Gardening

Gardening: 10 fast-growing, ultra-productive annuals that can be sown right now

In April, nature’s life force quickens day by day and every tiny seed sown is a powerful spell racing to transform itself

Cosmos/Cosmos bipinnatus are one of the superstars of the summer garden. Photograph: iStock

Fionnuala Fallon's face
Fionnuala Fallon
Sat Apr 6 2024 - 05:00

It’s April, that most magical of months, when nature’s life force quickens day by day and every tiny seed sown is a powerful spell racing to transform itself. With that in mind, below are 10 fast-growing, ultra-productive annuals that I wouldn’t be without, all of which can be raised from seed sown in the next couple of weeks.

Cosmos/Cosmos bipinnatus: One of the superstars of the summer garden, this fast-growing, floriferous half-hardy annual looks every bit as at home in a pot in a chic town courtyard garden as it does in a potager-style allotment, while it also makes a fantastic cut-flower. Depending on the variety, its daisy-like flowers can be of the purest white (examples include Cosmos ‘Purity’ and Cosmos ‘Fizzy White’), shocking-pink (Cosmos ‘Dazzler’), and ruby red (Cosmos ‘Rubenza’). For something extra special, seek out seed of the shimmering-pink Cosmos ‘Xsenia’ and the peachy Cosmos ‘Apricotta’. Cosmos likes a position in full sun and a free-draining, not overly fertile soil or compost.

For reliably good results, sow seed into a 2L-3L pot filled with a good-quality seed compost (ideally lightened with a handful of fine-grade vermiculite), bottom water by placing it in a shallow container of water up to its waist overnight, and then cover an upturned clear freezer bag sealed with an elastic band before placing them on a bright window sill to germinate. As soon as they do, start gradually removing the bag to slowly improve ventilation. Once full germination has occurred, remove the upturned bag and very gently water as required, taking care not to bruise any of that tender new growth. When those baby seedlings produce their first set of “true leaves” (leaves that look similar to the adult plants), prick them out into cell trays or individual small pots, quickly water them, and place them back in a bright, frost-free spot where they can grow on uninterrupted. Water as needed, always allowing the compost to partially dry out between waterings to reduce the risk of the dreaded “damping-off” disease. Nip out the growing tips at about 15cm tall and harden the young transplants off by gradually exposing them to cooler more variable growing conditions before planting them into their permanent positions in the garden or allotment at the end of May.

Leeks: Ultra-hardy, space efficient and versatile, this member of the onion family is a kitchen garden staple. Sow seed as for cosmos and then prick out the baby seedlings into deep root trainers for transplanting out into the garden in early summer. A late maincrop variety such as ‘Blue Solaise’ is suitable for sowing at the end of this month for harvesting next year.

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Runner beans/Phaseolus coccineus: Fast-growing, ultra-productive and delicious with pretty, pollinator friendly, edible flowers that add a brilliant splash of crimson-red to the kitchen garden, runner beans are one of the easiest and most generous of crops to grow. They’re also a great choice for small gardens or container gardens, concentrating most of their growth upwards rather than outwards. The classic variety is the heritage ‘Scarlet Emperor’ while outstanding modern varieties include ‘Enorma’. Runner beans love a rich, seep, moisture-retentive soil in full sun and need some form of sturdy support.

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Lettuce ‘Marvel of Four Seasons’ or ‘Merveille des Quatre Saisons’: The Chanel of lettuce varieties, this delicious, versatile, resilient heritage variety’s enduring appeal is fully justified. As good-looking as it is tasty, its crumpled bronze-green, puckered leaves are tender and juicy while it’s also reliably productive in less than ideal weather conditions. As for all lettuce, sow small amounts of seed shallowly, thinly and successionally every three to four weeks throughout the coming months, except in very hot weather (25 degrees-plus) which can inhibit germination. This frost-hardy annual does best in a friable, rich, moist but free-draining soil in full sun or light shade.

Sweet pea/Lathyrus odoratus: There’s still just about enough time (but hurry) to sow seed of what must be one of our most-loved hardy annuals. Fragrant, floriferous and full of joy, there’s nothing quite like the sight and smell of sweet pea in full bloom in a summer garden. Avoid direct sowing seed that will be slow and uneven to germinate and risks being eaten by rodents. Instead, my preferred method is to pre-chit the seed by placing it in damp kitchen paper in a clear plastic box in a cool, bright spot. Once they germinate, very gently sow each seed shallowly into root trainers or small individual pots to grow on. Nip out their growing tips once seedling reach about 15cm tall and plant out in the garden into cool, rich, deep, moisture-retentive soil in full sun. Countless garden-worthy varieties are available from the moody lilac ‘Nimbus’ to the charming pastel-pink ‘Piggy Sue’.

Coriander/Coriander sativum: A mainstay of many modern kitchens and a key ingredient in many Asian dishes, coriander is one of those herbs that you either loathe or love. From April-July, it’s best raised from seed direct-sown successionally and shallowly outdoors in situ, into rich, moisture-retentive soil in partial shade. Avoid sowing in very hot weather to reduce the risk of bolting and make sure to keep the soil moist until germination occurs. Recommended varieties include the bolt-resistant ‘Leisure’ and ‘Green Thunder’.

Morning Glory/Ipomoea purpurea: True, this heat-loving tender annual climber needs a warm, sheltered spot away from cold winds where it can bake in the heat of a summer’s day, but in return it will reward you with a stunning display of its violet-blue flowers for months on end. As long as it’s kept well-watered, morning glory will also thrive in the protected growing space of a conservatory where it can be teemed with other tender heat-lovers for a magical and long-lasting floral display that will continue until the first harsh frosts of late autumn. Sow seed this month into small individual pots under cover and with gentle heat. The classic variety is ‘Grandpa Ott’.

Beetroot/Beta vulgaris: One of those ultra-versatile vegetables that always tastes delicious whether grated raw in a salad, roasted in butter or herbs, or even added to a cake, I’d hate a world without beetroot. It’s also exceptionally good for you, being rich in antioxidants and phytonutrients that support good health. Rather than using the sowing method outlined above, it’s best to direct sow the seed shallowly outdoors successionally from mid-April to early June in drills into weed-free, friable, fertile, moisture-retentive soil (but not recently manured), spacing them 5cm apart and later thinning them to 10cm apart. The best all-rounder variety is ‘Pablo’, which is prized for its tastiness and reliability as well as its productivity.

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Rocket: Crispy, sweet, flavoursome, fast-growing and highly productive, rocket is one of those cut-and-come-again crops that deserves a space in every kitchen garden and allotment, no matter how small. Easy to grow in a window box or large pot, its peppery leaves are a classic summer salad ingredient as well as a delicious addition to a sandwich. Best direct sown successionally in small amounts from April-October in situ into a moist but well-drained soil in light shade (like lettuce, avoid sowing in very hot weather). Several varieties are available from the spicy wild-type rocket to modern cultivars such as ‘Astra’, which is especially fast-growing and productive.

English marigold/Calendula officinalis: Its jaunty golden flowers aren’t just pretty and pollinator friendly but also edible and good for you, while this hardy resilient annual will bloom for months on end in even a cool, wet summer. Impressively easy to raise from seed sown using the method described above for cosmos, it can also be direct-sown in situ at this time of year. Countless named garden-worthy varieties are available from the sooty-orange ‘Indian Summer’ to the apricot ‘Sunset Buff’. English marigolds like a well-drained soil in full sun or lightly shade.

This week in the garden

Sow seed of hardy herbs such as parsley, dill, chervil, coriander and fennel either into cell trays for transplanting into their final position in the garden in early summer, or directly in the ground into weed-free, friable, well-drained soil, making sure to take precautions to protect the emerging seedlings from slugs and snails. Recommended Irish stockists of seed include certified organic seed producer brownenvelopeseeds.com, greenvegetableseeds.com and irishseedsavers.ie

Early April is a good time of year to feed clematis, roses, hedges, fruit trees and fruit bushes by scattering a few handfuls of slow-release, general purpose, granular organic fertiliser on to bare soil around the base of the plants and then very lightly forking it in. Stockists include most good garden centres as well as online suppliers such as fruithillfarm.com and quickcrop.ie.

Dates for your diary

Saturday, April 6th (2.30pm-4.30pm), St Nessan’s Community School, Baldoyle, Dublin, D13 F6N3, Howth & Sutton Horticultural Society Annual Spring Show and Plant Sale, see hshs.ie for details; Sunday, April 7th (11am-5pm), Claregalway Castle Annual Spring Plant Fair, Claregalway Castle, Co Galway, with a wide range of stalls from the country’s top specialist nurseries, see galwaygardenfestival.com; Saturday, April 20th-Sunday, April 21st, the inaugural Festival of Gardens and Nature takes place at Ballintubbert House & Gardens, Stradbally, Co Laois, see festivalofgardensandnature.com for booking details.

Gardening