Need advice for SIP mix to keep soil dryer for certain herbs

[Vespertino]

Hi everyone!

I made a SIP out of a flowerbox for my french thyme, lemon thyme, oregano and sage. They tend to like dryer, or well-drained soil. I added extra pearlite and cedar mulch to the mix for aeration, but the plants don't seem to like it and I'm finding a lot of gradual leaf die-off where they turn brown and crumble, not due to under-watering of course. I did put black plastic lining over the top to seal in the moisture (and covered that with cedar mulch so it wouldn't look ugly), so I wouldn't get too much water evaporation in the Texas heat.

So what should I do?

My choice are:

1) Remove the plastic and let the top of the soil dry out
2) Water less often
3) Remove the plants and replace the soil with a different mix and then re-plant.

If my soil is the culprit, any ideas on what to add to the mix to make it ideal for the herbs?

Thanks!

[habitat_gardener]

I'd definitely remove the plastic! These are plants from dry, rocky hillsides. They like to dry out a bit, at least on the surface, but in my experience thymes planted in the ground thrive with lots of water (they're next to plants that I water a lot). I also don't mulch my herbs too much -- maybe a thin layer would be ok. For larger, woodier herbs, I use rocks or small pebbles rather than an organic mulch.

[Vespertino]

Thanks! I will remove the plastic ASAP. If that still doesn't work I'll remove the plants and mix in some fine pebbles into the soil and stick 'em back in.

[habitat_gardener]

To clarify -- I don't add pebbles to the soil, I use pebbles as mulch for herbs that are woodier instead of using an organic mulch. This has been especially successful with lavender cuttings. I mulch all my plants, and the lavenders do well even in small pots when I mulch them with small rocks. I don't use any special potting soil for them.

[Vespertino]

Thanks for the clarification. I've been meaning to get a bag of pebbles anyway and it looks like I may have more uses for them than originally thought

[greentiger87]

How humid is it where you are? Oregano/thyme can take the heat, as long as the air stays relatively dry.

You can try using turface or calcined diatomaceous earth. But I think it comes down to herbs like this not doing well in SIP's. At least not in our Texas conditions.

Dittany of crete, which is an oregano that's even more finicky, has been doing great despite the humidity - it's in a very rocky, coarse mix of turface, bark, and granite (the famous gritty mix), but I went heavy on the turface. It gets drenched everyday like everything else, and is thriving! Another of the same plant went into potting soil, where it promptly died as soon as we got heavy rains.

[Vespertino]

I think it's humid for DFW standards: around 40-30% humidity during the day I think? I'm not sure what the plants think about it, but it feels very dry to me; however I'm originally from the Northeast (NYC) where the summer humidity is so bad it's like being smothered in a hot, wet blanket.

I took the plastic off the top of the sip covering the soil today, so I'm going to let it dry out a bit before adding water to the reservoir. As it was over 100 degrees today that shouldn't take long . Fine gravel is on my shoping list.

[JamesL]

V,
Are you missing your NYC humidity? Lol
1010 wins just informed me that we need 2/10 an inch of rain in Central Park to make this the wettest June on record.

[Vespertino]

Hahahah! Yeah I heard the tri-state got a ton of rain. I don't miss the humidity but I do miss the sushi.