How to Grow Blackberries in California

Build a series of raised growing beds to plant your blackberry plants in. Each bed should be 4 feet wide and 8 to 10 inches high, with 8 to 10 feet of space between each row.

Plant your blackberry seedlings during December or January. Dig a series of holes 2 to 4 feet apart along the raised bed, each just big enough to hold the roots of the plant. Gently separate the roots with your fingers, then place the plant into the hole roots first. Ensure that the plant sits at the same height as in it's starter pot. Cover the roots with soil and press the soil down firmly with your fingers. Water each seedling generously.

Water your blackberry plants once every other day. During the months from May through October, provide blackberries with 1 to 2 inches of water per week. Check the soil once a day; it should stay continuously moist without drowning the roots. You may need to water the plants every day in the weather is particularly hot or windy.

Install a trellis system after your plants have been growing for one year. Install a thick timber post about 2 feet into the ground at each end of each row. Dig a hole approximately 3 feet deep for each pole. Pour 4 inches of crushed rock into the hole, and tap the surface down using a pole. Set the pole into the hole, ensure it is aligned vertically, then pour quick-set concrete into the hole 1 foot below the ground's surface. Refer to the concrete for exact mixing directions. The posts should extend at least 6 feet from the ground. Install thinner intermediate posts along the row at 20- to 30-foot intervals using the same method. If your rows are less than 30 feet long, install a smaller post in the center of each row. Staple three lengths of wire across the posts at 2-, 4- and 6-foot heights.

Apply mulch 3 to 4 inches deep to the soil, extending 2 feet from each side of your blackberry plants. Make sure the mulch stays topped up for the life of the plants. The mulch will hamper the growth of weeds which can threaten the health of your plants.

Fertilize your plants using organic fertilizers such as manure or compost in late fall or early winter. Divide the length of your row by two to obtain the ideal amount of fertilizer per row. For example, if your rows are 30 feet long, apply 15 lbs. of fertilizer spread evenly along the row.

Prune your blackberry plants once a year after the main harvest. Remove old branches, so that only the strongest canes remain. For erect varieties, only keep three to four stalks. Prune trailing plants so that six to 12 stems remain. Always keep the canes that appear to be the strongest. In addition, trim the top 2 inches from all of the stalks on your erect varieties once during each summer to promote new growth.