Question
Hi Maureen, I have inherited a cactus collection of about 500 cactus. 10 - 15 percent larger sized, 50 percent med size, and lots of babies.  They were in a greenhouse and in November of last year moved to my basement. They had little to no attention. Now they are in a greenhouse and I really do not know how to address the many issues. I had scale, spidemite and some evidence of over watering due to greenhouse vents open and rain leaked in and onto some of the plants so I have a few that have rot of some kind, I found a hole in the side of one that looks like a bug burrowed in, the cactus is a bit mushy, but the top is good.  I think my biggest problem was they were exposed to temps of below 40.  How do I water, fertilize and fix the sickies?  I am sorry to just dump this on you, but perhaps you can help me organize and prioritize my new passion!!! I simply love each and every one.

I know I am asking a great deal!!! Thank you so much.

Barbara

ps sorry no photos, perhaps if I knew what to photograph.

Answer
Dear Barbara,

  Dear Barbara,

Wow.  That's either a blessing or curse.  This is what I'd do. I would throw out any that are  diseased (even if the tops look OK), have infestation of spider mites or scale. Unless you want to devote the entire summer to these plants or are especially attached to them there are just too many to try to fix the ones that aren't healthy. ( if you feel like you can't part with them, then isolate them). Then I'd spray  the rest with an insecticide/ fungicide mix which you'll have to repeat in a few weeks. I suspect there are some succulents in there as well and I'd separate them from the cacti.  Succulents usually don't have spines and if they do, they are single, unlike cactus spines.

If you can, and haven't already, I'd move them outside and really clean the greenhouse with bleach till it 's squeaky clean. Of course enlist your friends to to this with you.  That many cactus in a greenhouse will always have some degree of problem, but keeping the environment clean and having good air movement with fans will go  a long way.

I don't know when your plants were last repotted, but they like to be at least every couple of years so you need to think about that.

Most cacti can stand temps into the 40's as long as they're not wet.  If you know some froze than throw them out.  If you're not sure, look at the roots and the base of the plant to see  if it's healthy.  it could look fine and rot will show up later so keep an eye on them.

Repotted cactus don't usually need to be fertilized unless they are in a soilless mix (which I recommend).  If you do use that type of mix than mix in some bonemeal, dried blood, superphosphate and fungicide.  I generally use a teaspoon of each to 8-10 gallons of soil.

You don't need to repot everything at once.  if the plant looks ok, roots aren't coming out the bottom and sides, etc. then just wait on those.  Do the ones that are really pot bound first and make sure the roots are healthy. You will save yourself some work if you can plant some of the babies in dish gardens that will take them awhile to out grow.

So to recap: throw out, spray,put outside, scrub, aerate ,repot.  For now water the ones that are really dry and for the ones you repot, wait a couple of days and gradually start to water. Leave the ones you can put outside out there for the summer.

For now water the ones that are really dry and for the ones you repot, wait a couple of days and gradually start to water. Leave the ones you can put outside out there for the summer.

That should get you started.  let me know about questions, problems etc.  If you can give me your email address we can correspond that way and you can send more than one picture at a time.

By the way, where do you live?

Good luck and tell me the story.  I'd love to see the greenhouse.

Maureen

Dear Barbara,

Thanks for the feedback.  If you need help or just someone to brainstorm with, my email is [email protected]. so sorry to hear about your loss.

And how did you acquire that greenhouse?

Maureen