whole and half strawberries on wooden chopping board

Doubtless God could have made a better berry, but doubtless God never did.
- William Butler

It may seem to be odd to be writing about a fruit that symbolises the epitome of high summer in the depths of winter, but there is method to my madness – especially this year. Late winter to early spring is prime strawberry-planting season, and due to the terrible weather that has plagued northern New Zealand this year, plants will be at a premium. Commercial propagators currently produce somewhere in the region of 13.5 million new plants each year, catering for both professional growers and home gardeners. With the bad weather having destroyed vast areas of commercial plantings, as well as reducing the number of new plants able to be propagated, there is a shortfall of some 4.5 million plants overall. In home garden figures, 2023 supply looks to be about a million plants short of demand, based on last year’s sales figures. This translates not only into less plants at the garden centre for gardeners like you and I, but also into less fruit on the supermarket shelf later in the season. Kudos to you if you pegged down some runners and propagated your own plants last summer; time to make friends with someone with an established patch if you didn’t.

Strawberries have timeless appeal for young and old – I have very early memories of regular visits to a pick your own farm as a child (the property is sadly now under a residential development) and my parents still call the fruit by the handle I gave them as a toddler (“tawbries”, if you must know). Burying my nose in a punnet of properly-ripe strawberries takes me straight back to the sticky-sweet berry aroma in the farm shop and the kindly face of the friendly proprietor. It’s no wonder strawberries have universal appeal. They are the perfect fruit crop, within the grasp of everyone from inexperienced gardeners to old hands, high-rise apartment dwellers to smallholders. With a little effort, a bowlful of berries is within reach – just make sure they are out of reach of the stickybeak birds. Nets are not optional!

Strawberries: a short family history

Strawberries belong to the genus Fragaria, nestled in the rather fruitful family Rosaceae. Most cultivated garden strawberries are hybrids, Fragaria x ananassa. Common belief is that the fruit got its name from the straw commonly used for centuries as mulch for the growing plants, but another potential derivative is from the Old English streawberige, where streaw not only meant straw, but also streawian, to strew, or “stray away” from the main plant, as the runners which produce new plants do.

A long-popular fruit, strawberries were initially gathered from the wild, and eventually when a more convenient supply was desired, plants were dug up and transferred to the home garden. In England, Henry VIII actually paid people to do this for him when establishing the gardens at Hampton Court in 1533. Given his reputation, one only hopes the correct plants were selected. By the 16th and 17th centuries, new varieties were introduced to Britain from Europe, and later from America, with the more highly-flavoured Fragaria virginiana arriving from New England, sent back by the early European settlers to the continent. This introduction bolstered the local genetics and flavour profiles, later greatly aided by the introduction of a further South American species discovered courtesy of French spy, explorer and fireworks enthusiast (order of career precedence unknown) Amédée-François Frézier in 1714. These plants landed in France and as the five survivors of the long voyage were all female, could only be propagated vegetatively and therefore weren’t much use for breeding. It took a further 13 years for fertile Chilean plants (Fragaria chiloensis) to reach Britain. The fruit produced by these somewhat fickle plants was something of a disappointment – large and sweet but bland. They seemed set to fade into oblivion until observant nurserymen noted they began to set fertile seed when planted next to F. virginiana plants. Some of these hybrid offspring were found to have not only increased vigour, but also combinations of the excellent flavour of the North American species with the good size of the South American varieties. Our modern strawberry cultivars have a mix of this Chilean and North American heritage to this day.

Strawberries aren’t actually true berries in the botanical sense. The fleshy red fruit we consume develops from the receptacle that holds the plant’s ovaries. What we call the ‘seeds’, contained on the surface, are actually a type of dry fruit known as an achene. Each of these is derived from one of the flower’s ovaries and these all hold a true seed inside each.

Suitable climates and growing conditions

Good news for strawberry fans – your favourite fruit can be grown right throughout New Zealand. Further north, strawberries are sometimes treated as annuals, with plants replaced each year, but further south they can be cropped continually for several years. The plants are quite short-lived, best replaced every three years as fruitfulness declines, but with careful maintenance you may get five years from your plants. Either way, it’s a good idea to make successive plantings to ensure a plentiful supply.

Strawberry varieties are divided into three main categories according to their fruiting type, and I’ll do my best to explain those here.

Short-day or summer strawberries

These flower in spring, and form flower buds in autumn once the day length drops below 10 hours. They are best planted in autumn, and the buds that form will stay dormant until the following spring. These are the early fruiting plants, producing their single crop in late spring to early summer. Because of this, they can be hit and miss in areas prone to late spring frosts. The fruit is generally larger than that of the ever-bearing types.

Long-day strawberries

Long-day strawberries need more than 12 hours of daylight to set flower buds. They produce two crops, one in late spring and one again in early autumn. These grow best in cooler climates; they produce less fruit in very hot summer conditions.

Everbearing strawberries

This type of strawberry doesn’t actually fruit year-round but isn’t affected by day length and will form flower buds at any time as long as it’s warm enough and all other growth parameters are met. Like long-day strawberries, they produce better in cooler temperatures. You may also see ‘day neutral’ strawberry plants mentioned, and while the terms everbearing and day-neutral may be used interchangeably, day-neutral strawberries are a subset of the ever bearers, with the former being a more reliable cropper during the summer period. The fruit is generally smaller than that produced by summer strawberries.

Long-day and everbearing types also produce fruit and runners simultaneously, so don’t crop as heavily or produce as many runners as the short-day types. Plant a combination of short-day and everbearing/day neutral types to ensure a season-long supply of strawberries.

Let’s not forget alpine strawberries (Fragaria vesca) either. The wild autumn-fruiting European strawberries of old gave rise to these small, sweet, hardy berries and they make fantastic ground covers with their abundant delicate leaves. I recently visited a property in the North Island in autumn and tiny flashes of bright red caught my eye in an expanse of lawn – they were in fact tiny wild strawberries, which obviously survived the occasional mow.

With some careful attention to detail, you can fashion a suitable environment for growing strawberries pretty much anywhere. In warm, high-humidity climates there will be an increased susceptibility to diseases, including botrytis (grey mould). The plants require a modicum of winter chill to break dormancy (generally 200-300 hours but can be up to 400 hours). Warm sunny days and cool nights will lead to well-flavoured fruit, but the plants are susceptible to high temperatures; fruit production and development will slow above 22°C. The lower tolerance limit for winter temperatures is -10°C, below this, strawberry plants are likely to suffer irreversible damage and will possibly die.

A general rule of thumb is to allow a square metre of garden space for every six plants (and I’ve heard the recommendation that six plants per family member is a good measure regarding how many plants you’ll need to keep everyone happy!). If planting in rows, allow 15-20 cm between plants. Expect a punnet’s worth of fruit from each plant in the first year, with yields decreasing with each passing season. Harvest on a dry day by cupping your hand around each fruit and pushing the stalk away from the green calyx ‘hat’ with your thumb. Leaving the calyx intact greatly enhances storage potential – use fruit where the calyx detaches promptly. As mentioned before, the plant’s lifespan is three to five years, so make successive plantings each year to ensure a constant supply of berries. Strawberry flowers are bisexual and self-fertile, with pollination aided by wind and insects.

You can propagate your own plants from the vegetative ‘runners’ that are sent out from the plant in mid-summer. In a plant’s first fruiting season, it is best to remove the runners as they appear to divert the plant’s energy into fruit production. In the second year, you can peg down the first plantlet produced on a runner into a small pot filled with potting mix (in turn partially buried in the soil it sits on). In early autumn, detach the potted runners from the parent plant and transfer them into their new growing bed. A word of caution – strawberry plants are highly susceptible to plant viruses and this method of home propagation can unwittingly proliferate the spread of such diseases. Detaching the runner before the mother plant flowers may help prevent viral spread. Buying plants from a reputable commercial supplier helps eliminate this issue altogether. Growing strawberries from seed is time-consuming and haphazard – best left to the breeders.

Site selection and planting

Short-day cultivars can be planted in the autumn (March to May) to give them time to settle in and crop well in their first year. Ever-bearing and long day types can be planted in autumn or spring. In particularly warm areas, you may be able to get away with winter planting. Regions prone to severe frosts should definitely delay planting until spring.

Choose a sheltered site, preferably in full sun. Drainage is an important factor as the plants will not tolerate cold, waterlogged soils and these will likely lead to root rots. Sandy or loamy soil types are best if planting directly into the ground. Make like commercial growers and plant your strawberries on raised mounds of earth, with or without black polythene plastic groundcover – or if you have the resources and want to save your back, try raised tables and grow-bags filled with specialised strawberry potting mix or coconut coir (the latter will require a proprietary nutrient solution to be applied to make up for the lack of soil-based nutrition). When planting, the roots need to be below soil level, gently firmed in, and the base of the crown (where the leaves arise from) at soil level, not buried.

Shallow-rooted, low growing strawberries are ideal candidates for pot culture too. You can buy purpose-designed strawberry planters for small gardens and balconies, buy a large planter pot and saucer, or simply cut holes in an unopened bag of potting mix and pop plants in the slits for a low-cost option.

Culture and care

An application of general compound fertiliser can be given in spring, allowing 200 g/metre. If you are intending to plant on mounds and use black polythene, work the fertiliser into the soil before mounding and covering. If you prefer to use organic fertilisers, work some fishmeal, compost and/or or sheep pellets into the planting holes. I like to apply a seaweed-based liquid fertiliser solution several times during the growing season – apply liberally around the base of the plant at approximately fortnightly intervals.

Strawberry plants like a constant supply of moisture throughout the growing season, but require less water when fruiting. A soaker hose or drip-tape are ideal methods, ensuring the water soaks straight into the soil. Try and avoid wetting the fruit and foliage unnecessarily.

It goes without saying that mulch is the strawberry plant’s best friend. Wheat, barley or pea straw are the obvious choices, with pine needles and newspaper also serviceable options. These help keep the moisture in, suppress weeds and also keep the fruit off the bare ground, preventing rots, mud splash and water damage.

I like to tidy up my plants at the end of the season by snipping off dead leaves and spent flower stalks at the base of the plant.

Pests, diseases and what to do about them

Apart from the aforementioned viral diseases, strawberries are susceptible to Phytophthora root rots and the fungal wilt diseases caused by Verticillium and Fusarium species.

As chemical control methods are often not desirable to home gardeners, or in the case of a lot of the chemicals used to fumigate soil to safeguard against the fungal diseases listed above, are just not feasible for domestic use, try employing the cultural controls listed below as they are your best bet.

Firstly, select a site with a light, free-draining soil type and form mounds for planting. Secondly, avoid planting strawberries where crops in the nightshade family (Solanaceae) have been grown within the last five years – this family is known to carry many of the above soil-borne diseases.

Thirdly, only procure virus-free nursery-grown plants and maintain them with care.

Apart from aphids and leafhoppers, insect pests are few and far between. Slugs can cause some substantial munch-holes where the fruit lies on bare ground. By far the biggest problem are the feathered variety of pests – invest in some nets or cloches and apply them once the fruit starts turning colour to ensure the bulk of the harvesting is done by your hands, not sharp beaks!

Varieties: My top picks

Aromas – (University of California Davis, 1996). A day neutral variety, purported to be resistant to spider mites. Produces good crops of firm but juicy fruit late-season.

Camarosa – (University of California Davis, 1994). A short-day variety. Early to produce, with large, firm sweet fruit, a popular PYO and commercial variety.

Seascape – (University of California Davis, 1992). An everbearing variety. A good summer and autumn cropper for cooler climates. Produces heavy crops of sweet-tart fruit.

Pajaro – (University of California Davis, 1979). A short-day variety. Produces uniform-size firm, well-flavoured fruit, cropping from October in northern New Zealand.

Alpine Yellow Wonder – a white-fruited F. vesca type with small but sweet cream-coloured fruit. Has the advantage of being ignored by birds, which don’t seem to notice the pale fruit. Hints of grapey, bubble-gum like flavour, and I personally detect parmesan cheese when they are overripe, but don’t let this put you off!

What to do with your crop

Strawberries are, of course, the perfect dessert fruit. Eaten straight away in the garden, or after a short trip to the kitchen, with a dusting of icing sugar and a plentiful splash of cream – what could be better on a summer’s evening? They also free-flow freeze well, and you can make an instant ice cream of sorts by dropping cubes of frozen strawberry into your food processor (earmuffs optional) along with icing sugar and processing to a rough dust, followed by your choice of cream or yoghurt to make a thick sludge to be served immediately in large dollops from a chilled bowl.

Strawberry jam is a perennial favourite; why not liven the flavour by adding orange zest, chopped rhubarb or elderflowers stripped from the stalk to your next batch? They also pair well fresh with balsamic vinegar and a dusting of black pepper – go on, try it! Or how about a splash of elderflower cordial if your taste is somewhat sweeter?

Larger strawberries cut into slices dehydrate well and are great added to muesli or trail mixes for tramping. One of my favourite fruit leathers is a mixture of lightly cooked strawberries plus stewed rhubarb and apple. Other options for long term storage and enjoyment of summer flavours in winter include strawberry vinegar for salad dressings and including layers of strawberries if you’re making a crock of the longstanding German favourite rumtopf. I’m keen to soak some super-ripe strawberries in a sugar and alcohol solution to make a kind of strawberry liqueur this year – if you are too, follow the recipe for orange liqueur in Your Backyard Fruit Bowl: Oranges and substitute sliced strawberries for the orange zest.

Historical information adapted from Stocks, C (2008) Forgotten Fruits: The stories behind Britain’s traditional fruit and vegetables. Random House, London.

Anna-Marie Barnes is an active member of the New Zealand Tree Crops Association who endeavours to grow and preserve as much of her own fresh produce as possible. When the weather’s no good for gardening, she can usually be found inside working on a batch of homemade cheese or soap.

The New Zealand Tree Crops Association is a voluntary organisation promoting interest in useful trees, such as those producing fruit, nuts, timber, fuel, wood, stock fodder, bee forage and other productive crops. Find out more about the NZTCA here: https://treecrops.org.nz/

Disclaimer: the information supplied above is of a general nature and provided as reference material only. In regards to pest and disease control, please consult your agrichemical consultant for suitable products, application rates and further region-specific information.

Image credits
Sliced strawberries – Engin Akyurt via pixabay.com
Strawberry plant – alyssapy via pixabay.com
Fragaria vesca plate – Public Domain https://commons.wikimedia.org/w/index.php?curid=9172
Strawberries in grow-bags – najibzamri via pixabay.com