Can You Help. Brown Marks Appearing On My Yellow Wave Phormiums

Question

Hello A Gardener planted some yellow wave phormiums For us in a border at the front of our house.. In October 2019. I have noticed browning/marks appear on them. Just wondered what this is, I hope they’re not dying? We recently (3 weeks ago) put slate down – and wonder if this has caused it.. They have only had one really good water (when planted) as the rain has done the rest and the gardener recommended they didn’t need to now.. I’ve text her.. and she’s not sure what it is.. But suggested a really one off good water / can you help shine a light on this – third image was when they were ok.. just after slate was put down.

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Answer 1

Depending on the condition of the slate, how much of it, and how dusty it was, then there is a likelihood of the soil pH having been raised too high. This can be confirmed with a soil test, and pH test. These articles will help:

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm

This article will give you more information on the care requirements of the plant:

https://www.gardeningknowhow.com/ornamental/foliage/new-zealand-flax/new-zealand-flax-plant-care.htm