How Often Should You Water Cosmos & Calendula Seeds?

Seed Differences

• Cosmos and calendula seeds are shaped a little differently, but are about the same size. While cosmos seed looks like a minuscule fingernail sliver, calendula seed appears similar to teeny cat claws with one end thick and the other pointy. Both need well drained soil will be easier to sow thinly if mixed with a bit of sand. Whereas calendula seed should be planted 1/4 inch deep, cosmos need to be barely covered with soil at about 1/16 inch deep. Another difference to remember when planting both is that, depending on the variety, cosmos can grow from 1 to 4 feet tall. Unless growing dwarf cosmos, they should be seeded toward the back of the flowerbed. Calendula grow from 6 to 12 inches tall, so they need the front row.

Watering During Germination

• Tamp down soil gently over both kinds of seed to keep them in place, then keep it moist, gently misting the soil so the seeds don't wash away or get exposed. The Los Angeles Times says to never let the cosmos soil dry out from the time the cosmos is seeded until it has been a seedling for two weeks. This could take 35 days, because cosmos sometimes requires 21 days to germinate. Depending on local weather, this may mean misting more than twice a day. This also should be enough for the calendula seed during germination, which will take 8 to 14 days.

Seedling Stage

• Texas A&M, however, suggests erring on the side of dryness and cutting back on water about 10 days after seeding cosmos. A good compromise may be keeping the seed moist during germination, however long that takes for the cosmos, then cutting back to once a day until the cosmos seedlings are two weeks old. More water is necessary at the front of the flower bed where the calendula should stay moist until well-established. Depending on climate and weather, this may mean watering the calendula more than once a day.

Watering As Plants Mature

• Although calendula are adaptable to dry conditions, it is wise to water them once daily. But cut back to once every two to three days for cosmos as the plants mature. They become bushier and bloom better when water is restricted. Increase watering if wilting occurs. Also, water at soil line to avoid making foliage vulnerable to fungi.

Other Considerations

• It isn't necessary to fertilize cosmos during the growing season if organic matter, such as compost, was added to the soil before planting. But the Agrihortico website indicates that calendula will do best if they receive a dose of liquid fertilizer about every 10 days. This schedule may need to be more occasional so the fertilizer doesn't accidentally overfeed the cosmos.