When to Take Cuttings
Erect, semi-erect and trailing or vine-type blackberry bushes are hardy in U.S. Department of Agriculture plant hardiness zones 5 to 10.
- In mild-winter
southern climates, where the soil warms and blackberries begin to grow a little
earlier in the season, the softwood cuttings may need to be taken in late winter or
early spring before the stem tips harden.
- In cooler, northern climates, take softwood cuttings in mid-spring or early summer.
The stems should still be succulent but snap easily if they are bent.
Take the cuttings in the morning. Use sharp, sterilized hand pruners to take the cuttings. Sterilize the pruners by soaking them in household disinfectant for 5 minutes, rinsing them in clear water, then drying them with a paper towel.
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Planting Site Selection
Select a full sun planting site for the rooted blackberry cuttings in the fall the year before taking the cuttings. Allow for 3 to 8 feet of space between cuttings. Test the soil pH and drainage capabilities at the same time. Dig a 1-foot deep hole and test the soil pH at this depth. Soil test kits and digital meters are available at garden centers. After taking the soil sample or using a digital meter to test the pH, dig down another foot and fill the hole with water. If the water drains within 24 hours, the soil drains quickly enough for blackberry bushes. If the water drains too slowly, select another planting site.
Blackberries grow best in soil with a pH of 5.5 to 6.5 but they will be fine as long as the pH is between 4.5 and 7.5. If the soil pH is lower or higher, apply lime or sulfur to adjust it:
- Raise the pH of 100 square feet of sandy soil by 1 unit,
or from 4.0 to 5.0, by mixing 4.5 pounds of lime into the soil. The same adjustment
in loamy soil will take 7.5 pounds of lime.
- Lower the pH of sandy soil by 1
unit by mixing in 4.8 pounds of iron sulfate. Make the same adjustment in loamy
soil with 19.2 pounds of iron sulfate.
Mix a 2- to 3-inch-deep layer of organic matter like compost, well-aged cow manure, sphagnum peat moss, composted pine bark mulch or leaf mold into the top 12 inches of soil. Mix it thoroughly into the native soil. Keep in mind that sphagnum peat moss will lower the soil pH.
Rooting Container Preparation
Prepare the rooting container before taking the cuttings. Pour a rooting mixture that is half coarse sand or perlite and half sphagnum peat moss into the container. Use clean, commercially packaged rooting mix ingredients. Flats, clay pots or plastic pots can be used as rooting containers.
If clay pots are used, soak them in water for a few hours before filling them with rooting mixture. Otherwise, the dry clay will absorb much of the moisture from the rooting mix.
Water the blackberry bush one to two days before taking the cuttings. Take 4- to 6-inch-long cuttings from new stem growth that is firm but still soft and succulent. Make the cuts just below a leaf or swollen growth bud. Use sterilized pruners or sharp scissors to trim off the leaves from the lower 3 to 5 inches of the cuttings. Trim any leaves remaining at the top of the cutting back by half.
Moisten the rooting mix thoroughly. Using a pencil, poke 2-inch deep planting holes in the rooting mix, spaced about 4 inches apart. The leaves on multiple cuttings must not touch or overlap each other when they are planted. Pour some rooting hormone into a small glass or bowl. Dip the cut end of each cutting into the rooting hormone, plant it 2 inches deep in the rooting mix then firm the mix around the base of the cutting. Put the planted cuttings in a clear plastic bag and seal it shut to hold in humidity. Use wooden craft sticks or straws inserted into the growing medium at the edges of the container to keep the bag off the cuttings.
Caring for Cuttings
Set the planted cuttings in bright but indirect light in a 70- to 75-degree Fahrenheit room. Mist the cuttings with room-temperature water every day. Moisten the growing medium if it begins to dry. The cutting should form roots in six weeks.
Potting Rooted Cuttings
Tug gently on the cuttings after three to four weeks to see if they have rooted yet. There will be some resistance if there are roots. If the cuttings do not have roots, they will pull out easily. Replant them and check them again after a few weeks. When they have roots, stop misting and leave the plastic bag open. After a few days, remove the plastic bag. Pot the cuttings up in individual pots with commercial potting soil. Set them where they will be exposed to morning sunlight. Water them as often as necessary to keep the soil moist.
Hardening Potted Cuttings
Move the potted cuttings outdoors to a shady spot a few weeks after potting them, as long as there is no longer any danger of frost. If they are outdoors and frost is predicted, bring them back indoors each evening. Get them used to bright sunlight and outdoor weather gradually for the next few weeks. After they are outdoors in the shade for a week or so, begin exposing them to cool morning light for a few hours each day. Increase the time in direct sunlight every few days until they are in full sun. Water them every day, if necessary, to keep the soil moist.
Planting New Blackberry Bushes
Plant the blackberry cuttings after they adjust to the outdoor elements. Plant them at the same depth they were growing in their pots. Space semi-erect and trailing varieties 5 to 8 feet apart and erect varieties 3 to 4 feet apart. Dig the hole a few inches wider than the pot. Leave the potting soil intact around the roots when setting the cutting in the hole. Fill in around the roots and potting soil with garden soil. Mix the garden soil in with any loose potting soil that falls away from the rootball while planting to form a more gradual soil transition. Water cuttings generously right after planting. Trim the top of the cutting down by 6 inches with sterilized pruners. Spread a 2- to 3-inch depth of organic mulch over the soil around the blackberry cuttings but keep it a few inches away from the stems to help prevent disease encouraged by wet mulch.
Caring for New Blackberry Bushes
Water the new blackberry bushes as often as necessary to keep the soil lightly moist for the remainder of the growing season. Water them from below the foliage with a soaker hose or watering can to help prevent foliar diseases. Do not give them fertilizer until they begin putting on new leaves the following spring. After they begin growing in the spring, sprinkle ¼ pound of 10-10-10 fertilizer on the soil in a 1 ½-foot wide ring around each blackberry bush.