It may be cool now, but certainly, by August we will experience some very hot weather. In mid to late summer, it is sometimes difficult to keep things blooming. Plan ahead to include annuals that can take the heat and like it. Fortunately, there is a good selection of these plants.
One flower that immediately comes to mind is the Moss Rose or Portulaca. This annual likes hot, dry and sandy soil. It does tend to close its blooms on cloudy days. Colorful zinnias are best in hot and dry conditions. They come up quickly after direct sowing in warm soil, but seedlings are readily available in the greenhouses. Look for the dwarf variety, 'Magellan' that has large double blooms or the 'Profusion' series with their daisy-like flowers. Cosmos are heat and drought tolerant. Some varieties can reach four feet, but 'Sonata' forms a bushy two-foot tall plant that comes in pink, red or white.
Fibrous begonias (wax begonias) do well in hot weather. The varieties with bronze leaves have the greatest resistance to heat. The dragon wing begonia may not look like much in the greenhouse, but during the hot part of summer, it is impressive. It will continue blooming until frost and all winter if you take it inside. Give it a large pot and fertilizer and it will cascade in full sun to light shade. Shade loving impatiens take off once the weather gets warm.
Gaillardia, African Daisy (Osteospermum) and Gazania are daisy shaped flowers that are heat and drought resistant. Most gazanias will close at night and on cloudy days. The bloom-happy Melampodium has quarter sized yellow daisies on a compact dwarf plant.
Low growing annuals that like heat include Alyssum, Portulaca, Petunia and Vinca rosea or Periwinkle. Vinca makes a nice edging plant, similar in appearance to impatiens. It will not flourish in cool weather. The warmer it is the more Alyssum emanates its honey-like scent. Petunias are drought tolerant once they are established.
Gaura, Celosia, Lisianthus, Cleome, Salvia and Angelonia add height to the garden or container. Cleome can reach six feet tall. Wispy Gaura is about three feet tall and sways in the wind. Celosia has feathery red, orange or yellow blooms that are extra heat tolerant, but buy the plants that are not in bloom yet. Lisianthus has lovely flowers that look like rosebuds. Either stake each one or pinch them off just after you plant them. Angelonia looks a little like snapdragons, but can handle hot dry soils and even humidity. Salvia farinacea 'Victoria' and some newer varieties are good blue flowers at 18-24 inches. Although cannas are tubers we treat them like annuals and they love heat and moisture.
You may need some middle-sized flowers to fill in your beds. Nicotiana (Tobacco plant) is good in heat and humidity. Gomphrena has pink, reddish-purple or white rounded clover-like flowers that dry well. Pentas (Star Cluster) provides good color in heat and drought. Heliotrope has fragrant deep purple flower clusters, but it must have heat to thrive. Marigolds come in many sizes so can be used for edging or for height.
Containers can get quite warm. A few trailing plants that like it hot are Scaveola (Fan flower), Lantana and Verbena. Scaveola needs lots of water and Verbena should not be allowed to dry down hard. They should all keep blooming throughout the season.
Many foliage plants are heat tolerant. Red Iresene, Plectranthus, purple leaved Alternanthera with its three-foot spread and Dichondra with silver-white foliage are some. You could do a whole garden with all the Coleus varieties, especially the solar series that grows well in the sun.
The nurseries and greenhouses are filled to the brim with an amazing array of colorful annuals. Make a selection that includes both cool weather and heat loving annuals covering all conditions and you will have something blooming all season.