Does Cosmos Need Fertilizer: How To Fertilize Cosmos Flowers

Pink Cosmos Flowers
(Image credit: Passakorn_14)

Its brightly colored flowers and hardy nature makes cosmos a favorite plant in beds and landscaping designs. Like many annuals, cosmos is almost self-sufficient when it comes to nutrients. Feeding cosmos plants is often a case of doing less to achieve more, as giving too much nitrogen will cause the plants to slow flower production. Learn how to fertilize cosmos the right way to ensure you have a plant covered in blooms instead of simple greenery.

Information on Fertilizing Cosmos

Information for feeding cosmos plants consists mostly of reasons why you shouldn't do it. Nitrogen encourages strong greenery and discourages the production of flowers. Most balanced fertilizer blends contain too much nitrogen for flowering annuals. It's a vicious circle some gardeners get stuck in: they don't see blooms, so they fertilize their plants hoping to encourage flowers. The more fertilizer they add, the fewer flowers will appear. Of course, when plants fail to bloom, an addition of phosphorus fertilizer for cosmos, such as bone meal, will alleviate the problem. Once the soil recovers from the excess nitrogen, however, cosmos will again be covered in masses of colorful blooms.

Tips for Feeding Cosmos Plants

So when do cosmos need fertilizer? Whether you plant your seeds in six-packs inside before the last frost date or you seed it directly in the garden, cosmos plants can use a small amount of fertilizer as soon as they are planted. Choose a fertilizer specifically made for blooming plants, which will have a low nitrogen count. Mix the minimum amount into the soil when planting seeds, and avoid feeding them for the rest of the season. Fertilizer for cosmos planted in containers is a little more crucial. Due to the small amount of soil available for roots to feed from, these plants need to be fed a bit more frequently. Sprinkle a half teaspoon of blooming plant fertilizer on the soil around each plant and water it into the soil. Repeat this feeding once every three to four weeks until the end of the flowering season. If your plants start to slow down on the flower production, cut back on the fertilizer for a couple of weeks to see if new flowers appear, then adjust your fertilizer schedule accordingly.