Soil improvement

Nearly all exotic plants require well drained soil. By this we mean that water when applied can quickly drain away from the base of the plant. For exotics from dry areas the ground should be gritty and as porous as a seive! This is valid for Yuccas, Agaves and Catcusses, for example.

Plants which grow on sloping ground in nature will only survive our winters if the roots aren't soaking in stagnant water. But also near hardy plants such as Phormium, which often grow in swampy ground in nature, can only survive with us in well drained soil.

Which type of soild does your garden have?

Compress a handful in your hand. If you could turn it into a pot you have clay or loam soil. If it's crumbly, then the structures fine for these types of plant. If it doesn't feel like clay but is nevertheless sticky, then it will need attention. Treat these difficult soils by mixing compost and/or potting soil with them.