Crop advice for
Thuja occidentalis 'Smaragd'

Stage 1: Cuttings

Make the cuttings ideally in late September – October, another option is between February – March. Artificial day length can stimulate quicker rooting during wintertime. Rooting is a crucial phase for Thuja. Cuttings require lower soil temperatures (Dec-Jan 14-15°C, Feb 16°C, March 17°C). In higher temperatures callus production can be limited! Avoid any EC peaks during this phase; maximum is 0.5mS during this stage. Also be careful with high amounts of urea. Do not use a water-soluble starter fertilizer for winter pottings.

Stimulate rooting with 5 g/m2 Peters Professional Plant Starter 10-52-10. Repeat this action before transplanting in April. When roots are developed a growth boost can be given with Universol Blue 18-11-18 10g/m2 (max 2x in 14 days). To finish the cutting phase Universol Violet 16-5-25 10g/m2/week can be given during the last weeks.

Stage 2: Vegetation (P9 cm -P11 cm)

The development of the roots and branches is the most important during this stage. Don’t focus too much on length. Increase the amount of fertilizer, once the plants have rooted successfully. Keep the EC low (0.5 mS) during the first 3 weeks after potting. Main growth happens in late spring and during September – October (November in southern countries). Keep the EC in the pot in these growth periods continuously around 1.0 mS/cm. Thuja occidentalis ‘Smaragd’ does not grow very fast. As plants are mainly grown outdoors, ensure a good base nutrition with Osmocote Exact Standard or Osmocote 5 mixed into the growing medium in the dose of 3 g/l. In summer period additional nutrition via irrigation is needed with 15-20 g/m2/week Universol Blue 18-11-18. Later in summer and autumn period change this to 15 g/m2/week Universol Basis 4-9-35 for strength and green color.

Stage 3: Finishing

Quality plants have a good length, shape, strength and deep green color. Thuja occidentalis Smaragd prefers low EC during the first month. Mix a base dose rate of 3 g/l Osmocote5 through the substrate when potting in early spring. Start from May/June with additional nutrition via irrigation with 20 g/m2/week Universol Blue 18-11-18. Switch from August to 15-20 g/m2/week Universol Orange 16-5-25 or to 15-20 g/m2/week Universol Violet 10-10-30 for finishing without additional growth. Do not use foliar feeding due to high amounts of urea as Thuja occidentalis ‘Smaragd’ is sensitive to urea. It can cause tip burn in combination with high irradiation.