Maytime rus in urbe

Come into the garden, folk, for the black bat Cam has soared and many of us need a bit of floral escapism, no doubt shared quite equably with plenty of his supporters. Yesterday, in true pathetic-fallacy style, was grey and a little bit rainy, but 10 days ago the weeks of pure spring sunshine came to an end with an afternoon of exceptional clarity, which happened to coincide with my meeting old university friend Jo at the Chelsea Physic Garden. By Saturday, when three of us took a bracing walk across Richmond Park to the Isabella Plantation and back, the murk was beginning to take over, but the grey skies offset the lime greens of leafing oaks, birches and beeches rather well.

Never have I seen the Physic Garden so riotous with high-spring bloom, though I know that other profusion will take over in the weeks to come. Chief wonder was my favourite blossom, that of the Judas Tree, which thrives above a meadow of bluebells with the mulberry just coming into leaf in front of it.

Not noticed this before, though: that the blossom grows immediately on the trunk's offshoots, a weird and rather wonderful effect.

As I'd hoped, the lovely Pia, our good friend and graphic designer at the CPG, walked past our lunch table in the sunshine; I was intending to go to the office and ask for her. She's just helped to produce the new guide, divided into colour-banded sections each led by an illustration from Gerard's Herbal of 1597. There were plenty of facts I hadn't absorbed before, such as the precise details of how the garden survived - first and foremost by Sir Hans Sloane's ingenious Deed of Covenant whereby he rented the garden, part of the Manor of Chelsea which he bought in 1722, to - and I cannot put it better than the guidebook, so I quote - 'the Apothecaries who had trained him...in perpetuity for a peppercorn [how appropriate!] rent of £5 per year. The same rent is still paid to his descendants today'.

Sloane, by the way, came from Ireland as apprentice and later made his fortune by returning to London from Jamaica with the yields of two trees, Cinchona pubescens and Theobroma cacao - respectively quinine and drinking chocolate. A copy of his statue still stands in front of what you may just make out as the flowering handkerchief or ghost tree.

I also didn't realise how close the CPG came to closure in the 19th century, which also saw its biggest changes. I had no idea that the Pond Rockery, an island oddly surmounted by fly-eating pitcher plants, is a Grade II listed structure, probably the oldest of its kind in Europe, and incorporates black basalt used to ballast Joseph Banks's ship on his voyage to Iceland as well as clam shells which travelled from Tahiti on Captain Cook's Endeavour.

My main concern on previous visits before I finally renewed my membership was with the initially ugly new educational gardens constructed in the south east corner. Now that the plants growing up make them look less stark, I can sort of see the point, though I miss what was lost. Still, there's one curvy path left round the back of the Garden of Useful Plants which takes you under the Chinese Paulownia lilacina, in flower last week.

The other paths that used to lead you past tree and herbaceous peonies have gone, but the peony collection at the north end of the Dicotyledon order beds is fine and I was surprised to find so many specimens already in flower, providing pollen for the garden's bee population (I'm hoping there's enough honey from the hives this year - the vintage I tasted was supremely floral, second only to jars from the Asco valley in Corsica in my experience).

Adonis aestivalis, the red ranunculus, is a close relative to blue love-in-a-mist, but rather more startling: the colour really did stand out as in the photo.

Otherwise the most conspicuous colour in these order beds was the yellow of Ferula communis, which looks like a special type of fennel but isn't actually categorised as such. Interesting to read that Prometheus was supposed to have brought fire to man in its stalk, and the ancient name 'narthex' leads me to suppose that the stalk was also a wand for the Bacchae.

Time ran out as usual but I had time to pay a quick homage to the glasshouse of mostly scented pelargoniums, a staple of the Physic Garden for more than 300 years. This, I think, is 'Ardens'

while in Glasshouse 4 to the south Ageratum corymbosum from Mexico was in full spate.

I left with only the most exquisite of tiny sempervivums but the next day I cycled to Rassell's nursery and picked up, inter alia, a promising specimen of the peony 'Buckeye Belle'. And on Saturday we dropped in on the Petersham Nurseries on the way back from Richmond Park. Despite the threat of rain, which didn't materialise until the evening, we had a bracing walk through copses and meadows, with oak trees in various stage of leaf,

to the Isabella Plantation, which I think I can't have visited since I was a child. This secluded wonderland was established in the 1830s and enriched by 50 kurume azaleas introduced from Japan in the 1920s by plant collector Ernest Wilson, now part of the National Collection. Although our friend Tilly rages at how they've hacked it back, I still imagined myself in far eastern wilds and was amazed by the riot of azaleas and rhododendrons not far from the entrance

The three-tier effect is unique to this time of year, of having bright splashes of colour in the middle between unfurling fronds

and gunnera

and the lime-green trees above. There were still plenty of magic corners and glades, as in this one where a grand old beech is foil to a uniquely coloured rhodedendron,

here, where another handkerchief tree can be more clearly discerned

and here, where another huge rhodie is foreground to more tree-leafing,

while by the end of the central stream heathers are thriving.

Next stop: friend Deborah's garden 'rooms' in Lacock, which should be in their prime.