Seed Germination Guide

This article was published originally on 1/13/2017

While gardeners can purchase bedding plants at garden centers and greenhouses in spring, many gardeners prefer to get a head start on the garden season by starting flower and vegetable seedlings indoors. Growing quality seedlings indoors requires high quality seeds, a well-drained growing medium, containers, proper temperature and moisture conditions, and adequate light.
Germination requirements (light and temperature) vary among the different annuals and vegetables. The various crops also differ in the length of time from seed sowing until the seedlings are planted outdoors.
The following chart provides germination and growing information for commonly grown annual flowers and vegetables. 

Light (1)
Temperature (2)
Temperature (2)
Time (3)
  Snapdragon L 70-75 60-65 8-10
  Wax Begonia L 70-75 60-65 10-12
  Periwinkle (Vinca) C 75-80 70-75 8-10
  Celosia C 75-80 70-75 7-9
  New Guinea Impatiens LC 75-80 70-75 8-10
  Geranium C 70-75 65-70 10-12
  Petunia L 75-80 65-70 8-10
  Scarlet Sage (Salvia) L 75-80 70-75 8
  Coleus L 70-75 65-70 8-10
  Marigold C 70-75 65-70 6-8
  Pansy LC 65-70 60-65 8-10
  Zinnia C 70-75 65-70 4-6
  Onion LC 70-75 65-70 8-10
  Dill L 65-70 65-70 5-6
  Kale C 65-70 60-65 4-6
  Cauliflower C 65-70 60-65 4-6
  Cabbage C 65-70 60-65 4-6
  Broccoli C 65-70 60-65 4-6
  Pepper C 70-75 65-70 6-8
  Watermelon C 75-80 70-75 3-4
  Muskmelon C 75-80 70-75 3-4
  Cucumber C 75-80 70-75 3-4
  Squash and Pumpkin C 75-80 70-75 3-4
  Tomato C 70-75 65-70 5-7
  Basil C 65-70 60-65 5-6
  Parsley C 70-75 65-70 6-8
  Eggplant C 70-75 65-70 6-8

(1) Light conditions during germination are critical for many annuals and vegetables. The seeds of some plant species require light for germination. (In the table above, seeds that require light for germination are designated with the letter L in the Light column.) After sowing these seeds, lightly press them into the germination medium, but do not cover them. The seeds of other flowers and vegetables require darkness (C) and should be covered with the germination medium. Finally, those designated LC should be lightly covered, leaving the seeds as close to the soil surface as possible.
(2) Temperatures are in degrees Fahrenheit.  The listed temperatures in the Growing Temperature column are daytime temperatures.  Night temperatures should be a few degrees cooler. 
(3) Crop time is the number of weeks from the sowing of seeds to planting outdoors.  

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