Edithcolea grandis: How to Make Your Persian Carpet Flower Bloom

You, like me, may have seen the flowers for these stapeliads online somewhere and thought to yourself “I’m good at growing plants. I could totally grow these. I would love to see the flowers!”

I too had those thoughts. I too thought it would be simple to just grow the plants and get flowers. I bought my first Edithcolea grandis during COVID, in 2021, and thought “well, I’ve done so well with other stapeliads, how hard could this be?”

HAH. This year, in the fall of 2025, is the first year I have ever had my Edithcolea grandis bloom for me. I’ve held back on writing a guide on how to grow these purely because getting them to bloom is a pretty important part of growing these prickly little plants, and it felt like I’d be missing a key part of their cultivation if I couldn’t tell you how to get them to bloom. With that…let’s start at the beginning: keeping them alive in the first place.

My Edithcolea grandis in October 2021, not long after I first acquired them

I’ve experimented with more organic material (as in – succulent soil) vs less, and I find a roughly 50/50 of soil to inorganic material to be the minimum for healthy roots and decent growth. It’s worth calling out that your soil composition and ability for it to drain matters a lot for your Persian Carpet Flower – as I discuss fertilizer and watering frequency later on, a very crucial piece of providing those things is how well the soil drains and how quickly it dries. 

Light Exposure (and temperature)

If you’re growing yours indoors, god speed. I have no idea how you’d keep these happy as far as temperature AND lighting is concerned, so use this section as inspiration rather than strict guidance. 

I keep my Edithcolea grandis in my greenhouse, and have done so pretty much since the day I acquired them. This means they get nice and hot all summer long, and are protected from freezing in the winter. 

Light exposure is also influenced by where in my greenhouse I keep them. Originally, they were on a bench, with my 40% shade cloth giving them some shade. In the last year, I also rooted a cutting in the ground along with several of my cheiridopsis, and that cutting has done well in nearly full sun. 

So… there’s two ways to measure the light needed for this plant. 

If you want to simply get it to grow, more shade helps. You’ll get more new growth in the form of arms and branches if the plant has more shade. That said, they need a certain amount of sun stress in order to bloom. 

I have typically judged adequate light exposure based on color: they should be nicely compact in growth, plump and not overly wrinkly, with a barely green stem and deep purple highlights. You may notice that one of the Edithcolea pictured above (the big, healthy looking one in the middle) is kinda looking that way. The one at the left is deeply purple, and the spines are tighter and closer together. The two plants were almost side by side in the greenhouse! 

In the case of the plants above, the difference in color can be explained by differences in soil composition: the one that was failing to thrive actually had more organic matter in the soil blend than the other. Combined with adding rock on top to help retain moisture (I used landscape gravel as top dressing), this actually held in too much moisture, and rotted out the roots. 

Even so – the two in the photo are good examples of “too much stress” (of some kind) and “not enough light”. Neither plant produced flower buds for me in 2022. 

I repotted the larger plant in the summer of 2023, and it promptly began to hate its existence. This photo is from October of 2023. 

Exclusively during summer, when it’s very hot, the extra day of puddle-sitting seems to have helped the straggling bits to root again. Not all of them, mind you, but a decent enough handful than the 12″ dish I used to pot up the larger specimen began to look like I was growing a plant, and not a pile of thorny brambles. 

In winter, I don’t water the greenhouse heavily enough to generate a puddle in the lowest corner (which slowly drains outside), and as a result the stapeliads I have on the floor of the greenhouse have much less access to water than they do in summer. This is important – they don’t go fully dormant in the cooler months, they just slow way down. They don’t need, and shouldn’t have, a lot of water provided. When in doubt, water less. 

I kept trying to move this big pot of Edithcolea grandis from under my bench to the top of the bench, and it’s thrown an absolute fit every time. It goes from developing the lovely green new growth, to intense stress colors and dehydration appearance. 

Adding gravel as a top dressing hasn’t helped. The only thing that has seemed to keep this plant happy in this particular terra cotta pot has been to keep it under the bench, where it receives extra water from the summer time watering puddle. 

Do I think you should have your Persian Carpet Flower sitting in water on a regular basis? No, I don’t. In my case, it seems to be helping what are effectively cuttings of the older, larger plant to re-root. Needing to have my plant sitting in water and getting babied with more shade is a sign I haven’t dialed things in for that particular specimen quite yet. At least, not enough to get it to bloom. 

Benign neglect as a care strategy

I also have a cutting I placed in the ground in spring this year, which has been watered as seldomly as everything else in that planter – and it’s thriving!

The entire area is a raised planter bed I created using retaining wall bricks, and the soil I added was a mashup of random bags I hadn’t finished using up. This included plain peat moss, raised garden bed filler, old orchid bark bags, succulent soil, and an old bag of houseplant dirt. 

I did include a bag of pumice to ensure good drainage, as I was planning to add some cheiridopsis to the planter (which has been quite successful). 

The watering routine for that planter is basically “when I remember” and/or “when it rains”. Next year, I’ll add some fertilizer around the Edithcolea to encourage blooms…but being in-ground so successfully was a pleasant surprise. We’ll see how it does over the winter months – it shouldn’t experience frost in that area, but it does get quite cold. Since the other plants have been fine in the greenhouse with temperatures down into the 30s, I suspect this in-ground specimen will be just fine as well.

My in-ground Edithcolea as of 10/2025: this was just a cutting I dropped on the ground and covered with some pebbles to protect the base while it rooted. 

August 21st, 2025 – the tiniest beginnings of buds! 

The exact type I used is linked for you here – Osmocote Smart-Release Plant Food Flower & Vegetable. 

Throw that on there at the start of spring, start of summer, and then mid-summer, add some more. 

Did I measure how much or follow the directions at all? No. I just eyeballed the pots and thought “hm, the earlier osmocote beads look faded, it should be coming up on bloom season, let’s give them some more” and that’s what I did. Extremely scientific and precise, I know, but hey – it worked! 

I’ve had buds develop in previous years, but they always dropped off before getting to any appreciable size. After multiple years failing at this, I realized it was likely due to the plants needing more consistent fertilizer and babying the second you see those bloom buds form. 

Things I am bad at: consistent fertilizer application.

Thus, we have osmocote – it’s a slow-release fertilizer that slowly degrades over time, releasing the plant food. I use it on just about everything in the greenhouse, but sparingly. I have used the blue powder fertilizer in the past, which was great for cacti. They do fantastic with my level of increasing laziness as the summer wears on. Edithcolea, on the other hand? If you want flowers, they need attention. 

August 29th, 2025 (notice the third bud has basically disappeared)

Near as I can tell, the things you need for buds to form are: 

• Enough light to make the plant blush purple
• Enough water that it’s plump, but not overly so 
• Consistent fertilizer through the summer months, but not an excessive amount

Yes, the trick is “a little of everything in just the right quantity”. Aim for your plant to be a similar shade of purple as mine, throw some osmocote on there, and pray. 

September 5th, 2025

Once the buds have formed, stop worrying about “just the right amount”. At that point, water them as soon as they’re dry, and keep up on it. They very much need additional water as they produce these flowers (at least in my environment). 

In my greenhouse, my usual “once a week, on the weekends” watering schedule was still working out so far. 

But…as the blooms get larger and larger, more water is needed to keep them growing (I realized).

There were notable increases in the sizes of the buds after watering, and the plant very clearly would devote more energy to the older, larger buds if I didn’t keep up on watering. 

Around this point in time, I just kept the hose up by the greenhouse, and I was watering the Edithcolea whenever it looked a little limp when I checked it in the morning. 

That was only one extra bit of water per week, but it made a difference! It was even more noticeable (and needed) once the flowers finally opened. 

September 11th, 2025

The first bloom opened, finally revealing the glorious, gorgeous flower I’ve been chasing for literal years. It was everything I dreamed, hoped, and wished for. 

I did not try and sniff it, as it is still a corpse flower relative, but it was beautiful. 

The need for water only increased with the other blooms reaching the size for opening. 

Very thirsty, September 13th 2025

Z**The photos above are at different times of day, so the color hues are a bit different. You should still be able to very clearly the the difference in the stems and how plump or stiff they are. 

So the lesson here is: once the flower buds have formed, they should only dry out a little before you water them again. I was extremely surprised that it only took 2 days for the plant to be as thirsty as it was! 

I did not need to add more fertilizer to keep the less mature blooms growing; it seems as though once the buds reach a certain size, they’ll keep growing so long as they get enough water. It’s also worth calling out that the plants were in my greenhouse…and it wasn’t as hot as you’d expect. Checking my temperature and humidity sensor, the temperatures and humidities for the week I had blooms were: 

**I watered the entire greenhouse on September 14th

The highest humidity occurred around 6 or 7 am most days, usually coinciding with the lowest temperatures. 

The highest temperatures occured around 2 or 3 pm most days, and usually coincided with the lowest humidity. 

I share the stats as a way for you to evaluate your own growing conditions and compare to my own. My plants’ need for water to keep their blooms growing and open was likely highly influenced by my consistently high temperatures in the greenhouse. The week of data provided above was a moderate week; earlier in the month, temperatures were quite warm (hitting 106 as a high for about a week), but it became consistently cooler as the month went on (the last week averaging the low 80s as a high temperature). 

If you’re growing your plant indoors, your conditions will vary considerably from mine, and you may not experience the same tribulations I’ve had when it came to water and fertilizer. Maybe my high temperatures gave the needed stress to encourage blooms, but those same temperatures required plentiful water that was a challenge to keep up with. 

The species is easy to rot out with excessive watering, too much shade, or just looking at it funny. 

As unpleasant as it is to wait, I do suggest getting your general cultivation for them dialed in before you focus on encouraging blooms. You’ll get a better sense of when the plant is thirsty, how much fertilizer to give it, and how to monitor for the right amount of light. More so than my other stapeliads, this one took a surprising amount of (the right) attention to get it to bloom. 

For me, this was a hard plant to coax flowers from! If you’re also in the “no flowers” club, share your plant and your woes with me on Instagram at @trexplants. 

If you had an easy time getting your plant to bloom and are confused by my level of detail and struggle, keep it to yourself, I don’t want to know. I do hate you a little. 

Only a little. 

Okay, and tell me what you did. I promise not to be mad if I was just really bad at this.