Perennials for alkaline soil
This section features the best perennial plants for alkaline soils, including Achillea, Astilbe, Brunnera, Campanula, Geraniums, Hostas, Phlox and Salvia. Alkaline or “sweet” soils are those with a pH of more than 7. This is commonly caused by a high content of limestone or chalk, which may also result in the soil being free draining and lower in nutrients than neutral, loamy soils. Thankfully, there are still plenty of wonderful flowering perennials to choose from for alkaline soils. Achillea are reliable, hardy, long-flowering herbaceous perennials producing an abundance of flowers in a range of bright and pastel colours from summer through autumn. Astilbe plants are attractive herbaceous perennials producing tall, fluffy flower plumes above frilly foliage from late spring through the summer. Campanula are cheerful perennials with nodding, bell-shaped flower heads, typically in shades of lavender, light blue, pink and white, held high on tall stems above toothed, mid-green leaves. They bloom heaviest from late spring to early summer but blooms can last for much longer.
Hardy geraniums are reliable stalwarts of the flower garden, producing saucer-shaped flowers, often with distinctive veins, renowned for adding colour and beauty to the garden from late summer through early autumn, just as many other flowers are starting to fade. Hostas are popular and distinctive, shade-loving perennials with large, lush tropical foliage and high spikes of summer flower spikes in shades of mauve through to white. Phlox are slender, showy, long-blooming perennials producing beautiful clouds of billowy star-shaped blooms from July right through to September with flowers available in almost every colour on the spectrum, including rare shades of blue. Last but not least, perennial salvias, also known as sage, are mainstays of the mid-summer flower garden, producing beautiful, tightly packed tubular flowers with a split lower petal in a wide range of colours spanning bright red, electric blue and lemon yellow from summer through autumn.