Roses. More on Growing Roses.pdf

Roses

Growing Roses

Lynn Ellen Doxon, Extension Horticultural Specialist

New Mexioc State University

Roses are one of the most popular garden plants. They

may be used as flowering shrubs in the landscape, but

they are at their best in properly spaced solid plantings.

Anyone can grow roses. Some gardeners try to grow

too many varieties or too many plants for the space

available. Ten well-chosen varieties, carefully main-

tained, produce more blooms and give far more plea-

sure than 50 poorly maintained plants.

tected from the hot sun in the late afternoon may give

better results.

Danger of Frost

In most areas of New Mexico, roses are not severely

injured by cold winter temperatures, although in the high

mountains they need some protection. Unseasonable

spring frosts or sudden drops of temperature in the fall

may damage tender growth in any area. Banking the

plants with soil in the late fall prevents injury in areas of

sub-zero temperatures (figure 1).

Types of Roses

There are many types of garden roses. Most popular

are tea roses, hybrid teas, hybrid perpetuals, floribun-

das, polyanthas, miniatures, and climbers. Of these,

the hybrid teas and floribundas are grown most often.

The choice is almost endless. The American Rose So-

ciety, P.O. Box 30,000, Shreveport, LA 71130, publishes

the national rating of all named varieties best suited to

your need, location, and preference.

Selecting the Location

Roses do best in sunny locations where they are shel-

tered from strong winds. Do not plant them under trees.

They grow best in well-drained, fertile loam soils. Soils

containing excessive amounts of alkali salts or other

harmful chemicals are not recommended for roses. You

can provide drainage in heavy soils or spots with an

impervious layer underneath by installing drain tiles or

by digging trenches and filling them with rock or course

gravel. If the water table is high where you want to grow

roses, raise the rose bed 12 inches or more above the

existing grade. Drainage can also be improved by in-

corporating 1/2- to 1/4-inch aggregate rock or charcoal

in heavy soils.

Fig. 1. Protect rose bushes against winter injury by cov-

ering the crown and lower canes with soil, after the first

hard freeze in the fall. Remove the mound of soil in the

spring when danger of a hard freeze has passed.

Condition of Nursery Plants

It is usually most economical to choose high quality

plants. Lower grades may be cheaper, but plants are

usually weaker and require greater care in transplant-

ing and maintenance. Plant loss is often higher with

lower grade plants. Most nursery professionals try to

keep roses in good condition after they are delivered.

Many bushes are coated with wax to prevent exces-

sive drying, but the wax can become a problem under

high temperatures. Rose bushes are usually shipped

dormant, with bare roots wrapped in moist packing

media to prevent drying. If the tissues are plump with

no shriveled bark the bushes are in good condition.

Avoid buying plants on which the tissues have dried

out and the bark is shriveled.

Need for Sun

Plant roses where they will receive six hours or more

of sun during the day. They may grow in shade but are

more susceptible to attacks by mildew and thrips than

when grown in full sun. Growers in southern New

Mexico find that flowers open and fade faster then those

grown in cool climates. Many varieties cease to bloom

when summer temperatures are above 90° F (35° C).

In areas with prolonged hot weather, a location pro-

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New Mexico Master Gardener Manual

Sometimes, conditions beyond the nursery’s control

cause rose roots to dry out. When this happens, the

plant may be slow to start growing or it may not grow at

all unless moisture is restored to the dry bush. Soak

the roots in water, or better still, cover the entire plant

with moist soil for several days, even for a week or longer

until the tissues have taken up the normal amount of

moisture. Only occasionally will a bush be so badly dried

on arrival that it cannot recover by either of these treat-

ments. Bushes with bare roots must be planted before

new growth appears. Plants that start to grow before

they are planted often die. Always select dormant plants

for bare-root planting.

Planting Time

February or March is normally the best time to plant

bare root roses in New Mexico. They may be planted

later, if you can find healthy, dormant bushes. Bushes

planted in the fall and early winter usually die back more

than those planted in the late winter. Plants growing in

containers may be planted throughout the growing sea-

son, although special attention is usually necessary to

keep these growing through the first summer.

Planting the Bush

Fig 2. Planting a rose — Survival and subsequent growth are highly

dependent upon the planting process. Numbered illustrations coordi-

nate with numbered paragraphs under Planting the Bush.

1. Dig the planting hole somewhat larger than the root

system. Mix a quart or so of peat, compost, or other

organic matter with the soil removed from the hole. DO

NOT add fertilizer to the planting mix; doing so delays

growth and can injure the developing roots. Make a cone

of the soil mixture in the planting hole.

2. Remove any broken or injured roots or canes, or

canes less than a pencil thickness in diameter. Spread

the roots over the cone of soil in a natural manner and

position the plant so the bud union (the swelling at the

stem’s base) is even with the surface of the soil. (In

colder parts of the state it should be one to two inches

below the surface.)

3. Work soil mixture around the roots to eliminate any

air pockets. Firm the soil around the roots and add more

soil until the hole is three-quarters full.

union remains at the proper level. Fill the remainder of

the hole with soil and tamp lightly.

5. Trim the plant to two to five strong canes, 8 to 12

inches long. Remove all weak and twiggy growth. Mound

soil 6 inches deep around and over the plant. This pro-

tects canes from drying out. When the buds sprout,

gradually remove the soil mound, probably within two

4. Fill the hole with water and allow it to soak in, then

refill it. After the water drains, check to see if the bud

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Roses

weeks or so. Check buds every two to three days.

Loosen the name tag so it does not constrict the cane.

When vigorous growth starts, fertilize the plants.

Transplanting

Occasionally, a growing rose bush must be moved or a

balled or container rose may need to be set out after

the buds have started growth. In this case, make cer-

tain that the soil around the roots, or in the container or

ball, is moderately damp so that it will not crumble and

expose the roots. Remove the container or burlap and

twine from the root ball and plant it so the graft union is

1 or 2 inches below the surface of the soil. Cut back

and thin out the top to compensate for loss of roots.

After planting the bush, protect it from sunburn for a

few days with burlap or other covering (figure 3).

is established the most active roots will be under the

tips of the branches. Irrigate around the perimeter of

the plant rather than at the base of the stem.

Depth of Irrigation:

Fig. 3. Diagram shows proper planting depth, to locate

the crown of the plant above the soil and mulch without

exposing the roots.

When irrigating, wet the soil to the full extent of the root

zone, approximately two feet deep. Do not add water

again until the surface of the soil becomes dry. Irriga-

tion should take place when the soil moisture is at the

point where the leaves begin to wilt. An inch of water in

sandy soils should wet the soil a depth of about 12

inches; in loams, 6 to 10 inches; in clay soils, 4 to 5

inches. To thoroughly wet an area 10 X10, 2 feet deep,

will require about 125 gallons of water for sandy soils,

190 gallons for loam soils, about 330 gallons for clay

soils.

Replacing the Declining Plant

Frequency of Irrigation:

A good rose bush, properly maintained, should pro-

duce satisfactory flowers for 15 years or more. In time,

however, bushes normally decline. When this happens,

it is better to replace them than to try to rejuvenate old

plants. Better varieties are constantly being introduced.

Do not replace a bush until you know the cause of its

decline. If the cause is crown gall, oak root fungus, ex-

cessive alkali, poor drainage, or root rot, you may need

to treat the soil by sterilization, leaching or installing

drainage before replanting. After such treatment, fol-

low the same cultural practices used in the original plant-

ing.

Sandy soils do not retain moisture very long and must

be irrigated every 4 to 10 days during the growing sea-

son. Loam soils retain more moisture than sandy soils,

and may need irrigating every 8 to 15 days. Clay soils

have high water-holding capacities and may need to

be irrigated only every 15 to 30 days. Weather also

affects the need for irrigation. During high temperatures

or high wind, it may be necessary to water weekly or

even twice a week in sandy soils. Learn to recognize

moisture stress by the color of the foliage. Leaves are

pale and limp when stressed for moisture. Check foli-

age in the mornings. Afternoon heat may produce similar

symptoms. Tillage may make a rose garden attractive,

but it usually causes loss of soil moisture. Till only to

control weeds. Mulch around rose bushes, conserves

moisture and controls weeds. Peat moss, compost,

straw, shredded bark, pecan shells, barnyard manure,

and lawn clippings are examples of materials used as

mulch. These also add organic matter to the soil as

they decompose.

Irrigating

For good growth, roses need a moderate amount of

soil moisture throughout their root zone. Watering too

often or too lightly encourages the development of a

shallow root system. Leave a basin around the plant

for irrigation until it becomes established. Once the plant

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New Mexico Master Gardener Manual

Some Common Soil Problems

Fertilizing

In general, New Mexico soils tend to lack nitrogen and

some may be slightly deficient in phosphorus. Most soils

in ‘New Mexico contain relatively large amounts of pot-

ash. These soils also often contain alkali salts and ex-

cessive amounts of lime-stone that interfere with the

availability of iron. This causes a condition known as

lime-induced chlorosis. Chlorotic (yellow) leaves on

plants growing in soils known to have a high lime con-

tent usually indicate this problem. If too much lime is

the cause, other plants nearby will also probably have

yellow leaves.

Do not guess at the cause of chlorotic leaves. Certain

viruses that attack roses also affect the green color of

the leaves. With viruses, the leaves are usually yellow

only in spots. Each mineral deficiency produces identi-

fiable symptoms.

Nitrogen deficiency causes pale green-yellow leaves,

short, weak stems, and small flowers of faded color.

Roses are heavy feeders on nitrogen. Recurrent bloom-

ing in the bush rose depends upon cycles of vegetative

growth. Blooms are borne on new growth, without which

only a few, weak-stemmed buds will develop. Nitrogen

is the main nutrient responsible for this required cyclic

growth. Vigorous shoots are developed, followed by

flower bud formation, repeatedly throughout the sea-

son. Abundant nitrogen is required to produce this veg-

etative growth. Because of this repeated growth pat-

tern, rose bushes need feeding every four to six weeks,

beginning just before bud break in early spring. Con-

tinue to apply nitrogen at four-week intervals until three

weeks before the average date of the first fall frost.

Ammonium sulfate or its equivalent applied at the rate

of 2 tablespoon full per plant should be sufficient for

most soils. These rates may be a bit high for fertile clay

soils, and somewhat low for sandy soils. Increase or

decrease application rates according to amount of ter-

minal growth the plant is making.

Excess of Alkali

Browning of the tips and margins of older leaves are

symptoms of salt burn. The browning may progress to

include the entire leaf. The occurrence of salt burn is

usually more prevalent in clay soils than in sandy soils.

When alkali salts are present in a soil in excessive

amounts, the first step is to leach out the soluble so-

dium and chlorine by heavy irrigation. The addition of

sulfur (at the rate of 1 pound per 40 square feet) helps

make these alkali salts more soluble. Good drainage is

required in removing alkali from soils.

Other mineral elements may occasionally cause prob-

lems when present in excessive amounts. For example,

excessive amounts of chlorine or total salts in the irri-

gation water may cause trouble.

Phosphorous deficiency may cause the older leaves to

drop without turning yellow; the stems may be weak-

ened; and bud development may be slowed as a result

of a small, weak root system. Phosphorous is essential,

especially for developing flower buds. The pre-bud-

break, early spring application of fertilizer should con-

tain both nitrogen and phosphorous in more or less

equal amounts. One-fifth to one-fourth cupful of 10-10-

0, 10-20-0, or 16-20-0 fertilizer or equivalent, worked

evenly into the soil underneath the canopy of a newly

pruned rosebush in early spring, provides ample nutri-

ents to get the plant off to a good start. Apply an equal

amount when new growth reaches 4 to 6 inches and

again when the first blossoms have faded. Additional

phosphorous should not be needed for the rest of the

season.

Use of Barnyard Manure

In general, New Mexico soils are extremely low in or-

ganic matter. To condition the soil into a mellow, friable

soil, organic matter is needed. Tight clay soils become

loose and crumbly with the addition of organic matter,

while loose sands acquire water-holding capacity.

Sources of organic matter include peat, compost, leaf

mold, decomposed sawdust, and barnyard manure,

probably the most widely used. Manure is usually avail-

able and less expensive than other forms of organic

matter, and it is usually higher in nutrient elements.

Never apply barnyard manure around rose roots at the

time of planting unless it has been corm-posted for at

least 12 months. Spreading 1 to 3 inches of partially

decomposed barnyard manure over a rose bed each

year is a good practice. Many growers use peat in plant-

ing, followed by topdressings of barnyard manure. A

warning, however, manure frequently contains weed

seeds, and feedlot manure often contains excess so-

dium.

Potash is seldom needed in New Mexico. Soil tests have

shown that most soils contain adequate amounts. Oc-

casionally, very light sands are low in potash. Even when

needed, an application of 1 tablespoonful of muriate of

potash, or its equivalent, per plant would be sufficient

for two years or longer.

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Roses

Iron deficiency first shows as a light yellowing in the

tips of the young leaves. In time, the area between the

veins becomes very yellow, while the larger veins re-

main dark green. Iron deficiency can be controlled by

applying iron chelates to the soil. Iron compounds can

also be applied as a foliar spray; this method is more

satisfactory than soil applications. Two or three spray

applications, applied early in the season, may be

needed. In some cases, compounds containing zinc

may also be needed to correct a chlorosis problem.

Therefore, it may be advisable to select a product con-

taining both iron and zinc. Take care to avoid spray drift

because iron compounds stain walls and driveways.

root; 6) leave 3 to 5 one-year-old canes, cutting each

one back to 18 to 24 inches.

There is always a question about how much to cut back

a rose bush. The time and amount to prune depends

on the type of rose, its use, variety, location, and vigor.

In the hotter parts of the state, bushes should be al-

lowed to grow larger than in the cooler parts. Higher

pruning will produce more flowers early, while lower

pruning produces fewer but bigger flowers later. When

pruning, first remove any dead, broken, damaged, or

blotched canes back to where the pith, or center of the

cane, is white and healthy looking. Next, remove weak,

spindly canes, canes growing toward the center of the

bush, the weaker of two canes that cross, and suckers.

Then, prune the remaining canes according to the di-

rections for that type of rose.

Magnesium deficiency causes a loss of green color simi-

lar to iron deficiency, but even the smallest veins re-

main green. Damage is most pronounced at the top of

the plant. Magnesium deficiency can be treated with a

chelated micronutrient fertilizer.

Hybrid tea roses should be pruned in late winter.

Bushes pruned in late fall or early winter may be in-

jured by cold and require further pruning in late winter,

resulting in more severe pruning than desired. Early

pruning also tends to induce early cane growth that is

subject to spring freezes. With varieties that tend to

grow very upright (Talisman, Sutter’s Gold, President

Herbert Hoover, and others) thin in the center and cut

back the remaining canes to outside buds. It usually

takes a rose gardener several years to learn to handle

each variety properly. With new varieties, prune care-

fully until you learn their growth habits. Since roses love

sunlight, they should be pruned so as to develop open

centers. Cutting canes back to buds that point outward

causes a bush to spread. Healthy canes produce blos-

soms for 4 to 6 years or even longer, but canes 1 to 2

years old usually produce the highest quality, longest

stemmed blossoms. When long, it may be difficult to

get new ones to develop near the base of the plant. In

general, properly pruned and managed hybrid tea

bushes develop several new canes from the crown each

year (figure 5). Select three to five of the one-year-old

canes that are located so as to form a bowl. It is best to

leave no lateral branches and remove all small twigs.

Cut canes back to 18 to 24 inches on moderately vig-

orous plants. Shoots on extremely vigorous plants may

be cut to 24 to 36 inches if they have space to grow

large. For exhibition roses, cut canes back to 6 to 10

inches. Plants often fail to produce new canes annually

from the crown. When this happens, it becomes nec-

essary to select laterals on older canes in lieu of new

canes from the crown. Removing soil and mulch from

around the crown to expose it to the sun usually in-

duces new cane growth. The vase, or open-center, sys-

tem of pruning induces cane development from the

Pruning

Pruning improves the quality of the blooms, regulates

the size and shape of the plant, and removes diseased

and damaged parts. The basic technique for most prun-

ing is to cut at a 45 angle 1/4 inch above the nearest

outward-facing bud with the higher point above the bud

(see figure 4).

Fig. 4. To prune hybrid tea and grandiflora roses 1) prune

high for more flowers earlier or low for fewer bigger

flowers later 2) prune out weak and crisscrossing canes;

3) remove growth an inch below a canker; 4) remove

damaged, dead or broken canes back to healthy growth,

5) remove sucker growth as close as possible to main

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