Are coffee grounds beneficial for asparagus growth?
Written by
Julia Anderson
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Coffee grounds are helpful to asparagus when properly composted, as they contain nitrogen and organic matter, which improve the soil. Used fresh, they are injurious to plants by rendering the soil sour and inviting the growth of the mould fungus. I compost them with leaves for six months before I use them.
Composting Process
- Mix ratio: 1 part grounds to 4 parts carbon-rich material
- Materials: Combine with dried leaves or shredded paper
- Duration: Allow 3-6 months for full decomposition
- Signs: Finished compost smells earthy not sour
Soil pH Management
- Acidic soils: Avoid in pH below 6.0 regions
- Alkaline soils: Use to gently lower pH above 7.5
- Testing: Check pH before and after application
- Limit: Apply max 1 cup per plant annually
Nutrient Balancing
- Nitrogen boost: Complements early spring growth
- Deficiency risk: Low phosphorus requires bone meal supplement
- Timing: Apply only during active fern growth phase
- Avoidance: Never use during crown establishment years
Caffeine residue in fresh grounds curtails the growth of asparagus roots. Caffeine reduces the elongation of roots, it is suggested, by 30 per cent. Be careful to compost well. The fumes disappear; I test my compost for maturity by planting out broad bean seeds, as they are the quickest to germinate. If they come up without delay, the compost is ready for use.
Apply coffee compost around the ferns and among the shrubs as they emerge in early spring. Cover them with a thin layer (1/2 inch) of compost, taking care to keep it from touching the crowns. Water it immediately, so that the food may be speedily supplied. Avoid using it in late summer, as it will cause tender shoots to emerge before frost has hardened the plants. I wait for the first sight of the 'spear.'
Observe for yellowing tips on your plants. If the leaves become lighter after application, it suggests that you need to add wood ash or a similar substance to your food to neutralize the acidity. Soil testing, at a minimum, every two years will help avoid the cumulative acidification of your soil. I determine my adjustments by the colour of the ferns, not the appearance of the spear.
Other uses include pest deterrent sprays. Steep used grounds in water for a couple of days, then strain and spray on ferns to deter beetles. This approach spares the soil but exploits the qualities of the coffee. I apply at dawn, when beetles will be dormant.
Read the full article: When to Plant Asparagus: Essential Growing Guide
