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Thornless blackberry varieties
Planting sites ___---------_
Preparing the soil _______
Spacing the plants ____
Setting the plants _____---
Fertilizing and watering
Cultivation _____ ___
H arvesting ---- 5
Preventing winter injury 6
Diseases and insects 6
Descriptions of thornless blackberries ________--------- 7
Department publications contain public informa-
tion. They are not copyrighted and may be re-
produced in whole or in part with or without credit.
Revised February 1975
ngton, D.C. Slightly revised October 1977
For sale by the Superintendent of Documents, U.S. Government Printing (il,,:,i
Washington, D.C. 20402
FOR THE HOME GARDEN
By J. W. Hull (deceased ) and F. J. Lawrence, ARS research horticulturist
For years home gardeners hesi-
tated to grow blackberries in their
backyard because of the annoy-
ance of the thorns. Then two
thornless blackberry varieties-
Smoothstem and Thornfrcr--
were developed by the U.S. De-
pa rtment of Agriculture. Two
newer varieties, Dirksen Thorn-
less and Black Satin, have also
been introduced by the Depart-
ment. Popular with home gar-
deners and proprietors of "you-
pick" enterprises, these produc-
tive blackberries are easy to han-
(lie and require little summer
pruning. The fruits are firm and
THORNLESS BLACKBEIIRR VARIETIES
Smoothstem, Thornfree, Dirk-
sen Thornless, and Black Satin
are genetically thornless black-
berries-all the cells have the
thornless character. When new
canes develop they retain this
Other thornless blackberries,
such as Thornless Young, Thorn-
less Logan, and Thornless Ever-
green, have a thornless character
only in the outer cell layer of their
canes. New canes originating be-
low the crown have thorns.
Thornless blackberries have
trailing or semitrailing canes that
are not self-supporting. They can
be grown along the ground in
their first season, but, thereafter,
must be trained on trellises.
Blackberries are planted in
early spring in the North; in late
winter or early spring in the
Blackberries vary in their abil-
ity to withstand cold, but none
should be grown where temper-
atures drop to 0' F. and below.
Planting sites for blackberries
must offer plenty of soil moisture.
This condition is especially neces-
sary while the fruit is growing
1 Horticultural Crops Research, Corvallis,
Almost any soil type, except
very sandy soil, is suitable for
blackberries if the drainage is
good-both on the surface and in
the soil. Plants can be harmed at
any season of the year if water
stands around their roots.
Preparing the soil
Prepare the soil as you would
for a vegetable or flower garden.
If you are establishing a new
planting, seed and plow under one
or two green-manure crops of
cowpeas or of rye and vetch. This
will condition the soil, and the
added organic matter and nitro-
gen will help produce an early
Spacing the plants
Leave plenty of space between
rows when planting blackberries,
or severe competition for soil nu-
trients and moisture will result.
Smoothstem and Thornfree are
vigorous varieties and should be
set 6 to 8 feet apart in rows that
are at least 8 feet apart.
Less vigorous varieties, such as
Thornless Young and Thornless
Logan, should be set 4 to 6 feet
apart in rows that are at least 8
Aline plants carefully in the
row to accommodate the trellis,
which will be constructed. (See
Setting the plants
Do not let planting stock dry
out. This condition can be pre-
vented by heeling in the roots.
To heel in, dig a trench in a
shaded area deep enough to hold
the roots. Open the bundles and
spread the plants along the trench
with the roots down. Cover the
roots with moist soil and firm the
soil down to eliminate air pockets.
If the plants are dry upon arri-
val, soak the roots in water for
several hours before planting or
If you do not plant immediately,
wrap the plants in polyethylene
bags and place them in a refriger-
ator until planting time.
Before setting the plants, cut
the tops (the old cane or "han-
dle") back to about 6 inches. This
is useful for handling the plants
and serves to mark their location.
After you make a planting hole,
set the root of the plant so that it
is about the same depth as it was
in the nursery, or slightly deeper.
Then firm the soil carefully to as-
sure good contact with the roots.
During the first summer after
setting the blackberries, vege-
tables such as beans, peas, or cab-
bage can be grown in the spaces
between rows. Their cultivation
will benefit the blackkberry plants
and put the unused portion of
your garden to good use.
Intercropping should not be
done after the first year of plant-
ing; when the blackberry plants
are of bearing size they will need
all available moisture and nutri-
After the first season, thornless
blalkberries should be trained on
trellises. This will assure clean
fruit, ease of picking, and help in
Many trellis arrangements and
training methods are satisfactory.
To construct a simple and effec-
Stretch two wires (gage size
12 or 14) between heavy end posts
set 15 to 25 feet apart in the row.
String one wire 21/: feet from the
-~- -. -S---
ground and the other about 5 feet
from the ground.
Staple the wires loosely to all
posts between the end posts.
(Wires must be loose enough to
allow for contraction in cold
Tie trailing canes horizontally
along the wires or fan them out
from the ground and tie them
where they cross each wire. Avoid
tying the canes in large bundles.
Thornless blackberries should be trained on a two-wire trellis. Set end posts 15 to
25 feet apart in the row. String one wire 2V2 feet from the ground and the other
about 5 feet from the ground.
During the first year, black-
berry canes grow vegetatively and
send out side branches. In the sec-
ond year, these canes bear fruit,
and then the canes die. (The canes
arising from the crown are bi-
ennial; they live for only 2 years.
The roots and crowns are peren-
Methods of training black-
berries largely depend on the
length of the growing season and
the degree of winter cold.
In northern areas, leave trail-
ing varieties of thornless black-
berry canes on the ground, under
the trellis, until their second sea-
son. Then, before the buds swell,
bring the canes up to the trellis
wires, wrap them in groups of
three or four, and tie.
Tie semitrailing blackberry va-
rieties to the wires in their first
In the South, tie new canes of
both trailing and semitrailing va-
rieties to the trellis as soon as
harvest is over. The old canes
should be cut out immediately.
After harvest, prune away old
canes and destroy them as a sani-
tation measure. In certain areas
of the South anthracnose and
rosette, both serious diseases of
blackberries, threaten crops. In
these areas, all the canes should
be cut out after harvest.
Before tying canes to the
trellis wire, remove any that are
weak, spindly, or broken.
Thin out to leave 12 to 16 new
canes. Tie these to wires, or de-
pending on the management plan
being used, leave them under the
trellis for the rest of the season.
Thornfree and Smoothstem va-
rieties require little summer prun-
ing; they do not tend to branch
freely and usually will not develop
more than three or four canes.
Before growth starts in spring,
prune all side branches back to 12
inches. Side branches that are
pruned will produce larger fruit
than those that are not pruned.
FERTILIZING AND WATERING
Mixed fertilizers are satisfac-
tory for blackberries. For best re-
sults, apply fertilizer in early
spring when growth starts and
again in summer just after har-
vest. Use a 10-10-10 commercial
fertilizer mix or a 10-6-4 mix at
the rate of 5 pounds per 100-foot
For late-ripening varieties, such
as Smoothstem and Thornfree, ap-
ply the fertilizer mix no later than
July. This is to avoid forcing a
late season growth that will be
subject to winter injury.
For the first year or two, before
the root systems of the plants de-
velop fully, spread 3 or 4 ounces of
the fertilizer mix in a 12-inch
radius around the base of each
Blackberry plants require
plenty of moisture while the
berries are growing and ripening.
The amount of water needed is
roughly equivalent to 1 inch of
rainfall per week. Irrigate suffi-
ciently to meet this requirement.
Mulching reduces the frequency
of watering. Good mulch mate-
rials include: seed-free straw or
prairie hay, pine needles, corn-
cob, wood chips, or cotton hulls.
Lawn clippings are not -ati-fac-
Blackberry plants need thor-
ough and frequent cultivation;
weeds and grasses compete for
moisture and are difficult to con-
Cultvate thornless blackberries
during the summer, and as often
as necessary to keep the weeds
down. To avoid harming shallow
roots of the plants, cultivate only
2 or 3 inches deep near the rows.
Unnecessary pruning of roots
stunts plant growth.
Discontinue cultivation at least
a month before freezing weather
Winter cover crops planted be-
tween the rows help to maintain
the structure of the soil, and re-
duce erosion. If a legume cover
crop is planted, valuable nitrogen
will be added to the soil.
Sow cover crops during the fall.
The following cover crops are
adapted to thornless blackberries:
field rye, vetch (a legume) and
rye, and spring oats.
Drill or broadcast the seed by
hand between rows. Plant at least
18 inches away from either side of
the row to allow air circulation
for the blackberry canes on the
Herbicides can be useful, espe-
cially in large plantings. Control
recommendations depend on soil
types, and weed species in various
areas. Contact your county agri-
cultural agent or State Agricul-
tural Experiment Station for local
Blackberries that are picked at
the proper time, handled carefully,
and stored in a cool place will stay
in good condition for several days.
Overripe or injured berries spoil
Harvest thornless blackberries
at least twice a week, but do not
pick thornless blackberries as
soon as they turn black. It is bet-
ter to wait 3 or 4 days and pick
when the color has a dull appear-
ance. This will assure a better
flavor, color, and wholeness, es-
pecially if you are canning the
Remember the following when
harvesting the berries-
Pick berries in the morning
while the temperature is still cool.
Blackberries picked in the morn-
ing do not spoil as easily as those
picked in the afternoon.
Pick carefully and do not
crush or bruise the fruit when
placing them in berry baskets.
Pick when the berries are
fully ripened but still firm.
PREVENTING WINTER INJURY
Winter protection is needed for
blackberries in areas where winter
temperatures are expected to go
below 10 F. Cold-hardy varieties,
however, need no special protec-
tion in the winter.
In areas with low winter tem-
peratures and cold, drying winds,
cover the canes with a layer of
soil, straw, or coarse manure.
This should be done after the
canes have become dormant, and
before the onset of severe cold
weather. Remove this protective
layer before growth starts in
Where winters are mild and
moist, such as in western Oregon,
canes of trailing varieties left
lying on the ground will be
damaged. It is best, in areas with
similar conditions, to tie the canes
to the trellis in early fall and al-
low them to stay up through the
winter. However, in areas with
severe drying winds, canes tied to
trellises are subject to winter in-
DISEASES AND INSECTS
Diseases and insects vary in
kind and severity from area to
area. For information suited to
your local conditions contact your
county agricultural agent or State
Agricultural Experiment Station.
To keep disease and insect dam-
age to a minimum-
Choose disease-resistant va-
rieties adapted to your area.
Burn diseased plants or canes.
Remove old canes soon after
Remove all wild blackberry
plants in the vicinity of your
Prune out and burn canes that
have been infested with insects.
Keep the garden free of weeds
and fallen leaves.
DESCRIPTIONS OF THORNLESS BLACKBERRIES
The thornless blackberry varie-
ties that follow are listed in their
approximate order of ripening.
Specific ripening dates will vary
with location and season. All the
varieties are partly susceptible to
The variety descriptions in-
clude: the degree of hard iness
(four degrees are given: Hardy,
moderately hardy, less hardy, and
tender) ; the duration of harvest;
the characteristics of the plant;
and the area of special adaptation.
For local variety recommenda-
tions consult your county agricul-
tural agent or your State Agricul-
tural Experiment Station.
Thornless Logan.-Less hardy;
harvest period is 10 to 15 days;
berry large, long, reddish, acid,
high flavor; plant is vigorous,
very productive. Grown on Pa-
cific coast. Not adapted to East.
hardy; harvest period is 10 to 15
days; genetically thornless, berry
is large, round, black, good flavor;
plant is vigorous but only moder-
ately productive. Widely grown in
hardy; harvest periods is 10 to 15
days; berry large, soft, wine col-
ored, very sweet; plant is vigor-
ous and fairly productive. Adapt-
ed in the South and Pacific States.
Cory Thornless.-Less hardy;
harvest period is 10 to 15 days;
berry large, black, sweet, soft;
plant is vigorous and fairly pro-
ductive. Grown on Pacific coast.
hardy; harvest period is 10 to 15
days; berry large, soft, wine col-
lored, very sweet; plant is vigor-
ous and fairly productive. Adapt-
ed in the South and on Pacific
Black Satin.-Hardier than
Thornfree and 12 to 14 days ear-
lier. Harvest period lasts 3 to 4
weeks; slightly more vigorous and
productive than Dirksen Thorn-
less (see below) but otherwise
very similar in fruit and plant
habits and in area of adaptation.
than Thornfree and about 3 weeks
earlier. Harvest period lasts 3
weeks; genetically thornless,
berry medium-large, firm, black,
slightly dull at full maturity, good
flavor, very little astringency;
plant is vigorous, healthy, and
very productive. Winter hardy
south of a line from Kansas City
to Urbana, Illinois, to central
Ohio to New Jersey and in the
Thornfree.-Hardy, harvest pe-
riod lasts for about 1 month;
genetically thornless, berry me-
dium, firm, black, good flavor;
plant is notably healthy and very
productive. Grown in central New
Jersey, southern Pennsylvania,
southern Ohio southward to North
Carolina and west to Arkansas,
and in the Pacific Northwest.
Smoothstem.-M o d e r a t e 1 y
hardy; harvest period lasts for
about 1 month; genetically thorn-
less, berry medium-large, black,
good flavor; plant is extremely
healthy and vigorous, very pro-
ductive. Adapted from southern
Maryland to North Carolina along
harvest period lasts for about 1
month; berry is large, exception-
ally firm, sweet, black; plant is
vigorous, productive, and healthy.
Best adapted to Pacific North-
U.S. GOVERNMENT PRINTING OFFICE : 1977 0-244-113
UNIVERSITY OF FLORIDA
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