Seeds: the inside story

January is the ideal time to start buying your seeds for the year ahead, writes RHS Chief Horticulturist Guy Barter. But where do they come from and how do you pick the right ones?

I love everything about seeds, and buying them is a high point of my gardening year. My dissertation was on seed-borne vegetable diseases, and I have closely followed the seed trade for many years, ever since I was involved in cauliflower breeding back in the 1980s. Here are some of the fascinating facts and top tips I've learned over the years:

Where do seeds come from?

Seed retailers rarely grow seeds themselves. Instead they buy their modern cultivars from breeding companies; and older cultivars from wholesalers and smaller-scale producers. 

British summers are often too wet and short for reliable seed production – most seed comes from countries with more suitable climates. Manually harvested crops such as cucumbers and tomatoes, are often produced in low-wage countries such as Kenya and China. New Zealand is a key producer of crops gathered with a combine harvester, including carrots and peas.

Old versus new

Vegetable gardeners are very fortunate in having plenty of choice. If you want modern breeding, clubroot-resistant brassicas and downy mildew-proof onions are recent examples: there is not much available to commercial growers that amateur gardeners cannot buy. Cheaper, older, non-Fhybrid cultivars are also available. Long established open-pollinated crops such as ‘Autumn King’ carrots and ‘Webbs Wonderful’ lettuces, are widely sold. Approved selections are grown to high standards by specialist growers, called ‘maintainers’. 

Choosing what to grow from this abundance is fun, and I love to try new introductions. Curiously 90% of gardeners buy the same seeds year after year, according to seed companies. This explains the persistence of outmoded cultivars such as 'Musselburgh' leeks or cauliflower ‘All-Year-Round’ – they will give a satisfactory crop but there are better cultivars.

Quality control – and a cautionary tale

Vegetable seeds must meet minimum purity and germination levels, so quality is assured. Only defined cultivars included on the National or EU lists can be legally sold, but the regulations also allow for the sale of non-commercial cultivars and ‘heirloom seeds’ maintained by dedicated ‘micro-suppliers’. 

Although seed growers generally raise seeds to be true to type, free of pests and diseases and with good germination and vigour, very occasionally things can go wrong.

In the summer of 2020, gardeners across the country reported harvesting bitter courgettes that caused unpleasant symptoms when eaten. Something must have gone wrong in a courgette seed raising field the previous year. The parent plants seem to have been accidentally pollinated with an off-type, possibly a gourd, producing progeny whose fruits were unusable.

Thankfully this is a rare occurence – and it does offer a reminder why some crops can't be reliably grown from seed saved at home. If you grow different varieties of squash, pumpkin, gourd, courgette and marrow in the same garden they will cross-pollinate. If you save seed from them, the resulting plants will produce fruit that is at best tasteless, and at worst harmful.

Pick of the crop

Independent RHS plant trials are a good place to start looking for alternative cultivars (I used to be in charge of the RHS trials field at Wisley too). Look for the RHS Award of Garden Merit (AGM) when buying seeds or download the RHS lists of recommended cultivars. Almost all trials reports are available to download free of charge on the RHS website.   


See also

Where to buy seeds

There are many mail order suppliers of vegetable seed. Here are a select few:

Thompson & Morgan 
Mr Fothergill’s
Kings Seeds
Johnsons Seeds
DT Brown
Suttons Seeds
Plants of Distinction
Real Seeds

Gardeners' calendar

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.