Merton Thornless blackberry variety

Rating [ 4.5 ]

Commercial thornless trailing variety with uniformed fruit and excellent aroma

Botanical designation

Rubus subgenus Rubus Watson 'Merton Thornless'

Variety denomination

Variety denomination - 'Merton Thornless'

Merton Thornless is the parent for

Merton Thornless is the parent for Smoothstem, Fantasia

Plants are

Plants are thornless

Bushes have

Bushes have trailing canes

Fruit weight is

Fruit weight is 4 g


Berries have a rounded shape

Fruiting habit

Fruiting habit - floricane fruiting (summer-bearing)

Flowering on floricanes starts in the

Flowering on floricanes starts in the second week of June

Ripening date (regular) -

Ripening date (regular) - second week of August

Productivity is

Productivity is 3 kg per plant

Cold hardiness is

Cold hardiness is excellent

Heat tolerance is

Heat tolerance is low

Country of origin

Country of origin - United Kingdom

Current status

Current status - obsolete or rarely used

Merton Thornless has been launched by John Innes Institute (United Kingdom) in 1941 year as first commercial mid-to-late season trailing thornless variety.
Fruits are produced on the previous year’s stems. The main distinctive feature of this variety were medium to large sized fruit and excellent blackberry flavor. Due to its compact growth (max. height is 2,5 m, but stem's length without cropping can achieve up to 7 m in length), this variety was an ideal for planting in small gardens and trials. Plants also demonstrate great yield in half shade or full sun. Merton Thornless has very high resistance to low temperatures (up to minus 26 C), but can be vulnerable to hard frosts on exposed sites.
Cropping season continues from mid August to mid September. Berries are 3-6 g in weight, have rounded or slightly elongated form and glossy black color. Yield is about 2-4 kg per plant, but can grow up to 6-8 kg, when using right cropping and fertilizer. A few strains of this variety exist with different flower colors, either white to pink.
Merton Thornless is still commercially grown in Iran and around the Caspian Sea region as it is highly adaptable, despite being a mid to late variety in colder Western climes. These warmer regions barely get 200 to 600 chill hours where winters are usually very warm. Merton Thornless is very popular in the UK, even though this variety is obsolete, also primarily used for its source of thornlessness in blackberry breeding.

Diseases resistance

What diseases is blackberry Merton Thornless resistant to?

Merton Thornless is resistant to most fungal diseases
Diseases susceptibility

What diseases is blackberry variety Merton Thornless vulnerable to?

No susceptibility to spicific pests or diseases has been observed for Merton Thornless
Useful Growing Guides

Useful Growing Guides:

Mary Carmen
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Reviews of the variety Merton Thornless

Review from [DAVE]

It starts to flower consistently from the 7th of June onwards due to its high GDH (growth degree hours) tested at the famous John Innes Institute in the England to be 18,900 hours. It's fruit size is on average 4g and can be 5g or more in good conditions. A few strains of it exist with different flower colours either white to pink. I grow a more pink flowering strain of it. All strains of it produce sterile seeds which if germinated will never produce viable fruit. Tip layer Merton Thornless only!
Merton Thornless blackberry plant appears to be the only blackberry of the thornless types to be totally resistant to wilt and root rot as well as other pathogens. Some info on Navaho Summerlong is that it is highly susceptible to root rot like its parent plant Loch Ness from which it's a hybrid cross as the other Navahos. BigandEarly has very high resistance to disease and viruses, but can like all blackberries die when waterlogged for long periods of time, unlike Merton which can regrow new canes from the crown and recover in time.

Review from [C. ROGERSON]

It's a delightful plant to grow, has a wonderful taste when ripe of the wild blackberry and can fruit anytime from early August onwards in a good summer giving a season of 6 weeks. Yields are moderate- about 3kg on average. It's okay to grow in a patio container and it gives a nice display of white flowers June.

Also it is very forgiving of any soil type and immensely disease resistant with good winter hardiness of minus 20 Celsius. Recommended for those with little space as the canes are short and stout and have moderate vigor. Pests tend leave it alone too! Ideal for both the novice gardener or expert alike.

Review from [D. GREEN]

I've grown reliable Merton Thornless for over two decades as it is great for blackberry and apple pie, but not fresh eating unless you get the hot summer. Time for a newer earlier fruiting desert cultivar. I will maybe go for an early fruiting blackberry Helen.

Review from [R. L.]

Merton Thornless is rather unique in that it is totally thornless and will never produce suckers nor its cuttings revert to thorns. It is very hardy and a good grower with moderate vigor - great for a large tub. The plant perse is highly self fertile, but its seeds are mostly sterile(won't produce fruits if grown from them), so don't sow them.
It will never suffer from frost as it flowers June onwards and has a relatively compact season of usually Mid Aug to end of Sept. I've picked crops of over 10 pounds in some years. It needs a good fertilizer to produce new canes, but even if it produces only one it will still load up with juicy fruit which are about as close to the wild taste as you will ever get.
Merton is only used for breeding new cultivars because of its stable thornless trait and its fruit went out of favour for U.S markets as they are quite soft so didnt ship too well. A true heritage plant from the famous John Innes Institute.
It is a superb cultivar for the home garden and unaffected by pests or disease still makes it a great choice for planting.

Review from [BERRY]

I have tried many of the above varieties over many years in an attempt to find one with a good wild flavour. Merton thornless has a fairly good flavour but hard pips and the various new and supermarket varieties are not very flavoursome. For me, the older very thorny Silvanberry is still the tastiest.

Review from [GUEST]

The older blackberry cultivars are the most disease and weather resistant. The newer thornless ones in my trials all have succumbed to rot despite good soil drainage. Merton Thornless has survived everything in my garden and keeps bouncing back each year to give a great crop of juicy blackberries mid Aug. Oregon Thornless is similar, but the fruits are quite smaller.

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