My pachypodium lamerei doesn't grow

[Ilovepalm]

Hi! In September 2017, I bought pachypodium seedlings in the supermarket. They were terribly flooded. I have transplanted them into a new earth with sand and perlite and larger pots. They looked great all winter, but now in the spring when I again exaggerated them, because they had dead grubs in the ground !! they started to turn yellow leaves, and new ones turn black. I do not know what's going on. I water them once every 10-12 days. They are in full sun. What's wrong with them? There are no worms in the pot. The first photo is from September 2017 and the second and next photos is up-to-date.

[Gonzer]

Your potting mix looks like a generic-type used for regular houseplants. Use a mix designed for cactus and succulents instead. 

[Ilovepalm]

I used a universal substrate with sand and perlite.

[Monòver]

They hate water. Use more perlite and less water.

Mine is outdoors in a pot. Now i am watering every two weeks and in Summer, once a week and the hottest weeks, twice a week.

You can see in this  last Summer picture how healthy it looks.

[Ilovepalm]

I also water every 10-12 days.Only that in my country have a different atmosphere (Poland).

[TexasColdHardyPalms]

Mine wont do much until summer kicks in full steam. They love 100+ heat and lows in the 80s. Mine have grown as much as 20" in one year.  I might water them once a month in that heat in pots. 

 

[Silas_Sancona]

^Agree with TxCold Hardy.. These go gangbusters with Heat, Heat /Humidity.. and not much water.. Here, the biggest issue is full sun.. I have seen a few take it but lost a nice specimen id grown for several years in the same exposure. Sunburned than rotted out. Same with other Pahcys I had.

Talking with CACASS members at a recent sale, most recommend filtered light after 11am or so in our area. Go figure that my specimen P. saundersii is alive because it sits behind shade cloth on a covered Patio. It and my surviving Adenium are in a soil mix that contains no more than 10% organic material as well.  

 

[Ilovepalm]

So I should give them more in the shade?

[Silas_Sancona]

^ I would imagine full sun should be fine where you are located.

  Here in Phoenix,(Arizona)  the sun is so intense this time of year that a lot of stuff that would easily tolerate full sun.. or, full sun most of the day in places like CA. or Florida can sunburn a lot easier.. or has been my own experience. Heat can be at such an intensity that during the summer, it isn't uncommon for places like the Desert Botanical Garden to place shade cloth over Cacti / other succulents which can take full sun the rest of the year.  They even put out signs to explain why the cloth is put out since most visitors wouldn't think that a cactus can sun burn. Many people also wouldn't know that if you water certain Cacti / Succulents too often when nigh time temps don't drop below 70F (21C), it can kill them.

Its not uncommon for our UV index to reach 10-12+ from May thru late August, or September.. Hard enough on anyone outdoors for any length of time. Imagine what that can do to plants, esp. things in pots.
 
-Nathan

[Ilovepalm]

I understand.