“The care and attention a rose gets underground is even more important than the care a rose is given above ground.” — Sam Jones, Master Rosarian
Everything we rosarians do in the rose garden is geared toward producing our best blooms possible. This month, we focus on what lies “down under” since our goal of multiple cycles of gorgeous blooms depends upon the health of our roses’ roots and the conditions they encounter in the soil.
The root system
Roots have two functions.
Anchor roots are long, thick roots you see when you plant a bare-root rose. These roots will the canes until the thousands of feeder roots develop. You want your planting hole to comfortably accommodate these roots, so dig a hole 18 inches deep and 24 inches wide. Cut broken roots, but don’t bend or shorten them to fit the hole. Irrigate deeply to encourage downward growth of these roots. This especially helps the plant in the summer.
Feeder roots are thin and fibrous. They absorb air, water and nutrients from the soil and provide nutrients in a liquid form to the plant so it can produce beautiful blooms and healthy foliage. These roots, which are fragile, grow best in a light, porous soil and can easily grow to a width of 2 to 3 feet. When you transplant a rose, dig a big rootball to avoid the shock that occurs when you break the feeder roots and impede water absorption to the plant.
Healthy soil is crucial
A porous, organically rich soil encourages deep growth of the anchor roots and ample food, air and water for our roses’ feeder roots. Soil contains important microorganisms such as bacteria, algae and fungi, but we need to periodically apply organic material such as compost, aged manures, humic acid and mulch into and onto our soils to ensure that the roots have the nutrients to provide our roses with everything they need to flourish.
Mixtures of organic ingredients such as blood meal, bone meal, cottonseed meal, alfalfa meal, seaweed and fishmeal can be found in formulas such as Bio-Start, Ada Perry’s Magic Formula, Mills Magic Rose Mix, Dr. Earth, BioSol or E.B. Stone. Add these to your soil this month following the instructions on the label. The microorganisms in our soil decompose these organics into a form that our plants’ roots can absorb for the plants’ use. Loose organically rich soil also attracts and encourages earthworms, which further benefit our roses by enriching the soil with their castings and opening up ageways for our plants’ roots to grow.
Covering our soil with a 3-inch layer of organic mulch protects our roses’ roots and enhances their function by keeping the soil at a moderate temperature in hot weather and also holding in water. Mulch also keeps the soil texture looser, allowing the feeder roots an expanded zone for growth and resulting in a greater intake of nutrients and water by the plant. Don’t walk on rose beds or tamp down the soil with your feet when you plant a rose; you want to avoid impairing the transfer of oxygen to the roots.
Grafted roots or own roots
Most of the roses you buy in nurseries are grafted roses composed of two varieties. The canes on the rosebush are your desired variety, whereas the roots are from a rose that grows well in our climate. The place they are ed is called the bud union. The plant takes its inherent qualities from the grafted cultivar, not the plant that was used for the roots.
Own-root rose
Unlike grafted roses, the roots of own-root roses are the same variety as their flowering tops. Miniature roses, some shrub roses, many old-garden roses and hard-to-find roses are often propagated from cuttings and are shipped in bands or sleeves. You can order own-root roses on the Internet from specialty nurseries such as Heirloom Roses, Rogue Valley Roses, High Country Roses and the Antique Rose Emporium.
Which root is better?
Grafting is the most efficient and least expensive method for growers to propagate roses. This method also produces a larger plant for the consumer to buy. The disadvantage is that grafted roses can sometimes put out growth from the rootstock below the bud union. This is called a sucker and it must be pulled out to stop its growth. Growers in colder climates often prefer own-root roses because freezing temperatures can easily damage the bud union and leave only the rootstock. Some rosarians claim own-root roses are healthier than grafted roses because they are less susceptible to viruses that may be spread by rootstock in grafted roses.
Different rootstocks
In our region, the rootstock is typically a plant called Dr. Huey because it grows well in California and propagates, stores and ships easily. Fortuniana rootstock is used in Florida as it is tolerant to nematodes, a common pest in Florida. It is a very vigorous rootstock and performs well in warmer states like California. Because its roots extend farther out than other rootstocks, the result is a bigger rose with larger blooms and the added bonus of being resistant to root nematodes. You will not find roses grafted on Fortuniana in the nursery, but you can order these roses from specialty nurseries such as K&M Nursery and Cool Roses. Multiflora rootstock is often used for colder climates and not often used in California because it does not generally grow as well in our alkaline soil.
Our roses’ roots are all-important to the need for a large and continual supply of food, air and water. If your blooms are disappointing, go back to basics and check whether all is well “down under.”
Perwich is a member of the San Diego Rose Society, a Consulting Rosarian and a Master Gardener with UC Cooperative Extension.
