The 7 Fastest-Growing Flowers to Sow Right Now – to Fill Your Yard with Beautiful Early Summer Color

A flower bed jam-packed with vivid early summer blooms sounds dreamy – a perfect start to the season. There are fast-growing flowers to plant in April to bring that vision to reality, and they are all super-simple to grow. If you want lots of flowers by early summer, these picks are for you.

The likes of alyssum, cosmos, gaillardia, nasturtiums, sunflowers, zinnia, and more can go from sowing to flowering in 10 weeks or less. If you sow seeds in April, you can look forward to beds or containers bristling with blooms come June.

For the last decade-plus, I have always grown flowers from seed. Whether it was for displays in the gardens I worked in, for cutting, or for my home garden, I always found immense joy in homegrown blooms. I have chosen seven of the fastest-growing flowers to plant in April, those that germinate fast and bloom in 6-10 weeks.

Where to Sow Fast-Growing Flowers

Whether you sow seeds indoors or outdoors will depend on your climate. If your soil has warmed to 50-55°F in April, you can sow many seeds outdoors and enjoy fast germination.

But those in milder climates are best sowing seeds indoors to get a head start. For each of these flowers to plant in April, I reveal some of my own sowing tips to help you have bustling flower beds or container gardens come early summer.

1. Sunflowers

Sunflowers are a classic summer flower. The mention of sunflowers may make you envision the quintessential bright yellow blooms, but you can find varieties with red, orange, or brown flowers.

Whether you grow statuesque sunflower varieties, dwarf sunflowers for pots, or something in between, they are show-stopping and one of the fastest-growing flowers to plant in spring.

Germinating in around a week in ideal conditions, and going from sowing to blooming in 8-10 weeks, plant sunflower seeds in April and you’ll be enjoying their flowers in early summer.

I have always started growing sunflowers indoors in early spring. As a half-hardy annual, it protects the seedlings from late frosts and cold snaps. Sow the seeds in small pots – biodegradable pots (like these Jiffy biodegradable pots on Amazon) are a great solution as they reduce root disturbance when you transplant seedlings.

If your soil has warmed enough this month, sow sunflower seeds in half-inch deep drills and try to space them 4-6 inches apart. Covering them with a cut recycled plastic bottle as a DIY cloche creates a mini greenhouse and stops slugs or snails from nibbling the seedlings.

See the range of sunflower seeds to plant at Amazon

See the range of sunflower seeds to plant at Walmart

See the range of sunflower seeds to plant at Burpee

See the range of sunflower seeds to plant at True Leaf Market

2. Zinnias

Zinnias are bright, cheery flowers that come in a variety of dazzling colors to uplift beds, borders, or pots. There are zinnia varieties in countless shades to bloom from early summer through to the first frost. As half-hardy annuals, you need to decide when to plant zinnia seeds carefully. Choose well, and your zinnias can potentially start blooming in 8-12 weeks.

An important point to remember when growing zinnias is that they dislike root disturbance. As many gardeners won’t be able to sow outdoors this month, because zinnias need the soil temperature to reach 60ºF to germinate, biodegradable pots are crucial to prevent troubling the roots when transplanting.

Fill the containers with a quality potting mix and place them in a greenhouse or warm windowsill where they can enjoy temperatures of 68-75°F. A heated propagator or heat mat (you can get a seed starting heat mat at Walmart) may be required to ensure good, speedy germination.

If your soil is warm enough in April, and the risk of cold snaps has passed, sow seeds a quarter-inch deep and 10-12 inches apart in the ground. When the seedlings reach 10 inches, pinch out your zinnias to encourage branching and more flowers.

See the range of zinnia seeds to plant at Amazon

See the range of zinnia seeds to plant at Walmart

See the range of zinnia seeds to plant at Burpee

See the range of zinnia seeds to plant at Botanical Interests

3. Nasturtiums

What is there not to love about growing nasturtiums? They look stunning, nasturtium varieties come in a kaleidoscope of colors, they are really easy to grow, the whole plant is edible, plus they are great for companion planting and keeping unwanted pests off your other flowers or vegetables. Can you tell I am a fan?

Add to that the fact that nasturtiums germinate reliably and grow fast. In ideal conditions, you’ll see the sprouts appear in a week, and the first flowers can be enjoyed 6-8 weeks from sowing. You can appreciate nasturtium blooms from summer into the fall.

Gardeners can plant nasturtium seeds directly into the garden after the frosts, once the soil temperature reaches at least 55°F. Sow them an inch deep and at least six inches apart, thinning to 10-12 inches once they germinate.

To grow the easy edible flower from seed indoors, fill three-inch biodegradable pots with potting mix and sow two seeds per pot. Put the pot in a greenhouse or on a warm windowsill, and the seeds will germinate quickly at 55-65°F. Keep the soil moist, but not waterlogged, and harden off the seedlings before planting them outside later in spring.

Many gardeners recommend soaking seeds for a few hours before planting their nasturtiums. It is not something I have done myself, and I still enjoyed good results. But it is worth experimenting with, as soaking seeds can speed up germination.

See the range of nasturtium seeds at Amazon

See the range of nasturtium seeds at Walmart

See the range of nasturtium seeds at True Leaf Market

See the range of nasturtium seeds at Botanical Interests

4. Marigolds

Marigolds are easy-to-grow annual plants you can grow in borders or pots to brighten up any space. They germinate quickly and bloom in bright shades of orange, gold, or red for many months. As great plants for pollinators and perfect flowers to plant in a vegetable garden to deter pests, they are great additions to any yard.

Gardeners can start marigold seeds indoors in April by filling seed trays or modules with a good potting mix and lightly covering them with a thin layer of more soil or vermiculite. The seeds will sprout in a week at temperatures of 70-75°F in a greenhouse, propagator, or on a warm windowsill.

In warmer gardens, the annual can be sown directly into half-inch drills, covered, and kept moist. Direct-sown marigolds may need protection from slugs and snails, either by using physical barriers (sharp materials like gravel or broken eggshells discourage them) to stop slugs from destroying plants, or by using beer traps (you can get slug and snail traps at Amazon) as a form of slug control.

See the range of marigold seeds at Amazon

See the range of marigold seeds at Walmart

See the range of marigold seeds at Burpee

See the range of marigold seeds at True Leaf Market

5. Gaillardia

Also known as blanket flower, gaillardia is a fast-growing flower choice for filling borders with exuberant orange, red, yellow, or white flowers. They take 6-8 weeks to start flowering and continue to do so from early summer through to late fall.

Most varieties of gaillardia are native plants that attract hummingbirds, butterflies, and other pollinators throughout the blooming season – making them a great choice for a wildlife garden.

Direct sow gaillardia seeds in the garden after the last frost. These seeds need light to germinate, so it is as simple as clearing weeds from your chosen spot, raking the soil level, and scattering the seeds over the surface. Keep the soil moist, but not waterlogged, and the seeds should reliably germinate.

The alternative is to plant the seeds indoors in April. Sow them onto the surface of trays, modules, and individual pots and keep them warm and moist. At temperatures of 70-75°F, gaillardia seeds should germinate within two weeks.

Once the plants start blooming, deadhead blanket flowers regularly to give yourself and your garden wildlife the longest-lasting display to enjoy.

See gaillardia seeds at Amazon

See gaillardia seeds at Walmart

See gaillardia seeds at True Leaf Market

See gaillardia seeds at Botanical Interests

6. Alyssum

Alyssum, also commonly called sweet alyssum, is a fast growing tiny flower that develops carpets of blooms within 9-12 weeks from sowing. It is an easy-to-grow annual with a sweet scent and masses of blooms, most often they are white, but you can also get pink and purple varieties.

Alyssum often makes a great choice for a plant to edge a flower bed with, or to grow alongside garden paths to spill over onto the hard landscaping. As well as looking highly decorative, alyssum also makes an attractive, fast growing ground cover to smother weeds while also attracting pollinators.

In early spring, sow alyssum seeds indoors or outdoors, depending on your climate. If you still have a risk of frosts, sow indoors as the seeds will germinate very quickly in warmer conditions.

Alyssum seeds are tiny and need light to germinate, so don’t cover them with any soil. They want 55-70°F for speedy germination, and can be transplanted outside after the frosts.

See the range of alyssum seeds at Amazon

See the range of alyssum seeds at Walmart

See the range of alyssum seeds at Burpee

See the range of alyssum seeds at True Leaf Market

7. Cosmos

Cosmos are hugely popular summer flowers, and for good reason. I have grown them year-after-year, hence their spot in this list of the top flowers to sow in April.

Let’s quickly rattle off some great traits about growing cosmos; they are easy-to grow, flower in 10-12 weeks from sowing, and continue to bloom for long periods of time. Gardeners can pick between types of cosmos in many bright colors, and the blooms make great cut flowers as they offer a long vase life. It all sounds good, right?

Plant cosmos seeds indoors in April if your soil temperature is below 60°F, as it will not germinate happily in colder soils. You’ll get much better success planting seeds indoors this month, and transplanting the seedlings outdoors once the soil warms.

Sow cosmos into trays, modules, or pots and sow the small seeds a quarter of an inch deep. For strong germination, use a greenhouse, propagator, or warm windowsill, where the seeds can get a temperature of 64-75°F, and keep the soil consistently moist.

When your plants reach 6-10 inches tall, pinch out cosmos to encourage lots of sideshoots and a prolific display of summer flowers. And to keep cosmos blooming, the secret is deadheading throughout the summer.

See the range of cosmos seeds at Amazon

See the range of cosmos seeds at Walmart

See the range of cosmos seeds at Burpee

See the range of cosmos seeds at True Leaf Market

See the range of cosmos seeds at Botanical Interests

What to Shop

If you are in search of more monthly planting inspiration, we’ve got you covered. You can see our guide on native perennials to plant in April to add more flowers to your garden for years to come, or check out this on fruits to plant in April for a garden full of homegrown fruit to enjoy straight from the tree or bush.

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