For beginner gardeners and houseplant enthusiasts who love to travel, cacti are some of the most popular plants to grow. They’re hardy, can withstand periods of drought, and by nature don’t need very frequent watering. But just how many types of indoor cacti are there? There are over 2000 species of cacti, split up among 87 genera. Some larger species, like the saguaro cactus, are primarily grown outdoors due to their large mature size; however, that doesn’t mean it’s impossible to grow them inside.
At this point, you’re probably wondering, “How do I know what kind of cactus I have? Is it even important to know, or do they all need the same care?” Knowing what kind of cacti you have is essential for proper care, and it comes down to physical characteristics.
Why it’s important to know what kind of cacti you’re growing
Knowing the kind of cacti you’re growing is just as important as knowing the different names for all your leafy, water-loving plants. Why? Because without that knowledge, you won’t know the best way to ensure happy, healthy growth. Every cactus species is different, and although there are some general guidelines you can follow, the nuanced aspects of their care can vary.
Cacti can have different flowering times, different pest problems, different solutions for spine loss, and more. While knowing how much light and water a cactus needs is essential to keeping it alive, you won’t know exactly what you’re dealing with without identifying your cactus.
Ways to identify your cacti
There are multiple ways you can identify your cacti! Even from just having them in your home, it’s easy to see that they can have different lengths, widths, and overall sizes of spines, as well as varying in shape and maturity size. The first step is to make sure what you’re dealing with is a cactus and not a succulent (although cacti fall under the blanket umbrella of succulents, not all succulents are cacti).
Cacti — even spineless ones, which do exist! — have areoles. The areoles are soft, cushion-like areas that the flowers, fruits, hairs, and spines on a cactus grow from. Although some succulents have spines, they don’t have areoles. So looking for this distinct organ, which is present in cacti after two to three weeks of life, is important.
Size and shape
Looking at the sizes and shapes of your cacti is a good place to start. Some cacti varieties will grow small and aggressive while others, like the saguaro cactus, have an enormous maturity size. Larger ones can be managed as indoor plants, and usually you’ll be able to tell whether they’ll be big or not based on their growth patterns.
The shape is a big factor, too. Although many cacti are globular and cylindrical, some have winding growth, and others grow in sections called pads. Is your cactus stubby and growing outwards, or is it thinner and growing tall? With over 2000 species of cacti, the shape and the size can do a lot for whittling down your options.
Stems and spines
The stems and spines are good indicators of what cactus you’re dealing with, especially when paired with its size and shape. Cacti stems can be smooth or ribbed, covered in spines or just sporting areoles. A stubby ribbed cactus may be a different variety than a ribbed cactus with column-like growth, so looking up identifiers in groups with getting you closer to figuring out what kind of cactus you’re dealing with. Some cacti even have tubercles (growths that sprout from the outer parts of the plant) that can be round or triangular, which are especially helpful for figuring out its species.
Because spines can look so different from species to species, they shouldn’t be overlooked. Some spines are small and hair-like, often appearing soft on the surface of the cactus. Others are thick and long, usually giving off more of an “if I touch this, I might die” feeling. Some varieties are even more unique, like the old man cactus (or Cephalocereus senilis). The old man cactus has what seems to be unkempt white hair growing all around it, and the hair actually covers up sharp yellow spines. Cacti with more unique spines will be easier to identify, but for others you’ll want to research multiple characteristics.
What are the flowers like?
A flowering cactus is rather peculiar, and if you’re lucky enough to have a bloom on yours, it’s a great way to identify what cactus you’re dealing with. Cacti can have bright or pale blooms, and some even have two-toned blooms with one color at the outer part of the flower and another at the inner part.
The timing and season in which the blooms grow can give a good hint at the species, too. For example, the highly-regarded Christmas cactus blooms from early- to mid-Winter; however, the similar-looking Thanksgiving cactus starts growing its blooms in late-Fall and they continue through mid-Winter. For these holiday cacti, the best way to identify them is to pay attention to what time of year they bloom.
Something to keep in mind, though, is that some cacti may need specific conditions to flower. If your cactus isn’t flowering, that doesn’t necessarily mean it won’t flower — especially if you don’t know what variety or species it is. If it doesn’t have flowers, you’ll want to leave out flowering habits altogether when identifying the cactus, otherwise you could be led down the wrong trail.
Are there leaves?
Perhaps the most unique factor to consider when identifying your cacti is whether or not they have leaves. Roughly 90 percent of cacti varieties don’t have leaves in any way, shape, or form, so right away your options are narrowed. Cacti leaves are rarely seen, especially since some only show leaves when new growth is forming. Although some grow leaves during any stage, pay close attention as you care for them during the growing season.
Is there an app to identify cacti?
If you can’t seem to Google the right things to get the result you want (does a different cactus show up no matter what characteristics you put in?), don’t worry! There’s an app for that. The iNaturalist app is one of the best cactus and plant identification apps, with over 1.3 million hobbyists and professionals that can help you figure out what kind of plant you’re dealing with.
iNaturalist can be downloaded on Google Play or Apple’s App Store and might be a good last-ditch effort to identify your houseplants. Knowing the kind of cacti you’re growing will enable you to provide more nuanced, individualized care to keep them happy, healthy, and thriving.
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