Training your roses to be more drought tolerant
Many factors, including the variety, can influence the capacity of a rose to be drought tolerant. Some roses are more drought tolerant than others by nature, but many roses can be trained to endure some drought. Cultural techniques to improve drought tolerance involve soil management, mulching and pruning, as well as the variety of rose and the time of year it is planted. Environmental factors include the depth and structure of the top soil, depth to the water table, mychorrhizal populations, and organic matter (mulch, compost).
Create deep root systems with deep, infrequent watering to a depth of 12 to 18 inches below the soil surface. This will enhance drought resistance and allow the plant to access more soil minerals. It will help prevent root rot from damaging plants and provides the plant access to a reservoir of water between irrigations. Deep root systems will help the rose to survive both droughts and winter freezes.
Use a drip system rather than a lawn sprinkler. Drippers put the water where it is needed--at the roots. Drip system emitters are designed to deliver varying amounts of water. Choose emitters that drip between 1 and 4 gallons per hour, depending on your soil type and the size of the plant. A 3 gallon drip emitter will emit 3 gallons of water per hour and will add 4.5 inches of water to the area. ( 3gallons x 1.56 inches = 4.5 gallons of water applied.) One gallon emitters add 1.56 inches of water over a square foot of dry ground and wet an area to a depth of about 1.5 inches, depending on the soil texture (clay, sand or loam) and how wet or dry the soil is when you apply the water.
Water to just beyond the width and depth of the roots system and allow the soil to partially dry between irrigations. Check with a moisture meter to determine the depth of soil moisture. You also can check the moisture by carefully digging down near the roots (be careful!) with a trowel or a long probe. Look for a difference in soil color. Wet soil is usually darker than dry soil; this can help you determine how deep the water is penetrating. Plants growing in sandy soil need to be watered more often for shorter periods of time than those growing in heavy clay soil. Plants growing in clay soil need to be watered less often, at slower rates because the water penetrates the soil more slowly.
Roses need at least 1 inch of water per week, and up to 2 inches during hot weather. You can estimate how many gallons or inches of water it takes to wet your roses to the depth of the root system. Use 1 gallon per hour (gph) drippers to apply 1-2 gallons of water for smaller plants like miniature roses. Place two 1-gph emitters 12 inches from the base of a shrub rose that is 1 to 5 feet tall. Add a third 1-gph emitter to a rose growing over 5 feet, and replace the 1-gph emitters with 2-gph emitters if needed. Because of summer watering restrictions, most gardens can only be watered 2-3 times a week in the summer, so all the required water for the week should be divided among those irrigations. Newly planted roses may need more water, so watch for wilt and other signs of drought stress.
When you water, be sure to wet the whole area of the root ball and then let it nearly dry out before the next watering. Plants cannot move water from one side to the other. If you water only one side, there will be growth on only one side. Watch for wilting, and water if needed.
Reduce irrigation frequency, not amount of water applied as the bushes grow. Well-established plants need less water than newly planted ones. After the first year, when the plants are established, they will be more adept at seeking water from a wider area of soil. Move the emitters farther away from the trunk of the plant and add more if needed for good coverage. Larger rose bushes will have roots spread over a wider area of soil than smaller ones. This means as your plants grow, larger bushes will require more water to ensure the water reaches all of their roots. If you have a problem with salt build up, you may need to apply a little extra water occasionally to leach salts below the root zones.
Use mulch to reduce the frequency of watering. A 3-4 inch mulch layer of shredded hardwood mulch holds moisture in the soil. Mulch insulates the soil and keeps it from drying out as quickly as it would under normal conditions, reducing the frequency of watering as well as the need for fertilization
Keep weeds under control. Don’t waste your valuable water on growing a crop of weeds that will compete with your roses for water.
Reduce feeding and fertilizing. The goal is to keep the shrubs alive and healthy. That may mean forsaking some blooms, but your plant will stay alive to bloom another day.
Provide some relief from the sun by creating some shade during the hottest times of the day. This will reduce water loss in your plants and increase the efficient use of water. A friend of mine created an “umbrella garden” when one of her large, shady oak trees fell, taking with it the shade. They liked the effect so well, they left them in place and never replaced the tree. Use umbrellas made from a light-colored fabric; white or reflective silver is the best. Between the shade of the umbrella and the reflection of the light colored shade, the heat buildup will be reduced, providing much relief.
In the end, roses are pretty forgiving plants. I am sure we are all guilty of coddling them more than they really need. Floribundas, hybrid teas and grandifloras will likely not bloom as often under drought, but they can survive with limited watering while still providing beautiful blooms. Miniature roses also do well in these kinds of situations and can out-bloom some of the other types of roses.
For more information and tips on how to keep plants alive under drought or water restrictions, please follow this link: http://anrcatalog.ucanr.edu/pdf/8553.pdf.
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