Prefers acidic soil
below pH 6.0 · 1 in the encyclopedia
Soil pH
Soil pH — what it affects, and when to bother.
pH is one of the more over-discussed topics in gardening. It genuinely matters, but not because plants dislike acidity or alkalinity in itself. It matters because pH controls which nutrients the soil will actually release.
Why pH matters
Nutrients in soil are only available to roots within certain pH ranges. Push the soil too far in either direction and nutrients that are physically present become locked up and unavailable — so a plant can show a deficiency in soil that contains plenty of what it needs.
Most vegetables sit comfortably between slightly acidic and neutral, which is why a great many gardens never need to think about pH at all. It becomes worth investigating when plants underperform for no obvious reason, or when a specific crop repeatedly struggles while its neighbours do fine.
pH preferences across the encyclopedia
Grouped by the range recorded for each crop. Most plants fall into the middle band, which is why a broadly neutral bed suits nearly everything.
Slightly acidic to neutral
pH 5.5 to 7.0 · 123 in the encyclopedia
Tomato, Capsicum, Chilli Pepper, Eggplant, Cucumber, Zucchini, Pumpkin, Corn, Beans, Broad Bean, Carrot, Beetroot, Radish, Onion
Tolerates alkaline soil
above pH 7.2 · 83 in the encyclopedia
Peas, Snow Pea, Spinach, Kale, Cabbage, Sunflower, Nasturtium, Lavender, Bok Choy, Brussels Sprouts, Kohlrabi, Agastache, Alyssum, Chamomile, Annual
These are preferences, not hard limits. Most crops tolerate a wider range than their ideal, particularly where soil is otherwise healthy.
Before you change anything
Test rather than assume
A cheap test kit is worth more than any guess based on what grows locally. pH also varies across a garden, so test the bed you are actually worried about rather than one sample for everything.
Change slowly
Soil pH shifts gradually and over-correcting is harder to undo than the original problem. Small adjustments across a season are safer than trying to fix it in one go.
Organic matter helps regardless
Compost tends to buffer soil towards the middle of the range and improves nutrient availability at the same time. It is usually the better first move than a targeted pH amendment.
When it is probably not pH
Uneven watering
Symptoms often blamed on soil — poor growth, dropped flowers, split fruit — are more commonly caused by irregular watering. Rule that out first, since it costs nothing.
Too little sun
A crop in insufficient light will underperform whatever the soil chemistry. Check sun hours across a full day before reaching for a test kit.
Same family, same bed
Repeated plantings of one family build up pest and disease pressure that looks like a soil problem — see the crop rotation guide.
Containers are different
Potting mix comes with a pH set by the manufacturer and drifts over time as you water and feed. Replacing mix is easier than adjusting it — see the small space guide.
Check the crop first
Each entry in the plant encyclopedia records its preferred pH range.
Record what you did
pH amendments act slowly, over months. Without a note of what was applied and when, it is impossible to tell whether it worked.
FAQ
Common questions from home gardeners.
What pH do most vegetables want?
Most sit comfortably between slightly acidic and neutral, roughly pH 6.0 to 7.0. Within that band the majority of nutrients remain available, which is why many gardens never need to adjust pH at all.
Do I need to test my soil pH?
Not as a matter of routine. It is worth testing when plants underperform without an obvious cause, or when one crop repeatedly struggles while others in the same bed do well. A cheap kit is sufficient for a home garden.
How do I raise or lower soil pH?
Garden lime is the usual way to raise pH; sulphur or acidic organic matter to lower it. Both act slowly and are easy to overdo, so small adjustments across a season are safer than a single large application.
Can pH be wrong in raised beds?
Yes. Imported soil or mix arrives with its own pH, which may not match what you expect, and it drifts over time with watering and feeding. Raised beds are worth testing separately from ground soil.
Is pH the reason my plants are struggling?
Usually not. Irregular watering, insufficient sun and repeated plantings of the same family are all more common causes. Rule those out first, since they are cheaper and faster to address.
Does compost fix pH?
Compost tends to buffer soil towards the middle of the range rather than dramatically shifting it, and it improves nutrient availability at the same time. It is generally the better first step.
Turn garden notes into a living plan.
Create a free account to save your garden layout, personal planting calendar, water and fertiliser schedules, seed inventory and harvest logs.
Create Free AccountUse Plotera like an app from your home screen.