The trees are found at Caerhays Castle Gardens, Trebah Garden, Tregothnan, Trewidden, Trewithen and The Lost Gardens of Heligan.
And this year, representatives from The Great Gardens have been invited to Downing Street to present a bouquet of magnolias along with Cornish MPs to celebrate the arrival of spring.
"The moment Cornish Magnolias flower, spring has arrived in England and we are delighted that this year No10 Downing Street is to acknowledge the arrival of spring in this way," commented Charles Williams, chairman of the Great Gardens of Cornwall.
"Cornwall's magnolias are multi-prize winning and truly stunning. This year the magnolias are particularly early and they are a sight not to be missed. We encourage all those interested in seeing gardens in full bloom to come down and see The Great Gardens of Cornwall."
"Cornwall enjoys a very early Spring - nearly a month ahead of the rest of the UK," said Iain Davies, head of gardens and estate at Heligan.
"The Great Gardens of Cornwall are stunning at any time of year, but one of the very best times to visit Cornish spring gardens is when Cornish Magnolias are in full bloom during the early part of the season".
In 2015, the first flowering Magnolia campbellii was recorded on 21 January, more than a full month before spring was announced in England on 3 March. (Spring has previously been declared on 19 February in 2013 and 3 March in 2014.)
With this year's unseasonably warm weather, the champion Magnolia trees were all eagerly monitored using bloomometers to see when they would be in full flower.
Williams – whose family has kept a diary of daily happenings in the Caerhays gardens since 1897 - added: "I can say with great certainty that this is a uniquely early magnolia season. We saw our first flowering magnolia, (a hybrid of M. mollicomata and M. Campbellii) on January 3. In 2010 or 2011 we had a magnolia flower on the table in very late January but this beats all known or conceivable records by about a month. Quite staggering."
It was Toby Ashworth, proprietor of The Nare Hotel, who introduced the concept of Cornwall's Spring Story to promote, monitor and announce the arrival of Cornwall's early Spring. Ashworth harboured a strong belief that his hotel guests were missing out on the best of Cornwall's spring by visiting in May, when the most splendid sight of all – the flowering of the magnolias – occurred much earlier in February and March each year.