Summer can make you want to fill every empty spot in the garden. The problem is that not every plant is ready for hot soil, intense sunlight, and long stretches of warm weather.

Some flowers are at their best during the cool days of spring and fall. Plant them during the hottest part of summer, and they may spend more time trying to cope with the heat than putting on new growth. Wilting, scorched leaves, fewer flowers, and stalled growth are all common signs of summer stress.

That doesn’t mean every plant on this list will automatically die if planted in summer. Growing conditions, local climate, watering, and the plant’s stage of growth all matter. Still, these are plants that are often easier to establish during cooler weather.

Dahlias (Dahlia spp.) — Image Credit: Deposit Photos

Wishbone Flower (Torenia fournieri)

Wishbone flowers are popular for containers, window boxes, and hanging baskets because they produce plenty of colorful blooms. They prefer consistent moisture and can struggle during long periods of intense heat.

When temperatures stay high, flowering may slow, and the foliage can start looking tired. A shady afternoon location and regular watering can help, but planting during a cooler part of the year usually gives these plants an easier start.

Forget-Me-Nots (Myosotis sylvatica)

Forget-me-nots are best known for their small blue flowers that brighten spring gardens. They naturally prefer cool conditions and tend to fade as summer temperatures arrive.

Trying to establish them during the hottest weeks of the year can leave them struggling before they have time to settle in. Spring or early fall is usually a better time to give these delicate plants a new home.

Dahlias (Dahlia spp.)

Dahlias can grow well in warm climates, but newly planted dahlias may need extra attention during extreme summer weather. Their large flowers and broad foliage can lose moisture quickly under intense sun.

Established plants can handle summer much better than newly planted ones. If you plant dahlias during a hot spell, keeping the soil consistently moist and giving them protection from extreme afternoon heat can help reduce stress.

Impatiens (Impatiens walleriana)

Impatiens are favorites for shady beds because they can fill them with flowers. They prefer cooler, sheltered conditions and can wilt quickly when exposed to prolonged heat.

Direct afternoon sun can make the problem worse. If summer is already in full swing, planting impatiens during a cooler stretch and choosing a spot with afternoon shade gives them a better chance of settling in.

Fuchsias (Fuchsia spp.)

Fuchsias are beautiful container and hanging-basket plants, but wide varieties prefer mild temperatures and protection from intense afternoon sun.

Hot, dry weather can cause flower production to slow, while the leaves may wilt or scorch. In areas with very hot summers, fuchsias are often easier to keep healthy in a sheltered location or during the cooler months.

Garden Violets (Viola spp.)

Violets are much happier during cool spring weather than during the peak of summer. Their delicate leaves and flowers can struggle under strong sunlight and high temperatures.

Wide varieties naturally slow down or go dormant once the weather becomes hot. Planting them during spring or fall gives them time to establish before extreme temperatures arrive.

Sweet Peas (Lathyrus odoratus)

Sweet peas are famous for their fragrance and colorful flowers, but they have little patience for summer heat.

Once temperatures climb, flowering can slow dramatically, and the vines may begin to fade. In areas with mild winters, sweet peas are often planted in fall or early spring so they can flower before the hottest part of the year.

Pansies (Viola × wittrockiana)

Pansies are classic cool-season flowers and are usually much happier during spring and fall.

Once temperatures remain high, pansies can become stretched out, produce fewer flowers, and eventually decline. Planting them in the middle of a hot summer often means spending more time keeping them alive than enjoying their flowers.

Lobelia (Lobelia erinus)

Lobelia produces delicate blue, purple, pink, or white flowers and looks especially good spilling over the sides of containers.

The plant prefers cooler conditions and consistent moisture. During hot weather, the flowers may become sparse, and the foliage can dry out. Spring or early fall is often a better planting window, particularly in areas with hot summers.

Columbine (Aquilegia spp.)

Columbines put on much of their best display during spring. Their unusual flowers attract hummingbirds and other pollinators, but the plants often slow down once summer temperatures arrive.

Newly planted columbines can have a difficult time getting established during a heat wave. A partially shaded spot and regular moisture can help, but cooler planting conditions are usually easier on the plants.

Lady’s Mantle (Alchemilla mollis)

Lady’s mantle is prized for its rounded foliage and clusters of small yellow-green flowers. It generally prefers cooler conditions and can look worn out during long stretches of hot weather.

Leaves may develop brown edges or wilt when exposed to excessive heat and dry soil. Planting during spring or fall gives the perennial more time to develop its root system before dealing with summer temperatures.

Snapdragons (Antirrhinum majus)

Snapdragons are another cool-weather favorite. Their tall flower spikes can put on a beautiful display in spring, but intense summer heat often causes flowering to slow.

In some climates, snapdragons may take a break during the hottest part of the year and produce more flowers once temperatures drop. Planting them during cooler weather gives you a better chance of enjoying their blooms before the heat arrives.

Foxgloves (Digitalis purpurea)

Foxgloves are classic cottage garden plants that prefer mild conditions and some protection from harsh afternoon sun.

They can struggle if planted during extreme summer weather, particularly when the soil dries out quickly. Their tall flower spikes are also more likely to perform well when the plants have had time to establish before hot weather sets in.

Primroses (Primula vulgaris)

Primroses are among the flowers that signal the arrival of spring. Their colorful blooms thrive in cool weather, but wide varieties dislike prolonged heat.

Once summer arrives, flowering usually slows and plants may retreat or become dormant. Planting primroses during spring or early fall gives them a more comfortable start than putting them into hot, dry soil during midsummer.

Summer planting isn’t always a mistake, but timing matters. If the forecast calls for weeks of extreme heat, waiting for a cooler stretch can save a newly planted flower from unnecessary stress. For these cool-weather favorites, giving the roots time to settle in before the hottest part of the season can make a noticeable difference in how well they perform.