Cedar Planters for Berries

(Question)

Hi Gardeners
I am planing to move Black Raspberries as well as Strawberries and Raspberries from the ground to cedar planters as we are having landscape done and I want them localized. How do i determine the appropriate size of a wooden planter based on the number of shoots so that they can survive the winter and have space to grow? I figure they must be a least 2ft deep. I live in Toronto, thus zone 6. My planters will face south. I plan to build 3 planters for the different plants.
Any help would be appreciated.
Regards

(Answer)

Hello, and thank you for your questions,  while it is difficult to provide specific recommendation for planter size, we can advise that these should be large and deep enough to accommodate the plants without crowding them.  Often containers 61-91 cm (24-36) inches wide and deep are recommended, but this will vary depending on the number of plants you plant per container.  Below is additional information specific to your berries.

Note that container size is usually discussed in terms of volume capacity (litres) as opposed to dimensions; I’ve tried to include both where possible.

Raspberries:

  • Red raspberry canes grow in an upright manner, however black raspberry canes are long and trailing. The planters for each should be designed to accommodate (show off!) these characteristics.
  • Consider the size of your plants:
    • For compact raspberry varieties a container of around 25 litres would work well.
      • Diameter: approximately 36 cm (14 inches)
      • Base 28 cm (11 inches)
      • Height 33 cm (13 inches)
      • Note that compact berry varieties tend to be better suited for the smaller spaces containers offer.
    • If the raspberry plant is taller than 1 metre (3 feet) it will need a 40 litre container to provide for enough root space, nutrition and added weight to prevent the plant from falling over.
      • Diameter 50 cm (20 inches)
      • Base 35.5 cm (14 inches)
      • Height 45 cm (18 inches)
    • As raspberry plants are quite deep-rooted – the root system is found in the top 2 feet of soil – some resources recommend that the container should be a minimum of 60 cm (2 feet) deep
    • If you have more than one plant, plant 75-90 cm (30-35 inches) apart from one another, except red raspberries, which can be planted at 60 cm (24 inches) distance.
    • Another option is to consider using half-barrels or 5 gallon pots, to allow enough canes to grow in future years.  Depending on the container size, you may fit in 3-6 canes per container.  For example, half barrels made of untreated wood are available on-line and many hold around 80 litres of soil and are 65-68 cm (26-27 inches) in diameter and 40 cm (16 inches) height.

Plant the raspberries at the same depths they were growing in the soil.  Make sure the hole is wide and deep enough for the plant and does not crowd its roots, which you should spread out in the planting hole.  Cover with 10-15 cm (4-6 inches) soil, packing carefully around the roots. The highest point where roots are attached to cane is 2.5-5 cm (1-2 inches) below the soil.

Strawberries:

Strawberries do not like to be crowded, so the size of the planter would depend on the number of plants you are planting.  Three plants per 0.09 square metres (1 square foot) of soil (e.g., a 12 inch x 12 inch (30 cm x 30 cm) pot) would be appropriate.  Strawberry plant roots are quite shallow, with most roots found in the top 15 cm (6 inches) of soil. When planting the strawberries, plant the crowns (where the roots and stems meet) immediately above the soil line and then pat the soil around the plant roots.  Do not cover the crowns with soil.

  • For strawberries, which have shallower roots than raspberries, the container should have at least the following dimensions
    • Diameter: 25-30 cm (10-12 inches) – to accommodate 2-3 strawberry plants. A wider pot would permit the plants to spread and send out lots of runners.
    • Height: 20 cm (8 inches)

Additional considerations:

Wood: Cedar is a terrific option for the wood planters, as it is relatively resistant to rot.  As the berries are edible, make sure the wood has not been pressure treated, or  sealed, or otherwise exposed to toxic chemicals that could leach into the soil.

Drainage: Ensure the container has good drainage.

Insulation: Cover both the raspberries and strawberries with a layer of mulch and wrap with burlap, blankets or bubble wrap to protect them during the winter.

Plants: Make sure that the plants have been pruned before moving them – trim any dead or damaged branches, to help with air circulation and minimize diseases.  Ensure there is no debris or leaf material in the containers, these could harbour pests/diseases.

Soil: Use good quality, fresh,  potting soil (not soil from the garden). Apply mulch around the base of the plants, to help insulate roots and retain moisture.  Water infrequently ,but don’t let the soil dry out completely – check the planters and water when the top 2.5 cm (1 inch) of soil feels dry.

Thank you for contacting Toronto Master Gardeners, hope you find good results!