Question
Good Morning!! I would appreciate any advice regarding the soil preparation and appropriate planting time for this plant. Thanks!!!

Answer
Lychnis 'Maltese Cross' is a dependable, long lived perennial -- no fuss no muss.  Autumn or Spring planting is preferred, but this is tough enough to take mid-Summer transplant without a sweat.

It thrives in plain vanilla Soil with good drainage and a healthy microbe population -- i.e., don't use chemical fertilizers, which is salt based and will instantly wipe out many nutrient generators.  If your Soil is poor, add organic matter -- semi-decomposed Autumn leaves, aged compost and/or manure, bagged Humus and/or any of the 'organic' soil amendments like bloodmeal, bonemeal, etc.

Alternately, it will still grow and bloom satisfactorily if you use traditional chemical fertilizers and honor the basic needs of full -Sun and regular water through mid-Summer, esp in those awful heatwaves.

But they'll do better without that stuff.  I just mention it because some people can't get off the Miracle-Gro wagon.

Full Sun is one non-negotiable demand you cannot cut corners with on this plant.  Some people think they'll plant it in semi-Shade, and make up for it with extra fertilizer.  That's like saying, Gee I'm low in gas, but I don't have any in the trunk, I think I'll put in more windshield washer fluid.

Like most perennials, Lychnis does not bloom as long as, say, most annuals.  But it's one of those dazzlers that leaves the party with everyone wishing it would stay another hour.  And that, as Martha would say, is a Good Thing.

Other than that, this plant has no special needs, comes with no surprises, and will come back for an encore year after year after year as long as you meet its basic needs.

THE LONG ISLAND GARDENER