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Cosmos

Use our zone-based planting guide to know when to plant cosmos.

Plant name Zone Start seeds indoors (spring/fall) Start seeds outdoors (spring/fall) Plant seedlings/transplants outdoors (spring/fall) Plant spacing # plants per person
Cosmos 3a April 1-15 On/around May 15 (after last frost) On/around May 15 (after last frost) 12-18 inches n/a
Cosmos 3b April 1-15 On/around May 15 (after last frost) On/around May 15 (after last frost) 12-18 inches n/a
Cosmos 4a April 1-15 On/around May 15 (after last frost) On/around May 15 (after last frost) 12-18 inches n/a
Cosmos 4b April 1-15 On/around May 15 (after last frost) On/around May 15 (after last frost) 12-18 inches n/a
Cosmos 5a March 1-15 On/around April 15 (after last frost) On/around April 15 (after last frost) 12-18 inches n/a
Cosmos 5b March 1-15 On/around April 15 (after last frost) On/around April 15 (after last frost) 12-18 inches n/a
Cosmos 6a March 1-15 On/around April 15 (after last frost) On/around April 15 (after last frost) 12-18 inches n/a
Cosmos 6b March 1-15 On/around April 15 (after last frost) On/around April 15 (after last frost) 12-18 inches n/a
Cosmos 7a March 1-15 On/around April 15 (after last frost) On/around April 15 (after last frost) 12-18 inches n/a
Cosmos 7b March 1-15 On/around April 15 (after last frost) On/around April 15 (after last frost) 12-18 inches n/a
Cosmos 8a Feb. 1-15 On/around March 15 (after last frost) On/around March 15 (after last frost) 12-18 inches n/a
Cosmos 8b Feb. 1-15 On/around March 15 (after last frost) On/around March 15 (after last frost) 12-18 inches n/a
Cosmos 9a 4-6 weeks before planting outdoors Jan. 15-Feb. 15; Sept. 15-Oct. 30 Jan. 15-Feb. 15; Sept. 15-Oct. 30 12-18 inches n/a
Cosmos 9b 4-6 weeks before planting outdoors Jan. 15-Feb. 15; Sept. 15-Oct. 30 Jan. 15-Feb. 15; Sept. 15-Oct. 30 12-18 inches n/a
Cosmos 10a 4-6 weeks before planting outdoors Jan. 15-March 15; Sept. 15-Oct. 30 Jan. 15-March 15; Sept. 15-Oct. 30 12-18 inches n/a
Cosmos 10b 4-6 weeks before planting outdoors Jan. 15-March 15; Sept. 15-Oct. 30 Jan. 15-March 15; Sept. 15-Oct. 30 12-18 inches n/a
Cosmos 11a 4-6 weeks before planting outdoors Jan. 15-March 15; Sept. 15-Oct. 30 Jan. 15-March 15; Sept. 15-Oct. 30 12-18 inches n/a
Cosmos 11b 4-6 weeks before planting outdoors Jan. 15-March 15; Sept. 15-Oct. 30 Jan. 15-March 15; Sept. 15-Oct. 30 12-18 inches n/a