Gardening

I hope this isn’t too off-topic for this community. I also posted this in !greenspace@beehaw.org so sorry to spam but I’m not sure which is the best place…

I have an old grass patch that I want to replace with Irish moss. Would love some advice on how!

Location: Seattle, USA.

Space: 15x12 foot section, partly under a laurel and a deciduous tree.

Soil: I’m not at all knowledgeable about soil, but heres what I know… It was originally just dirt with a on old lilac in it, then the lilac was replaced by grass, then 95% of the grass died during a construction project last year. Now it’s hard-packed soil and random tufts. It gets a small amount of leaves and other debris from the trees above it.

Sunlight: Direct sun for about half the day, then shaded by a house. Sunnier at one end than the other.

Questions:

1. What organic material (if any) should I use to condition the soil? How should I apply it?
2. I’ve read that 5-5-5 NPK fertilizer is good for Irish moss, but also that too much nitrogen is bad. Should I go lower nitrogen? How much fertilizer anyway?
3. How often should I water? How thoroughly?
4. I bought a small number of plugs to experiment in one corner before going all out. What’s the best way to fill in between them with seeds?