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Spring vs autumn lawn fertiliser: which month, which bag

Updated: October 2026

It is late September, the summer bottle is still a third full, and the lawn looks as if it needs a feed. Spring vs autumn lawn fertiliser is that choice. A high first number after August pushes soft growth into cold and disease. A 6-5-10 bag in April is the other mistake. This page only settles the season for the seven saved listings. Full pack choice is on the [lawn fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/lawn-fertiliser). The figures are the saved listings and RHS month pages from 21 October 2026. This is not a turf trial.

It is late September, the summer bottle is still a third full, and the lawn looks as if it needs a feed. Spring vs autumn lawn fertiliser is that choice.

Our top picks

Miracle-Gro Miracle-Gro Complete 4 in 1, 360 m²

Best overall

Miracle-Gro Miracle-Gro Complete 4 in 1, 360 m²
8.7/10about £24.94
View offer
A1Lawn A1 autumn winter fertiliser, 10 kg

Alternative

A1Lawn A1 autumn winter fertiliser, 10 kg
8.9/10about £34.20
View offer
Miracle-Gro Miracle-Gro Fast Green 1 litre

Rank 3

Miracle-Gro Miracle-Gro Fast Green 1 litre
9.0/10about £11.70
View offer
On this page
  1. 1.What each number is doing in that month
  2. 2.When the growing-season packs in this set stop
  3. 3.When the 6-5-10 packs are the ones on the label
  4. 4.The lawn that should get neither

What each number is doing in that month

Nitrogen drives leaf. Phosphate (P2O5) and potash (K2O) are the other two marks. The RHS points high nitrogen at mid-spring and says not to continue it after August. Leftover summer feed is the wrong bottle in September. Here, 6-5-10 on A1 and both Miracle-Gro autumn boxes is the autumn pattern, not a timid spring feed and not a 3-12-12 from a trade calendar. The Complete bullets print no NPK. Fast Green’s 1:0:0 field is not one. The maker page declares 27-0-0 with iron (Miracle-Gro Fast Green). You do not have to feed in both seasons. Other checks are on the lawn fertiliser buying guide.

When the growing-season packs in this set stop

The Complete 4 in 1 bullets say established lawns, April to September, after frosts: the about £15 tub (B0G3PT35T9) and the about £24.94 bag (B0FZC3X2F1). September is inside that window. October is not. Fast Green’s Amazon file states no month. The maker page says March to September. A fast green-up does not make it an autumn feed. Shade does not cancel the stop date. The RHS allows an autumn feed, or a half-rate spring feed, for shaded grass (lawns in shade). Half rate is half the printed rate, in the months that pack allows, not a high-nitrogen spray in November.
Miracle-Gro Miracle-Gro Complete 4 in 1, 360 m²

Testsieger

Miracle-Gro Miracle-Gro Complete 4 in 1, 360 m²
8.7/10about £24.94
View offer

When the 6-5-10 packs are the ones on the label

Past August, if the lawn is poor rather than dry, open a listing with an autumn window. A1 (about £34.20) says autumn and winter, prints 6-5-10 and 35 g per square metre, and has 615 ratings. The 80 m² autumn box has burn notes in five ratings. The 360 m² bag prints 6-5-10, not the gram rate. The maker PDF does print 35 g (autumn 360 m² label). Two ratings are not a result. GreenCare prints no NPK. Rates are on how to apply lawn fertiliser.

The lawn that should get neither

A wildflower sward stays unfed. Brown grass after a dry August needs water, not a September dose. Do not work waterlogged, frosty, or very wet or very dry ground. A 6-5-10 on frozen soil is still the wrong day. Autumn hardening will not kill dandelions. By late October the Complete window has closed, so an autumn bag with no weed list is not a way to finish the weeds. Once the month fits a poor lawn, the job split is on best lawn fertiliser by job.

Common questions

Can I use the rest of a summer feed in October?
No. The RHS September lawn page says leftover summer feed is the wrong product. In this set, that means do not empty a Complete 4 in 1 tub, or a Fast Green bottle whose maker window ends in September, onto the lawn in October. Store it for the next April-to-September window if the label allows, or dispose of it as the label says. Switch only if you have an autumn pack and the lawn is poor enough to need it.
What is the difference between a high first number and 6-5-10?
A high first number, such as the maker’s 27-0-0 on Fast Green, is mostly nitrogen for leafy colour in the growing season. A 6-5-10, printed on A1 and both Miracle-Gro autumn boxes, keeps nitrogen lower and potash at 10. That is the autumn pattern in this comparison. It is not a diluted spring feed, and it is not the 3-12-12 ratio from unrelated trade examples.
Which listings in this set are for April to September?
The two Complete 4 in 1 products say so on the bullets: the 80 m² tub at about £15 and the 360 m² bag at about £24.94, both for established lawns after frosts. Fast Green’s Amazon bullets do not state a month. The maker page says March to September. None of those three is an autumn 6-5-10.
Which listings print an autumn window?
A1 says autumn and winter. Both Miracle-Gro autumn boxes say September, October or November. GreenCare says autumn and early winter. A1 and the two boxes print 6-5-10. GreenCare does not print an NPK. The 360 m² autumn bag has two ratings, and the 80 m² box has burn notes in five ratings.
Is Fast Green an autumn product because it greens in a day?
No. A fast colour change is what the hose-end reviews describe in a few days. The Amazon listing does not name an autumn month, and the maker page limits the spray to March to September with a high-nitrogen declaration. Green in a day is not the same job as a 6-5-10 before winter.
Do I have to feed in both seasons?
No. The RHS says most lawns need no feed, and an autumn feed only if the grass is poor. One season, or neither, is a normal outcome. Buying a spring tub and an autumn bag as a pair is optional, and only when each label matches a month when the lawn actually needs it.
What if the soil is frozen or soggy in October?
Leave it. The RHS October page says not to work a lawn that is waterlogged, frosty, or very wet or very dry. Wait for workable soil inside the autumn window, or wait until spring. Putting 6-5-10 on frozen ground does not store the benefit underground in any way these listings claim.

Related pages

Weed and feed or a plain fertiliser

Lawn fertiliser

Best lawn fertiliser UK: which pack fits your lawn

Lawn fertiliser UK: what to check before you buy it

How to apply lawn fertiliser without stripes or scorch

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are the saved amazon.co.uk figures for the seven listings, not a live crawl on 21 October 2026. A score is stars plus review count, not a turf trial. Iron in a fertiliser is not an approved moss killer. A pet-return line is only what the bullets print.

  1. RHS, lawn care in spring and summer (retrieved 21 October 2026)
  2. RHS, lawn care in autumn (retrieved 21 October 2026)
  3. RHS, lawns in September (retrieved 21 October 2026)
  4. RHS, dead patches in lawns (retrieved 21 October 2026)
  5. RHS, moss in lawns (retrieved 21 October 2026)
  6. Fertilisers Regulations 1991 (retrieved 21 October 2026)
  7. GOV.UK, manufacturing and marketing fertilisers (retrieved 21 October 2026)
  8. HSE, pesticides in the garden and home (retrieved 21 October 2026)