At least 1.5 m²16 ft². If your bed is smaller, the planner grays this plant team out, says why, and offers the nearest adaptation that fits. It never swaps in something else without telling you.
What it looks like planted
4 × Sage
11 × Thyme
The real placement on an example 5 ft bed, the same layout the planner draws.
Between seasons
The whole planting stays in place year-round.
What it claims
One regime - sharp drainage, full sun and low summer water - which vegetable irrigation breaks
How it works: These species are adapted to dry-climate Mediterranean conditions, with gritty, fast-draining soils and low summer water. In wet or heavy, poorly drained soil the root zone stays waterlogged, starving the roots of oxygen and rotting them; excess water and rich fertility compound the rot risk and, in these aromatic herbs, thin the essential oils that carry the flavor.
Evidence: checked against 3 sources in the research-based literature.
Common sage prefers full sun and well-drained, medium to dry soils that mimic those of its Mediterranean homeland
What to keep in mind
Nothing here feeds or guards another plant. These five are together because they want the same thing (gritty, fast-draining soil, full sun and water only when dry), and because the vegetables they usually get planted among want the opposite. The pizza garden keeps its herbs for the kitchen; this bed keeps them alive. Marjoram, savory and tarragon stay out until a source read for each of them puts it in this group.
Who does what, and the swaps
Each job in this planting can be done by more than one plant. The usual choice comes first, and each swap says what it costs.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: Zones encode average annual minimum winter temperature, which governs whether a woody perennial survives to spring. It is the wrong quantity for an annual, which never sees winter.
A zone that is too warm is a second, different mechanism. Mild winters do not kill a perennial; they fail to chill it. Deciduous fruit crops need a winter dormancy period to break bud and set fruit, so in a zone milder than a plant is adapted to it may survive and never crop. Only the cold end is enforced, because only winter survival follows from what a zone measures; the warm end gets advice and is never refused.
That warm limit is a property of the cultivar, and that limits what this rule can do. Chill requirement is published per variety and varies enormously within a species, so a species-level ceiling says "the modeled range does not reach your zone", never "no plant of this kind will crop for you". So above its range the planner still offers the plant, with advice to choose a cultivar rated for your zone.
Evidence: checked against 1 source in the research-based literature.
Winter cold-hardy cultivars adapted to the colder regions of Oregon (such as zones 5 to 7), may not grow normally in regions of the Willamette Valley (zone 8) where winters are warmer and plants receive less winter chill.
Plus 2 working notes on how the sources were read.
The Mediterranean culinary herbs the extension herb guides group together on one regime (Clemson HGIC 'Herbs'; Univ. of Maryland Extension 'Care of Herbs'), grown as a bed of their own, which is how those guides describe siting them.
