Understanding Apple Pollination Groups for Better Crops

Why a lone apple tree sulks

Every spring someone writes to me about the same disappointment: a handsome apple tree, smothered in blossom, that produces barely a handful of fruit. Nine times out of ten the tree is perfectly healthy. It simply has nobody to pollinate it. Apples are, with a few exceptions, self-sterile — the pollen of a variety cannot fertilise its own flowers, or those of another tree of the same variety. Every 'Cox's Orange Pippin' in the country is a clone, so two Coxes in neighbouring gardens are no help to one another at all.

What a tree needs is pollen from a different, compatible variety that flowers at the same time. Get that right and the same tree will suddenly crop heavily. Get it wrong — a 'Discovery' partnered with a late-flowering 'Court Pendu Plat' — and you will wait a long time for a decent harvest.

How the flowering groups work

To make this easy, apple varieties are sorted into flowering groups, usually numbered one to six. Group 1 blooms earliest, Group 6 latest, with roughly a week or so between each. The gap matters because apple blossom is only receptive for a few days, and pollen is only viable for a short window.

The practical rule is simple: choose a partner in the same group, or in the group immediately above or below. Groups overlap at the edges, so a Group 3 tree and a Group 4 tree usually flower together quite comfortably. Group 2 with Group 5 is a gamble that rarely pays off.

Bear in mind that your soil, shelter and local climate shift things. A warm, south-facing wall can push a tree a week or more ahead of the same variety in an exposed northern field. Late frosts can also wipe out early blossom entirely, which is why Group 1 and 2 varieties are best left to mild, sheltered sites.

A rough guide to the groups

• Group 1 (very early): 'Beauty of Bath', 'Irish Peach' and 'Keswick Codlin'. Lovely in the south-west, risky almost anywhere else.
• Group 2 (early): 'Grenadier', 'Egremont Russet' and 'Idared'.
• Group 3 (mid, the busiest group): 'Cox's Orange Pippin', 'Discovery', 'Worcester Pearmain', 'Sunset' and 'Katy', plus 'Bramley's Seedling' (see below).
• Group 4 (mid-late): 'Charles Ross', 'Ellison's Orange', 'Golden Delicious', 'Gala', 'Kidd's Orange Red', and the cider stalwarts 'Dabinett' and 'Yarlington Mill'.
• Group 5 (late): 'Newton Wonder', 'D'Arcy Spice', 'Cornish Gilliflower' and 'Edward VII'.
• Group 6 (very late): 'Court Pendu Plat' and 'Crawley Beauty', along with a few old winter keepers. They dodge the frost but need a long season to ripen.

Triploids, crab apples and choosing partners

Some varieties — 'Bramley's Seedling', 'Blenheim Orange', 'Ribston Pippin' and 'Ashmead's Kernel' among them — are triploids. Their pollen is largely sterile, so a triploid cannot pollinate anything else. It still needs pollinating itself, which means it requires a diploid partner nearby. If you plant a Bramley and a Cox together, the Cox will pollinate the Bramley, but the Bramley gives nothing back — so the Cox needs a third variety, such as 'Sunset' or 'Egremont Russet', to crop well.

Where space is tight, a crab apple is the finest insurance you can plant. 'Golden Hornet', 'John Downie' and 'Evereste' flower over a long period, produce abundant pollen and are happy to pollinate almost any apple nearby. A few varieties are described as partially self-fertile — 'Katy', 'Falstaff' and 'Charles Ross' are the usual names — but even these crop noticeably better with company.

Dessert, culinary and cider apples all cross-pollinate freely. There is no rule that says a cooker needs another cooker; a 'Michelin' is perfectly happy with pollen from a 'Worcester Pearmain'.

Weather, bees and a helping hand

Pollination is a partnership with insects, and insects are fussy. Honeybees generally stay in the hive below about 14°C, while bumblebees will work from around 10°C or even lower — another good reason to encourage them with early-flowering comfrey and dead nettles nearby. Cold wind, heavy rain and strong gusts all keep pollinators grounded exactly when your blossom needs them most.

If your tree is a wall-trained espalier or a single cordon with no obvious partner, you can pollinate by hand. Collect pollen on a soft brush or a rabbit's tail tied to a cane, working gently from flower to flower in the middle of a dry, mild morning. Move between two varieties and label nothing — the bees will finish the job.

Watch the forecast too. A single night of sharp frost during full bloom can destroy the crop, so if a cold snap is due, drape fleece over wall-trained trees or run a little water into the soil beforehand, which helps slightly.

Putting it together in a real orchard

Aim for pollinators within about 20 to 30 metres of each other, and ideally 15 metres or less. Bees tend to work in straight lines along a row, so in a larger planting the traditional approach is to alternate varieties or plant every third tree as a pollinator such as a crab apple. In a garden, a trio of 'Cox', 'Sunset' and a crab apple will cover each other beautifully.

If you have room for only one tree, choose a family tree with two or three varieties grafted onto the same trunk — they flower together by design — or simply beg a neighbour within a few gardens' distance to plant something compatible. Orchards have always been communal things. Get the flowering groups right, and the trees will do the rest, year after year, with very little asked of you.