Blackberry Plant Growth
In blackberry plants, the root is perennial and the cane is biennial. A plant that is planted in the late winter-early spring of 2005 will bear a crop of berries in the spring-summer of 2006.
It will grow a "bush" that will average 30" wide and tall. We plant our propagation stock in rows five feet apart and many of the side branches overlap with the adjacent row.
In the fall, the plants produce the fruit buds that will develop into fruit clusters when the plants come out of dormancy the following spring. Each fruit bud will grow a short branch that will have 4-8 berries.
When the plant comes out of dormancy and starts to leaf out and develop flower buds, the roots also start to send up new canes. The existing bush or canes that are preparing to put on berries are called FLORICANES. The new canes that are coming up from the roots are called PRIMOCANES.
In the first year the blackberry plant branches out very close to the ground. Some branches may come out right at ground level. In all years after the first year the primocanes grow straight up without branching. By the time that the berries get ripe some of the primocanes will be six feet tall. By the time the harvest is over many of the primocanes will be 8'-10' long and starting to curve over at the top.
The primo canes need to be cut off at about 42". We let them get up to eight feet or so before we cut them back. As soon as you cut the canes off, the lateral branches start to grow. In the past, we have cut the primocanes off when they were only four or five feet tall. They reach that height during the middle of the picking season. The lateral branches grew out so fast that we had this new growth interfering with picking the berries. By waiting to cut the canes off, the harvest is over before the new growth can interfere with the picking.
After the floricanes have finished bearing fruit, they die. As the floricanes are dying back the primocanes are growing out. The hedge of berry plants is always there but it is all new canes every year. After harvest, the recommended cultural practice is to cut off the old dead and dying canes and haul them out of the berry patch. They should be burned to help minimize disease and insect infestations that might winter over in the old canes.
Topping The Canes When the plants are in full fruit production, the roots will be sending up new canes that will bear the harvest next year. Where as these first year plants are from 30"-42" tall depending on the variety, these new canes grow to the light and get up above the plants that are bearing the fruit. During the picking season we have to go through and cut these new canes off at 36"-42" tall. Picking time is a busy time and it's not unusual for these new canes to get up 7'-8' tall before we get them trimmed back. If they are topped too early, the lateral branches start growing and will get in the way of picking.
Deadwooding When the fruiting season is over, the canes that bore the fruit this year will all die. By that time, there is a pretty full hedge of new canes so your row is all renewed. Then it's time for the pruning phase that we call "deadwooding." We take pruners and cut the old wood that just finished bearing fruit off at the ground, pull it out of the row, and haul it to the burn pile. Burning this deadwood is recommended for disease control.
Fruit Production In the dormant season, January and February, we prune back the laterals that grew out during the summer. How many buds do we cut off? It really depends on the vigor of the plant. All the limbs will have buds on them. Every bud has the potential to produce a cluster of 6-8 berries. If the limb is slender there should be about 6 buds left on. If the limb is strong, there can be up to 12 buds left on. There is a temptation to not cut off enough buds but the better pruned the plants are, the higher quality fruit they will produce.
New Plants The first cutting on new plants will be the fruit production phase. Check the limbs to see if they will be able to support the buds that are present. If not, trim as suggested above. In the first dormant season you will want to cut off all the bottom limbs that are close to the ground. It is worthless to have the fruit trying to grow where it gets on the ground and is difficult to pick. It is better to encourage higher growth.
Blackberry Planting Information
Planting Bare Root Blackberry Plants Plant into a grass and weed free strip that is minimum of 24" wide. If you use a tiller, two passes will make a good width for a plant bed. Make a furrow along the center of this strip. We use the furrow attachment on our rear tine tiller. On a smaller scale, the planting furrow can be made with a hoe. Any composted organic matter that can be incorporated into this planting strip will be a plus factor for the new plants.
Plant the plants in the furrow 3"-4" deep and 24" apart in the row. Space rows 10'-12' apart. Pack dirt around the bare roots. Then water each plant to insure good soil contact. Ideally the row is then mulched. If no mulch is available the 24" strip along the plants will need to be hoed to minimize competition. Mulching is much easier and the plants love it. The soil can not be allowed to dry out until the plants have developed a root system.
Blackberries need adequate water. We have drip tape on all our berry rows.