Struggling philodendrons

[Christopher Dillman]

Planted these giant philodendrons three years ago on my slope, south facing Zone 10a coastal Encinitas.

Once twice as big and green, now they've shrunk and remain in this stasis. 

They've been on a drip 2 days a week, 8 min ea day. Been adding gypsum, palm gain, happy frog soil conditioner periodically. Still in this stasis.

Worth it to give them a good drench with the hose say twice a week? Even add some of these nutrients? Do I hit the reset button and start over with new Philos? TIA!

[TropicsEnjoyer]

Thats strange, in your climate they should be thriving without question. How long ago did you fertilize? I would expect them to respond quickly. Maybe it has to do with the soil itself, too alkaline or acidic, I have no experience with pH effects though. Hopefully others can advise you as well. 

[PlantMorePalms]

Those are pretty tough plants in general, but that looks like a pretty steep slope and it doesn't sound like they're getting a lot of irrigation unless your emitters are very high GPH. I would try watering more, especially since they also look like they get a lot of sun in that spot. 

[metalfan]

I agree need more water

[Palms1984]

On 12/15/2025 at 9:50 PM, Christopher Dillman said:

Planted these giant philodendrons three years ago on my slope, south facing Zone 10a coastal Encinitas.

Once twice as big and green, now they've shrunk and remain in this stasis. 

They've been on a drip 2 days a week, 8 min ea day. Been adding gypsum, palm gain, happy frog soil conditioner periodically. Still in this stasis.

Worth it to give them a good drench with the hose say twice a week? Even add some of these nutrients? Do I hit the reset button and start over with new Philos? TIA!

It probably needs more water and some sulfur will definitely help it.  The soil here in coastal San Diego is very alkaline.  

[Christopher Dillman]

On 12/19/2025 at 1:02 AM, Palms1984 said:

It probably needs more water and some sulfur will definitely help it.  The soil here in coastal San Diego is very alkaline.  

Would dropping in some SulPoMag take care of that? Intrigued with that prescription.

And naive question - how does sulfur combat the alkaline issues with SD soil? Thank you!

[Silas_Sancona]

3 hours ago, Christopher Dillman said:

Would dropping in some SulPoMag take care of that? Intrigued with that prescription.

And naive question - how does sulfur combat the alkaline issues with SD soil? Thank you!

Agree with others ..increase your irrigation.

 

Regarding sulfur,  sul po mag will help but less so during the cooler months compared to when the plants are in active growth ( warmer months )

While the effect is temporary / gradual, applying sulfur will increase the acidity of alkaline soil when added. Helps break up heavy clay soil as well ..to some degree at least.

I myself would start dumping piles of leaves around those specimens to start getting more organics into the soil around them / lower the soil's native ph more permanently.

Grow fine in our native, highly alkaline soil ..as long as they get regular water ..and some  afternoon shade.