YOU can buy an identical copy of a book either cheaply online, or from an oak shelf in a historic bookshop. Sources of plants are equally varied, with the complication that plants are living, non-uniform, and come in different sizes and phases of growth. With plants, it definitely helps to see what you are buying - and smell and touch, come to that.

I have been plant shopping in two different contexts, and I can recommend both as the focus of a great day out. The first, during the unseasonably warm spring weather, was at a nursery in the rolling countryside north of Bath, Special Plants. The owner, Derry Watkins, was botanising on Crete under, I learnt via Twitter, leaden skies. She seemed to be beaming all the sunshine home. The plants, propagated at the nursery, were coming alive and shouting "Buy me!"

In this situation, you need advice in order to make sensible choices for your own plot. This was on hand in the form of good signage - "plants for shade", and so on; and helpful labelling - "Matthiola perennis 'Alba', the most fragrant plant in my garden", "Diascia personata, tall but self-supporting. Pink flowers all summer. Hardy."

More important than that were the cheerful and knowledgeable staff, who asked about my garden, then made informed suggestions, and steered me gently away from impulse buys. During the summer, Derry and her architect husband's garden is open on certain days. It is sculpted from the landscape, and a living lecture on the concept of "right plant, right place".

There were no aids to restraint at the Columbia Road flower market, in Bethnal Green. I arrived by overground at Hoxton, and walked from there, encountering more and more people clutching large plants to their chests: a lemon tree here, a startlingly blue hydrangea there. And trendy young urban types holding large bunches of flowers. It certainly lifted the spirits.

The market opens at 8 a.m., and that is the time to go if you don't like crowds. It closes at 3 p.m., and some prices are reduced in the last hour or so. There is plenty of East End banter: "I'm not sellin' 'em, I'm givin 'em away," one vendor said, referring to trays of fuchsias.

It is easy to get carried away in the sea of blooms and bodies. But it felt fun, and horticulture can be a bit snooty sometimes. You had to look hard to find a Latin name, and most of the plants will have been grown indoors, on the Continent, in perfectly controlled environments; so they might sulk for a bit.

But the signs for cords, rhodoes, osteos, or other abbreviations, made it very accessible. There were lovely containers on sale in the street's little shops; so a trip to Columbia Road could get novice gardeners started, and, if they make the odd mistake, so what? The plants were cheap, and definitely cheerful.

Special Plants is open daily, March to October. For information about garden open days, visit www.specialplants.net.

Columbia Road Flower Market is every Sunday: www.columbiaroad.info.