Basil Problems
Ocimum basilicum
Basil is one of the most rewarding herbs to grow at home — fast-growing, abundantly productive, and perfect for a sunny windowsill. Regular harvesting keeps it bushy and prevents bolting.
All Basil Problems
⚠ CriticalBasil — Downy Mildew on Basil
Yellow, angular patches appear on the upper surface of leaves, following the leaf veins, while a fuzzy grey-purple mould develops on the underside directly beneath the yellowed area. Affected leaves eventually turn brown and collapse.
⚠ CriticalBasil — Fusarium Wilt on Basil
One side of the plant wilts and yellows while the other side may still look healthy, often with dark streaking visible inside the stem when cut open. Affected plants decline steadily and rarely recover once symptoms are advanced.
⚠ ModerateBasil Leaves Turning Black
Leaves develop dark, blackened patches or turn black entirely, often appearing suddenly after a cold night or exposure to a chilly draft. Affected tissue feels limp and doesn't recover once blackened.
⚠ MinorBasil Bolting and Flowering Too Early
The plant sends up tall flower spikes earlier than expected, and leaf production slows as energy shifts toward flowering. Leaves harvested around this time often taste more bitter than usual.
⚠ MinorBasil — Leggy, Sparse Basil Stems
Stems grow tall and thin with wide gaps between leaf sets, giving the plant a sparse, straggly appearance rather than the bushy, full form expected of healthy basil.
⚠ MinorBasil — Yellowing Leaves on Basil
Leaves turn pale yellow, typically starting with older, lower foliage while new growth at the top stays green. Growth may also slow overall compared to expected vigour.
⚠ MinorBasil — Aphids on Basil Plants
Small clusters of soft-bodied insects gather on new growth and the underside of young leaves, often leaving behind sticky honeydew residue and causing mild curling of affected foliage.
⚠ ModerateBasil — Japanese Beetles Skeletonising Basil Leaves
Leaves develop a lace-like, skeletonised appearance as the soft tissue between veins is eaten away, leaving only the leaf's structural framework. Metallic green-and-copper beetles may be visible feeding directly on the plant.
⚠ ModerateBasil — Bacterial Leaf Spot on Basil
Small, dark, water-soaked spots appear on leaves, sometimes with a yellow halo, and may merge into larger irregular dead patches in humid conditions. Affected leaves can look tattered as tissue within the spots dries and falls away.
⚠ CriticalBasil — Root Rot and Wilting in Container Basil
The plant wilts and looks unwell despite consistently moist or wet soil. Roots, when checked, are brown, soft, and mushy rather than firm and pale, sometimes with a sour smell from the potting mix.
⚠ MinorBasil — Slow or Stalled Growth in Basil
The plant produces very few new leaves over an extended period and generally looks stalled rather than actively growing, despite otherwise appearing healthy and green.
⚠ ModerateBasil — Whiteflies on Basil
Tiny white, moth-like insects fly up in a small cloud when the plant is disturbed, and can be found clustered on the underside of leaves. Affected foliage may develop sticky honeydew residue and a general lack of vigour.
⚠ MinorBasil — Sunscald and Leaf Bleaching on Basil
Pale, bleached, or papery patches develop on leaves that were recently moved into much stronger direct sun than the plant was previously accustomed to, particularly after being hardened off too quickly.
Basil Care Guide
Light, watering, humidity, fertilising, repotting and propagation — everything you need to keep your Basil thriving.
Full care guide →See how growers fixed these problems
Browse real Basil grow diaries from the community — treatments, timelines, and results.
Browse community diaries →Common Basil Questions
Why is my basil turning black?
Yellow, angular patches appear on the upper surface of leaves, following the leaf veins, while a fuzzy grey-purple mould develops on the underside directly beneath the yellowed are… Read the full guide →
How do I stop basil from flowering?
One side of the plant wilts and yellows while the other side may still look healthy, often with dark streaking visible inside the stem when cut open. Affected plants decline steadi… Read the full guide →
How often should I harvest basil?
Leaves develop dark, blackened patches or turn black entirely, often appearing suddenly after a cold night or exposure to a chilly draft. Affected tissue feels limp and doesn't rec… Read the full guide →
Can I grow basil indoors in winter?
The plant sends up tall flower spikes earlier than expected, and leaf production slows as energy shifts toward flowering. Leaves harvested around this time often taste more bitter … Read the full guide →
