17 Flower Seeds to Sow Mid-Summer

There are plenty of fast-growing flowering annuals you can sow in midsummer to enjoy flowers into fall in colder climates. Have a look at the choices and get your seeds ready so you don’t miss out.

There are also lots of edible crops to start now. See 20 Vegetables to Sow Mid-Summer for Fall for suggestions.

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Sowing Seeds for Late Summer Blooms

After the flourish of spring planting, many of us take it easy in the summer garden, just tending to some weeding, harvesting some early fruit and vegetable crops, and trellising vining plants.

But there’s a huge reward ahead if you make time to sow seeds in the middle of summer.

The seeds I’ve listed here are flowering annuals. I’ve also got a midsummer sowing plan for cool-tolerant vegetables here.

Getting Started

To get started, you will need to know your average first frost date and hardiness zone. I’ve provided links below to lookup this information.

This information is intended for gardeners in zones 4 to 8 (ish) simply because that’s what I’m most familiar with.

What we choose to sow is based on how many days we have before first frost. That number should be greater than the “days to maturity” or “days to bloom” listed on the flower seed packet plus a week or two if possible.

The most important step is to get your seeds asap.

You will sow directly outdoors unless it’s unusually hot or dry. If conditions are extreme, indoor seed starting or a covered patio may be better options.

Flower Seeds to Sow Mid-Summer

Once you know how many days you have until first frost, browse your favorite seed sellers to see what fits your timeline.

I’ve provided a chart (below) listing average days to bloom to help refine your options. But, even within the same species there can be wide variations in timing, so, if one variety doesn’t work, another might. Sunflowers are a good example: some dwarf varieties need just a couple of months where the tall varieties with large heads need several months more.

You’ll also notice that some flowering annuals are labelled as hardy or half-hardy. This means they can tolerate some cold around frost time which is great for a longer bloom time.

And, as always, avoid any plants known to be invasive or problematic in your area.

The number of days to germinate listed are based on numbers provided by several seed companies and apply to growing in the recommended conditions including the preferred soil temperature at sowing time. So read your seed packets to give your seeds their best start and allow more time if your conditions are not optimum.

I’ve linked to Botanical Interests seeds below. You can find more seed sellers here: United States | Canada.

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Seed Suggestions

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1Amaranthus

Amaranthus (Amaranthus spp.)

Full sun

2Cornflower

Bachelor’s Button / Cornflower (Centaurea cyanus)

Full sun

Seeds

Cornflower | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
60-70°F (15-21°C)

Tip
Can also sow around last frost for next growing season.

Days to Germinate
7-14

Days to Bloom After Sowing
65-75 (9-10 weeks)

3Butterfly Flowers

Butterfly Flowers (Tithonia rotundifolia)

Full sun

Seeds

Butterfly Flower (Mexican Sunflower)| Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
70°F (21°C)

Days to Germinate
7-14

Days to Bloom After Sowing
80 (11 weeks)

4Calendula

Calendula (Calendula officinalis)

Sun or Part Sun, Cold-Tolerant

Seeds

Calendula | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
70°F (21°C)

Tips
Pinch back to encourage bushier growth.
Look for tall varieties (not dwarf) if you want cut flowers.

Days to Germinate
7-21

Days to Bloom After Sowing
45-56 (6-8 weeks)

5California Poppy

California Poppy (Eschscholzia californica)

Sun

Seeds

California Poppy | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
55°F (12°C)

Tip
Can also sow outdoors after last frost for next growing season.

Days to Germinate
14-21

Days to Bloom After Sowing
60-75 (8-10 weeks)

Tips: Mid-Summer Garden Tasks: What To Do Now

6Cosmos

Cosmos (Cosmos bipinnatus and C. sulfureus)

Sun

Seeds

Cosmos | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
70-75°F (21-25°C)

Days to Germinate
7-10

Days to Bloom After Sowing
70-84 (10-12 weeks)

7Flax

Flax (Linum usitatissimum)

Sun

Seeds

Flax | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
50-80°F (10-27°C)

Tip
Can also sow after last frost for next growing season.

Days to Germinate
21

Days to Bloom After Sowing
50-60 (7-8 weeks)

8Marigold

Marigold (Tagetes sp.)

Sun

Seeds

Marigold | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
70-75°F (21-25°C)

Tip
Can also sow indoors in vermiculite 6-8 weeks before last frost or directly outdoors around last frost for next growing season.

Days to Germinate
4-12

Days to Bloom After Sowing
42-70 (6-10 weeks)

9Morning Glory

Morning Glory (Ipomoea purpurea)

Sun

Seeds

Morning glory | Botanical Interests (US Shipping)
Avoid Bindweed (Convolvulus arvensis) also known as “morning glory” which is highly invasive.

Seed Sowing Soil Temperature
70-85°F (21-30°C)

Tip
Outdoor seed starting may be slower than indoor.

Days to Germinate
10

Days to Bloom After Sowing
100 (14 weeks)

10Nasturtium

Nasturtium (Tropaeolum majus)

Sun, Cold-Tolerant

Seeds

Nasturtium | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
55-65°F (12-18°C)

Tip
Sow indoors or directly outdoors.
Part-shade makes a leafier, sprawling plant.

Days to Germinate
7-10

Days to Bloom After Sowing
60 (8 weeks)

11Nigella

Nigella (Nigella damascene)

Sun

Seeds

Nigella | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
65-70°F (18-21°C)

Days to Germinate
10-15

Days to Bloom After Sowing
65-75 (9-11 weeks)

12Poppy

Poppy (Papaver spp.)

Sun

Seeds

| Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
Perennial 68-70°F(20-21°C)

Annual 60°F(16°C)

Days to Germinate
14-28

Days to Bloom After Sowing
55 (8 weeks)

13Phlox

Phlox (Phlox drummondii)

Sun, Cold-Tolerant

Seeds

Phlox | Botanical Interests (US Shipping)

Seed Sowing Soil Temperature
60°-65°F (16°-18°C)

Tip
Can also direct sow when ground is workable in spring.

Days to Germinate
5-10

Days to Bloom After Sowing
50-65 (7-9 weeks)

14Sunflower

Sunflower (Helianthus annuus)

Sun

Seeds

| Botanical Interests (US Shipping)
Look for dwarf varieties.

Get my best tips for growing sunflowers here.

Seed Sowing Soil Temperature
70-75°F (21-25°C)

Days to Germinate
14

Days to Bloom After Sowing
75-100 (10-14 weeks) Check for your variety.

15Sweet Alyssum

Sweet Alyssum (Lobularia maritima)

Sun or Part Sun, Cold-tolerant

Seeds

Sweet Alyssum | Botanical Interests (US Shipping)
Look for dwarf varieties.

Seed Sowing Soil Temperature
55-70°F (13-21°C)

Tip
Seeds require light to germinate: sow on soil surface.
Dwarf varieties spread as ground cover and reseed.

Days to Germinate
8-10

Days to Bloom After Sowing
50-60 (7-8 weeks)

16Sweet Pea

Sweet Pea (Lathyrus odoratus)

Sun

Seeds

Sweet Pea | Botanical Interests (US Shipping)
Be sure they are annuals. The perennial (L. latifolius) is invasive.

Seed Sowing Soil Temperature
55-65°F (12-18°C)

Tips
Soak seeds in moist paper towel for 1 day prior to sowing.
Best sweet pea growing tips
How to save sweet pea seeds

Days to Germinate
28

Days to Bloom After Sowing
50-60 (7-9 weeks)

17Zinnia

Zinnia (Zinnia elegans)

Sun

Seeds

| Botanical Interests (US Shipping)

Seed Starting Soil Temperature
70-80°F (21-26°C)

Tips
Can also sow directly outdoors after last frost.
Pinch stems for more flowers.
Save zinnia seeds for next year.

Days to Germinate
5-24 days

Days to Bloom After Sowing
50-60 days (7-8 weeks)

For late winter and spring sowing indoors, see 30 Flower Seeds To Start Indoors.

Time to get your seeds and start sowing.

~Melissa the Empress of Dirt ♛