The Cosmos plants are actually half-hardy annual plants that grow flower, set seed and die all in one year, but unlike hardy annuals, the Cosmos plants can’t withstand low temperature. The Cosmos plants are quick and easy to grow from seed, flowering in as little as twelve weeks, and can be added to borders and pots for a burst of showy color. To give your cosmos a long flowering season you can sow the cosmos seeds early, indoors, in March or April. Once they’ve sprouted and they have 2 pairs of leaves you can transplant them into individual 7cm pots and grow on under cover. 

In May you can easily harden them off for a week by placing in an open cold frame or on a patio, before planting them out where they are to flower. Feed them with a liquid tomato fertilizer when the first buds appear.


How to Grow Cosmos from Seed

The following are the steps on how to grow cosmos from seed;

Start by filling a seed tray or small pots with sieve, good-quality seed or multi-purpose compost. Make sure you lightly firm down the compost with the back of your hand or a small block of wood.

Just sow the cosmos seed on the surface of the compost, if possible one seed per cell. You can sow a small pinch of seeds on the surface of each cell, and then cover with a 3mm layer of sieved compost or vermiculite. Just place them in a tray of water to moisten the compost, and then label.

Place in a heated propagator at 64.4 °F - 77.0 °F, or you can cover with a clear plastic bag. When the cosmos seedlings have about two pairs of leaves you can transplant into individual 7cm pots and grow them in indoors.


The Things You Will Need

-         You need multi-purpose, peat-free compost

-         You need seed tray or small pots

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