7 Fast-Growing Flowers to Plant in August for Fall Color
August can feel like the end of the gardening season, but it’s actually a great month to squeeze in one more burst of color. If you choose the right plants, fast-growing flowers to plant in August can fill gaps, refresh tired containers, and keep your garden looking lively until the first frost.
The key is to focus on flowers that either bloom quickly from seed or settle in fast when planted as young transplants. In many regions, warm soil still helps roots establish quickly, especially if you keep the plants watered and mulched during hot spells.
What to consider before planting in August
Before you buy seeds or starts, check two things: your average first frost date and your USDA hardiness zone. If your frost date is early, you’ll want the fastest bloomers or nursery-grown plants. If you garden in a milder climate, you may have enough time for a bigger range of flowers.
As a general rule, choose plants that:
- flower in 45 to 70 days from sowing, or quicker from transplants
- tolerate some late-summer heat
- benefit from deadheading to keep blooming
- work well in containers, borders, or quick fill-in spaces
For best results, water deeply after planting, mulch lightly to hold moisture, and give new seedlings some afternoon shade if your August weather is intense.
7 fast-growing flowers to plant in August
1. Calendula
Calendula is one of the best choices for a late-summer sowing because it grows quickly and can bloom in cool weather. The cheerful yellow and orange flowers bring an instant seasonal feel to beds and pots, and they often keep going until cold weather shuts them down.
Why plant it now: It germinates readily in warm soil and moves fast from seed to bloom.
Tip: Sow seeds directly where you want them to grow, then thin seedlings so they have room to branch out.
2. Nasturtium
Nasturtiums are wonderfully easy-going and one of the quickest flowers to reward you. They’re ideal for edging a path, spilling from hanging baskets, or covering bare ground with bright blooms and round leaves.
Why plant it now: It grows fast, handles a bit of neglect, and often does better in lean soil than rich soil.
Tip: Give nasturtiums plenty of sun for the best flowering, but don’t overfeed them or you may get leaves instead of blooms.
3. Sweet alyssum
If you want fragrance as well as color, sweet alyssum is a smart pick. It forms low, airy mounds of tiny flowers that soften the edges of containers and attract beneficial insects.
Why plant it now: It grows quickly, fills in gaps fast, and often blooms repeatedly in cooler weather.
Tip: Keep the soil evenly moist when plants are young so they establish without stress.
4. Zinnias
Zinnias are one of the most dependable summer-to-fall annuals, especially in warm regions. If you transplant them in August rather than start from seed, they can still give you weeks of bold color in pink, orange, red, coral, and cream.
Why plant it now: Young plants establish quickly and can bloom right through the late season.
Tip: Choose compact or dwarf varieties if you want fast results in containers or front borders.
5. Marigolds
Marigolds are a classic late-season plant because they’re quick to grow, easy to find, and reliable in full sun. Their warm colors look especially good in autumn containers or mixed with fading summer annuals.
Why plant it now: They bounce back fast after transplanting and flower continuously with regular deadheading.
Tip: French marigolds are usually the best bet for a shorter timeline than larger African types.
6. Cosmos
Cosmos are delicate-looking, but they’re surprisingly speedy once established. Their ferny foliage and daisy-like flowers give beds a light, airy look that works well when other plants start to look tired.
Why plant it now: Smaller cosmos varieties can go from seedling to bloom fairly quickly, especially in warm weather.
Tip: Avoid overwatering and overfertilizing; cosmos prefer a lighter touch.
7. Sunflowers
Not all sunflowers are towering giants. Dwarf and quick-maturing varieties can still be planted in August in many areas, especially if you want a cheerful fall accent or a mini pollinator patch.
Why plant it now: Some smaller varieties bloom in a relatively short time and bring instant impact.
Tip: Check the days to maturity on the seed packet and choose the shortest options if frost is approaching.
How to help late-planted flowers bloom faster
A fast-growing flower still needs the right conditions to perform well. A few simple steps can make a big difference.
- Prepare the soil. Loosen compacted ground and mix in compost if your bed looks tired.
- Water deeply. Shallow watering encourages weak roots; deep watering helps plants settle in.
- Mulch lightly. A thin layer of mulch keeps the soil from drying out too quickly.
- Remove faded flowers. Deadheading encourages many annuals to keep producing buds.
- Use transplants when time is short. If your first frost is near, nursery-grown starts give you a head start.
Best places to use fast-growing flowers in August
These quick bloomers are useful anywhere you need a fast visual boost. Try them in:
- empty borders where spring annuals have faded
- containers on patios, porches, or balconies
- vegetable garden edges to attract pollinators
- window boxes for a late-season refresh
- bare patches in the front yard that need a quick cover-up
If you’re short on time, combine a few transplants with direct-sown seeds. That gives you both immediate color and a second wave of blooms later in the season.
A simple August planting plan
Not sure where to start? Here’s an easy approach:
- For instant color: buy marigolds, zinnias, or cosmos starts.
- For fast seed sowing: choose calendula, nasturtium, alyssum, or dwarf sunflowers.
- For containers: mix a taller plant like zinnias with low spillers like alyssum or nasturtiums.
- For pollinators: include calendula, cosmos, and sunflowers near herbs or vegetables.
Even if summer is fading, your garden does not have to look sleepy. With a little planning and the right flowers, August can be the month that carries your beds and containers beautifully into fall.
