General gardening topics

How to grow bedding plants from seed such as Lobelia, Marigolds, Petunias and Begonias

Last updated on May 18th, 2022

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There is nothing quite like an array of stunning bedding plants to add colour to your garden. You can purchase the summer bedding plants at the end of spring, usually around April or May, but why head to the nursery multiple times when you can grow bedding plants from seed when you can have much more fun growing your own? And the satisfaction you will feel when the time comes that they are in full flower.

When you grow from seed you will probably save a little money, especially if you already have a propagator, save time shopping around, and gain a wider selection of choices because you can get many more bedding plants types as seeds than you can in trays, from even the biggest garden centres.

Sow seeds early around January and February

For most of these bedding plants, you can start inside using a propagator in January or February, consider using a heated propagator for a more constant and faster germination rate. The sooner you sow the seeds, the sooner you can get the plants to their flowering stage because this does usually take a good few months. 

super7 self watering propagator is designed to fit onto the windowsill in your home. It features a self watering feature which keeps the soil moist for better germination.

Bedding plants need between 18-21°C to germinate successfully

The key to success is providing the plants with light and warmth, steadily. Most seeds need between 18-21°C to germinate which is why we recommend investing in a propagator if you don’t already have one.

Grow lamps, heat mats, and all of these things can help you maintain steady temperatures, especially if you are starting early and you can get a good propagator for a reasonable price. 

What you need:

  • Good quality seed compost or multi-purpose compost that has been sieved.
  • Seed tray or small pots or both (7,9 & 10cm are ideal). Enough for the plants you are propagating.
  • Heated propagator (not essential but advised).
  • Your favourite bedding plant seeds.
  • Vermiculite to cover the seeds.

Prepare the seed trays and pots

With all of your supplies ready, now is the time to fill your seed trays or containers with seed compost. If you use multi-purpose compost then we recommend sieving the compost beforehand. Tap each container or seed tray to settle the compost. 

You can see our recommended multi-purpose compost in our guide here.

Sowing seeds

Space the seeds evenly over the seed tray or containers. Cover them with a fine layer of vermiculite or the compost, a little tip if you cover with compost is to use a sieve or use an empty plastic pot and sieve the compost through the holes.

Sowing summer bedding in trays

Label the trays and containers

Be sure to label each container or area of your propagating tray so that you know what is growing where. Water the containers well with a fine spray, it’s sometimes better to soak them in a tray of water from the bottom by placing them in a larger tray of water. 

Summer bedding seedling growing in tray

Place inside a heated propagator or onto a warm windowsill

Place the seed trays or pots inside your heated propagator. Some kits come with all the things you need, including detachable plastic lids that fit over the trays or pots and have vents on top to release condensation occasionally. Setting the temperature to 18-21°C is possible, some propagators do not have the option to set the temperature and are usually set to the ideal temperature already.

Make your own little propagator

If you don’t have a propagator, you can make this yourself with a pot and a plastic lid or bag tented over the pot, propped up with sticks or pencils to prevent the plastic from coming into contact with the plants.

Thin out seedlings into individual pots

As they grow, you will need to thin out the biggest seedlings from each and move them into slightly larger pots. It is for this reason that you put multiple seeds in a single container.

When you place them in a new pot be sure to water them regularly and apply a fertiliser every 4-6 weeks thereafter to encourage healthy new growth. This will prevent them from drying out and help them in their early growth.

Transplanting summer bedding into larger pots

Plant them outdoors around May or later

Once they are fully grown and their roots systems are fully established, you can move them outdoors. It is important that you wait until the risk of frost has passed, and for most parts of the UK, this is usually May.

Osteospermum being planted in rows

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