12 Fast-Growing Annuals You Can Still Plant Right Now For A Burst Of Late-Summer Color

There is still plenty of time to fill your beds and pots with color before summer fades. Some annuals grow so quickly that planting them now will still reward you with weeks of blooms before the first frost arrives. Whether you have bare spots in the garden, an empty planter on the porch, or you just want to freshen things up, these speedy growers deliver fast results. Grab a trowel and let’s find the perfect plants to brighten the rest of your season.

1. Zinnia

Few flowers race from seed to bloom as eagerly as the zinnia, sometimes flowering in just six to eight weeks. Toss a handful of seeds into warm soil now and you will have vivid color long before fall settles in.

Zinnias thrive in the heat that stresses out other plants, making them a smart pick for August planting across most US zones. They come in nearly every shade except true blue, so you can build a bed that pops or keep it soft and pastel.

Cut a few stems for a vase and the plant responds by pushing out even more buds. Butterflies treat a zinnia patch like a diner, adding movement and life to your yard right when the garden could use a second wind.

2. Sunflower (Dwarf Varieties)

Everybody pictures towering sunflowers, but the dwarf types stay knee-high and bloom fast enough to still make a show if you plant them today. Varieties like Teddy Bear and Suntastic can flower in roughly two months from seed.

Because they stay compact, these little suns fit beautifully in pots, window boxes, and the front edge of a bed. No staking, no toppling in a summer storm.

Here is a fun bit of trivia: sunflower heads track the sun across the sky when young, a habit called heliotropism. Once the flower matures it settles facing east, greeting the morning like it is waiting for coffee.

3. Cosmos

Airy, feathery, and almost weightless in a breeze, cosmos bring a wildflower-meadow softness that heavier blooms cannot match. They shoot up quickly and start flowering in about seven weeks, which makes late planting totally realistic.

Poor soil is actually their friend. Rich, pampered ground gives you leaves instead of flowers, so skip the fertilizer and let them fend for themselves.

Bees and small beneficial insects love the open, dish-shaped blooms. Scatter seeds in a sunny gap and you will have a swaying cloud of color that keeps going until frost knocks on the door.

4. Marigold

Dependable to a fault, marigolds are the plant your grandmother probably tucked around her tomatoes, and for good reason. Their pungent scent may help deter certain garden pests while the plants themselves bloom nonstop with almost no fuss.

French marigolds in particular grow fast from starts or seed and keep their tidy mounded shape all season. Deadhead the spent blooms and they reward you with a fresh flush within days.

Their warm orange, gold, and rust tones lean into the coming autumn palette, so they bridge the gap between summer brightness and fall coziness better than almost anything else on this list.

5. Nasturtium

Peppery, edible, and downright cheerful, nasturtiums earn their spot by doing double duty as garden color and salad garnish. The whole flower is edible, with a bite similar to watercress.

Seeds germinate quickly and sprawl within weeks, either trailing over a container edge or climbing a low trellis. Like cosmos, they actually prefer lean soil and will sulk if you overfeed them.

Gardeners sometimes plant nasturtiums as a trap crop, luring aphids away from prized vegetables. Pretty, tasty, and hardworking is a rare combination in one easy seed.

6. Celosia

If you want something that looks nothing like the rest of your garden, celosia is your answer. Some types form velvety plumes like little flames, while the crested varieties look almost like coral or a brain, in the best possible way.

Heat and humidity only make celosia happier, so a late-summer planting suits it perfectly. It grows fast and holds its color for weeks without fading.

The blooms also dry beautifully, keeping their shape and hue long after the season ends. Snip a few before frost and you have a bouquet that lasts through winter on the mantel.

7. Petunia

For sheer flower-per-square-inch value, petunias are tough to beat. Pick up a few starts from the garden center and they will fill a hanging basket or window box with color almost immediately.

Spreading types like the wave varieties cascade over container edges and keep blooming right up until cold weather. A quick pinch of the leggy stems keeps them bushy and covered in flowers.

They handle the tail end of summer heat well as long as you keep them watered, and they come in a dizzying range of colors and patterns. Want stripes, solids, or ruffled edges? There is a petunia for that.

8. Calendula

Often called pot marigold, calendula is not a true marigold at all, but it shares that same sunny disposition. It sprouts quickly and can begin flowering within about six to eight weeks of sowing.

Cooler nights at the end of summer actually suit it, so it often looks its best when other annuals start winding down. That makes it a clever choice for extending color into early fall.

The petals have a long history in kitchens and home remedies, sometimes tossed into salads for a splash of gold. Beautiful, useful, and quick, calendula is the overachiever of the late-season garden.

9. Alyssum

Low, frothy, and honey-scented, sweet alyssum spreads into a fragrant carpet faster than you would expect from something so delicate looking. It fills gaps at the front of beds and softens the edges of containers within a few short weeks.

The scent alone is worth planting for, drifting up on a warm evening like a whiff of dessert. Pollinators, especially tiny beneficial wasps and hoverflies, cannot resist it.

When the heat backs off in late summer, alyssum often perks up and blooms even more heavily. Tuck it around taller annuals to knit the whole planting together.

10. Bachelor’s Button

Craving true blue in the garden? Bachelor’s button, also known as cornflower, delivers one of the purest blues you will find in any annual, and it grows with almost reckless speed.

Scatter seed on bare ground and thin the seedlings a bit, and you will have wiry stems topped with those electric blooms in no time. They shrug off dry spells and poor soil like champs.

Legend has it young men once wore the flower to signal they were in love, which is how it earned the bachelor name. Whatever your reason for planting it, that blue is hard to look away from.

11. Portulaca

Got a scorching, dry spot where nothing seems happy? Portulaca, or moss rose, actually thrives there. This succulent-leaved sprawler stores water in its fleshy foliage and opens jewel-toned blooms in blazing sun.

It grows quickly and requires almost nothing from you, making it ideal for that neglected strip along the driveway or a sun-baked container. Skip watering for a few days and it barely notices.

The flowers open in bright light and close up when clouds roll in, so a portulaca patch practically tells you the weather. For hot, forgotten corners, it is a small miracle worker.

12. Nemesia

Slightly under the radar compared to petunias and marigolds, nemesia deserves a lot more attention for late plantings. Its little snapdragon-shaped blooms cover the plant in soft, sometimes two-toned colors that look almost hand-painted.

Growth is quick and compact, so it settles happily into containers and the front of borders. Many newer varieties carry a light, sweet fragrance that surprises people who lean in for a sniff.

Cooler late-summer temperatures suit nemesia beautifully, often triggering a fresh burst of flowers just as the season turns. If you want something a little different that still performs fast, this is the one to try.