Labour Day, New Zealand’s public holiday to celebrate a shorter, eight-hour working day, is ironically when our gardeners traditionally head outside for some hard toil in their vegetable beds, eagerly preparing the soil, planting and sowing up a storm.
But caution is advised – it may be too early for many seeds or seedlings to go in.
Take tomatoes, one of the most popular crops grown in our domestic gardens. Along with planting garlic on the shortest day and harvesting it on the longest, the Labour Day planting of tomatoes has become a perceived wisdom the length of the country.
Regrettably, it is only a viable practise in some regions, such as warmer, predominantly frost-free Northland, Auckland, Tauranga and other hotspots. Climate change and microclimatic variations aside, in most parts, it is prudent to wait.
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Wellington and Christchurch gardeners should consider mid-November a safer time to plant, while in Dunedin gardeners are advised to hold off until later in the month, or early December.
As a very general rule, New Zealand is divided into three climatic zones. The warmest, classified as subtropical, covers Auckland and Northland, most of the North Island coast, Golden Bay and the upper West Coast.
The bulk of the South Island’s inland and a chunk of the North Island roughly from Ohakune to Te Urewera comprises the cool mountain region, with the remainder – coastal South Island and much of the North Island – being classed as temperate.
The warmer the site the sooner it can be planted with semi-hardy vegetables. Planting too early is a gamble which seldom pays off. Both low soil and air temperatures can check plant growth and very often the plant will fail to catch up with those kept under cover until the appropriate planting time.
That said, soil can be warmed prematurely with the likes of glass and plastic cloches installed several weeks before popping in any seedlings. The same placed over plants can protect them from the worst of the cold, but they may need removing in the heat of the day to avoid burning sensitive young seedlings.
Soil in raised beds, containers and mounds will also heat up more quickly than the ground. (Smaller containers unfortunately will heat up the soil too much for many root crops.)
Bales of straw can also offer a cosy home for tender seedlings. Simply create a planting hole by forcing apart a section with your hands, filling it with compost and soil and planting. One bale will easily support two tomato, pepper or courgette plants. Once the season is over, the straw can be used as mulch or added to the compost.
Protection from draughts and chilling winds, and being sited somewhere sunny, can also enable successful early planting.
Tomatoes aren’t the only vegetables sensitive to cold. Several other members of the solanum family prefer warmth throughout their life, including sweet peppers, chilli peppers, aubergines, cape gooseberries and tomatillos.
Most of the cucurbits like warmth too, with courgettes, squash and pumpkins generally being hardier than cucumbers and gherkins.
Melons and luffas are less hardy again. Gardeners in cooler areas should opt for faster-maturing and smaller varieties of cucumbers and rock melons, or use glasshouses.
In choosing crops, remember that many, such as melons, cucumbers, luffas and even some pumpkins need about four months to mature fully before the first frosts cut them down.
Sweet corn and Florence fennel are more crops that will suffer if sown or planted outside too early. Often there is no hurry. Sweet corn, for example, may be successfully sowed right through December in most regions. Successive sowings and plantings will extend a crop’s season.
While cool-climate gardeners aren’t advised to plant or sow as many crops this weekend as their warmer counterparts, for those chomping at the bit, there are still many that can go in.
Dwarf, runner and climbing beans, carrots, celery, kale, kohl rabi, leeks, lettuce and a host of other salad greens, parsnip, peas, radish, spring onion and swedes are amongst the vegetables that may safely be sown or planted out.
Many lettuces, spinach and silver beet can be grown year-round in most of the country, although in summer it pays to grow the former out of the noon sun, which can cause it to bolt.
While it is too late in the season for asparagus, Brussels sprouts and onion seedlings to be planted in warmer zones, gardeners in the cooler districts still have time to get them in. These gardeners, however, should avoid planting basil outside for a few more weeks.
Parsley and coriander may be sown now everywhere. Like lettuce, the latter prefers noon shade.
By all means head down to the garden centre and snap up your favourite tomato varieties and the like before they sell out, but be wary of planting them out too soon.
Keep them on a sunny window ledge or verandah for a few more weeks and the rewards will be yours.
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