I live in zone 6b near Boston. I planted two small (maybe 4") lavenders in pots six weeks ago--one in plastic and one in a fabric grow bag. They came from a greenhouse at a good local nursery, but I put them in full sun gradually after I repotted them. The plants have room to grow in their pots. I amended the potting mix with coarse sand and compost, but no fertilizer because I was told not to for lavender. I top dressed with pea gravel. I've been deathly afraid of over watering and have been giving them small amounts of water when they were dry several inches down and the moisture meter said they were dry. I planted hidcote and munstead. Some of the larger leaves on the hidcote turned yellow with crispy browntips. The roots are fine. There's no fungus or rot and there's new growth near the crown. It's been boiling hot and very sunny here (90+). The soil pH is 7 and I don't think there's excessive nitrogen in the soil, which I read can also cause yellow leaves. I've been trying to figure this out for weeks, but everyone's advice is either incomplete or contradictory.

I thought they looked unhappy after heavy rain so I bring them inside and put them under a grow light if heavy rains are forecasted. I'm sorry to go into so much detail, but I've been going a bit mad trying to figure this out.

Do you think the yellow leaves and crunchy brown tips could be from the shallow watering and letting the soil get very dry? Yesterday I switched to deep watering until the water runs out the bottom and then wait under the top two inches are dry. They don't look thrilled today, slightly more yellow. Is there anything else I should/shouldn't do? Will they just be a little confused until I get them on a better regime of deep waterings and drying out, but not completely dry?

Thank you for reading this novella and any help you can give me will be greatly appreciated.