Larkspur, Cornflower, and Poppies Started in Elegant Back of Garage Cutting Garden

It's time to sow seeds in my garden like a sailor on shore leave with just days to live. But, when exactly? The backs of seed packets are vague and often offer little guidance, so below is a bit more guidance gleaned from the internet.

With afternoon temperatures near 48, a new garden bed behind the garage was prepared. Gone are a bunch of hostas that were mere placeholders last season until a better idea was hatched. That idea now is a cutting garden. Larkspur, poppies, and cornflower were sown today as soil temperatures were around 38, but, at that temperature, germination could still be weeks away.

Cleome
When: After last frost when ground is warm, although one site from Virginia Tech suggested late fall or early spring.
That's Neat: Needs oscillating temperatures of at least ten degrees. Germination is best with 80 degree days and 70 degree nights. Light is necessary for germination.
Sources: Garden Guide, Floridata, Plant Files, Virginia Tech, How Stuff Works, Goldsmith Seeds

Bachelor Button / Cornflower
When: 1 to 2 weeks before last frost.
Sources: Dave's Garden, Garden Guide, Virginia Tech Weed ID Guide

Corn Poppy "American Legion" Papaver rhoeas
When: As soon as soil can be worked.
Light: Full sun to partial shade.
Sources: Ovm-Seed, Dave's Garden, Taunton, Gardening Tips, Suite 101, Texas A & M, Michigan State,Iowa State, Purdue University (fantastic guide to all sorts of flowers), UC Riverside

Celosia Cristata / Celosia argentea "Pampas Plume"
When: Outdoors, when soil temp is about 60 F and all risk of frost has passed.
Sources: Texas A & M, Purdue University, U. of Md., Yankee Harvest, UVM

Larkspur Consolida ajacis
When: As soon as soil can be worked.
Light: Sun to partial shade
That's interesting: Poisonous if ingested, yet the genus, consolida, is a reference to its medicinal ability to heal wounds.
Sources: Garden Guide, U. Maryland, Texas A & M, U. Maryland, Colorado St., Brooklyn Botanic, Calendula and Concrete, Gardener's Network

Zinnia Zinnia elegans
When: After the danger of frost has passed and soil sufficiently warmed.
Sources: Virginia Tech, University of Kentucky, Iowa State, U. Wisconsin, U. Florida

Nasturtium Trapaeolum majus
When: After all danger of frost has passed.
That's neat: An aphid magnet, it's a good decoy to plant in vegetable gardens. Fully edible with a taste akin to watercress.
Sources: U. Kentucky, U. Wisconsin, Garden Guide, Texas A&M

General Sources
Seeds of Change, Seed Database from Hort Net