When to Plant Seeds for a Flowering Spring Garden

By   | Last Updated :   January 7, 2022 | Filed In :   Growing Guides

The earth is waking up after its winter sleep and the time to sow seeds for a bright and cheery flowering spring garden is close at hand.

But before you begin, remember that timing is key to growing healthy plants. Start seeds too early, and the seedlings may turn leggy and pot-bound. Start too late, and the plants may never bloom.

In this post, we’ll talk about the right time to plant seeds and flowers for spring. We will also list some beautiful annuals, biennials, and perennials that you can easily start from seeds.

when to plant seeds for a flowering spring garden

When to start planting seeds for spring

To figure out when to sow your seeds for spring, you need to know three things: the last frost date, growing time of the seeds, and outdoor planting time. Let’s take them one at a time.

Last frost date

frosted leaves

Photo by Andrew Ridley on Unsplash

You can find the average last frost date in your area here. This will help you plan your sowing time. As a rule of thumb, sow your seeds 4 to 10 weeks before the date of the last frost.

Growing time of the seeds

Next, check the growing time of the seeds. You should be able to find that on the seed packet. You can start cold-hardy seeds in February, for example, but don’t sow sun-loving seeds until March, or until the danger of frost has passed.

Outdoor planting time

Finally, note the outdoor planting time. Cold-hardy seedlings can go outside by the end of March but warm-season seedlings will only survive after April, as most parts of the UK are frost-free by then.

When to plant flowers for spring

black hero tulip with emerald blue creeping phlox spring container combo

Image credit: @thepsychgarden

Springtime in the UK can be particularly capricious. Some days the sun might come out, other days the clouds may reign supreme. So, it’s good to keep an eye on a gardening calendar to know when you can start planting flowers outdoors.

January and February are quieter months for your garden. But you can use this time to prepare your flower beds, clean winter debris, till the soil and add mulch.

The beginning of March will be a brighter month for your spring garden. You can plant hardy geraniums, marigolds, and dahlias around this time but make sure to keep them covered with a frost cloth. It’s still cold outside and they will need some protection at night.

By April, after the threat of frost has passed, you can be more daring with your spring garden. Plant as many colourful flowers as you please, from delicate primroses to cornflowers and sweet Williams.

Most spring-blooming flowers begin to bud by the end of April or the beginning of May. So, after months of hard work, you can simply relax in your spring garden and watch your plants bloom.

How to sow spring seeds

indoor seedlings for spring

Image credit: @ugeshni_k

Once you know the right time to sow the seeds, you can start them indoors and transplant them later. Or put them directly in your flower beds.

Sowing outdoors in spring can be risky since the cold weather might kill the seeds. On the other hand, starting your seeds indoors using tiny containers or seed trays is safe and easy.

Important: Make sure you keep the seeds in a warm, dark room to germinate.

Once the seeds turn into seedlings with a tiny leaf or two, make sure to give them the care they need. They’ll need plenty of light to grow healthy so keep them on a sunny windowsill.

Tip: If it’s a dull and rainy spring, get a grow light. Place it 3 to 4 inches above your plant babies and keep it on for at least 12 hours a day.

Remember to water your seedlings every couple of days, or when the top layer has dried. But don’t overwater them. Doing so may result in damping off disease and other fungal and mould problems.

Good to know: You can feed the seedlings a little liquid fertiliser but not too much because they are just babies.

You also want to keep seedlings from getting leggy and weak-stemmed. You can gently brush the tops back and forth with a ruler. This will slow down their growth and help build stronger stems. After that, it’s only a question of time until you can transplant them to your flower beds.

hollyhock seedlings for spring

Image credit: @sow_good_seed

15 Spring annuals, biennials, and perennials to grow from seeds

Whether you start your spring seeds indoors or sow them directly in the flowerbeds, you may wonder which ones to get started with. Here are some easy annuals, biennials, and perennials to grow from seeds.

Spring annuals

spring annuals

Grow your own graceful cosmos flowers. Image credit: @thegardeningsoul

Annuals may last only a season or two but they can create a cheery spring display to mark the end of winter. What’s more, they require little in the way of care and protection.

Annuals you can easily grow from seeds include:

Spring biennials

spring biennials

Sweet Williams are gorgeous in pots, borders and as cut flowers. Image credit: @bloomsfromthebarn

Most spring biennials make a rosette of foliage in their first year. They also store energy during this time to burst into blooms in their second year.

Easy-to-start biennials you can sow in early spring include:

Spring perennials

spring perennials

Grow dahlias for their impressive blooms. Image credit: @splishsplash_ro

Growing perennials from seeds can turn your garden into a flowering delight with little expense. Some perennials may not flower the first year, or the blooms may not be large but be patient and you’ll see them bloom gracefully in the years to come. After all, patience is one of the most important skills for a gardener, right?

Spring perennials you may want to add to your garden include:

Flowering spring garden FAQs

Before you start planting seeds, you may want to go through a few commonly asked questions about a flowering spring garden.

How do I prepare my garden in spring?

When you first get back to your garden after the winter, start by clearing up the flowerbeds. Pick up stray leaves and debris, prune all dried foliage, and remove weeds.

Next, give your trees and shrubs a good trim so you can shape them before the new leaves form. Factor in the shade they will be giving the flowers. Then prepare the soil by tilling it. You can also add some mulch at this stage.

preparing garden for spring

Image credit: @muddyalis

How rapidly will my seeds grow indoors?

Seeds can take 7 to 14 days to germinate indoors. Most seeds love warm, dark rooms with temperatures between 18 to 24°C (64 to 75°F).

Once germinated, let your seedlings rest indoors for about 3 weeks before transplanting them outdoors. Make sure the seedlings are strong enough by checking that they have at least two sets of true leaves.

Can I start seeds for spring outdoors?

Because the great British winter weather is unpredictable, planting outdoors can be a gamble. Frost, snow, cold showers, almost everything can ruin your seeds even before they germinate.

It’s better to start your seeds indoors in a dark, warm room. You can transplant them to your flower beds once they have germinated. If you do plant seeds outdoors, make sure to use a frost cloth to shelter them.

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