When to plant dill in zone 5a
In zone 5a, the average last spring frost is May 15 and the first fall frost is Oct 1. Here is dill's whole year, counted from those dates.
Dill wants well-drained soil with organic matter. Minnesota calls for slightly acidic soil. Texas A&M gives pH 5.8–6.5 and sandy or loamy ground, and says the plant can take a light frost down to about 25°F once it is growing. Shelter tall hollow stems from wind.
Sow directly. Dill transplants poorly. Both Minnesota and Texas A&M say to wait until frost danger has passed. The calendar marks the average last spring frost; delay the sowing if frost is still in the forecast. Texas A&M also wants soil near 70°F. Minnesota's seed depth is ¼ inch. Texas A&M says ¾–1 inch, so check the packet if your soil crusts.
Thin seedlings to 10–12 inches when they are about 2 inches tall. Texas A&M spaces plants 12–15 inches. Minnesota says you can sow again every 2–3 weeks through midsummer. That repeat is not given a fixed count here, because the source does not say how many sowings fit before midsummer. Give the plants at least 6–8 hours of sun.
Outdoor plants mature about 90 days after seeding. Leaves can be cut earlier, once they are large enough, and the flavor is best before the flower clusters open. For seed, cut heads just before the seeds turn tan, or 2–3 weeks after bloom, and dry them in a bag. No published week count turned up for how long one planting keeps giving leaves.