In every gardening year there are losses as well as gains, a minus for every few plus points. Our biggest loss this year has been the sumach tree (Rhus typhina) which grew outside the dining room window. In a thoughtless moment last winter we tipped a pile of logs at its base, meaning to come back and stack them properly later but never quite getting round to it.

The logs by themselves shouldn't have been a problem, but hanging in the branches of the tree were several bird feeders filled regularly with sunflower seeds. As the winter progressed there was a build up of sunflower husks in between the logs, which formed a thick, slimy blanket around the base of the trunk.

Trees, especially shallow rooted trees like beech, cherry and Rhus, do not like a change of level at their base. While it's well known that excavations around roots and removal of soil from a tree's base will be harmful, it's less well appreciated that adding material such as soil, thick layers of grass clippings or compost can be equally dangerous. The buried roots become deprived of oxygen and eventually die, causing die-back in the branches above or even (as in our case) the death of the whole tree.

To add insult to injury, the bark of a buried trunk may begin to rot, allowing the entry of pathogenic fungi and bacteria. Bad news for our tree.

On the plus side this year, a large number of plants have self-seeded themselves around the garden, popping up in the most unlikely places and in the most attractive combinations.

Our free' plants have included annuals such as purple and pink clary, Californian poppies, English marigolds, red nasturtiums, white and purple tobacco plants and the green-flowered Nicotiana langsdorfii.

Perennials that have seeded themselves into the borders include the blue grass, Elymus arenarius, marjoram, evening primrose and the purple-flowered drumstick primula, Primula denticulata. I found several small seedlings of Japanese maple beneath the parent tree, while a seedling of Rosa glauca is a special bonus as the parent plant is not even in our garden.

After carefully weeding out those coming up in inappropriate places, the annuals have been allowed to grow and flower where they germinated.

I have potted up the perennials for planting out later in the year, probably in spaces left by deceased annuals.

And the sumach? Well, there are suckers appearing nearby, one of which might be persuaded to grow into a replacement, and when the original tree is cleared out and the logs tidied away there will be space to plant something new.

Jobs for the gardener this week:

Summer prune apples and pears now that the new wood has had a chance to ripen. Cut back all long growths to three or four buds from the base; this will let in light to ripen the fruit and will encourage the formation of next year's fruit buds.

Clip back lavender bushes lightly to remove the old flower heads.

Take cuttings of hydrangeas; they root best if inserted singly in small pots, this minimises root disturbance when they are potted on.