Garden for any length of time and you soon discover that it’s a skill which requires us to have one eye fixed beadily on the present and the other firmly on the future. An example is that group of plants known as hardy annuals, which can be sown either at this time of year or next spring, the all-important difference being that if we sow them now, we’re almost certainly guaranteed much bigger, better, longer-flowering, more floriferous plants next summer.
The magic and irreplaceable ingredient here is time. Allowed the luxury of it, these baby seedlings spend the cool, dark months of late autumn, winter and early spring developing their infant root systems below ground and their leafy structures above ground, giving them a huge head-start when it comes to bursting into active growth in early summer. This also makes them far more resilient to challenging growing conditions (for example, the cool, dry, windy springs of recent years), a great advantage given the increasingly unpredictable seasonal variations that are a symptom of climate change.
But wait a minute, I hear you say, surely these short-lived, floriferous fireworks of the garden won’t tolerate the average Irish winter? To which the answer is that yes, they absolutely will. Indeed, unlike half-hardy annuals (their more short-lived, far more hoity-toity, cold-sensitive cousins), hardy annuals will tolerate surprisingly low temperatures just so long as they’re given free-draining soil where their root systems won’t succumb to winter rot. For this reason, in wet gardens it’s best to overwinter the seedlings/ young transplants in containers, cell trays, root trainers or raised beds.
How to propagate them? Most gardening books will tell you that hardy annuals are best direct-sown into their final flowering positions in the garden or allotment rather than into seed trays or pots. But the reality is while this has its distinct advantages, it presents its own challenges in terms of protecting the young seedlings from pest attack or from being overwhelmed by vigorous weed growth. It also presumes that we’ll have suitable empty space available in our gardens at this time of year when the reality is that this is often not the case. For that reason, most hardy annuals are best sown into seed trays/ pots and then “pricked out” as young seedlings into modules/cell tray/root trainers for transplanting into the garden later this autumn or in spring.
That said, there are some kinds of hardy annuals that so deeply resent root disturbance that they must be direct-sown if they’re to perform well. One example is love-in-a-mist (Nigella), the oh-so-pretty flowering annual and cut flower known for its delicately beautiful blooms which typically come in shades of blue as well as white and pink. A plant that absolutely hates to be transplanted at any stage of growth, it’s best to broadcast the small, jet-black seed on to well-prepared, weed-free soil and then just barely cover it with the lightest dusting of soil as it needs light to germinate well.
Other species of flowering annuals have long, tapering root systems (rather like a carrot) that resent being transplanted unless this is carried out while they are very young. Examples include Ammi majus and Ammi visnaga; two tall, elegant umbellifers whose snowy-white flowers resemble a kind of refined version of cow parsley and are excellent for giving a contemporary, meadow-style feel to a flower bed or summer container. Another example is the opium poppy (Papaver somniferum), a hardy annual known for its ability to generously self-seed around the garden, with flowers that come in many beautiful shades and in double and single form. The sun-loving Californian poppy (Eschscholzia californica) is another hardy annual that resents being transplanted as does the many cultivated forms of the field poppy (Papaver rhoeas). So does larkspur or annual delphinium (Consolida ajacis) as it’s sometimes known.
If you don’t have space available in your garden at this time of year to direct-sow any of these plants, then it’s important to minimise disturbance to their sensitive root systems. The best way to do this is by sowing the seed into individual deep root-trainers for transplanting the young plants into their permanent positions in late autumn or in spring.
Other kinds of hardy summer-flowering annuals are also best grown in these kinds of deep root trainers as a way of protecting the seed and baby seedlings from pests. An example is sweet pea which, despite the traditional advice so often given to direct sow it into its permanent position in the garden, is very vulnerable to being eaten by rodents, slugs and birds at the seed and/or seedling stage. Instead, you’ll get far better results by pre-chitting the seed.
To do this, place it some wet kitchen paper, pop it into a small, lidded container and then put it in a cool room. Once the seeds show obvious signs of germination (typically within 7-10 days), they can be very gently transplanted into individual root trainers filled with a good quality seed compost. Bury each chitted seed about 2cm deep, taking great care not to damage its emerging root and stem, then water generously and place the root trainers somewhere outdoors, ideally on a garden table or bench.
It’s also a good idea to place a temporary layer of netting over them until your sweet pea seedlings have properly emerged and established to protect them from greedy rodents and birds. Unlike the other hardy annuals I’ve mentioned above, sweet pea doesn’t benefit from being sown in late summer/ early autumn. Instead hold off until October/early November when growing conditions are cooler and plant out into the garden in late March.
This brings me to another common mistake that gardeners often make when it comes to growing hardy annuals, which is to treat them too kindly by mollycoddling the young seedlings indoors. This is the very opposite of what they need and want, typically resulting in weak, leggy plants that are particularly prone to damage from pests and diseases. Instead it’s best to give them cool bright conditions just as soon as they’ve germinated by placing them either outdoors or in an unheated glasshouse, polytunnel or cold frame. The gardening version of tough love, this will give you much stronger, healthier, more resilient plants. Difficult to believe, I know, but don’t fret, they’re called “hardy” for a reason.
Five great hardy annuals to raise from seed sown in August and September
Ammi visnaga ‘Casablanca’: An early flowering variety of Queen Anne’s Lace with tall, very decorative white umbelliferous flowers that are loved by pollinators and are great for cutting. Pre-chill the seed in a fridge for a couple of weeks before sowing to boost germination rates.
Consolida ajacis: A tall, graceful hardy annual with slender spires of flowers in shades of blue, lavender and pink, its seed needs darkness and cold temperatures to germinate. For best results, pre-chit the seed by mixing it with damp sand or vermiculite and then placing it in a small freezer bag in the fridge for three to four weeks, removing it once you see signs of germination and then very gently transplanting the individual seeds into root trainers.
Nigella papillosa ‘Delft Blue’: One of the loveliest varieties of Love-in-a-a-Mist, its moody blue-purple and white flowers are followed by very decorative seedpods that are also gorgeous in a dried flower arrangement. Direct-sow shallowly as described above and thin seedlings to a spacing of 6cm-8cm.
Agrostemma githago ‘Bianca’ (white corncockle): A tall, beautiful, white-flowered form of corncockle, this hardy annual wild flower has become ultrafashionable in recent years. Best direct-sown, it can also be sown into root trainers for transplanting out into the garden in late autumn/ spring,
Linaria moroccana ‘Licilia series’ (annual toadflax): A dainty annual species of toadflax with slender spires of colourful pollinator-friendly flowers, this is a great hardy annual to direct-sow into a large container at this time of year for a very pretty display next summer. Make sure to sow very shallowly (the seeds need light for germination) and to keep the soil/compost damp until seedlings emerge.
Recommended Irish seed suppliers include all good Irish garden centres as well as specialist online suppliers such as Galway-based seedaholic.com while suppliers of root trainers include Cork-based fruithillfarm.com
This week in the garden
To help polytunnel crops to stay healthy and productive at this time of year, as growth slows and light and temperature levels start to dip, it’s important to be very vigilant in terms of good ventilation, adequate irrigation (but don’t overdo it), regular removal of dead, damaged or diseased plant material, and liquid feeding.
All of the above will pay rich dividends in terms of keeping your plants happy.
Of all the many different types of spring flowering bulbs, daffodils (narcissus) really appreciate being planted in early autumn (September) to allow the bulbs sufficient time to develop healthy, viable root systems. So do your best to get them in the ground sooner rather than later.
Dates for your diary
Sunday, August 28th (9.30am-5pm): Airfield Gardens, Dundrum, Co Dublin, the Irish Specialist Nursery Association is holding a plant fair with many members of the association in attendance selling herbaceous perennials, trees, shrubs and garden paraphernalia, see irishspecialistnurseriesassociation.com and airfield.ie for details
Tuesday, September 6th, Ballyknockan Farm, Castle Ellis, County Wexford Y21A526, the Irish Dahlia Society’s National Show will take place, admission free. To submit an entry, please contact Pat Thornton at firstname.lastname@example.org or Trevor Stevenson at email@example.com
Saturday, 10th — Sunday, September 25th, Mount Venus Nursery, Mutton Lane, Dublin 13 is holding its annual autumn plant sale with a wide variety of plants discounted down. See mountvenusnursery.com
Saturday, September 10th (9am — 5pm), Hall 6, RDS, Ballsbridge Dublin 4 (Anglesea road entrance): admission free, Mr Middleton’s annual Flower Bulb Open Day will take place with a huge selection of bulbs available including many new and unusual varieties. See mrmiddleton.com and rds.ie/getting-here for directions.