When to Fertilise, and When Not To

Feed the growth you want, when the plant can use it

Fertiliser applied at the wrong time is at best wasted and at worst harmful. The principle behind the timing is simple: nutrients are useful when a plant is actively growing and able to take them up, and a liability when it is not.

The general rule by season

Spring, as growth begins — the main application for most plants. Growth is starting, demand is rising, and the season ahead is long enough to use what you apply.

Through the growing season — light supplementary feeding for heavy feeders and anything in a container, where nutrients leach with every watering.

Late summer onward — stop. This is the timing error that causes real damage.

Winter — no.

Why late feeding is a problem

Nitrogen applied late in the season pushes a flush of soft new growth at exactly the point when a plant should be hardening off for winter. That growth does not have time to mature, and it is the first tissue damaged by frost.

On woody plants the damage can be significant, and it is entirely self-inflicted. Stop feeding trees, shrubs and perennials from late summer.

By plant type

Vegetables. Clemson HGIC provides crop-specific liming and fertilising guidance, and it is worth following because vegetables differ widely. Heavy feeders such as sweetcorn, tomatoes and brassicas want a side-dressing partway through the season; legumes fix their own nitrogen and want very little.

Established trees and shrubs. Most in reasonable soil never need feeding at all. A mature shrub growing normally in mulched ground is not waiting for fertiliser.

Containers. The exception to almost every rule. Nutrients wash out with each watering and the plant cannot forage beyond the pot, so regular dilute feeding through the growing season is genuinely necessary.

Lawns. Timing is regional and depends on whether the grass is cool- or warm-season. Follow local extension guidance rather than a generic calendar.

New plantings. Do not feed at planting. A plant that has lost roots cannot use the nutrients, and high nitrogen pushes top growth the damaged root system cannot support. Wait until it is visibly growing.

When not to fertilise at all

Without a soil test, if you are applying phosphorus. Many long-cultivated gardens already hold plenty, and Clemson warns that indiscriminate addition can be harmful where levels are high.

Into dry soil. Water first, or apply and water in. Fertiliser salts concentrated around dry roots cause the leaf-scorch symptom usually described as fertiliser burn.

To a struggling plant, as a diagnosis. Feeding is not a treatment for a plant that is failing from overwatering, poor light or root damage — and it frequently makes those worse.

The most useful habit

Little and often beats one heavy application, particularly for containers and for anything in sandy soil where nutrients leach quickly.

And measure. Doubling the rate does not double the growth; it raises the salt concentration around the roots, which is the mechanism behind most fertiliser damage in home gardens.