What Plants Don’t Like Coffee Grounds? A Guide to Avoiding Harm

Coffee grounds are often touted as a natural fertilizer for plants. The grounds are rich in nitrogen, potassium, phosphorus and other nutrients that are beneficial for plant growth. However, not all plants thrive with the addition of coffee grounds. Using coffee grounds improperly can potentially damage certain types of plants.

In this article, we’ll explore what plants don’t like coffee grounds and why along with tips for safe usage.

Overview

Coffee grounds can positively impact plants that:

• Prefer acidic soil pH which coffee can help lower.

• Need a boost of nitrogen. Coffee grounds are high in nitrogen.

• Have poor soil structure Coffee grounds can improve drainage and aeration

However, coffee grounds are not universally beneficial. Their acidic pH and ability to retain moisture can negatively affect plants such as:

• Plants that prefer alkaline soil – Coffee will lower pH too much.

• Plants prone to fungal diseases – The grounds can exacerbate disease.

• Plants sensitive to caffeine – Coffee contains caffeine.

• Young plants and seedlings – Too strong for young plants.

When using coffee grounds in your garden, it’s essential to be strategic. Test soil, use proper amounts, and avoid plants that won’t benefit.

Why Are Coffee Grounds Problematic for Some Plants?

Coffee grounds can potentially cause issues for certain plants for a few key reasons:

Acidity

• The grounds contain organic acids and lower pH.

• Plants that prefer alkaline soil will suffer in overly acidic conditions.

• Common examples include lavender, lilacs, orchids.

Moisture Retention

• Coffee grounds help soil retain moisture.

• Too much moisture can lead to root rot and fungal issues.

• Particularly problematic for arid plants like cacti.

Nutrient Imbalances

• Grounds are very high in nitrogen.

• Too much nitrogen can inhibit fruiting and flowering.

• Affects plants like blueberries and bulbs.

Caffeine

• Coffee contains caffeine, which some plants are sensitive to.

• Caffeine can stunt growth or damage plant tissues.

• An issue for roses, hydrangeas, and geraniums.

Fungal Diseases

• The moist, acidic environment from grounds can encourage fungal growth.

• Very harmful for plants prone to fungus like tomatoes and squash.

By understanding these potential issues, we can avoid using coffee improperly.

What Plants Should You Not Use Coffee Grounds With?

Here are some specific plants that do not respond well to coffee grounds:

Flowers:

• Lavender
• Lilacs
• Daffodils
• Roses
• Hydrangeas
• Geraniums

Fruits:

• Blueberries
• Gooseberries
• Blackberries

Vegetables:

• Celery
• Broccoli
• Cauliflower
• Eggplant
• Lettuce

Herbs:

• Oregano
• Sage
• Thyme
• Mint

Houseplants:

• Ferns
• Orchids
• Jade plants
• Pothos

Succulents/Cacti:

• Aloe vera
• Sedum
• Sempervivum
• Snake plants

Trees/Shrubs:

• Magnolia
• Birch
• Maple
• Pine
• Spruce

This list covers many common plants that prefer to avoid coffee grounds. However, it’s not exhaustive, so research specific plants thoroughly before using coffee. When in doubt, err on the side of caution.

Tips for Using Coffee Grounds Safely

If you want to gain benefits from coffee grounds while avoiding potential issues, here are some tips:

• Test soil pH before and after adding grounds.

• Use sparingly – no more than 20% of compost mix.

• Avoid direct contact between grounds and plant stems/leaves.

• Don’t add grounds to the soil of young seedlings and plants. Wait till well-established.

• Water plants well after applying grounds to prevent burning.

• Mix grounds thoroughly into soil – don’t leave piles that can breed fungus.

• Adjust usage based on soil drainage – less for poorly draining soil.

• Never use freshly brewed liquid coffee – dilute used grounds instead.

• Start with smaller amounts and increase slowly while observing plant health.

• Improve drainage if the soil stays soggy after adding grounds.

Following these tips, you can unlock the benefits of coffee grounds while avoiding potential drawbacks.

Alternative Uses for Coffee Grounds

If you don’t want to use grounds directly on your garden plants, here are some other ways to utilize them:

• Add to compost pile – provides nitrogen source and aerates material.

• Use as mulch – repels slugs/snails, retains moisture, adds organic matter over time.

• Make fertilizer tea – soak grounds in water, dilute and apply the liquid.

• Help attract earthworms – worms are drawn to the grounds.

• Deter cats from soil – sprinkle on top, cats dislike the aroma.

• Absorb odors in fridge – place grounds in open container to soak up smells.

Don’t let extra coffee grounds go to waste! With a bit of creativity, you can put them to use in many ways around your home and garden.

Many plants can gain benefits from the addition of used coffee grounds as an organic fertilizer and soil amendment. However, coffee is not a universally suitable solution for all plants. Grounds can potentially create issues for plants that prefer alkaline soil, are prone to fungal diseases or sensitive to caffeine. By using coffee grounds cautiously and avoiding plants that don’t respond favorably, you can harness their nutrients while preventing any harm. With proper utilization focused on acid-loving and nitrogen-hungry plants, coffee grounds can be a sustainable gardening boon.