BEING out in the fresh air is one of the best bits of being a gardener.

The fresh air in Cumbria is especially clean and often moist, which means that we share our gardens with several forms of plant-life not generally recognised as garden plants.

These include the lichens, mosses and liverworts, all of which are worth a closer look through a magnifying glass in order to appreciate their true beauty. Lichens are composed of two separate organisms, a fungus and an alga, neither of which can survive without the other. The fungus absorbs starches and sugars from the algae, while the alga extracts water and minerals from the fungus.

Incredibly, there are around 20,000 different forms of lichen in the world. Some form thin skins on rocks and garden walls, in colours ranging from black through grey and green to bright yellow.

Others grow into dense, branching thickets on the twigs and branches of trees and shrubs, and these can cause concern to the gardener.

Lichens are occasionally so prolific that they can threaten to overwhelm a slow growing shrub or small tree. They can be carefully picked or rubbed off but, since the real problem is the slow growth of the host shrub, the best cure is to feed and mulch the shrub, improving its vigour and helping it to outgrow the lichen.

While mosses can look quite attractive growing in the cracks in paving, they can quickly take over in damp, shady areas, making paths and patios dangerously slippery in wet weather (I won't get started on the problems of moss in lawns maybe another day!).

Conventional weed killers will not kill mosses, but there are several proprietary paving cleaners now available in garden centres and ironmongers that will do the job. Some are more effective than others, so you may have to try a few before finding the one that best suits your conditions.

Liverworts are those flat, shiny, dark green growths that seem to appear quite spontaneously in stale compost on the top of plant-pots. They quickly cover the surface of the pot, excluding light and moisture from the rightful occupants, their fruiting bodies looking just like tiny, green cocktail umbrellas.

It's best to deter liverworts from colonising your plant-pots by potting up seedlings regularly and keeping the surface of pots pricked over with the pointy end of a label or any other convenient, sharp implement.

A thin layer of fine gravel on top of pots of seeds will prevent liverworts from getting a hold before the seeds have time to germinate.

Jobs for the week:

l Clip box and privet hedges, checking first to make sure there are no birds nesting in them.

l If there are no late frosts forecast, plant out summer bedding and put out hanging baskets from this week onwards.

l Sow runner beans, sweet corn and courgettes in the vegetable patch.