"God made a mistake when he didn't make me an artist," she declares, stretching her arms out joyfully towards her slice of horticultural heaven. "I feel this is like my canvas and my flowers are my paints and my colours. That is my raison d'etre."
Her sense of the dramatic has filtered into La Petite Vallee, her private garden, a five-minute drive south of St Peter Port, which is part of a new RHS tour featuring visits to both public and private gardens in Guernsey and its smaller neighbour, Sark, which spans just a mile wide by a mile long.
In summer at La Petite Vallee, great fronds of soft purple wisteria drip from its woody framework attached to the house. Jennifer's personal Garden of Eden evolves endlessly as you explore, revealing a cornucopia of planting, from the traditional to the exotic.
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Jennifer is able to grow such an eclectic mix, largely because Guernsey – and the neighbouring Channel Islands off the Normandy coast – has such a temperate climate.
Just an hour's flight away, the islands are said to be the sunniest location in the British Isles, claiming more then 2,000 hours of sunshine per year with virtually no frost.
It's no surprise then, that Guernsey is a hotbed of horticultural production and our tour host, the smartly attired king of clematis Raymond Evison, 28-times Chelsea Gold Medal winner, is testament to that.
He's a celebrity among gardening enthusiasts and locals alike, and his nursery produces two million clematis a year, which are exported worldwide to destinations as diverse as China and Japan.
A genial gentleman who works tirelessly to promote horticulture in Guernsey, Raymond gives us a tour of his 8.5 acre nursery on the east coast. As we walk through a network of glasshouses, he explains his specialism in growing compact types which produce blooms not just at the top of the plant but all the way up the stem.
Some of the palm-sized flowers are double and blousy, others delicately striped, in every shade from deep purple to cool white.
It's fascinating both for novices and experts alike, as we are shown how the trial clematis are graded and why some plants don't make the shop floor.
Beginners should not be intimidated by his horticultural celebrity - Raymond is so approachable, not fazed by answering the most basic 'How do I grow?' questions, to more complex conundrums about propagation, cross-pollination and genus.
It's a pleasure just to be able to chat to the man whose plants we have undoubtedly all come across in a garden centre at one time or another.
Yet there are blooms all over the 24 square miles of Guernsey, including more than 1,000 window boxes, hanging baskets and other planters in the capital St Peter Port alone, adding a colourful stamp to this pretty town's cobbled streets and picture postcard marina. That's before you find an array of flora and fauna in the island's historic Victorian Candie Gardens, once part of a private estate.
The tour, which allows a maximum of 28 people, has been designed with three different types of garden lover in mind, explains Susie Brand of the RHS.
"We have people who just like pretty gardens and aren't interested in the Latin names of plants, or the details of how they are grown; enthusiastic amateurs who regularly go on garden-themed holidays, and specialist lovers with particular interests in botanical elements."
Partners who aren't interested can always explore the many idyllic beaches, coves, cycle paths and coastal walks the island has to offer.
I embark on a cliff-side trail along the south coast, a windy diversion where it's easy to admire the rocky coastline and the Pea Stacks, a group of pink-tinged granite jagged outcrops at Moulin Huet Bay, which inspired Renoir to paint a series of pictures when he visited the island in 1883.
As we walk along a segment of the signposted coastal path - you can walk around the whole island, but it's 40 miles, so planning is required - we see pint-size white sea campion, clusters of pale yellow Alexanders (horse parsley) and inhale the scent of wild garlic, also known as three-cornered leek. In summer, the banks are splashed with pink and purple wild orchids, pink foxgloves and an array of other wildflowers.
Back on the official RHS route, garden guide Pierre, a ruddy-faced, bearded volunteer who doubles up as Santa for the children at Christmas, welcomes us into Saumarez Park Victorian Walled Kitchen Garden in the west of the island, still a work in progress, which he has been involved in for 10 years.
Pierre is a mine of information on the history, cultivation and future prospects for the garden, and its impressive greenhouse in which heritage tomatoes and other traditional plants are grown.
While records are scant, it is believed the walled garden was built in mid-Victorian times and volunteers aim to replicate the methods used – and plants grown – in that era. In rectangular beds there are all manner of edibles, from Guernsey chives to Ishikura, a type of spring onion.
More than 300 varieties of fruit and vegetables are grown here, which were all recorded pre-1900. "It's a living museum," Pierre enthuses.
I step back in time again on the second leg of the tour in Sark, part of the Bailiwick of Guernsey with its own set of laws and its own parliament. An hour-long ferry journey from Guernsey, It has only 600 residents, no cars and the only vehicles are tractors, bikes or a horse and carriage.
Choosing the latter, a 15-minute journey to Stocks Hotel takes us past a small grocery store, described as the 'Iceland of Sark', visitor centre, post office, school, playing field and vineyard. There's one doctor on the island and his emergency response vehicle is a tractor.
In a place where the postman also mends washing machines, the small community needs to be – and is – resourceful.
The hotel has its own permaculture garden, using low-input sustainable agricultural methods, and fresh seasonal produce - including rhubarb, raspberries, asparagus, celeriac and sorrel - is served to guests. Resident chickens provide the breakfast eggs and it's hard to believe that just four years ago, this was a bare field where horses grazed.
Later, we walk to the horticultural jewel in Sark's crown, La Seigneurie Gardens, set between flower-strewn granite walls, mature woodland, towers and battlements of one of the most historic houses in Sark, which dates back to 1675.
Its riot of summer roses, fragrant lavender and climbing clematis is a sight to behold, made possible by the wealthy Seigneurs, or titular rulers, who presided from the early 19th century, and now maintained by La Seigneurie Gardens Trust.
I feel happily lost in time on these two floral islands with their own laws, their own quirky ways and their tremendous community spirit. They have surely sown the seeds of success.
Hannah Stephenson from the Press Association was a guest of RHS Garden Holidays (www.rhsgardenholidays.com, 020 3735 1855), the specialist travel division of the Royal Horticultural Society, operated in partnership with Brightwater Holidays.
A five-day Private Gardens of Guernsey and Sark holiday costs from Â£1,195pp, departing June 1 and September 21, 2017. Price includes flights from London Gatwick to Guernsey, return ferry crossings from Guernsey to Sark, four nights' dinner, bed and breakfast, three nights at La Barbarie Hotel and one night at Stocks Hotel, visits to selected private gardens and the services of a professional tour manager.
For more information on Guernsey, go to www.visitguernsey.com