Water your garden - how to keep it green in heat and drought

Water is critical to plants and nothing brings that home like a hot dry summer. Most gardeners use twice as much water as they need to keep their garden thriving.

Annuals, including everything from impatiens to cucumbers, need the most water. Sun loving plants in containers also can require daily, if not twice a day watering, to prevent stress.

Medium water use plants, such as shrubs, woody perennials, and trees planted within the past year or two, need to be watered during hot, dry, weather.

Mature trees and drought tolerant plants need less water than those listed above. Moisture-loving plants such as hydrangeas can become stressed and may need extra water to keep them looking their best.

Transpiration and evaporation are the processes that make the plants you watered this morning droop in the afternoon.  Water evaporates out of plants through the underside of the leaves, the stems and flower petals. It is challenging to keep some plants looking good no matter how much water they receive.

Shade can help. Pots can be moved under trees and arbors and other vulnerable plants such as tomatoes can be draped with shading cloth.

2012 USDA zone map

Since everyone’s weather is going to be hotter, consider replacing plants that struggle every year, with more heat and drought tolerant ones.  In general, annuals (plants that complete their life cycle in one growing season) have more shallow roots than woody perennials, so dividing and adding more perennials will help reduce next year’s water needs.

Adding organic matter increases the water-retention capacity of the soil structure, reducing future water needs. The best practice is to add 4-inches of organic material every year.

The more established a plant is when hot dry weather arrives, the more likely it is to thrive. Perennials are planted in the fall so they have time to develop deep roots before summer arrives.  

They still have to be watered regularly the first summer and for up to five years after planting.

One or two inches of water per week should be provided in any week there is no rainfall.

An easy way to measure the water falling from the sprinkler is to tuck a tuna can into the bed. When it is full, move the sprinkler.

Mulch is key to a healthy summer garden. It insulates the soil surface from becoming too hot, protects plant roots, prevents water-stealing weeds from growing, and reduces evaporation.

Mulch actually changes the structure of soil, leading to increased root growth, better oxygen movement, and more nutrients being available to plants.

Clemson Cooperative Ext.

Mulch that has not already decomposed promotes soil granulation which is the action of soil micro-organisms improving clay soil.

Organic mulches that nourish the soil include:  Shredded bark, shredded leaves, pine needles or pinestraw, sawdust, grass clippings, straw, hay, cottonseed and buckwheat hulls, pecan shells, cocoa hulls (do not use if you have dogs), peat moss, and compost. Water both before and after applying mulch.

Healthy plants tolerate heat and drought better. Avoid fertilizing drought spells when plants stop growing. It is better to fertilize in spring and fall when temperatures are cooler.

Cutting back and pruning helps reduce the amount of leaf surface. Avoid severe pruning but pinch and prune off up to one-third of the plant.

Our favorite waterer

  Watering methods that work include soakers, sprinklers that keep the water flow close to the ground, drip systems and similar soil-moistening methods. Watering 4 or 5 feet into the air evaporates up to 70% of the water. Irrigating in the morning allows time for the plants’ leaves to dry during the day. Watering in the evening can lead to mildew on zinnias and fungus on roses if the leaves remain wet overnight.