Providing extra calcium on the surface of my bonsai soil has made a huge difference in the amount of growth I’ve experienced this year.

Use 2-3 desert-spoonfuls on a 12"/30cm wide pot. Apply twice per season in soft water areas or when using rainwater, once per season in hard water areas is sufficient. .

Elm, Hawthorn, Box, Olive, Spindle, Oak, Yew, Cedar, Cherry (especially Prunus mahaleb) all really enjoy small amounts of calcium in the soil; this does raise the pH a little so care must be taken with any acid-loving or lime-hating species such as Azalea or Acer palmatum.

From ProBio Carbon

"A new product developed in 2024 to help calcium deficiencies in trees. In general, the bioavailable Ca:Mg ratio should be 2:1.

Sometimes in soft water areas calcium is not bioavailable at an effective level for alkali environment trees. Deficiency may then result in disease symptoms. To combat this, we have developed a calcium rich shell product coated with plant growth promoting bacteria.

These bacteria act as a delivery vehicle to bio transform the calcium in the shell and deliver it in a form to where it's needed in the tree."