There’s a small patch in the allotment – around 2 metre squared – which I’ve somewhat neglected to date. In the spring it’s a sea of blue when the bluebells flower, and in the summer a large comfrey plant rises, attracting hundreds of bees. Other than that, and a few well established ferns, it’s a bit of dead zone. My initial instinct was to keep the bluebells in situ, but after doing some research into the Spanish invaders, I’ve changed my stance. Apparently, the Spanish invaders crossbreed easily with our native blue bells to create a fertile hybrid – that’s a problem for our native plants because over time it will dilute their unique characteristics. One day we may have no native bluebells left!
On that note, I’ve spent the last couple of weeks digging up the bulbs and now I’m embarking on a transformational project to turn the area into a small rockery. With very little experience in this department, I thought I’d share some of the key information that I’ve discovered about how to go about it:
What should I plant in my rock garden?
Ideal plants for rock gardens include alpines, sedum, low growing perennials (such as wallflowers and forget-me-nots), heathers, herbs and lichens. Alpines originate from high altitude regions and so they appreciate good drainage and high light levels. Here’s a list of recommendations from the RHS about ideal plants to put in your rockery:
- Campanula ‘Birch Hybrid’ AGM
- Crocus kotschyanus AGM
- Penstemon pinifolius AGM
- Sempervivum arachnoideum AGM
- Sedum ‘Bertram Anderson’ AGM
When should I build a rock garden?
Autumn and winter are the best months to construct features because summer flowering has ended and there are fewer jobs to do. However, in terms of planting you rockery, save this for spring when there are more plants available. Plants can then establish themselves for a growing season before the challenge and enemy of rock plants – winter wet – arrives.
How to build a rock garden
Aim to use an open position away from overhanging trees or tree roots, where plants will receive sun for the greater part of the day. Choose a position with good drainage and avoid frost pockets if possible. Choose local stone which will be in keeping with your surroundings and try to get it in a range of sizes so as to construct a natural looking outcrop. Ensure that the area is weed-free, by hand weeding or using herbicide.
Placing the stone
- Select large stones to act as ‘keystones’. Position the larger of these first and place the remaining ones so that the strata look natural.
- Use a spade to dig out hollows to set the stone into.
- Aim for a naturalistic look when setting the rock in place. The rocks should tilt backwards, with the strata running the same way.
- Use weed-free top soil for the top layer of the rock garden, working it underneath and between the stones to set them firmly in place. Soil-based potting media such as John Innes No1 with added grit (up to 30% by volume) are weed, pest and disease free
- Bury the stones up to a third of their depth, firming them in place.
Planting the rock garden
Water the plants and place them in position while still in their pots. Allow for the plants’ height and spread when fully grown. Remove the plant from the pot, tease out the roots slightly and remove any weeds from the surface of the compost. Make sure the plants are planted firmly in the compost mix and are top-dressed with gravel or grit.
Here’s a few pictures of rock gardens that I’ve found particularly inspiring. For now I need to get on with the heavy rock work…