Growing Healthy Roses

Growing Healthy Roses is Common Concern

Each week, Master Gardeners answer dozens of gardening questions from throughout Ventura County on their free helpline, operated by the University of California Cooperative Extension, as well as at various workshops and educational programs. 

Although these volunteers handle many different gardening topics, roses are always among the most popular subjects – especially how to grow healthy roses without relying on pesticides and fungicides.

In this first column of a multi-part Q&A series, we tackle this thorny topic.  First, we look at basic rose gardening tips; in future columns we’ll discuss some of the best ways to fight common pest and diseases, as well as other gardening subjects.

Question 

I’ve just planted several beautiful roses in my garden.  How can I keep them healthy?

Answer  

Growing strong, healthy roses is easier when you follow some basic principles. 

Start Healthy:  Let’s assume you’ve started with healthy roses in varieties that tend to be disease resistant.  You’ll also want to ensure these rose varieties are suitable for your area.  This is particularly true of coastal climates. 

Growing Conditions:  Are your roses planted in the right spot?  Adequate sunlight is critical.  Most roses need at least six hours of direct sunlight daily.  Air circulation also contributes to plant health.   Allow plenty of space between your roses for growing room.  Also consider planting other flowers and herbs near your roses.  Plant diversity attracts beneficial insects and reduces the risk of pests and diseases.

Proper soil drainage is important, because it helps prevent root rot and other diseases.   If you have heavy clay soil that drains slowly, you might want to move your roses to a raised bed. 

Irrigation:  Watering roses is a fine art.   Too little water can lead to defoliation and sun burnt rose canes, as well as spider mite problems.  Overwatering or poorly drained soils can lead to root diseases and nutritional deficiencies in the plant. 

To determine how much water your roses need, consider the weather and soil type.   Roses need less water in areas with summer fog than in areas with arid summer heat. Sandy soils require more water than clay soils, which tend to retain moisture.  For best results, check the soil moisture regularly.  

Soaker hoses or drip irrigation systems deliver water to the soil and avoid wetting foliage, which can lead to fungal diseases.  If you water overhead with a sprinkler, water in the morning so foliage dries throughout the day.

Mulch:  Mulching roses helps conserve water and improve soil structure.  Mulch also helps control weeds and protects roots in hot summer months.  Apply 2-3 inches of organic materials, like shredded leaves, compost or fine wood chips.  Keep mulch several inches from the plant trunk. 

Fertilize:  Roses grow best in slightly acidic soil (pH 6.2-6.8).  Many California soils have a pH above 7.0.  These soils are still suitable; however, the risk of micronutrient deficiencies grows as pH increases, particularly above 7.5.   Add more acidity to your soil with natural fertilizers such as alfalfa meal, cottonseed meal, blood meal and bat guano. 

You want to encourage healthy plants, but avoid over-fertilizing roses with high nitrogen fertilizers.  These can over-stimulate plant growth and encourage aphids and diseases.  Organic or natural fertilizers help avoid the problem of over-fertilizing, because they release nutrients to your roses slowly. 

 Regular feedings of compost and other organic materials improve your garden’s overall health.  Compost improves water retention and provides beneficial microorganisms to the soil.  Sandy soils with little organic matter may need to be fertilized monthly during growing season.  Clay soils with lots of organic matter may need to be fertilized only once a year. 

More Help:  Want more rose gardening tips?  Free gardening advice is available by calling the Master Gardener Helpline at 805/645-1455.  The helpline is staffed Tuesdays and Thursdays, 1-4 p.m.

If you would like more information: Master Gardener Helpline,email at mgventura@ucdavis,edu or call us (805) 645-1455.