Sempervivum Diseases, Problems, and Pests

Posted by @goldfinch4 on
As a rule, sempervivums are tough little plants that can put up with a lot of abuse before they’re overwhelmed. Not many plants are as resilient as these guys, yet even they face some dangers.

Sempervivums very seldom get viruses or bacterial/fungus infections, so that's great news for gardeners.  However, we humans have a tendency to want to nurture our plants, and we often kill sempervivums with kindness.

The main requirement of sempervivum plants is well-draining soil, whether they are planted in containers or in the ground.  After they’re planted, we can generally leave them alone – other than to admire them, that is.  I would guess that more sempervivums die from getting too much water than for any other reason.  Rot first shows up when the lower leaves get sort of translucent-looking and start to discolor.  Once they start to rot from too much moisture, you have to act quickly to save them.  Dig them up, remove the rotting leaves, and in a few days replant them.  If the rot wasn't too bad, they should recover just fine.

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Signs of rot from too much moisture

Sunburn:  Even though sempervivums like sun, they can burn if placed in too much sun.  The warmer the area you live in, the more they should be protected from sun during the hottest part of the day.  If it’s not practical to move them to a shadier location, put up some kind of a shade cloth to protect them during extremely hot, sunny weather.

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Too much sun can burn your plants

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Shade cloth tent

Aside from too much water and sun, they do have a few other enemies.

Mealy bugs and aphids:  These pests most often bother sempervivums that have been raised indoors, in a greenhouse, or outside in damp weather.  If your plants are grown outside, beneficial insects will often take care of this problem for you.  If you only have a few plants, you can try to remove the bugs using a Q-Tip and rubbing alcohol.  For a more serious infestation you can use insecticidal soap, or if all else fails an insecticide. Be aware that with an insecticide you’ll kill the beneficial insects too, so use it as a last resort.  Aphids seem to be attracted to sempervivums that etoliate (stretch out and get weak).  Try moving your sempervivums to a sunnier location after you have the aphid problem under control. These insects usually don’t kill the plants, but they may cause temporary disfigurement, which the plants eventually will outgrow. 

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Sempervivum starting to etoliate

It’s worth noting here that whenever you acquire new plants, you should always isolate them for several weeks until you’re sure they didn’t bring bugs or other problems home with them.  The last thing you want to do is plant them with your other plants and infect all of them. 

Deer and rabbits:  On rare occasions, mostly in late winter or spring when food is scarce, you might see deer or rabbits dining on your sempervivum.  Deer, and to a lesser extent rabbits, can do great damage by eating sempervivums right down to the roots.  Luckily, these animals aren’t a problem in most areas.  I’ve found Plantskydd works well to ward them off. 

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Deer damage

Moles and voles:  These rodents don’t eat the plants, but they do push them out of the ground when tunneling.  They can destroy large areas in a single night.  This typically doesn’t occur where plants are established and well-rooted.  On occasion, voles may take a bite out of a leaf, but that’s generally enough to convince them to look elsewhere for a meal.

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Dogs and cats:  Dogs cause most of their destruction by their love of digging and also by their sheer size when running through gardens.  We all know what cats like to do in a garden and it can be extremely difficult to find a way to deter them.  One option might be to place netting over your plants until they decide to move on.  However, cats can be welcome if you have a rodent problem.  You’ll have to decide which is the lesser of the evils.

Chipmunks, squirrels and 13-lined ground squirrels:  They all love to dig and to bury nuts in containers and in the ground, and they can make a mess of things in a hurry.  Pulling rosettes off plants also appears to be great entertainment for them.  A layer of chicken grit or small stones might deter them, but I personally have found that Plantskydd works the best to deter these pests too.  Fake owls placed around your gardens work, but these should be moved every few days to remain effective.

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Toads:  Once in a while an overzealous toad might push a newly planted sempervivum out of the ground, but not often.  I welcome them as they do a good job keeping our mosquito population down.

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Slugs and snails:  For these pests, finding a sempervivum patch is like finding a smorgasbord.  A bite here and a nibble there will result in a lot of damage. A top dressing of sharp pebbles or grit might help, as the sharp edges can cut them so they avoid crawling on it.  You can also try the normal slug deterrents, but nothing beats a few good (real live) garden snakes. 

Birds:  Birds can cause a number of problems.  For one, they seem to enjoy pulling labels out of the ground. (Some dogs, children, and grandchildren find this fun too.)  It’s thought that birds might be doing this to explore for small worms in the holes the labels created, so it’s a good idea to double label your plants.  In addition to the obvious label, also bury one in the ground close to the plant.  That way you’ll always have a backup to ID your plants.  Like squirrels, birds seem to enjoy pulling rosettes off plants or even pulling entire plants out of the ground.  I’ve even had problems with birds taking dust baths in the open areas between sempervivums in my newly planted beds.  In their frenzied excitement at finding such wonderful dust to bathe in, they send my plants flying in every direction.  I’ve resorted to placing short stakes around the outside of the bed and criss-crossing string back and forth around the stakes and over the bed about 6” off the ground.  That seems to discourage them from playing in my garden, but it isn’t the prettiest solution.  You might try putting bird netting over your plants.  Rubber snakes or fake owls may also work, but you'll need to move them every few days or the birds will get used to them and won't be afraid anymore.

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Worms:  Now don’t get me wrong – I LOVE earthworms!  But the little buggers seem to like to come out of the ground at night directly underneath my sempervivums.  I know because I see the holes where my plants used to be.  Again, this isn’t a problem with established plants, but the worms will shove newly planted sempervivums right out of the ground.  So I’ve come up with a way to protect my plants:  I straighten out small paper clips and stick 6-8 of them in the ground around each newly planted sempervivum.  It works great!  (And I also think it causes tunneling rodents to take a detour around my plants.)  Of course, visitors see all the little wires sticking up in my gardens and think I’m a little crazy, but that’s a small price to pay to save my plants.

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If you look close, you can see the paper clips

Weeds:  I know this seems obvious, but it’s very important to remove weeds as soon as you see them.  Once they become established in a sempervivum patch, it’s a nightmare to try to remove them.  If I’m not able to dig or pull them up, I dip a Q-Tip in Roundup and carefully brush it onto the weed.

Even though this looks like a long list of potential problems, chances are you’ll experience very few of these with your sempervivums.  These are wonderful easy-care plants that are quite forgiving.  In fact, your biggest problem will probably be finding room for your ever-increasing collection.

 
Comments and discussion:
Thread Title Last Reply Replies
Sempervivum Diseases, Problems, and Pests by valleylynn Jun 4, 2021 9:49 AM 8
Hens and chicks by kjnivens Jan 8, 2021 8:22 PM 2
Plantskydd by chelle May 19, 2013 1:31 PM 2



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