If there’s one gardening ritual that truly marks the beginning of spring, it is surely seed-sowing. In the case of most gardeners, the kind that we reach for at this time of year is typically that of fast-growing but short-lived annual species that complete the cycle of germination, growth and fruiting or flowering within just a few months before dying off with the first harsh frosts of autumn. Examples include many different kinds of vegetables as well as countless types of flowering annuals typically used for creating colourful summer displays.
Perennials, by comparison, rarely get a look-in, which is odd when you consider that for almost the same amount of faff, effort and expenditure, you’re getting plants that will endure for years rather than mere months. Not only will they endure, most will naturally bulk up over time to the point where – like the horticultural version of the loaves and the fishes – large established clumps can then be easily divided to give yet more plants for your garden or to give away to friends. Most of these perennial species are also far better equipped to withstand weather extremes, an increasingly useful attribute given climate change.
Which kinds to grow? Examples of garden-worthy perennials that can be raised from seed sown under cover in spring include different species of verbena, a versatile genus known for its pretty, pollinator-friendly flowers and its easy ability to add an airy, contemporary touch to any planting scheme. Best known is the enduringly popular Verbena bonariensis, a perennial species with tall, slender flower stems topped with tight clusters of pollinator-friendly, indigo-purple blooms.
Once established in a garden, this obliging plant will also happily self-seed about the place. Less well known is its equally elegant, ornamental cousin, Verbena hastata, commonly known as blue vervain. Floriferous and long-flowering, both species bloom throughout the summer and early autumn months. These graceful, hardy perennials need a position in a well-drained, not overly-rich soil in full sun.
The same is true of the ultra-versatile, fast-growing, mat-forming plant known as yarrow (Achillea millefolium), another highly decorative, pollinator-friendly perennial that can be easily raised from seed sown under cover at this time of year. Modern seed strains such as Achillea “Summer Berries” and “Summer Pastels” have revolutionised this decorative, long-flowering species in terms of the wide range of colours now available to gardeners. Ultra-versatile in the garden where it works as brilliantly in a traditional cottage garden-style border as it does in contemporary prairie-style planting, yarrow is also brilliant as a cut flower, acting as the perfect “filler” in a home-grown bouquet of colourful summer blooms.
Geraniums
The mainstay of countless planting schemes, hardy perennial geraniums (the true geraniums rather than the half-hardy Pelargonium species commonly known by the same name) also provide months of colour as well as acting as useful, weed-suppressing ground cover. Many different types can be raised from seed sown in spring to give generous quantities of young plants to quickly and affordably fill a new border.
A vast genus that includes a huge range of species, examples of garden-worthy perennial geraniums (or cranesbills as they’re also called) that can be raised from seed sown under cover at this time of year include: the resilient, semi-evergreen, shade-loving Geranium macrorrhizum; the sun-loving, easy-to-grow Geranium Orchid Blue, which forms neat hummocks of foliage covered with a multitude of saucer-shaped blue flowers in summer; and Geranium Purple Haze, a new, long-flowering strain with handsome, dark foliage and plentiful violet flowers that is happy to grow in sun or light shade.
Yet another colourful mainstay of many Irish flower gardens is the perennial known as avens (Geum). Two classic varieties that have comfortably stood the test of time and can be raised from seed sown under cover at this time of year are the scarlet-flowered Geum chiloense "Mrs Bradshaw" and Geum "Lady Stratheden", which is prized for its jaunty, egg-yolk yellow flowers. Both are enduring favourites of the well-known Dublin gardener Helen Dillon – a mark of horticultural excellence if ever there was one – who has grown them for decades.
Obliging, versatile, long-flowering (especially if you shear off the flower stems soon after they fade) and exceptionally long-lived, these reliable, hardy and easy-to-grow perennials form low, semi-evergreen mounds of foliage from which the slender-stemmed flowers emerge in late spring/early summer. Best in a moist but well-drained soil in full sun, these add a hot sizzle of brilliant colour to the front of a border and are also useful as cut flowers.
For something a little more understated but equally undemanding, sow seed of the hardy perennial known as Tellima grandiflora, an elegant woodland species that forms low hummocks of scalloped, semi-evergreen leaves from which slender stems of lime-green flowers emerge in late spring/early summer. Tolerant of a wide range of growing conditions from full sun and a free-draining soil to a damp, shady spot, this hard-working, super-hardy perennial will even cope with the extreme challenges of dry shade.
Globe thistle
Examples of other perennials that can be raised from spring-sown seed and are worthy of a place in any Irish garden include: the globe thistle (Echinops ritro). a sun-loving species with silver-blue, spiky, globe-shaped flowers that appear in late summer; heuchera, a genus prized for its handsome foliage and dainty flower spires; many different species of the spring-flowering columbine (Aquilegia); and different species of damp-loving, shade-tolerant astilbe, whose feathery flower plumes appear in summer.
Others include many different kinds of campanula, or bellflowers as they’re commonly known, from the low-growing, shade-loving, mat-forming Campanula carpatica or Carpathian bellflower to loftier kinds such as Campanula lactiflora, a tall species suited to the back of a sunny border; various species of Echinacea, the sun-loving genus prized for its brilliantly colourful, bee-friendly, daisy-shaped flowers; and ornamental species of hyssop (Agastache), a large genus of fast-growing perennials with liquorice-scented foliage that includes the award-winning Agastache hybrida “Astello Indigo”, a variety that will flower in the first year from spring-sown seed, producing its bee-friendly, indigo-blue flower spikes throughout the summer months.
For best results when it comes to sowing seed of any of the above, it is generally best (but not essential) to use a heated propagator. Along with a good-quality seed compost, what is essential is to follow the instructions on the seed packet, something that almost all of us gardeners are guilty of occasionally neglecting.
For example, seed of some species mentioned above needs light to germinate (examples include verbena, agastache, campanula and astilbe ), so should be surface-sown, gently pressing the seed on to the compost before covering it with just the lightest sprinkle of vermiculite, compost or sharp grit. Others may need to be tucked in a fridge or left outside in cool conditions for a little while to trigger germination. Once the seedlings have produced their first set of true leaves, it is important to quickly prick them out into modules or cell trays and keep them in a bright, cool,but frost-free spot in preparation for hardening them off in late spring and then moving them outdoors.
Finally, bear in mind that patience is always a virtue when it comes to propagating perennials from seed as they are typically slower to germinate than fast-growing annuals. But the wait is most definitely worth it.
Recommended seed suppliers of a wide range of ornamental perennial species include seedaholic.com and jelitto.com and all good garden centres.
This Week in the Garden
Rhubarb is a hungry, thirsty plant that needs a humus-rich, moisture-retentive but well-drained soil in full sun or light shade to really flourish. To keep it in good shape and encourage the generous production of its edible stems, now is a good time of year to mulch around the base of the plant with a 5-7cm deep layer of well-rotted manure or garden compost, taking care to keep it away from direct contact with any emerging stems. This will also help to protect its root system during times of drought.
As temperatures begin to rise over the coming weeks, slugs and snails will start becoming active. Protect emerging herbaceous plants, young seedling and transplants from the damage that they cause by practicing good garden hygiene, hoeing soil to expose any buried slug eggs to hungry birds and bright sunshine and regularly checking the base of pots and containers for slugs or snails that might be using them as a convenient place to hide.
Especially vulnerable plants may need the added protection of slug traps or slug pellets. If you’re using the latter, choose a brand that uses the organically-acceptable ferrous phosphate as its active ingredient rather than metaldehyde, which is dangerous for garden wildlife as well as family pets.
