however, mean that your Pencil Cactus needs to be in constant, direct sunlight to grow properly. Full sun means that your plant should be in bright, direct sunlight for at least six hours. 

Depending on where the windows are located in your home, six hours of full sun may very well be possible to grow a healthy Pencil Cactus.

Moving your Pencil Cactus will be more difficult if it is planted outside, so make sure that you choose a place where the sun will not be blocked by your house, trees, or other plants for some or most of the day. 

Water Requirements

Since Pencil Cacti are a variety of cactus, Pencil Cacti need very little water.

Most succulents can be watered once a month, but the Pencil Cactus can be watered less than this every two weeks or so.

If you think that you are watering your cactus too much or you do not know when to water your Pencil Cactus, pay attention to the soil. Only water when the soil is dry to the touch, 

Pencil Cacti are drought tolerant, so you do not need to worry about underwatering this plant as much as even other kinds of succulents. In fact, less water means that your Pencil Cacti will grow even better.

Is The Pencil Cactus Poisonous? 

The Pencil Cactus itself is not poisonous but does contain a sap that is poisonous.

The milky sap inside a Pencil Cactus is poisonous to people and animals when it is ingested in any way. It can cause allergic reactions on the skin as well.

The sap can also cause temporary blindness if it gets in your eyes.

Though there is no arguing that the Pencil Cactus is poisonous, it is not deadly. There is a very low chance that getting the sap on your skin or ingesting it will kill you. Even so, it is suggested to do everything you can to prevent coming into contact with the sap. 

What Happens If I Touch A Pencil Cactus?

You should not touch a Pencil Cactus.

The best practice when handing a Pencil Cactus is to do so while wearing gloves

As mentioned, the Pencil Cactus itself is not poisonous; it is the sap inside the cacti that can be dangerous. Wearing proper hand coverings means that you will not chance coming into contact with the sap inside the Pencil Cactus. 

Some of the negative effects of the Pencil Cactus’s sap are:

  • Burning eyes
  • Numbness in skin and other affected areas
  • Shortness of breath
  • Various symptoms of anaphylactic shock

Does The Pencil Cactus Need Full Sun?

Yes, the Pencil Cactus needs full sun. 

In order to get the best potential out of your Pencil Cactus, it is recommended that you plant or place your Pencil Cactus in an area where it will get at least six hours of direct sunlight every day.

While your Pencil Cactus may not die from lack of sunlight, it will:

  • Have uneven growing patterns based on how much sunlight it is getting
  • Become thin
  • Look sickly
  • Grow thin

Overwatering is a bigger culprit when it comes to a droopy, sad looking Pencil Cactus, but it is still important to place your cactus where it will get adequate sunlight.  

Can I Put My Pencil Cactus Outside?

Yes, you can grow your Pencil Cactus outside – in fact, that is how it is most commonly grown in the United States.

Since the Pencil Cactus is both drought and winter hardy, so temperature fluctuations are not a major concern for the plant. 

As long as your Pencil Cactus has full sun and a well-draining soil, then it will be happy growing outside. 

When grown outside, Pencil Cacti grow large and wide enough to be grown as a shrub or hedge. 

What Kills Pencil Cacti? 

Pencil Cacti are a hardy plant, but they are not omitted from potential threats, such as:

  • Overwatching, which can cause root rot 
  • Certain pests, like spider mites and mealy bugs
  • Fungal infections, though it is not common

Keep an eye out for anything that looks off with your Pencil Cactus, like:

  • Soft roots
  • Dead stems
  • Signs of pests
  • Droopy, brown or gray stems 

How To Propagate A Pencil Cactus

Propagation of the Pencil Cactus is similar to what would be done with other varieties of succulents:

  1. Use a sharp, sterilized knife or pair of scissors
  2. Put on a pair of gloves to avoid touching the plant’s sap
  3. Off of a piece of the plant of about 6 inches 
  4. Allow the cutting to dry out for about a week before placing the cutting in a pot of soil
  5. Wait for about 4 weeks for the plant to root

Once your cutting has rooted and is beginning to grow, you can choose the new home for your Pencil Cactus – whether that is inside or outside your home.