Question 1

Why do my tomatoes have black patches on the bottom?

Accepted Answer

That is **blossom end rot** — a sunken, leathery, dark brown or black patch on the base of the fruit, opposite the stem. It is not a disease and not a pest, and no spray will fix it.

The cause is a **localised calcium shortage in the developing fruit**. Calcium is essential for building cell walls, and where it is insufficient the cells at the fruit's growing end collapse.

The important point is that the soil usually contains plenty of calcium. The problem is almost always **delivery, not supply**. Calcium travels up the plant dissolved in water, so anything that interrupts water movement stops it reaching the fruit — even while the plant looks healthy.

The usual causes are therefore about watering:

**Irregular watering.** Letting plants dry out then soaking them is the most common trigger, which is why container and growbag tomatoes suffer far more than plants in open ground.

**High temperatures**, which increase transpiration through the leaves and divert water away from fruit.

**Excess nitrogen**, which drives rapid leafy growth that competes with fruit for calcium.

**Root damage**, from hoeing too close or from transplanting.

**Very acidic soil** can genuinely limit availability, which is worth checking if the plants are in the ground.

The fix is consistent watering — little and often rather than flooding after drought — plus mulching to hold moisture, using a high-potash tomato feed rather than a high-nitrogen one, and avoiding disturbing roots.

Affected fruit will not recover and should be removed so the plant does not continue investing in it. The rest of the truss is usually unaffected once watering is corrected.

Peppers, courgettes and aubergines get it too.

Question 2

Why are my tomatoes splitting?

Accepted Answer

Splitting is caused by uneven growth rate, which almost always traces back to inconsistent water. The skin sets at a certain size; if the flesh inside then expands faster than the skin can stretch,

Question 3

Why do my houseplant leaves have brown crispy tips?

Accepted Answer

Brown, dry tips are a water-balance problem in the broadest sense: the leaf edges are the furthest point from the roots, so they are the first tissue to be sacrificed when water delivery falls short

Question 4

Why does my fruit tree crop heavily one year and not the next?

Accepted Answer

It is biennial bearing — a self-reinforcing cycle in which a heavy crop in one year prevents flower bud formation for the next, producing alternating years of glut and almost nothing. The mechanism.

Question 5

Why does an overwatered plant look exactly like a thirsty one?

Accepted Answer

Because both end in the same place: the roots cannot take up water. The plant wilts for the same immediate reason in both cases, which is why the symptom is genuinely ambiguous and why so many

Question 6

What do the NPK numbers on fertiliser mean?

Accepted Answer

They are the percentages by weight of the three nutrients plants need in the largest quantities: nitrogen (N), phosphorus (P) and potassium (K), always in that order. A fertiliser labelled 10-5-5

Question 7

How do plant diseases spread?

Accepted Answer

Through a small number of routes, and knowing which one a given disease uses tells you exactly which intervention will work — most garden disease advice fails because it addresses the wrong route.

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