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The pH value is an important building block in plant development, especially with regard to nutrient availability and soil fertility, i.e. the activity of soil communities. Some plants need acidic soil, while others need neutral or alkaline soil.

In a nutshell

  • pH value describes the acid and base content of the soil
  • Too low a value reduces the activity of soil organisms and thus the decomposition of organic material
  • If the value is too high, this leads to a reduced supply of phosphorus, iron and magnesium
  • A value of 7 is considered neutral, below that is acidic, and anything above that is alkaline (basic)

Plants that do well in acidic soil

Plants that need acidic soil are particularly ericaceous plants. They can be weakly acidic (5.51-6.50), acidic (4.51-5.50), and highly acidic (<4.50). Most species prefer a value between 4.5 and 5.

vegetable plants

Cucumber (Cucumis sativus)

  • Soil slightly acidic to neutral
  • Well drained, nutritious, humic
  • Loamy soils with a high humus content are ideal
  • Sunny location and humidity of 80 percent
  • Depending on the variety as climbing plants or creeping bushes

Tip: Do not plant cucumbers after carrots or potatoes. There is a risk of transmission of viruses or wilt fungi.

Radish (Raphanus sativus)

  • quite tolerant in terms of pH (between 5.5 and 7)
  • Loose, deep, loamy sandy soil with a high humus content
  • Loves full sun locations
  • Too little sunlight leads to storage of nitrate in the tubers
  • Only fertilize radishes cautiously with nitrogen.

Rhubarb (Rheum rhabarbarum)

  • pH for rhubarb should be slightly acidic
  • Nutrient-rich soils with good storage capacity
  • Tolerates sun and partial shade
  • Too much sun leads to premature flowering
  • Good plant neighbors include beans, peas, spinach, kohlrabi, and lettuce

Tomatoes (Solanum lycopersicum)

  • Tomato soil should be slightly acidic
  • Humos, rich in nutrients, permeable, fresh and moist, free from coarse components
  • Work in compost or horn shavings in nutrient-poor soils
  • Add water reservoirs such as coconut fiber, perlite or bentonite to sandy soils
  • Make loamy more permeable with sand or lava split
  • Plant loves sunny, warm and rain-protected locations

fruit trees

Blackberry (Rubus)

  • Soil pH between 5.5 and 6.5
  • Rich in humus, not too light, well-drained
  • Potassium content should be high
  • On very moist and heavy substrates, ridge cultivation recommended
  • In full sun, most flowers

Blueberries (Vaccinium corymbosum)

  • Blueberry is a lime fleeing plant for acidic soil
  • Humos, well drained and aerated
  • Softwood mulch keeps soil acidic
  • Full sun is ideal
  • Partial shade is tolerated

Tip: Blueberries are very sensitive to saline fertilizers.

Raspberry (Rubus idaeus), Currant (Ribes), Gooseberry (Ribes uva-crispa)

  • Thrive on slightly acidic soil
  • Neither too acidic nor too calcareous
  • Nutritious, humic, permeable
  • It is best to mulch regularly
  • Sunny, warm and wind-protected locations
Red currant

Passion fruit (Passiflora edulis)

  • Climbing plant for light, deep, well-drained soils
  • Slightly acidic substrates with a high humus content
  • Wind-protected, warm, sunny to semi-shady locations
  • Cultivate frost-sensitive varieties in tubs
  • Passiflora incarnata is particularly hardy
Flesh colored passion fruit, Passiflora incarnata

Cranberry (Vaccinium vitis-idaea)

  • Cranberry grows on acidic soils with a low pH (4-5)
  • Poor in nutrients, permeable, rich in humus and sandy
  • Thrives best in sunny locations
  • Also tolerates partial shade
  • Ideal plant partners are blueberries and azaleas

ornamental plants

Japanese maple (Acer palmatum)

  • Very adaptable, from sandy humic to sandy loamy
  • Slightly acidic to neutral soil
  • Preferably in the slightly acidic range
  • Compacted and very heavy soils are taboo
  • Full sun to half shade, sheltered from the wind

Tip: The crown shape and autumn colors are at their most beautiful in full sun and free-standing.

Garden azaleas (Azalea)

  • Lime-free, cool, humus-rich, acidic to slightly acidic soil
  • In heavy soils, incorporate drainage
  • Wind-protected place in the semi-shade
  • Or bright location without blazing sun
  • Avoid root area of large trees

Hydrangeas (Hydrangea)

  • Soil should be slightly acidic
  • Loose, humus rich and moist
  • Partial shade or sun, depending on the variety
  • Flowering period from July to September
  • Sufficient watering is the be-all and end-all

Jasmine (Jasminum officinale)

  • Thrives well in acidic soil (4-6)
  • Loose substrate enriched with compost or bog soil
  • Warm, sunny locations protected from wind and rain
  • Also tolerates full sun, provided it is sheltered from the wind
  • High water requirement during flowering

Tip: Water only in the morning or evening to avoid sun damage.

Laurel rose (Kalmia)

  • Preferred pH in the acidic to slightly acidic range
  • A value above 5.5 can result in deficiency symptoms
  • Sandy-humic, moist and low-lime substrates
  • Loves sunny to partially shaded places
  • Kalmia leaves are poisonous

Rhododendron (Rhododendron hybrids)

  • Acidic to slightly acidic soils
  • Exception INKARHO rhododendrons, tolerate value up to 7
  • Also loose, humic, permeable to water and lime-free
  • Partial shade with high humidity optimal
  • The higher the humidity, the sunnier the location can be

Shrub Peonies (Paeonia suffuticosa)

  • Slightly acidic to alkaline substrates (5.5 to 7.5)
  • Deep, well drained and fertile
  • Prefers medium-heavy, humus-rich loamy soil
  • Thrive in sun and partial shade
  • The sunnier, the more moisture is needed
Paeonia suffruticosa, tree, shrub peony

Plants for soils with a neutral pH

A neutral soil value means that acids and bases are present in the soil in a balanced ratio. Most plants thrive on neutral to slightly acidic soil (6.5 to 7.5).

vegetables

Cauliflower (Brassica oleracea var. botrytis)

  • High demands on soil fertility
  • Permeable, deep, loamy with a high humus content
  • Loamy and loess soils optimal
  • Sunny and wind-protected locations
  • Protect the inside of the flower from the sun by folding over the leaves

Lamb's lettuce (Valerianella)

  • Optimum pH between 6.5 and 7.5
  • Prefers calcareous, sandy loamy soil
  • Weak feeders with low nutrient requirements
  • Location should be in full sun
  • Spring onions, tomatoes, radishes good neighbors, brassicas bad
Valerianella locusta, lamb's lettuce

Carrots (Daucus carota ssp. sativus)

  • Soil composition sandy-loamy, humic, deep
  • Avoid stony soil
  • If the soil is too heavy, a ridge culture is recommended
  • Sunny to partially shaded locations
  • Do not use fresh compost (carrot fly)
  • Good mixed culture with onions

Paprika (Capsicum annuum)

  • Vegetables for neutral to slightly acidic soils
  • Preferably sunny locations
  • Mulch film can also warm up the soil
  • Otherwise well-drained, sufficiently moist substrate with a medium-high nutrient content
  • Improve light sandy soils with compost or humus
  • Use conventional vegetable soil for pot cultivation
  • Young plants are sensitive to high salt levels
pepper plant

Radish (Raphanus sativus subsp. sativus)

  • Weak feeders with a short cultivation time
  • Light to medium-heavy, humus-rich, evenly moist soil
  • Sunny and airy locations, preferably lowlands
  • Do not plant next to cucumbers and other cruciferous vegetables
  • Do not apply fresh manure or badly rotted compost

Brussels sprouts (Brassica oleracea var. gemmifera)

  • Ideally pH of at least 6.8
  • Heavy feeders thrive on humus and nutrient-rich soil
  • Copes with most soil types
  • Prefers heavy substrates with a high proportion of clay
  • Work in compost or stable manure in the previous year
  • Mixed culture with cucumbers, peas, radishes and spinach possible

Tip: Generally, grow cabbage at the same location after three years at the earliest and not together with other cabbage types.

Spinach (Spinacia oleracea)

  • Thrives best on deep, well-drained, humus-rich soil
  • Prefers partially shaded places
  • Change location annually
  • Harvest begins 10-12 weeks after sowing
  • Soil should always be moist

fruit

Pear (Pyrus communis), plum (Prunus domestica), apple (Malus domestica)

  • Slightly moist, humus-rich, loamy, well-drained soil
  • Value above seven leads to chlorosis
  • Rose plants do not tolerate waterlogging
  • Warm, full sun and sheltered location
  • The more sun, the more flowers
  • Pear needs more warmth than apple
  • Fruits smaller in partial shade and delayed ripening

Strawberry (Fragaria)

  • Loose soil, rich in humus and nutrients, neutral to slightly acidic (5.5-6.5)
  • Structural improvement by covering with manure or straw
  • Work mature compost into heavy soil several weeks before planting
  • Full sun, wind-protected, not windless locations
  • Maintain a strawberry break of at least three years (crop rotation)

Peach (Prunus persica)

  • Shrubs for slightly acidic to neutral soils (5-7)
  • Permeable, loose, nutritious
  • Gravelly-loamy, sandy-loamy and sandy-clayey soils are ideal
  • Wine-growing areas and sunny rock gardens particularly suitable
  • Protect the flowers of these rose plants from late frosts

Sweet cherry (Prunus avium)

  • Deep, loamy, neutral to basic soils with a high lime content (6.5-10)
  • Fruit for airy, full sun and warm places
  • Best aroma in sunny locations
  • Avoid locations that are endangered by late frost
  • Acidic, wet and sandy soils increase risk of rubber flow
Prunus avium, wild cherry, sweet cherry

Perennials, shrubs and other ornamental plants

Blue Cushion (Aubrieta)

  • Dry, well-drained soils in the neutral range
  • Gravelly-loamy or gravelly-sandy
  • If necessary, enrich with humus or sand
  • Gravel drainage recommended
  • Full sun and semi-shady locations
Bluecushion, Aubrieta

Lilac (Syringa)

  • Soil permeable, loose, calcareous, rich in nutrients and humus
  • Tolerates short-term drought
  • Waterlogging and soil compaction are not tolerated
  • Prefers sunny, wind-protected locations, tolerates partial shade
  • Dwarf varieties well suited for container cultivation
Syringa vulgaris

Lilies (Lilium)

  • Loose, well-drained soil
  • Enrichment with humic leaf compost recommended
  • Full sun location
  • Willingness to flower is lost in the shade
  • Protect root area from direct sunlight
Source: Alejandro Bayer Tamayo from Armenia, Colombia, Lirio japonés - Azucena (Lilium 'harmony') - Flickr - Alejandro Bayer, edited by Plantopedia, CC BY-SA 2.0

Tip: Ground cover, perennials or annual summer flowers are suitable as shade providers.

Daffodil (Narcissus)

  • Soil well drained, moderately fertile
  • Lime and nitrogen inhibit growth
  • Sand and clay recommended
  • Preferably sunny locations
  • Humid and sunny in spring, dry in summer

roses (pink)

  • Medium-heavy, low-salt, low-acid, loamy, humic and sandy soil
  • pH between 6.5 and 7.0, depending on the variety
  • Location neither too sunny nor shady
  • Floor should be able to dry quickly
  • Near trees, root competition

Clematis (Clematis)

  • Soil pH between 6.5 and 8.0
  • Rich in humus, fresh to moist, calcareous
  • Climbing plants for semi-shady locations, no direct sunlight
  • Be sure to shade the bottom 30-50 cm of the plant
  • Clematis is one of the poisonous plants

Plants for alkaline soils

A pH value above 7.5 is referred to as basic soil. Few plants prefer an alkaline soil value. In addition to plants that prefer basic soils, there are those that also tolerate basic substrates.

ornamental plants

laburnum

  • Thrives well on slightly acidic to strongly alkaline soils (6.0-8.0)
  • Also accepts alkaline to slightly acidic
  • Mix regular garden soil with compost and sand
  • Pay attention to a sunny location
  • Flowers and seeds poisonous to humans and animals

Summer lilac (Buddleja davidii)

  • Not too difficult, sandy to loamy, calcareous subsoil
  • Acidic to strongly alkaline
  • Warm, sunny, shady to partially shaded places
  • Sensitive to frost when young
  • All parts of the plant are poisonous

frequently asked Questions

How important is soil pH for plants?

This value plays an important role in nutrient activity. An incorrect soil value significantly restricts plant growth. If it is too high, the nutrient absorption of phosphate and other trace elements is reduced. A value that is too low indicates that the soil is too acidic and the activity of microorganisms is reduced.

Is there a way to change this value?

If the value is too low, you can temporarily increase it by adding lime. Coniferous compost or peat can be incorporated to lower it.

How can you measure pH?

The easiest way to measure it is with appropriate test strips from the hardware store. The actual value can then be read from a color scale. The soil samples should be taken from different places.

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Garden maintenance