Encouraging Growth of Theresa Bugnat variety
A friend has a Rogosa Rose of the Theresa Bugnat variety. They've had it for 5 years. It blooms but, doesn't appear to be growing or bushing out. What's the best maintenance practice to encourage growth?
Rugosa roses are a good choice for southeast Alaska. Water drainage is important for Rugosa roses. They grow well in sandy soils. But Rugosa rose will not do well even in a sandy soil if the water drainage is not consistently good. They respond positively to additions of organic matter. Most modern roses are warm climate varieties which lack winter hardiness, and hardening off the plant is critical, even in milder climates. Unlike modern roses Rugosa roses are hardy. They need to harden off for the winter but the plants have a natural tendency to slow growth and harden off at the end of the season. Rugosa roses are known to produce large rose hips. The hips essentially are a crop that drains the soil nutrient resources that should be replaced by fertilizing. Consider removing the rose hips after the plant flowers or thinning the flowers to reduce the soil nutrient demand of the plant. All that said consider these possible issues: the Rugosa rose plant came from the nursery root bound and the roots are entwined and not moving outside the root mass; the soil is nearly completely sand / sandy gravel with little if any organic matter; the soil lacks essential plant nutrients; the location is subject to frost heaving which is limiting root development. If the roots are entwined root pruning may be necessary. Rose plants do not respond well to root disturbance, so any root pruning should be undertaken as a last resort. If the soil is sandy with low organic matter, peat moss as a soil amendment is recommended. The organic matter should be 6% or higher. It is difficult to incorporate organic matter once the rose is in the ground. Addition of organic mulch over time will increase the soil organic matter. Mulching is an ongoing process. At the end of the growing season add winter organic mulch four to six inches deep if the ground is subject to frost heaving or snow cover is not present throughout the winter. When the threat of spring frost is past gently pull the organic mulch away from around the rose so that the soil warms. Then add fertilizer when soil warms above 50oF. There are a number of commercial rose fertilizers on the market which may not take into account the higher plant nutrient demands of Rugosa roses, nor their ability to harden off at the end of the season. Follow the recommendations from the fertilizer manufacturer but apply the higher of the recommended fertilizer rate. Some references recommend a slow release fertilizer. If the soil is sandy, or the location is susceptible to frost heaving, a slow release fertilizer would be a good choice. (Do not fertilize after mid-July.) After fertilizing gently move the winter mulch back around the rose and add several inches of new organic mulch (like compost or composted steer manure). Many plants which grow rapidly in other regions may take years before growing in southeast Alaska.