The big border bellflowers can reach, in some cases, to well over 1m tall, but the carpeting kinds do well to top 30cm. However, being small and spreading, they take on a different role, filling space at ground level. These are used on rock gardens but also find other places to grow, notably on walls in some cases, and can look great in gaps in paving. These are small species adapted by evolution to survive in challenging mountain conditions.

The wall bellflower has been magnificent this year, with a great show of small purple-blue bells – so much so that it has covered itself with flowers, obscuring the foliage. It makes a close mat of small, rounded, dark-green leaves from which a covering of blue bell-shaped flowers arises in early summer. It is widely grown, especially in old town gardens.

This plant, Campanula muralis, comes from mountainous areas of Croatia. But it is at home where it is not too warm or too dry in summer. It is called wall bellflower because it is often seen growing on old stone walls, actually rooted into the wall, with questing stems finding their way in the walls to emerge further along.

Sometimes it grows at ground level, sometimes at the top of the wall, but very often it pops out from cracks and joints across the height of the wall. Although it can look like the bellflower has been cracking the plaster, this is not the case. It exploits existing weakness in the structure of a wall, such as loose mortar, bricks or plaster. Bellflower looks especially well in old brick walls too, the purple-blue colour contrasting with the red bricks.

The wall bellflower can be grown in a rock garden and looks well tumbling over low retaining walls, but it is a bit too vigorous for a small rock garden, tending to overpower small rock-garden plants, which are less robust and vigorous.

Even more vigorous is Campanula poscharskyana, which is widely grown in gardens, presumably passed around, but sold in garden centres too. It is a good plant for the base of a wall or a bed, where it can fill the ground layer. It produces long flowering shoots that trail over rocks, low walls and the soil surface. These shoots carry masses of open bell flowers and often they get into a tangle of early summer colour. As the flowers fade, the tangled top-growth can be cut away and a new, more tame, set of leaves and some late flowers are produced.

While the spreading habits of the bellflowers mentioned are a bit exuberant, some other small bellflowers are better behaved. A real gem is Campanula carpatica, native of the Carpathian Mountains. This forms a broad clump of foliage with masses of upward-facing broad, open bell flowers to around 30cm. It often covers its surface with blue-purple flowers. There are selections, such as ‘Jewel’, which is dark blue and compact. ‘Bressingham White’ has large white flowers and ‘Turbinata’ has pale lavender blue flowers.

This plant looks great when grown in a gravel area, making a low mound of flowers, or pretty green foliage when not in flower.

Smaller again is the little bellflower known as ‘fairy thimbles’, Campanula cochlearifolia. It is a low, creeping form with spreading rhizomes that send up shoots with tiny bell flowers. These are usually light blue, by contrast with the darker purple-blue colour of the others mentioned. Some are so pale that they have an attractive silvery appearance. This is a rock-garden species, less vigorous and neater in its habits. There are other alpine bellflowers, but they are more of special interest, while the ones mentioned are for general use. CL

Trim thyme and other herbs

Thyme and other herbs, such as sage, flower at this time of year and a lot of the plant’s growth goes into flowers and seed-heads. While flowering is pretty and the flowers can be left in place on plants that are grown as much for their ornamental value as for their kitchen use, it is a good idea to clip over the plants before, during or after flowering. Just clip off the flowers and a bit of the stem below using a hedge-clippers. It is a very quick little job to do and the plants respond with a flush of new growth of nice fresh herbs later in the season. Give a good soak of water if the weather is dry.

Fruit, vegetables and herbs

Plant out young winter cabbage and cauliflower varieties, if not already done. Sow quick-maturing vegetables, such as radish, lettuce, white turnips, pak choi, mizuna, spinach and rocket. Water potatoes and peas if there is dry weather. Use vegetables as soon as they are big enough.

Lawns

Grass growth has been good in recent weeks, with rain and some hot weather, when some lawns started to dry up. If growth is adequate, feeding is not necessary, but can be applied in a damp spell to encourage growth on poor lawns. Do not feed a wild-flower lawn. Trim lawn edges.

Trees, shrubs and roses

Young trees and shrubs, planted in the last year, might have signs of drought. If trees are not showing growth at the tips of the branches, they may be suffering. Prune shrub roses and ramblers that have finished flowering, removing shoots that have flowered and tying in new shoots.

Flowers

Bedding plants in pots and baskets are now in need of sufficient watering and feeding. Because the roots have now filled the pots, watering has become more critical. Feeding every two weeks is essential to keep the plants growing strongly now. Sow seeds of lupins, mallows and foxgloves.

Greenhouse and house plants

Continue watering and feeding greenhouse plants. Be certain to water plants in pots or growbags regularly. These can easily dry out. Train and side-shoot tomatoes and cucumbers. Take summer cuttings of fuchsia, magnolia, rose and clematis. Check for pests, as they can increase rapidly.