12 Plants That Like Coffee Grounds

Highly valued for their richness in caffeine and for the delectable flavor they impart to beverages, coffee grounds have become a home staple all over the world. Who would’ve thought that this gift from nature, though initially bitter and highly acidic, would benefit plants too? Rich in nitrogen, potassium, and phosphorus, coffee grounds contain many of the essential nutrients required for plant growth and survival.

Lauded as an organic ingredient for compost, a mulch additive, and as a potential alternative to chemical fertilizers, coffee grounds may be a safe form of plant food for acid-loving species. Some horticulturists may warn against using fresh or unbrewed grounds, which contain more caffeine and acid. Used coffee grounds pulled straight from the filter of a coffee maker, however, will have lost some of their strength and should be less harmful.

Coffee grounds can be raked into the substrate or into compost (including vermicompost) to increase porousness and lower pH levels. As they organically enrich the soil, they also help repel troublesome insects and snails.

While grounds are a rich and natural source of nutrients, keep in mind that the roots of some acid-sensitive plants (e.g. lavender, tomatoes, rosemary) may not be able to tolerate exposure. Moreover, in substrates that are already rich in nitrogen, the added nutrients may stunt plant growth. Coffee grounds are thus best used in nutrient-poor soils and for plants that thrive best in slightly acidic conditions.

1) Hortensia (Hydrangea spp.)

One of the most fascinating things about hortensias is the color variability of their charming blooms. Dependent on the soil’s pH and its richness in aluminum ions, the bloom color varies from blue to pink to red. If the soil is slightly acidic (pH < 7), the inflorescences are more likely to be blue or purple. Inversely, if the soil is slightly basic, the flowers are increasingly pink.

If you find that your hortensias produce pink blooms, you may experiment with altering the colors of new blooms by introducing coffee grounds into the soil. The coffee grounds, which are acidic, are likely to lower your substrate’s pH, inducing the production of blue blooms. For this to work, aluminum ions need to be present in the soil as well. Note that some Hydrangea cultivars and species are more likely to produce blue pigments than others.

The most popular ornamental species in this group of plants include H. macrophylla, H. paniculata, and H. serrata. Coffee grounds are best added to the substrate around the base of well-established Hydrangea species in late fall. Aim to introduce grounds up to just 3 times a year to avoid shocking the roots of the plant and causing stunted growth. To prevent the surrounding area from smelling too much like coffee, thoroughly work the grounds into the soil.

2) Azalea (Rhododendron spp.)

Frequent favorites in lush gardens with flowering shrubs, azaleas are stunning ornamental plants with an array of bloom colors. In spring, the brilliantly colored inflorescences can dramatically change the appearance of these shrubs, causing them to look like large bouquets. The best flowering rates are usually observed in areas with woodland conditions, slightly acidic or humus-rich substrates, and partial or dappled shade.

Depending on the species and where they are grown, azaleas may be deciduous or evergreen. Even in optimal conditions, some of them are known for being quite slow-growing and sensitive to pests and diseases. Regardless, carefully cultivating them is usually worth it for their long-lived blooms. Able to last up to several weeks long, the blooms tend to produce a highly toxic and potentially medicinal nectar.

If you intend to fertilize your azaleas with coffee grounds, keep in mind that they are not necessarily heavy feeders. Application of grounds into the soil around the plant should serve the purpose of lowering pH levels to its preferred values (around 4.5 – 6) for good growth. The grounds should ideally be introduced in mulch or compost and they should not be pressed onto the plant itself.

3) Highbush blueberries (Vaccinium sect. Cyanococcus)

Cultivated blueberry shrubs usually fall under the classification of highbush blueberries. The most popular species, which is grown for ornamental purposes and for its economically important fruit, is the northern highbush blueberry (V. corymbosum). Compared to wild blueberries, this species produces larger fruits and can grow up to 3.7 meters (12 feet) tall in optimal conditions.

To grow healthy specimens of highbush blueberries, the substrate’s pH needs to be markedly acidic. These plants favor pH levels along the range of 4.8 – 5.2, which is why coffee grounds may be effective as a soil additive. To fertilize blueberry bushes, make sure to work the grounds into the top few inches of soil. This way, they can break down at a faster rate and are less likely to affect the growth of any sensitive plants nearby.

Apart from lowering pH levels, coffee grounds should provide blueberry shrubs with the nutrients they need to produce fruits. Nitrogen, potassium, phosphorus, magnesium, calcium, and copper are some of the elements required for proper fruit development. Some horticulturists may warn against using grounds due to their caffeine content. If you’re concerned about the traces of caffeine stunting fruit growth, you can add the grounds to compost first and then apply the compost around the shrubs.

4) Lily of the valley (Convallaria majalis)

An herbaceous perennial with lovely ornamental features, lily of the valley is known for its bell-shaped blooms and alluring odor. This species’ scent, which is considered a classic fragrance, has inspired some of the world’s most famous perfumes. Once the national flower of both Yugoslavia and Finland, this flowering plant comes in many cultivars that have received the RHS Award of Garden Merit.

As C. majalis is a mesophile, it favors mild climates and usually thrives best in partial shade. Although it is usually advisable to grow this species in slightly alkaline substrates, it is able to tolerate mildly acidic soil. Old or used coffee grounds, which should have a lower acidity profile compared to freshly ground coffee, are the more appropriate choice for providing nutrients to its delicate roots.

It’s important to note that lily of the valley is a highly toxic species that may cause undesirable symptoms when ingested by animals or humans. The plant, including its berries, contains dozens of cardiac glycosides. Make sure it is grown in areas that are difficult for children or pets to access.

5) Carrot (Daucus carota subsp. sativus)

Known best for its specialized taproot, for which it is selectively bred and cultivated across the globe, the humble carrot is a biennial vegetable with a rich nutritional profile. Its fast-growing cultivars get their vivid orange coloration from a combination of carotenes, which are metabolically converted into vitamin A. Carrots also have high amounts of vitamin K, vitamin B, and free sugars.

Most types of carrots thrive best in soil with slightly acidic to neutral pH levels. For their taproot to grow into a favorable shape and produce a high ratio of cortex to core, they should be situated in sandy loam. Heavier soils are only tolerated if they do not hinder drainage. Used coffee grounds can be thoroughly worked into patches of soil where you intend to germinate your carrots.

Coffee grounds should provide the seeds and seedlings with a boost of nutrients to stimulate plant growth from the point of germination. While improving harvest rates, the slightly acidic grounds should also dissuade pests from coming too close to your growing carrots! Cultivating other acid-loving companion plants should also help these root crops thrive.

6) Radish (Raphanus raphanistrum subsp. sativus)

Producing red, white, or greenish brown globes of globular to cylindrical taproots, radishes are rapidly growing annuals. Known for their unique flavor in cooked dishes and for their sharp taste in salads, they come in many varieties that are extremely important in East to South Asian cuisine. Often mistaken as turnips or parsnips by the untrained eye, radishes can easily be grown in home-based vegetable gardens.

Radishes thrive best in regions with moderately warm temperatures. In areas with markedly cool or intensely warm temperatures (> 25˚C or > 77˚F), the crop may take several weeks longer to mature and reach harvest size. The best conditions for the growth of the taproot include a loamy substrate, full sun exposure, and a slightly acidic to neutral pH level. Just as coffee grounds can increase harvest rates and speed up germination for carrots, they should promote the growth of radish seedlings.

Radishes can thus be germinated and grown alongside carrots, in the same substrate where used coffee grounds or coffee-rich compost is worked into. Coffee grounds slowly release nitrogen, so they are able to provide a stable supply of this nutrient for at least the first few days to weeks of radish growth.

7) Roses (Rosa spp.)

With flowers that are unrivaled in their popularity, roses are cultivated almost everywhere. These ornamental plants are used for many purposes, ranging from decorative and artistic to medicinal and aromatic. There are more than a hundred rose cultivars that have received the RHS Award of Garden Merit. Some of the most commonly cultivated types include English roses, tea roses, and wild roses.

Many Rosa varieties may benefit from fertilization with coffee grounds as they favor substrates that are rich in organic matter. The nutrients provided by the grounds can help improve the general quality of the soil as well as fortify and hasten the growth of the plant. When used in moderate amounts, they also optimize the substrate’s acidity profile and attract beneficial worms.

If you intend to fertilize your roses with coffee grounds, aim to do so at the beginning of their peak growth period (spring). Avoid adding the grounds past fall as they can damage roses that are about to become dormant. You can either sprinkle the grounds directly on the substrate around the rose bushes (watering them afterward to help distribute their nutrients) or you can mix them into a water solution beforehand.

8) Philodendron (Philodendron spp.)

Known for their stunning leaves, which can grow to enormous sizes, philodendrons are some of the most popular houseplants. Healthy specimens favor mild temperatures and are able to thrive in shady areas. They are fairly easy to grow and can be propagated using the stem cuttings of mature plants. As a result, their colonies have become naturalized in many countries outside of their native range.

Capable of growing in an epiphytic or terrestrial manner, philodendrons send out sturdy roots that tend to grow toward soils with their favored conditions. They prefer slightly acidic pH levels ranging from 6.0 – 6.5. As a result, coffee grounds can be used as a natural source of required nutrients for growth. However, you’ll need to make sure that the soil pH is close to neutral prior to introducing the acidic grounds.

When used in the right concentrations and applied at the proper time, coffee grounds can significantly aid in boosting the health of nutrient-deficient philodendrons. They can be introduced into the substrate of mature plants as part of compost or as liquid fertilizer (such as compost tea).

9) Camellia (Camellia spp.)

With hundreds of species and thousands of hybrids, Camellia is a diverse genus of flowering shrubs and trees. Evergreen in their native range, these glossy-leafed plants favor naturally irrigated substrates with acidic conditions. Those grown in gardens and for commercial purposes, including the famous tea camellia (C. sinensis), tend to have a rapid growth rate and produce eye-catching blooms.

As they are well-adapted to acid-rich soils, camellias can thrive in substrates that are amended with coffee grounds. The nitrogen from the grounds can aid in optimal leaf growth, while the leached phosphorus promotes flower and fruit production. The aroma of coffee should help prevent pests from attacking the shrubs.

Coffee grounds can be introduced to the substrate around the base of camellia shrubs in various ways. The simplest way is done by simply sprinkling the grounds onto the surface and using a rake or shovel to work them through the top few inches. Avoid leaving the grounds on top of the substrate as they can form a layer that dries out and repels water, preventing it from draining evenly through the substrate.

10) Gooseberries (Ribes spp.)

Gooseberries, or currants, are cultivated for their fruits and for their ornamental features. Shrublike, these plants favor environmental conditions in areas that are close to streams or in regularly moistened meadows. Many species are favored by larvae as a source of food. Their berries, many of which are edible for humans (e.g. white currant, blackcurrant, red currant), usually appear from June to July.

As gooseberry bushes favor slightly acidic soil conditions, coffee grounds may be used as a fertilizer and as a natural means of reducing pH levels in alkaline substrates. The grounds should be mixed into compost first so that they are less likely to scorch the roots of the bushes and inhibit fruit growth. The nutrient-rich compost can then be incorporated into the soil around the base of the bushes.

One of the most common gooseberry species in cultivation is R. sanguineum. Although this species is native to western North America, it is quite popular among horticulturists in the UK. Valued for its sweetly scented and delicate inflorescences, it can vegetatively reproduce to form dense stands in moist soils. Occasional fertilization with a coffee-filled compost should help increase rates of flower and fruit production.

11) African violets (Streptocarpus spp.)

Also referred to as saintpaulias, African violets belong to a small group of about 6 – 10 flowering herbs. Well-loved in cultivation for their fascinating leaves and vivid flowers, they are often grown as indoor plants. In the wild, many of their populations are threatened or endangered due to the conversion of land into agricultural zones. Thriving best in cloud forests, which are tree-rich biomes with low-level cloud cover, they are sensitive to temperature and moisture fluctuations.

During the growth period of African violets, they may be fertilized with coffee grounds. Sprinkling used grounds into the surrounding substrate should help release nitrogen and create slightly acidic conditions, which may improve foliar health. These plants thrive best in soils with a pH range of 5.8 – 6.2, so the grounds can be used to amend regular potting mixes with a neutral pH level.

Coffee grounds should only be introduced into the soil if you haven’t fertilized the plant beforehand. While it should not necessarily take the place of a balanced, store-bought fertilizer, its addition on top of one may not do African violets any good. If you do opt to use grounds, apply them with a light hand or mix them into compost beforehand.

12) Jade plant (Crassula ovata)

One of the most commonly grown succulents in indoor locations, the jade plant or money tree is believed to impart luck. For ornamental purposes, it can be grown as a bonsai of sorts; its basal stems expand when its branches are carefully pruned. Distinguished by smooth, shiny, and fleshy leaves, it now comes in remarkably colorful hybrids with varied leaf shapes.

As jade plant favors slightly acidic soil, it can benefit from being fertilized with coffee grounds. Alkaline soil may adversely affect its health, so the grounds can also be used to lower the substrate’s pH in pots that are prepared for cuttings and for repotting older specimens. It can even be watered with diluted cold-brewed coffee. The added nutrients should help enhance the color of the leaves and aid in shoot reinforcement.

When using coffee grounds for your jade plants, make sure the particles have not been exposed to milk, sugar, cream, or syrup. The grounds should ideally be black and pure so that they don’t inadvertently attract pests. When providing the coffee as a compost tea, thoroughly dilute at least 2 cups of the grounds in 5 gallons of water. The soil’s pH levels should be checked beforehand to ensure that the coffee doesn’t bring an already low pH level to potentially lethal values.