Thompson & Morgan

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Sunflower 'Mongolian Giant'

Helianthus annuus

Hardy Annual

 Customer Rating

Fun to grow, producing flower heads up to 45cm (18in) across with individual seeds up to 3½cm (1½in) long. As well as producing large yellow flower heads, Sunflower Mongolian Giant will be the envy of your neighbours as it grows up to 420cm (14ft) tall.

Culinary note: Some parts of these flowers are edible. Try toasting the seed kernels for a healthy snack. For more details about edible flowers click here.

Companion planting: Try growing sunflowers with chives to deter aphids.

Useful links:

Companion Planting

Ideal For:
cottage gardens, wildlife gardens, specimen plant
Flowering Period:
July, August, September
Sowing Months:
March, April, May
full sun
    • 1 packet (10 sunflower seeds)

    • Despatch: Within 1 days
    • £2.39
Sow seeds March to May. Sow seeds thinly, 12mm (½in) deep in drills 45cm (18in) apart in well cultivated soil raked to a fine tilth or direct into small containers. Germination takes around 21 days. For earlier flowering: Sow indoors, individually in 7.5cm (3in) pots at 20-25C (68-77F). When well grown, gradually acclimatise to outdoor conditions before planting out after all risk of frost has passed.

When large enough to handle, thin to 45cm (18in) apart.

It is wise to provide these tall stems with some added support as they grow.

Seeds and garden supplies will normally be delivered within the time period stated against each product as detailed above.

Despatch: Within 24 hours applies to orders placed online from Sunday to Thursday. Orders placed online on Friday or Saturday will be despatched on Monday. Please note that for Bank Holiday weekends, orders placed Friday to Sunday will be despatched on Tuesday.

Plants, bulbs, corms, tubers, shrubs, trees, potatoes etc are delivered at the appropriate time for planting and will be stated on the product page or in your order acknowledgement page and email.

Orders for packets of seed incur a P&P charge of £1.95.
Orders which include any other products will incur a P&P charge of £4.95.
Where an order includes both packets of seeds and other products a maximum P&P charge of £6.90 will apply - regardless of the number of items ordered.

Please see our Delivery / P&P page for further details and details of any surcharges that may apply to certain destinations.

  1. So so.

    By Jay Cantebrigge 31-08-2016

    Ten seeds and only 2 plants grew. 100's of seeds harvested but they all turned hollow so are not viable for planting again. What's the point of sunflower's if you can't harvest and replant?! Achieved only 8ft and 6 ft from the 2 plants that did grow.


    Thank you for your review. I am sorry to learn of your disappointment with your purchase. At your earliest convenience please contact our Customer Care Department at, one of our agents will be more than happy to look into this further for you.

  2. Update

    By Peter Humphrey 23-08-2012

    Despite the awful weather this year all the seeds germinated but they are not as tall as last year only eight feet and the flower heads not as large.Even so they are imposing flowers and the bees love them!

  3. Flowers not as large

    By Peter Humphrey 22-08-2011

    Full germination and plants were a variety of heights ,the shortest being 3 meters the tallest almost 6 meters I used a nearby conifer as a post to tie the stem to. A great source of interest to my neighbours young lad. I have already bought the seeds for next year. I will try for larger flowers next year .

  4. Will not germinate!

    By Timothy Peters 10-05-2011

    I have had no success at all trying to grow these! Seed compost, mutli-purpose compost, garden soil, in a propagator, on the windowsill, outside - I've tried every combination but not a single seed has germinated. Also, as an experiment I planted some ordinary sunflower seeds from a packet of bird food and they started growing within a couple of weeks! Very disappointing, to say the least.

  5. Mongolian Giant - germination

    By Simon Bartlett 22-10-2010

    I grew these seeds this year and had no difficulty with germination.

  6. Germination.

    By Rex Berry 23-09-2010

    This variety proved very difficult to germinate and grow on in a greenhouse. When they did germinate they were often distorted seedlings. I bought three packets and hoped that, as a new variety, that, this year, you might give more detailed advice on germination and growing on. I'm afraid that Unwins "seeds for kids" Sunflowers did very much better! I'll give "Mongolian" one more try!

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