Heat-proofing Annual Flowers

Summer is fast approaching, and in many parts of the country that means heat and humidity, both of which can stress flowering plants, especially annuals. Here are five easy steps you can take now to heatproof your plants and ensure a long season of color and vigorous growth in your garden.

1. Choose the right plant
Plants have different preferences in growing conditions. Cool-season annual flowers like pansies and snapdragons are perfect for spring and fall plantings, but will fade in summer's heat. If you want bright color and healthy plants in high summer, choose heat-lovers like dahlias, geraniums, lantanas, petunias, verbenas and vinca since they all thrive in full sun. For shadier spots, choose coleus and impatiens.

2. Enrich garden soil
Adding organic matter such as compost to garden beds loosens soil and encourages plant roots to grow large and strong, improving the plant's ability to take up water. Organic matter also improves the soil's ability to absorb and retain water.

3. Top with organic mulch
A two- to four-inch layer of bark chips, pine straw or other organic mulch conserves moisture and insulates soil against the hot sun and drying winds.

4. Water properly
Water plants deeply, but infrequently, making sure the water penetrates to the depth of the plants' roots. A soaker hose is a good investment; the water seeps out slowly so moisture is absorbed right at the root zone rather than running off. Use a trowel to check that soil is moistened to the proper depth. Then wait to water until soil has dried out somewhat. Plants will develop deep, drought-resistant root systems this way.

5. Provide some shade during midday
Remember that in the hottest part of the country, even sun-loving plants appreciate a little shade relief when the sun is at its hottest at midday. Choose a planting area that gets a bit of shade from other plants, structures, awnings, house eaves, etc. Annuals planted on the east side of a leafy shrub, for example, will get full sun all morning but filtered sunlight in the afternoon. Trees with high, thin canopies also provide a light shade when the sun is high in the sky. The best thing to do is observe where the sun is when you're in your garden at different parts of the day during summer, and take your cues from that.

 

Container-grown annuals
Annuals growing in pots need extra attention in hot, dry weather because their root systems are contained and can't reach out in search of water. The soil in containers also heats up and dries out more quickly than regular garden soil. Here are a few guidelines to get your potted plants ready to withstand the summer heat.

* Plant in moisture-retaining potting soil
Use a potting mix formulated specifically for container plants -- it will have the right balance of good drainage and water-holding capacity. Some potting mixes also contain wetting agents or water-absorbing polymer crystals that further improve water retention. Potting soils containing slow-release nutrients will help keep plants growing vigorously all summer long.

* Use non-porous containers
Non-porous containers made from plastic, glazed pottery or resin will retain water better than porous containers, such as unglazed pottery, terra cotta and wood.

* Select relatively large containers
Plants in small containers may need watering twice a day in hot, sunny weather. If possible, choose containers that hold at least three quarts of soil.

* Use self-watering planters or drip irrigation
Self-watering containers incorporate a reservoir and a wick. All you have to do is fill the reservoir with water. As the plant uses moisture, water is wicked up into the soil. Self-watering containers are especially useful when you aren't available to water your plants on a daily basis, or if you have small containers such as window boxes. Remember to check the reservoir regularly and refill as needed.

* Consider drip irrigation
Alternatively, pots that can be grouped together can be connected to a drip irrigation system. Drip irrigation delivers water slowly immediately above, on or below the soil's surface. This helps minimize water loss due to runoff, wind and evaporation.