PLANTOMETRY

Seed Starting Calculator

Know exactly when to start seeds

Pick a crop and your key date. Plantometry counts back from frost or your transplant date to tell you when to sow indoors, when to move plants out, and when direct sowing is an option.

Seed-starting timing is crop-specific, so a crop is required here.
The average last spring frost for your area. Look it up by ZIP if unsure.

Your sowing timeline

  1. Start seeds indoors

    Canterbury bells (Campanula medium) isn't typically started indoors — it's usually direct sown. See below.

  2. Transplant / plant out
    August 9, 2026

    Harden off, then transplant once frost risk has passed.

  3. Direct sow (alternative)

    Canterbury bells (Campanula medium) is not usually direct sown; start with transplants for best results.

Canterbury bells (Campanula medium) is usually grown from purchased plants, so seed-starting steps may not apply.