Professional gardening tips No.2 (Growing Annuals from Seed - Airy & Romantic)
08 May 2020
Growing Annuals from Seed - Airy and romantic annuals that act as fillers both in the garden and in flower arrangements
Written by Clare Foster
Photographs by Sabina Rüber
Some of the most useful annuals or biennials to raise from seed are those that can be used to plug temporary gaps in the flowerbed. Ethereal in nature, these soft, romantic plants can be woven like lace through a border, padding it out, ‘lifting’ the other plants and making the whole thing look fuller – the horticultural equivalent of Botox, perhaps. Because it is cheap to raise multiple plants from seed they can be used repeatedly, linking other more dominant plants and giving a sense of cohesion and connection – and, even better, many of these plants will self-seed, so that once you have introduced them to your garden they will return year after year.
Early on in the year it is the biennials that take centre stage, having germinated the previous year and already formed strong plants before flowering in their second spring. For early spring the humble forget-me-not is the easiest filler, used as a pretty foil for tulips and other spring bulbs, famously seen at Great Dixter where bold-coloured tulips such as ‘Ballerina’ or ‘Burgundy’ stand proud above an undulating layer of sky blue forget-me-nots. Many forms are available including white and pink varieties, but the best are the blues – Myosotis sylvatica ‘Blue Sylva’ has pretty sky-blue flowers with a yellow eye, while ‘Mon Amie Blue’ is a paler shade of blue. Another essential spring biennial is honesty, known for its silvery round seed pods. The best variety I know is Lunaria ‘Corfu Blue’ which is a bushier, more substantial plant than the wild form, with purple blue flowers. Plants will self-seed readily, forming clumps that have strong visual impact. Sweet rocket, Hesperis matronalis, flowers slightly later in May and June; again the white form works particularly well as a filler, its scented starry flowers floating in swathes like soft feather pillows. All these biennials are extremely easy to grow from seed sown direct into the border in late spring, and can also be sown in modular seed trays for transplanting later on – in fact the only problem you’re likely to have once they are established is the job of weeding out excess seedlings.
My favourite filler plants are the cow parsleys – Ammi majus, Ammi visnaga and Orlaya grandiflora – whose lacy flowers and ferny foliage look just as good in a vase on the kitchen table as they do in a border. Ammi majus has the most delicate blooms of the three, with small clusters of tiny white flowers exploding outwards on narrow stalks; look at the flower head upside down and marvel at the way nature has constructed it. The lesser-known A. visnaga has more densely clustered and domed flower heads and therefore offers slightly more visual interest from a distance. The cultivar ‘Green Mist’ has a greener tinge to its flowers, and looks wonderful with purple or blue larkspur. Last year I grew both ammis from seed sown under cover in early spring, but they will produce sturdier plants if you sow in trays or pots in September, overwintering the seedlings in a cold frame and planting out in late spring. They can also be sown direct in late spring for a later summer flowering. Both are easy to germinate and need little attention once in the ground.
Orlaya grandiflora has a trickier temperament, although its charming broderie anglaise flowers make its presence entirely worthwhile. Germination can be sporadic, so it is always best to sow under cover, either in September if you have a cool dry place to keep them over winter, or in early spring. Sowing two seeds to a cell in a modular tray is what grower Tamsin Lovatt recommends. I failed miserably with Orlaya last year, but was saved by Tamsin who supplied me with expertly grown seedlings that did well in the border once they got past the wettest part of the year. Another annual umbellifer is dill (Anethum graveolens), better known for its use in the kitchen but equally valuable for its acid-green flowers, which like ammi grow to about 90cm. For a slightly more robust version, try the florist’s dill, A. graveolens ‘Mariska’. With a similar colour note but looser, floppier lime-green flowers, Bupleurum rotundifolium ‘Grifithii’ is useful for filling gaps anywhere in the garden, slotting in naturally next to almost any other plant and excellent as a cut flower too, lasting for ages in a vase. It can be sown direct in late April or started off under glass either in the autumn or early spring.
Different in appearance from these umbellifers are what I call the butterfly plants, including gypsophila and Gaura lindheimeri, both of which produce a cloud-like profusion of pretty flowers that add a breezy lightness to a border. Gypsophila elegans ‘Covent Garden’ is delicate and lovely, with sprays of simple single white flowers on wiry stems. Easy to grow from seed, it can be sown direct into the ground in April or May. Gaura is actually a short-lived perennial but often treated as an annual as it can easily be lost in our cold winters, and in any case grows readily from seed. The cultivar ‘Whirling Butterflies’ describes the flowers admirably – pinky-white starry flowers with long anthers that flower on and on from early to late summer. ‘Siskiyou Pink’ has flowers of a darker rose-pink that wave in the breeze on graceful arching stems, and like ‘Whirling Butterflies’ grows to about 75cm. (G. lindheimeri itself is taller, growing to about 1.5m). Sow gaura seed under cover in autumn or early spring, but resist the temptation to plant it out too early. Keep potting it on until it reaches a good size and then use it to fill gaps that appear in that awkward middle-of-the-summer period when the profusion of early summer is over. My last butterfly plant is something quite unexpected: a larkspur. The annual forms of larkspur are better known for their upright spikes of dense flowers like their cousins the delphiniums, but there is one species, Consolida regalis, that has a much more relaxed, airy demeanor, with a multi-branching habit and clouds of small flowers. The cultivar ‘Snowcloud’ is the one to look for as a filler, and it can either be sown direct or under cover, although it is easiest to grow in pots first, so that they can be dotted effectively around the border. Try growing it with other annuals peeping up through it.
All of the plants mentioned here will grow in almost any good, well-drained soil, and most can either be sown in situ in late spring or under cover in autumn or early spring. I have found the most economical and time-efficient way to sow the majority of annuals is to use modular trays, sowing one or two seeds to a cell, which cancels out the need to prick them out and saves wastage from sowing a whole seed packet into a large seed tray. Other people prefer pricking out into modules or small pots, or even chitting the larger seeds before planting individually in pots. There is no right or wrong way – it is just a matter of experimenting and finding out what method works best for you.
All these annuals appear in Clare Foster’s book, The Flower Garden; how to grow flowers from seed, published by Laurence King and available on Clare’s website www.budtoseed.co.uk.