Star Apple Fertilizer Program, University of Florida

Fertilizer Program for Caimito Trees in the Home Landscape

From the Horticultural Sciences Department, Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences, University of Florida

In Florida, young trees should be fertilized every 1 to 2 months during the first year, beginning with ¼ lb (114 g) of fertilizer and increasing to 1 lb (455 g) per tree. Thereafter, 3 or 4 applications per year in amounts proportionate to the increasing size of the tree are sufficient, not to exceed 20 lbs per tree per year.

Fertilizer mixtures containing 6 to 10% nitrogen (N), 6 to 10% available phosphate (P2O5), 6 to 10% potash (K2O), and 4 to 6% magnesium (Mg) give satisfactory results with young trees. For bearing trees, potash should be increased to 9 to 15% and available phosphoric acid reduced to 2 to 4%. Examples of commonly available fertilizer mixes include 6-6-6-2 [6 (N)-6 (P2O5)-6 (K2O)-2 (Mg)] and 8-3-9-2 [8 (N)-3 (P2O5)-6 (K2O)-3 (Mg)].

From spring through summer, trees should receive 3 to 4 annual nutritional sprays of copper, zinc, manganese, and boron for the first 4 to 5 years. Caimito trees are susceptible to iron deficiency under alkaline and high-pH soil conditions. Iron deficiency can be prevented or corrected by periodic soil applications of iron chelates formulated for alkaline and high soil pH conditions. Periodic applications of ferrous (iron) sulfate may be made to trees growing in low-pH soils.

Year	Times per year	Amount/tree/application (lbs)¹	Total amount/ tree/ year (lbs)	Nutritional sprays (times/ year)²	Iron chelate drenches (oz/tree/ year)³
1	4-6	0.25–0.5	1.5–3.0	4-6	0.25–0.5
2	4-6	0.5–0.75	2.0–3.0	4-6	0.5–0.75
3	4-6	0.75–1.0	3.0–6.0	4-6	0.5–0.75
4	3-4	1.0–1.5	3.0–6.0	2-3	0.75–1.0
5	3-4	1.5–2.0	4.5–8.0	2-3	0.75–1.0
6	3-4	2.0–2.5	6.0–10.0	2-3	1.0–1.5
7	3-4	2.0–2.5	6.0–10.0	2-3	1.0–1.5
8+	2-3	3.0–4.0	6.0–12.0	2-3	1.5–2.0
¹ Use 6-6-6-2, 8-3-9-3, or a similar material. ² The nutritional spray should contain zinc, manganese, boron, molybdenum; they may also contain iron. Foliar sprays are more effective from April to September. ³ Iron chelated soil drenches (iron plus water) will prevent iron deficiency in high-pH, calcareous soils; foliar iron sprays are generally not effective. Apply soil drenches from April through September.

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Bibliography

Crane, Jonathan H., and Carlos F. Balerdi. "Caimito (Star Apple) Growing in the Florida Home Landscape." Horticultural Sciences Dept., UF/IFAS Extension, HS1069, Original pub. Jan. 2006, Revised Jan. 2009 and Nov. 2016, Reviewed Dec. 2019, EDIS, edis.ifas.ufl.edu/hs309. Accessed 12 Apr. 2017, 15 Apr. 2020.

Published 15 Apr. 2020 LR