Autumn gardening - Rock gardens

Autumn is the major time of the year for a rock garden overhaul. Any fallen leaves need to be removed and the stems of rampant plants must be cut back - don't delay this because once the rockery is overrun by weeds and/or ends up completely swamped by one or two alpines that have run amok, you have no choice but to tear the whole planting up and begin again. Invasive plants, especially those in the vinca and ranunculus families, require close watching or they will spread rapidly, destroying the appearance of your rock garden, and actually killing neighbouring plants. If you have a plant that seems to be getting away from you, autumn is the time to either prune the plant, propagate the new growth, or remove it from the garden entirely.

This is also the time to divide your plants. As a rule of thumb, when perennials such as Armeria, Lavender and Iris need to be divided, they have no middle growth and look paler and less tall than they did last year, and may have smaller flowers too. Generally you should divide them in two or more and replant the outer sections, as the middle is likely to be the oldest and most warn out part of the plant.

Resettling your perennials gives you a chance to think about where you want to plant your spring flowering Anemones, Crocus, Snowdrops, Winter Aconite, and Daffodils, which should all be planted now.

Alpine troughs and other containers rely totally on you for water and their needs depend on the heat, the size of the container and the material it is made from. Don't cease to water in autumn but make sure you use the subsoil test - push your finger a couple of inches under the grave to see if the earth there feels wet or dry. As soon as plants slow down their growth, you can slow your watering to send them into dormancy.

Rock garden photograph by Xerones, used under a creative commons attribution licence