Peat based (or a peat alternative) type compost is ideal.

Now this is the time to decide if you want to sow your seeds in plug pots (preferred), plant pots, trays or inserts.

It is also time to calculate how many trays, inserts or pots you will need to sow the number of seeds you are going to sow.

You can sow 1 cosmos seed in a plug pot (preferred), 5 seeds in a 7.5cm (3inch) pot, 20 seeds in a half size seed tray or 50 seeds in a full size seed tray

Sieve enough compost, on to your potting bench, or potting tidy/caddy, to fill all your plug pots (preferred), pots or trays.

Don't discard the sieved out lumps and bits. These can be used in the bottom of larger patio pots when planting them up with your own home grown plants. (Save the lumps and bits in an old compost bag until needed).

Fill the plug pots (preferred), pots or seed tray/s with compost to about 5mm below the rim (this does not need to be exact - about 5mm will do).

Lift the pot or tray to a height of about 15cm (6 inches) and gently tap it on the bench. Do this about three times. This will settle the compost into the pot or tray to about the correct level.

The compost should now be about 10mm (1/2 inch) from the top of the pot or tray. This does not have to be exact so don't worry if it is a couple of mm higher or lower. It will make no difference to the end result.

Take your correct size tamper and gently level the surface of the compost. DON'T push the tamper with any force. All we want to do here is level off the surface of the compost, NOT compact it.

*This gives an ideal surface to sow the seed on.

That's it. You have now successfully filled your first tray or pot with compost.

Now Fill the rest of your trays or pots in the same way.

*(Doing this correctly will increase your propagation success rate).

This is the fun part, sowing the seeds.

Cosmos seeds are large enough to easily handle individually .

Sow 1 cosmos seed on the surface of the compost in the plug pot (preferred) or if using plant pots, trays or inserts so the quantities as detailed above.

Make sure the seeds are not bunched up in the middle or to the side of the pots, trays or inserts. They should be evenly sown over the surface of the compost.

All that is needed now is to cover the seeds with a very light "dusting" of sieved compost. Just enough to cover the seeds and no more.

When you have sown all your seeds don't forget to label them with plant name and date of sowing.

Watering

Water your plug pots (preferred), pots or trays with great care.

With your mist sprayer, set at it's finest spray, filled with tepid water and held at about 100mm (4 inch) from the pot or tray, lightly spray the surface of the compost. Don't get to close, or overdo it here, you will disturb the seeds which is exactly what you don't want to do!

The idea is to settle the surface of the compost with the fine mist from your sprayer. This prevents the seeds being disturbed.

Now fill a container, large enough to put the tray or pot in, with tepid water *(preferably water that has been standing in a warm place for about twenty-four hours) and definitely NOT rainwater, use good old tap water!

Stand the tray or pot in the container of water and leave it until you see the surface just becoming moist.

This usually happens fairly quickly so don't be tempted to go off and do something else.

*Do not overdo the watering process, you don't want the compost saturated, or your seeds may rot and not germinate.

*(By doing this correctly you will greatly increase your chance of success).

Germination

Cover your pots or trays with glass or clear plastic (or preferably, for ease of use, place in a propagator - unheated will do).

Keep your tray or pot in the light, (not direct sunlight) and maintain a temperature of 20C to 25C (68F to 77F).

After Germination

When your seeds have germinated and are large enough to handle and if you have used plug pots (preferred), pot the seedling, still in its plug pot directly in to a 7.5cm (3inch) pot.

If you have have sown your cosmos seeds in pots, trays or inserts transplant them individually into 7.5cm (3inch) pots.

Be very careful handling the seedlings. Do not handle them by their stems as this will cause irreversible damage resulting in the seedling collapsing.

Handle the seedlings very gently and only by their leaves.

Tease the seedlings roots out with great care ensuring not too many roots are damaged. Time and care taken hear will really pay dividends giving your seedlings the best possible chance of growing on successfully.

Use a good quality potting compost for transplanting your cosmos seedlings. A sieved peat based or peat alternative compost will be fine.

When you have transplanted all your seedlings don't forget to label them with plant name, sowing date and transplanting date.

Water your pots with great care.

Fill a container, that is large enough to put your pots in, with tepid water *(preferably water that has been standing in a warm place for about twenty-four hours) and definitely NOT rainwater, use good old tap water!

Stand the pots of seedlings in the container of water and leave it until you see the surface just becoming moist.

This usually happens fairly quickly so don't think about going of and doing something else.

*Do not overdo the watering process, you don't want the compost saturated, or your seedlings will rot and die.

*(By doing this correctly you will greatly increase your chance of success).

Keep the transplanted seedlings in good light (not direct sunlight) until they are large enough to be hardened off.

Aftercare

Plants should be gradually hardened off by placing them outside, in a sheltered position, during the day.

A cold frame with the lid open is ideal for this. If it is very cold during the day close the lid, but watch out for excess condensation.

If there is excess condensation prop the cold frame lid open slightly until the condensation disappears.

Bring them in at night to avoid severe frosts.

When they are ready for planting out, make sure it is after the last frosts.

If you want any further information on this garden plant please feel free to CONTACT US

Back to annual main page to see how to propagate and grow more of your favourite annual garden ( backyard ) plants.