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What comes to mind when you think of cactus?  

Perhaps the first thing you think of is the spines. If you have ever been unfortunate enough to have been pricked by a cactus, you’ll likely never forget that most of them have needles.  
*Did I ever tell you about the time I worked on golf course landscape and backed into a teddy bear cholla and got an entire piece lodged in the back of my leg?
 
Besides being painful to those who get too near to cacti, did you know that there are important reasons that cacti have spines?

Golden barrel cactuses (Echinocactus grusonii)

First, let’s look at the spines of cactus for what they are – the main part of cactus often functions as a modified stem, and its needles are the leaves.
 
The most obvious function of cactus spines is to protect the cacti from animals and people. There are, however, a few animals who aren’t deterred by the sharp spines of cacti such as javelina, tortoises and pack rats.

Saguaro cactus (Carnegiea gigantea) spines

 
Suprise, the primary function of the spines are to actually shade the cactus.
 
Although just one small spine would hardly provide shade, thousands of them can provide enough.
 

Why is sun protection needed for the surface of cacti? The shade from the spines let the cactus lose water through the atmosphere. This helps keep the cactus temperature relatively low.

Black-spine prickly pear (Opuntia macrocentra)

 Another function that the spines serve is that they help certain species of cacti such as cholla to root and spread.

Teddy bear cholla (Opuntia bigelovii)

Spines of the Cholla are specialized to detach and attach onto anything that comes to close. There are tiny barbs at the tips which grab on to anything that gets too close. It almost appears as if they ‘jump’ off of the main cactus as they latch on the unlucky recipient.

Segments of the Cholla are usually moved and then fall off and grow in better conditions. If you have ever seen cholla growing in large groups, this is why. 
**If like me, you are ever unlucky enough to find a piece of cholla embedded in your clothes or worse, your skin – you can use a comb to help pull out the barbs.  When hiking in the desert, it is easy to get them stuck on your shoes.  I usually grab a rock and use it to push off the Cholla segment.  When all else fails, a good pair of needle-nose pliers works.
 

Two young saguaro cactuses are emerging from the shelter of a creosote shrub.

Hopefully, you have a new appreciation for cacti and their spines.  But, it’s still important to be careful because it hurts when you get pricked!


Do you like prickly cactus?  

I have a few favorites, one being santa-rita prickly pear (Opuntia violaceae var. santa rita). The color contrast of their blue-grey pads and the shades of purple are so striking in the landscape.  

This cactus makes a beautiful accent plant for the landscape. Both the pads and fruit are edible, (but you might want to remove the spines first ;-). Cold temperature and drought intensify the purple color.

Santa-rita prickly pear is native to the Southwest regions of North America. They can grow as large as 6 ft. X 6 ft., but can be pruned to maintain a smaller size.  Pruning is done carefully, by making pruning cuts at the junction where the pads connect.


Lovely yellow flowers appear in spring followed by red fruit in the summer months.  Javelina, rabbits and pack rats will sometimes eat the pads. Pack rats use the pads to make their homes.

The pads of the prickly pear are covered with clusters of 2″ spines as well as tiny spines known as glochids. Glochids are incredibly irritating to the skin and detach from the pad very easily. Their tips have a small barb, which makes them difficult to remove from your skin.  If you need to handle them, use a few layers of newspaper or a piece of carpet. Do not make the mistake of touching the pads with gloves because the glochids will attach to your gloves and render them useless, (I ruined a perfectly good pair this way). 
 
 **There are different ways to remove these small spines, including applying Elmer’s glue (letting it dry and then pulling them off), but many people have reported greater success using duct tape. 

 

 
USES: In addition to serving as an accent plant in the landscape, this prickly pear species can also be used as a screen. Some may be surprised to learn that they also make excellent container plants, just make sure they are not near any foot traffic areas. They do well in full sun or light shade in well-drained soil.
 
MAINTENANCE: Prickly pear is very low-maintenance plants. I always use tongs to pick up the pads that I have pruned, or you can use newspaper.  
 
Although they are incredibly drought-tolerant, watering once a month during the hot summer months, in the absence of rain, will be appreciated and will improve the appearance of your prickly pear. Shriveled pads indicate acute drought-stress.
 
 

Many people believe that the appearance of white, cotton-like areas on the pads is a sign of a fungal infection. However, it is caused by a small insect that secretes the white cottony mass, called cochineal scale.  Control is straightforward – simply spray off it with a strong jet of water from the hose – that’s it!

 
PROPAGATION: Prickly pear can be planted from seed, but there is a much easier way. Just cut off a pad that is at least 6 inches tall. Put the pad upright, in a shady, dry place for at least about two weeks. This allows a callus to form at the bottom.  
 
Plant with the cut end down, do not water for the first month because the bottom is susceptible to fungal infections. After the first month, water every 2 – 3 weeks until established.  If planted in the summer, provide shade until established (about three months). *I generally do not recommend planting in the winter but encourage waiting until spring when the soil warms up. 
 
If you have a large prickly pear, you can prune it, or you can start over by taking it out and cutting off some of the pads and plant them in the same place. Many of my clients have done this and been happy with the results.
 
INTERESTING HISTORICAL FACT: The Aztecs would cultivate prickly pear cactus infected with cochineal scale because the insects secrete a dark red dye with crushed. This was used to dye cloth. The Spanish exported this dye from Mexico back to Europe where it was used to dye royal garments and British military uniforms. The dye was highly valued by the Spanish, next to gold and silver. It takes 70,000 insects to produce 1 pound of dye.
 
*This is but one of many beautiful prickly pear species available to the home gardener.   Do you have a favorite species of prickly pear cactus?