One of the great pleasures of gardening is finding plants that Mother Nature has sown for the gardener - those little free samples that crop up from time to time in the most unexpected places.

Jacob's ladder, Welsh poppies, red and white valerian, aquilegias ... there can be quite a list of free plants to be found, especially along the base of walls and steps, and in ground that is thin, stony and free from competition from more aggressive weeds.

To be able to benefit from these free gifts you have to be brave enough not to bury all the soil in thick mulch (if weed seeds can't get enough light to germinate then neither can flower seeds).

This works well if you have kept on top of weeding for several seasons beforehand, so most of the seeds that have fallen onto the soil are flower seeds and not weed seeds.

You also have to be able to spot the difference between a germinating seedling that you want to keep and a weed seedling that needs to be removed as soon as possible.

This takes a bit of practise - many is the time I have hoed through a patch of seedlings only to decide later that they were something I wanted to keep.

The bigger plants around about a patch of seedlings are often a clue as to their identity.

Lenten lilies, Helleborus orientalis, frequently germinate around the base of parent plants, as do erythroniums and martagon lilies.

In places where annuals such as poached egg plant, love-in-a-mist or Californian poppies have been sown in previous years, free seedlings will often germinate in the following years.

It's also worth looking in neighbours' gardens to see what may have seeded from over the fence.

Tree seedlings often appear in the spring and summer following a good autumn.

This year we have hundreds of beech seedlings coming up beneath the trees and along the edges of shrub beds at Brockhole.

A few years back it was oaks that had a bumper year - we are still digging oak seedlings out of the centre of shrubs, where they have escaped attention for a while and managed to put down a strong taproot.

Sycamore and ash seem to germinate well every year and there are generally a few seedlings of berberis, cotoneaster and holly to be found about the place.

Where tree seedlings germinate in places that are difficult to plant up, because the ground is steep or the soil is thin and rocky, we weed carefully around them, wrap them in a rabbit or deer guard, and leave them to grow on.

A tree that has germinated naturally will often grow twice as fast as one that the gardeners have planted, especially in its early years.

Jobs for the gardener this week:

_ Now that bedding plants and half-hardy perennials are all planted out, this is a good time to clean out the greenhouse (if it's not already full of tomato plants).

_ Summer prune wisterias to encourage next year's flowers.

Shorten long side shoots to three or four buds, and tie in any strong leaders.

_ Mulch runner beans with a thick dressing of compost or farmyard manure, up to two feet on either side of each row, to feed the plants and keep the roots cool and moist.