How to Use Coffee Grounds for Citrus Trees Effectively
Coffee grounds can feed citrus trees, but only after composting and only in small doses. Used grounds hold nitrogen and a few other nutrients, yet they can't be counted on to acidify soil, no published evidence shows they repel pests, and fresh coffee grounds can damage plants. The sections below cover which coffee grounds citrus trees tolerate and which they don't. Do lemon trees like coffee grounds? Lemons need nitrogen like other citrus, and composted grounds supply some in small doses, while a fertilizer labeled for citrus still covers their nutrition.
Benefits of Coffee Grounds for Citrus Trees
Used coffee grounds are rich in nitrogen, with proteins making up over 10 percent of their weight. Composted grounds hold about 2 percent available nitrogen, which is less than most commercial fertilizers, but that nitrogen is less likely to wash away through leaching and runoff. Potassium is usually the largest mineral in used grounds, followed by phosphorus and magnesium. Calcium in coffee grounds is a minor contribution, and trace minerals such as iron and copper appear in very small amounts.
Composted grounds also add organic matter, which binds soil together and creates pore spaces that improve water absorption. Earthworms pull grounds deeper into the soil, which improves soil structure. Citrus in home landscapes is also less likely than grove citrus to show mineral deficiencies, because the soil already holds more organic matter.
Grounds get credited with raising soil acidity, but used grounds have little lasting effect on pH levels. Decomposing grounds have ranged from mildly acidic to somewhat alkaline, and any change stays close to the grounds. Citrus prefers slightly acidic soil with an optimum pH of 5.5 to 6.5, and many home trees do fine without any attention to pH.
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Effects of Caffeine on Citrus Trees
Small amounts of caffeine stay in the grounds after brewing, along with chemicals such as protective phenolics and the essential oils behind the aroma of coffee. Fresh coffee grounds are phytotoxic to a variety of plants, and soil with 25 percent grounds has shown growth stunt and lower germination rates. Fresh grounds also drop soil pH sharply, which can harm microorganisms in the soil and keep a plant from taking up nutrients.
Bacteria and fungi break down caffeine and the nitrogen-rich compounds in grounds over several months outdoors, releasing nitrogen a tree can use, which is why decomposed coffee grounds carry less risk than fresh ones.
Coffee grounds get billed as a natural pest deterrent, an insect repellent, and a snail and slug repellent. No published evidence shows they repel or kill any garden pests, and the idea of grounds as a natural barrier against garden critters is unproven too.
Using Coffee Grounds on Citrus Trees
Confirm the tree needs nitrogen before adding anything. Pale or yellowish-green leaves and slowed growth point to a shortage, and a soil test settles it. If nutrients are already at optimal or high levels, skip coffee grounds in any form.
Coffee grounds belong in the compost first, where they count as green material, so balance them with brown material such as dry leaves or wood chips, at 1 to 4 parts brown for every part green. Keep grounds under 20 percent of the compost pile, and let hot grounds cool before they go in, since heat kills beneficial microbes. A pile built mostly of grounds can turn phytotoxic. The grounds bring calcium and nitrogen to the pile along with potassium and phosphorus, and the finished compost feeds the good bacteria in the soil that make nutrients more available.
Small doses matter most when grounds go on directly: never add more than a few ounces per square foot, and keep the layer to half an inch or less. A one-inch layer of straight grounds is double that ceiling, and the fine particles compact easily, which cuts water absorption and air movement. Skip mulching with straight grounds for the same reason.
Mulch isn't recommended around citrus trees, and any you do use stays at least a foot from the trunk. Clear weeds and sod from the base of the tree too, because weeds next to the trunk can promote foot rot.
Compost works alongside fertilizer, and for home citrus a slow-release fertilizer labeled for citrus goes on twice a year, in February or March and again in September or October, about 1 to 1.5 feet from the trunk, following the label. Regular watering still matters, especially for young trees.
Safety and Risks of Coffee Grounds for Citrus Trees
Fresh coffee grounds, meaning unused grounds straight from the bag, can sharply lower soil pH, and heavy applications of spent grounds can suppress plant growth. Citrus wants slightly acidic soil, and soil below pH 5.0 needs dolomitic limestone instead of more acidity, so test before adding anything. Keep grounds away from seedlings and newly sown seed, where reduced germination and growth have shown up in many species. Take these precautions with every application: compost first and keep doses small, and keep any mulch a foot from the trunk.
Check out our Citrus Trees Collection!
Starting With a New Citrus Tree
Everglades Farm carries the Meyer Lemon Tree for anyone starting fresh. Newly planted trees get regular watering first, and fertilizer begins three weeks after planting or when buds start to swell.
Frequently Asked Questions
Do Lemon Trees Like Coffee Grounds?
Lemon trees need nitrogen, and composted grounds supply some along with organic matter. A fertilizer labeled for citrus still covers their nutrition, and fresh grounds can damage them.
Are Coffee Grounds Good for Citrus Trees?
In moderation and after composting, they add nitrogen and organic matter. Fresh grounds and thick layers cause problems.
Can You Put Fresh Coffee Grounds on Citrus Trees?
No, fresh coffee grounds can sharply lower soil pH and harm plants, so compost them first.
How Much Coffee Grounds Should You Add Around a Citrus Tree?
Add no more than a few ounces per square foot, and keep a direct layer to half an inch or less. In a compost pile, grounds should stay at 20 percent or less of the total.
Can You Use Coffee Grounds on Potted Citrus Trees?
Composted grounds suit small plantings and potted plants, as long as the compost is finished and the dose is small.
References
University of Florida IFAS Extension, "Citrus Culture in the Home Landscape"
https://ask.ifas.ufl.edu/publication/HS132
UF/IFAS Home Citrus, "Fertilizing"
https://crec.ifas.ufl.edu/home-citrus/fertilizing/
Washington State University Extension, "Using Coffee Grounds in Gardens and Landscapes"
https://pubs.extension.wsu.edu/product/using-coffee-grounds-in-gardens-and-landscapes-home-garden-series/
Cornell Cooperative Extension SOIL3 Project, "Coffee Grounds for Nitrogen"
https://blogs.cornell.edu/soilnow/coffee/coffee-grounds-for-nitrogen
Cornell SoilNOW, "Composting and Coffee Grounds"
https://blogs.cornell.edu/soilnow/coffee/composting-and-coffee-grounds
