Soaking up the rays from nature's flowering giants

It’s easy take your sunflowers to new heights – then sit back and enjoy their golden splendour

THEIR HUGE golden flowers have been lighting up gardens and allotments all over the country this month, where they can be found like an army of lofty giants standing guard over carefully tended vegetable plots. The tallest ones have names such as Skyscraper, American Giant, Mammoth Russian, Green Goliath and Kong, and have stout stems that are at least twice the height of a grown man. Some have solitary flowers that are the size of dinner plates or bigger, while others, like the variety being grown in the OPW’s walled kitchen garden (1,200 plants) are branching or “multi-stemmed”, with several smaller flowers per plant. Yes, it’s sunflower season in the walled kitchen garden, set in the grounds of the Phoenix Park Visitor Centre, and what a colourful sight it is.

“This year, we deliberately chose a variety of sunflower called Soraya that doesn’t get too tall, because we didn’t want the plants to screen off distant views of the garden,” explains OPW gardener Meeda Downey.

“Also, you have to take more care of the very tall-growing varieties, which can get damaged or even broken by strong winds. The taller they get, the more chance there is of them getting damaged, so we weren’t aiming to break any records. Even with the shorter variety that we’re growing, a few flower stems have snapped or bent over in the last couple of weeks.”

But while the OPW gardeners aren’t trying to grow their sunflowers to competition standard, plenty of others are. According to the wonderful website of the European Giant Vegetable Growers Association (egvga.webs.com), the present world record for the tallest sunflower stands at 7.76m (25ft 5in) and was grown by Martien Heijms of the Netherlands in 1986, while the world record for the largest sunflower, a whopping 82cm in diameter (32.25in), has been held since 1983 by a Canadian woman called Emily Martin. There’s even a record for the most flowers produced on a single plant – 837 – held by Melvin Hemker of the USA since 2001.

So how do you grow a giant sunflower? These monsters of the plant world are annuals, meaning that fresh seed must be sown each spring if you want the huge golden daisy-like flowers to appear in your garden come summertime. Serious competitors begin by sourcing their seed from a proven record-breaking variety. Try PP World Record Seeds (pandpseed.com) for varieties such as Norm Craven 99 (tall), Multi-head Hemker (many flowers), Greystripe (big flower) or Mammoth Russian-Diane’s Strain (big flower). The Mayo-based seed suppliers Seedaholic (seedaholic.com) sell Kong (tall) as well as many other interesting varieties, while Thompson Morgan stock Russian Giant (tall).

Remember also that sunflower seeds need heat (60-65°F/10-13°C) and space to germinate properly, which is why Meeda and fellow OPW gardener Brian sowed them into individual pots (7.5cm diameter) in the nearby heated glasshouse back in late April, before planting them out in late May, after all risk of frost had passed.

The young plants went into well-prepared, weed-free soil that had been heavily manured the previous autumn before being rotovated in spring. “We planted them in a sunny, protected spot and into slightly raised ridges, because sunflowers hate cold, wet soil,” explains Meeda. “Then we left about 30cm (1ft) between each plant and about 75cm (2.5ft) between the ridges, and also added some of the granular fertiliser OSMO to the soil. Slug pellets (the organically approved Ferramol) are a good idea at that stage also, in case of damage. Brian then gave the plants a couple of liquid feeds during the summer as sunflowers are very greedy feeders.”

Greedier again will be any potentially record-breaking sunflowers, but competitive gardeners should still beware of overfeeding the young plants. The garden writer and Chelsea Flower show judge Graham Rice (grahamrice.com) advises using a high-nitrogen liquid feed to begin with, before changing to a balanced or high-potash feed to strengthen the stems. Stake the plants as they begin to grow skywards, pinching out any side shoots if your ultimate goal is height. Keep them well-watered (a mulch can be useful at this stage) and then watch out for saboteurs, for it appears that breaking sunflower records can sometimes be a dirty business.

In Britain (I can’t find any records for Ireland), it looks likely that the longstanding “tallest sunflower” record (23ft 6.5in, established by F Kelland of Exeter in 1976) will finally be toppled this summer by seven-year-old Charlie Townshend, whose sunflower was just 15cm (6 inches) short of establishing a new British record when it was last measured earlier this month. And who knows, perhaps there’ll be an equivalent record-breaker in Ireland this year also.

Less competitive gardeners, of course, will be happy to just admire their sunflowers and marvel both at how well they suppress weeds (sunflowers’ roots release a chemical that inhibits their growth) and how supremely attractive they are to such a wide range of insect and bird life. In the OPW’s walled Victorian garden, the sunflowers are covered in bumblebees, honeybees, wasps and hoverflies who are gorging themselves on the nectar- and pollen-rich flower. Later on, the gardeners will leave the flowers as food for the local bird population, who will feast on the ripe seeds which are rich in protein and unsaturated oils.

You may, however, wish to harvest the seeds for yourself, in which case you’ll need to have grown a variety that produces grey- or white-striped seed (the black-seeded types are best for oil or birdseed). To harvest seed, Seedaholic seed suppliers suggest that you “cut the heads off when they begin to yellow at the back and hang them upside down in a dry location away from rodents and birds. Once dry, rub the seeds off and soak overnight in 4 litres of water with one cup of salt in it. Dry in a 250°F oven for four to five hours and store in an airtight container.”

Whether you harvest seed or not, the flowers are an excellent way of attracting pollinating insects into the vegetable garden.

In fact, so attractive are sunflowers to bees and other pollinators that in 2008, phenologists at San Francisco State University launched The Great Sunflower Project (greatsunflower.org), inviting gardeners in the US and Canada to record how many bees visited the sunflowers in their garden over a given period of time. The aim is to map bee activity according to the data recorded, but particularly in relation to the bee’s role as an urban pollinator (just like the bees in the OPW’s walled garden, which are vital to its fruit and vegetable production).

There’s even a handy bee quiz on the website, which gives hints on how to tell a bee from a wasp or a fly (bees are generally hairier, carry “loads” of pollen, and don’t hover). Given the popularity of the sunflower in Ireland, a similar study in this country should be eminently possible, and would make for very interesting reading.

As long, that is, as we don’t all grow sunflower varieties that grow to such lofty heights that a ladder would be required to see exactly what insect-life was feeding on the flowers.

If that’s a worry, grow the dwarf sunflower Irish Eyes instead, which is available from Suttons Seeds and grows to a neat 45cm (18in) high. You won’t win any prizes, but at least you’ll have a great excuse to indulge in a bit of blatant patriotism.

• The OPW's Victorian walled kitchen garden is in the grounds of the Phoenix Park Visitor Centre, beside the Phoenix Park Café and Ashtown Castle. The gardens are open daily from 10am to 4pm

• Next week, Urban Farmer will give an update on the pumpkin harvest in the walled garden.

• Fionnuala Fallon is a garden designer and writer