Admittedly, their previous visit was during the height of the Millennium Drought when the gardens were looking a bit shabby. However, in recent years our city's floral centrepiece has undergone a renaissance. A long-term water supply from Lake Burley Griffin has been secured, a knock-out Red Centre Garden created and an imaginative range of unique events introduced.

To try to prove to my disgruntled visitors that our national gardens are once again worthy of a visit, I set out on a solo quest on one of the hottest days this summer to spend a day exploring them.

It's a bit of a secret that for a modest fee you can hire a guide for a private tour of the gardens at a time of your choosing. So, although the gates don't open until 9am, to beat the predicted heat I meet Harley Dadswell, a volunteer guide, on the dot of 8am.

Dadswell looks a bit surprised to see me not only lathered from head to toe in suncream but also carrying a bulging daypack. "That's a lot of gear for a one-hour tour," Dadswell says. So I explain that our excursion is just the first leg of my planned nine-hour odyssey.

In our ramble around the gardens' central precinct, Dadswell bamboozles me with facts about our native plants. He says the gardens "have over 6300 species which represent around a third of Australia's native plants", and he also highlights many of the plants such as the quandong (Santalum acuminatum) which are showcased in the gardens' new Aboriginal Plant Use Trail.

However, most of our time is spent exploring the Rainforest Gully. It's hard to believe today, but this moist forest complete with towering palms, ferns and rainforest trees was developed from a naturally occurring dry gully which supported only scattered eucalypts, shrubs and grasses.

"The transformation of the gully began in the 1960s when the first rainforest plants were planted to represent rainforest types along the east coast of Australia, with Tasmanian rainforest at the lower end of the gully and mountain rainforest of northern Queensland at the upper end," Dadswell says. "If you follow the trail through the gully, you can effectively walk the entire east coast rainforests in 10 minutes!

"Not surprisingly this is a popular spot on a hot day. Due to the canopy closure it can be up to 10 degrees cooler in here at midday."

With the mercury already racing into the mid-20s, and forecast to hit 35, I'll need as many of these heat-busting tips as possible to make it to 5pm.

Once out of the rainforest we marvel at the acrobatics of a new holland honeyeater (Phylidonyris novaehollandiae) as it darts about among the plethora of banksia and grevillea. Then we glimpse an eastern spinebill (Acanthorhynchus tenuirostris). Relative to its size, this amazing little bird has the longest bill of any Australian honeyeater and, even better, it comes so close that I don't need to use my binoculars to appreciate its plumage.

What I really like about Dadswell's botanical expose is the way he links the plants to stories in our social history. Yarns like the walking stick palm (Linospadix monostachya), named because "they used to cut the stems and carve them into walking sticks for returned soldiers after World War I" and the nardoo fern (Marsilea drummondii) which may have contributed to the demise of Burke and Wills on their 1861 expedition.

"After their return to the Cooper, left to fend for themselves, the explorers finally found some nardoo and ate it," Dadswell says. "But they didn't realise that nardoo seed, if not correctly prepared, is toxic and robs the body of vitamin B1."

With Dadswell's tour of discovery coming to an end, it's time for a snack of my own. I keep well clear of the nardoo fern (you can't pick or eat anything growing at the gardens, poisonous or otherwise) and d make a beeline for Floresco – the gardens' cafe. After my morning's lesson in Flora 101, the choice is simple, it's got to be wattle seed pancakes.

As I farewell my erudite guide, he points out a vibrant purple flower on a small shrub near the cafe.

"That's the desert hibiscus (Alyogyre huegelii) from Western Australia." says Dadswell says. "Each flower only lasts a day or so."

Looking at the dazzling five-petalled flower, clearly in its prime, it's hard to imagine how it could wane so quickly.

Needing to work off my generous serve of pancakes, I grab my backpack and stride off with purpose. With more than 120 kilometres (yes, that many!) of track and dozens of intersections, this is like a choose-your-own-adventure. However, I don't get far before, captivated by the antics of the Gippsland water dragons darting around a pond, I stop at the Rock Garden. These curious critters, which grow up to one metre long, have tails which form two-thirds of their length. The tail is laterally compressed to act like an oar when swimming. Apparently this shutter-friendly population, arguably the most photographed in Australia, originates from a population in the Molonglo River. When it was dammed to create Lake Burley Griffin in the early 1960s, they moved upstream along Sullivan's Creek and across to the gardens.

Further on, at the Red Centre Garden where I keep looking up at Black Mountain Tower to remind myself that I'm not trekking through the harsh sand dunes of the Northern Territory, I get up close to he larger-than-life model of a Thorny Devil (Moloch horridus). The sign explains that it can drink just by standing in the rain, or from dew that settles on its body overnight, which runs down grooves between its scales and directly into its mouth. Amazing.

Having chalked up 16 kilometres on my pedometer, and parched from my desert sojourn, I heed Dadswell's advice to seek refuge from the heat in the rainforest. It's near perfect timing for the mist sprays which maintain optimal humidity levels for the plants have just started to fire up. I follow the mist as the jets sequentially come on, first at the top of the gully and ending in the Tasmanian section about an hour later. Divine! Thirsty, I even try the thorny devil trick but most of the water runs off my akubra rather than into the corners of my mouth.

While drying out, I tuck into my picnic lunch among 70 species of our country's favourite tree on aptly named Eucalypt Lawn. There will be more than 1000 people here this weekend for Summer Sounds, the gardens' live music series, but now I've got it to myself.

With the temperature still rising, I scurry past the desert hibiscus on the way to the cafe for an ice-cream, and as Dadswell had predicted, it's already looking a bit worse for wear. A bit like me.

Serendipitously, I walk past a sign pointing to the Jindii Eco Spa, which opened just under a year ago. One of its summer specials promises "a soothing and refreshing massage which evokes memories of escaping to the seaside". I need little persuading.

Turns out it's more than just a massage, it's a sensory extravaganza, complemented by the gardens' surroundings. Bianca, my therapist, welcomes me with a smoking coolamon ceremony and my treatment finishes with a cup of Yulu tea, a mix of lemon myrtle, wild lime and rosella, aniseed myrtle and davidson plum. Invigorating!

Outside the shadows are growing and the water dragons becoming more active. It's almost 5 o'clock. I make it to the main gates just as the ranger starts to close them. What a day. A decade ago the gardens were run down, bordering on a national embarrassment, but there's a real buzz and sense of expectation now.

There are even plans to establish an eco-lodge which I can't wait to open because one day isn't enough to explore our revamped national treasure. Who knows, maybe my interstate friends might even join me in being one of the first guests to book in.

Australian National Botanic Gardens: Clunies Ross St, Acton Open 10am-5pm daily. Visitor centre open 9.30am-4.30pm daily. Entry to the gardens is free, but there is paid parking $3 an hour. Private tours from $5 a person. More: Ph: 02 6250 9588 anbg.gov.au/gardens

Summer Sounds: Live music every Saturday and Sunday until February 7 (5.30pm-7.30pm). Food and drink stalls have everything from barista coffee, cold beer, ploughman's platters, wood fired-pizza and that essential ingredient for a perfect balmy summer night – handmade gelato ice-cream. Concert entry: $5 a person, $2 concession and kids under 12 free.

Plan ahead for: Delicious AfterDARK tours, an exquisite evening of fine wine, delicious food and by a ranger-guided night tour of the gardens, $75 a person. From 7pm Friday, February 12, and Friday, March 4 and March 11.

Did You Know? Water dragons can remain under water for up to two hours.

Jindii Eco Spa: In a quiet nook of the gardens, it offers a range of spa treatments using natural Australian botanic products. Gift certificates available. Ph: 02 62578777 or jindii.com.au

CONTACT TIM: Email: timtheyowieman@bigpond.com or Twitter: @TimYowie or write c/- The Canberra Times, 9 Pirie St, Fyshwick. You can see a selection of past columns here.

Clue: New suburb, lots of blackberries.

Degree of difficulty: Medium

Last week's photo resulted in a friendly family tussle between June McKenzie of Fisher and her son Ian of Weston. However, bragging rights ended up with June who pipped Ian to the post by correctly identifying last week's photo, as the fairy sign on Potato Point Road on the way into Potato Point, near Tuross Head. Janice Baker laments that "until recently there were a number of nearby trees decorated with all sorts of fairy paraphernalia, delighting many", which Liz Stergio says "were sadly removed by council who claimed they were a fire risk".

How to enter: Email your guess along with your name and address to timtheyowieman@bigpond.com. The first email sent after 10am, Saturday, January 30, 2016, with the correct answer wins a double pass to Dendy cinemas.