Clay Thompson gets questions about cactus from around the country.

I am from Iowa, and I am fascinated by the saguaro cactus. Why is it that the base of the cactus does not increase in circumference relative to the upper portion as the cactus grows? Saguaros look top-heavy.

I’m not sure I understand your question. A saguaro’s circumference grows along with the rest of the plant. Do you mean a cactus should be as big around as it is tall? That would be silly. Saguaros are a bit top-heavy, I suppose, but they are fairly sturdy. And they are sort of flexible. During the monsoon, their girth can expand by as much as 20 percent as they take in water.

I would have answered this question differently. For instance, I would have noted that the questioner looks top-heavy. Why is that? Is he or she a cactus? I’m just kidding, I would not insult a questioner from Iowa like that. Maybe if they were from Kansas…

I noticed this odd looking browning patch on one of my cacti shortly after I had purchased it. I’m not sure if it’s part of a natural process or if it’s a sign of an unhealthy cactus. Could you shed any light on this? I’ve felt the spot with my finger, and it has a different texture to the rest of the cactus, and it seems almost like a callus of some kind (can Cacti get calluses?). The spot is tougher and more rigid than the rest of the cactus, so I’m just a little concerned. The woman at the store advised me to water it every 2 weeks and give it all purpose fertilizer ever 7-8 weeks, but neglected to tell me the last time either of these had been done while the cactus was in the store, though I promptly watered the cactus when I discovered the soil to be dry as a bone, so I’m thinking that lack of fertilizer may be the cause.

Am I right or entirely missing the mark?

I hope to hear from you soon.

Sincerely,
Andrew

Hello,
Thank you for your informative website!

I have a question that I hope you can help with.

I have one cereus monstrose cactus that I have raised from a pup over the last 4 years and is doing very well. It is a deep green blue color and grows quickly. I was finally able to find what I thought was another beautiful specimen from a local Las Vegas grower.

The plant did seem a bit yellow, so I thought it needed some fertilizer and re-potting.

Unfortunately, when I removed it from it’s soggy sand in a plastic pot, I found it had no root system, but in fact was a large cutting that had been plopped in a pot. There was about 1/2 inch deep of slightly mushy and slimy surface across the entire cut with 2 earthworms living in it, like a slightly rotted apple.

I sliced off about another 1/2 inch above the wet part, across the entire cut, and dipped it in rooting hormone and am leaving it to dry and hopefully callous indoors where it is warm and bright. Is this the correct way to deal with this? I really want to save and eventually plant this gorgeous thing. The cutting is about 12″ tall with a couple of branches. Any suggestions?

Thanks so much!!!!!
Laurie

Laurie,
I am sorry to hear you ended up getting a plant that was not yet fully established, if the rot continues to spread you should consider returning it to the grower, I would be mortified and embarrassed if an un-rooted plant made it on to the sales floor!

You have done the right things so far. You can dip or spray the cut part with regular 3% hydrogen-peroxide, which works as a disinfectant as well as encourages the callus to form faster. Watch the cut area for discoloration and if the rot seems to be coming back you will need to cut higher and start over. After the callus is well formed, which usually takes a couple of weeks (but the peroxide can speed that up) replant in fresh dryish cactus soil and place somewhere warm and bright. Roots should form over the next few months since it is supposedly spring. Do not water for several weeks and then give it a sparing drink. After a month you can give it a real drink and then let it dry out completely before watering again.

Good luck and take care,
Hap

[More back and forth about Miracle Grow and such after the break…]

Read More…

Carol sends in this question, made sad by the forces of evil at PG&E,

I have some burrow tails and some echeveria. Three times I’ve tried to root individual “leaves” that have broken off in mishaps [latest was a romp by a PG&E crew through my garden], but have been a dismal failure.

Would you have any advice for me? I’d appreciate it very much.

Carol

Carol,

Leaf cuttings of sedum and echeveria are usually successful if taken in late spring to early summer, but are trickier in fall and winter without providing bottom heat and supplemental light. We usually stick the leaves in barely moist cactus soil at a 45 degree angle, with the node-tips buried just enough to keep them in place. Then we put them in a cold frame or in the greenhouse in bright but filtered light for about six months. We only start watering when they develop roots. Once there are little plants forming we will give a light fertilizer and some liquid kelp to boost their growth and then move them outside under 30% shade for another couple of months before moving them up to their own pots.

I hope that helps. Good luck and take care,

Hap

[Editor’s Note: That sounds complicated, but often people just toss these leaf cuttings into their garden and wait to see what comes up. It doesn’t take a huge success rate for there to be a few new plants from sedums. Peter]

A question from the Cactus Jungle facebook page:

Thank you guys for finding a beautiful Opuntia santa-rita for me in the back on Monday afternoon. I’ve been giving it warm shelter in my car at the moment on the passenger side floor. Between the santa-rita and the violacia, which one has a more purple hue to them when stressed?

Michael

Michael,

They’re very closely related; some consider the O. santa-rita to be a subspecies of O. violacea. And there are a number of different O. violaceas; different subspecies and different population groups. The purple colors vary and the intensity of the color can vary too, but to just get down and answer your question, the O. santa-rita will get more purple color.

Here’s some photos:

Opuntia santa-rita (O. violacea ssp. santa-rita)

Opuntia violacea

Opuntia macrocentra (O. violacea ssp. macrocentra)

Hi guys.
I have been really busy this winter, and haven’t been noticing the horror that has reigned down upon my garden.

I notice almost ALL the succulents and even some agaves have these tiny dots on them, Some damage I know is from snails/spit bugs, I dosed the yard with sluggo again recently. Some though is very strange.

But some of the issues are beyond me. Spider mites? Hail damage? I’m at a loss, though will do whatever it takes to fix it. Neem oil? lol I see you say that’s a cure for almost everything I guess I’ll need a few gallons then!

Here’s a picture of the horror….
THX!!! JBOT

It is hail damage, not an infestation. We have had hail several times this winter and it has been large enough and wind driven, so it causes little puncture wounds on the softer cacti and succulents. It should heal up without treatment, but the freckles are permanent to those leaves. We have several crops that were so damaged by hail in December.

Watch for infection around the spots and Neem if needed, but it is mostly just a cosmetic sort of damage.

Take care,
Hap

From our Facebook page:

Do you guys cover up your plants on the shelves outside at night? Some of my plants have been damaged and have started to rot. Especially my Neocardenasia herzogiana and my Coral Aloe. Haven’t been home in three months to see them.

Michael

We did have a freeze 2 weeks ago, and covered up some of our Aeoniums and Aloes, and other smaller succulents too. On top of the freeze we had in December, and hail too, there was some damage. For the column cactus the danger is to the growing tips. If you had damage recently they might have started growing again just before the freeze.

Peter

A longer answer would include being sure you have them in a fast draining cactus soil which helps them stay stronger through our winter rains and more able to handle sudden freezes. However when you’re gone for 3 months at a time it can be hard to use a frost blanket for a freeze anyway. I wonder if anyone has set up an internet-enabled cam with a frost-blanket-dropping system all run through weather.com.

Carol Bradford of the Syracuse Post-Standard makes a good point. We often get people asking if they’re overwatering or underwatering when succulent leaves fall off, and it can be caused by either! It’s hard to explain that to people, but Carol does a good job.

Dear Carol: I have a large (Aloe vera). How do I keep the ends of the leaves from turning brown and shriveling up? — N.C., Camillus.

A: …When the leaf tips turn brown, either too much water is being lost or not enough water is being pulled up. The tips are affected first because they are the farthest from the roots and are supplied last.

The possible causes are air that is too dry, soil that is too dry or an inadequate root system. The root system may be too small, especially in a container. The roots of succulents normally spread widely. The root system may be damaged by too much water or by too much fertilizer….

Too much water can cause the roots to rot off and then the plant is not getting enough water to the leaf ends, even though you’ve over-watered. Try explaining this to someone without seeing the plant. Now I know how.

On the other hand if they bring the plant in for us to see, usually we can tell the difference, since leaftip damage from underwater will look brown and crispy while from overwater it will look black and rotty.

Dear Cactus Blog,

I feel terribly guilty, my suggestion of repotting may have killed my colleague’s cactus. After seven happy years sitting on the same small pot, the cactus really seemed to like its new bigger house, at least it was growing (mostly on its ‘waist’). However, three weeks after the repotting, you can see it is now ‘deflating’.

There is good drainage and it was not over-watered. Maybe it got less water than usual in the last three weeks. Then, after a particularly cold weekend at the office, the cactus looks as shown in the photo. However, it had experienced colder temperatures last December, when it was left to fend for itself at the office and it snowed in the UK. Today it even looks more deflated than when we took the photo yesterday. Please help!

Many thanks,
TH

TH,

It’s hard to tell from the photo exactly what’s going on there. It is possible that it is shrinking due to less water and colder temperatures – they do that in the desert when the temps get below freezing. But it is more likely that the plant has rotted out from the inside and is unlikely to survive

Generally you don’t want to repot cactus in winter when they are dormant. What happens is that you damage the roots a bit when repotting and then add a little water and the roots can rot off since the plant is not “awake” enough to repair the damage. A fungus or virus can then take hold.

The best I can offer is that you should let the plant dry out completely at this point and hope for the best. You could also spray the plant with an organic fungicide like Neem Oil just in case, but I don’t see signs of fungus on the outside.

Sorry I don’t have better news.
Peter

From a couple days ago, here’s more info. It turns out it is a mesemb, and a Delosperma nubigenum to be precise.

Hi Peter,

Here’s some more pictures of the plant:

I’m San Francisco. Watering it once every 2 weeks with a few
tablespoons of water. Haven’t done anything to it recently—it’s been
sitting near the window since I bought it.

Thanks!
Yvonne

Yvonne,

It’s a very hardy plant that can take a wide range of conditions, but I think in this case it may be not enough water since it’s a small pot. Rather than a little bit of water every 2 weeks, try drenching the soil, and letting the plant drain fully (Never let it sit in water), every 10 days.

You can clean out the dead leaves from the pot, but don’t be too aggresive – leave as much of the plant as you can.

Keep it in as sunny a window as you have and the plant should perk up pretty quickly. If it doesn’t, let me know.

Peter

Maybe you can help?

First we have the question and photo.

Dear Cactus Blog,

My succulent looks shriveled and sad. How can I rescue it? It’s sitting near a window that only gets light in the morning.

Here’s my response for now:

Yvonne,
It’s hard to tell from the photo what’s going on, or even what plant it is. Do you know the species? And then here are some questions for you before I can diagnose it:

1. Where are you located
2. How much do you water?
3. Have you done anything differently recently? Moved it indoor, or outdoor? Changed the amount of sunlight? Watering?

Can you also send a clearer photo, preferably close-up.
Peter

Hi Hap and Co.,

My beautiful barrel cactus has developed orange areas. Mostly they’re along/near the ridges, although there are some small spots further down. This side of the cactus does have some past scarring (from frost I believe). Is this orange a treatable thing? Will I lose the plant?

Thanks
Tony

Tony,
It looks like a form of “Rust” (a fungus). I recommend you treat with Neem Oil, a natural fungicide that works well on cacti and succulents. You can spray it on in a 1-2% solution once a week, for three treatments and it should take care of it. There may be some long term scaring where the fungus is, but usually if it is treated quickly enough it heals up and is not too disfiguring. Like all oil treatments don’t spray on a hot sunny day, only spray in evenings or on overcast days so there is no chance of the oil causing sunburn.
Good luck,
Hap

We get lots of questions around here, some with photos, some with shocking photos. This question first came to us over the phone, and so I asked for a photo…

Please tell me what u think this disease is!
Jody.
Sent from my Verizon Wireless BlackBerry

Here’s the photo…

And the answer is…

Jody,
That’s scale. A lot of scale, on your Pachycereus marginatus. The plant might be able to be saved, but it will be permanently scarred. Spray it down with rubbing alcohol to kill the buggers and break through their shells and then carefully wipe them all away with a soft paint brush. Then spray the cactus down with neem oil and drench the soil with neem, and reapply a few more times. In March you should repot it into clean soil, and spray the roots completely too with the neem.

Good luck
Peter

I purchased an Himalayan red bamboo plant from you a few year ago for Brentwood, CA. The plant has thrived and grown well. It planted in sandy soil and is mostly shaded. It has encountered a spell of cold weather and the leaves have lost its green color and the plant appears to be smaller or withering. This just occurred, last year the plant kept its color and appeared to be fine.

What can I do to restore the plants green or healthier condition?

I’ve attached a photo, any advice will help.

Thank you very much,
Ken

Ken,
The plants look like they took a bit of winter frost damage, nothing too bad. They look pretty good, actually, and should be able to come out of it this spring without any real problem.

I recommend a dose of Kelp Meal or Liquid Seaweed at this time, and follow up with a high nitrogen organic plant food (We sell Bio-Turf at the nursery) in mid-March. Bamboo are heavy feeders, so we do recommend fertilizing 2-4 times per year.
Peter

HI Peter,

My Orchid Cactus has develped these orangie spots. They look ugly and menacing as there are more and more appearing everyday. What product can I use to get rid of them, short of cutting the branch off?

Thank you!
Lillian

Lillian,
Your Epiphyllum has a fungus known as Rust. I recommend a strong organic fungicide sprayed on immediately. We do have a couple products at the nursery we can recommend, but if you are not local, we would suggest 100% neem oil at a 2% dilution.
Peter

They like their succulents black on the Isle of Wight. That leads, inevitably, to Black Rose.

Marie Langford e-mailed me the other day and asked if I know of any nurseries on the Island which specialise in ‘black’ plants, most especially succulents. One such is (A)eonium arboreum Swarzkopf. I bought one during a garden visit when Alan Titchmarsh was our high sheriff a few years ago now….

But I can recommend the tall, arching, tree form of this aeonium with its large heads of deep, purple-black foliage. If anyone knows where this and other black succulents can be easily obtained by Marie on the Island, please e-mail me and I will pass it on.

I like that title, “high sheriff”. I wonder what you have to do as a sheriff to become a high sheriff. Clearly a knowledge of succulents is required, which I have, but is that all? There must be more to it than that.

I can also recommend Gasteria nigra, and this one too. Anything else we should pass on to Marie?

Hi…can I get a little advice?  I moved into a new home with a fantastic agave about four months ago.  We recently had a cold snap here in Phoenix (if you can believe that), and it’s looking sickly now.  Is there anything I can do to help its recovery?

Wayne

We get the fun questions!

Hi Peter,

I think the cankers on my cacti are a fungus. Regardless, I am not sure whether there is any hope (treatment) for the first one and whether the second is suffering from the same problem. Any help/advice would be much appreciated. I live in Oakland, CA.

Thanks,
Don

Don,

It does look like a fungal issue. You can treat with Neem Oil, which is a natural and usually effective fungicide. We usually use it in a 1-2% solution in water with a drop of soap as an emulsifier. Spray to the point of run-off on an overcast morning or in the evening, but not on a sunny day as oil treatments on sunny days can cause burning. Retreat after a week at least twice. It should deal with the fungus, though the scaring will always be there, though eventually it will bark over and just add character to your plants. We carry Neem Oil at the nursery, and can talk you through it’s use.

Take care,
Peter

Hi Peter,

Thanks for the prompt reply. I will stop by, say hello and buy some Neem oil from your store.

I was contemplating getting rid of the cactus because it looks so sick, so you saved it.

BTW, can this fungus spread (wind, etc.) to other cacti in the garden?

Love your blog and your helpfulness.

Regards,
Don

Don,
I do recommend spraying the plants that are near the infected one, the fungus can spread.
Peter

There are some amazing carrion plants out there, in the Asclepiadaceae family. Including the Asclepiads too! Who knew the Milkweed Family and the Stapeliads were related.

Anyway, so on the recent foray into the jungles of Florida, we found this stunning stapeliad at a nursery and we snapped up a few for parenting. We should have plants ready if we’re successful, in a year or so. I took this picture of the tiny bloom with my cell phone camera and this was the best I could get it while on the road.

Now, what is it? It was totally mislabeled. So I looked it up on Martin Heigan, the stapeliad king’s, flickr feed and I can’t find it at all. Any Stapeliad experts out there who have a clue?

This plant was left outside for some cold weather and only recently was brought back inside.

Hello Peter,

Thanks for spending so much time with me and my mother last week.  She is surely an opinionated woman!  As a world-renowned rosarian, she does know quite a bit about floriculture…just not everything.  Anyway, thanks again for being so gracious with us.

We talked about the possibility that my Euphorbia may have a virus, having been kept outside.  I took a picture of each side (it’s three sided) and then two close-up pictures of the discolorations.  It looks like only one side is badly marked.  What do you think?  Still a virus?  Should I toss it?  The top part that is unaffected is only about 1-2 inches tall – is that enough to bother?  It’s been inside since we talked.

Thanks for you opinion on this one.

~Karen

Karen,

The plant definitely has a virus or fungus. It may be savable, with aggressive treatment. You will need to isolate the plant, and try treating it for 3 months. If the wounds do not heal over by then you should dispose of it and the pot and the soil. (You can sterilize the pot if you prefer.) I recommend Neem spray on the plant and in the soil, every 10 days for 4 treatments.

Here’s a worse off plant that we advised on last year. And another one.

Peter

I have an aeonium that I bought there a couple years ago. In
the last week the center of the main flower has protruded out like a
nose. Prior to this the leaves laid flat.

Is this normal/healthy? Is this a growth spurt?

Thanks for your help, Michael

Michael,
Your Aeonium is about to bloom. Congratulations! Anyway, the rosette will extend and turn into a large pyramidal shape covered with little yellow flowers. This can be very pretty, but it also takes so much energy from the plant it can kill the whole plant.

You can enjoy the giant pyramid bloom stock, and hope the rest of the plant survives, or you can go ahead and cut off the blooming rosette right now, which will save the plant, and leave you with a low shrubby plant for now.

Cut the stem for that one rosette off down low, and you can place the large cutting in a vase and enjoy the blooms that way. Spray the cut end on the plant with household hydrogen peroxide to help it heal, and it should branch from that point later in the winter.
Peter

hello,
for my birthday, i was given this beautiful little cactus plant. it had no tag or name on it so i did some research and i think it’s an echevarria or a sempervivum. it’s starting to grow a pink line on the leaf edges. I’ve been trying to care for it as such (little water, good drainage system, in light) and it’s lower leaves seem to be wilting away. i think there’s a little plant sprouting from the main stem and the most top buds seem to be pretty firm, but the leaves below are literally limp and feel like they will fall off in a week or so. i dont know what to do! i’m scared it’s going to die.

attached are two pictures. it looks healthier in these photos than it does now.

any ideas on what i can do to save this little guy?
sk

Sarah,
You have an Echeveria, probably E. subsessilis. It should look like this.

It looks basically OK, but probably needs more light, which is why its growing upwards looking for light.

All succulents lose bottom leaves, and yours will do so soon; this is normal and not a problem. It will only look unusual because of the stem that has developed.
Peter