Seeds and plants germinate and grow at different temperatures, so it's important to know what their tolerance is before you start to plant them.
Only the hardiest plants can be sown when the soil is cold in early spring (10°C+). This is the time to plant bok choy, broad beans, broccoli, kale, leeks, peas, radishes, spinach, spring onions, strawberries and turnips. Artichokes and asparagus tolerate the cold too but you won’t get a crop in your first season – you will need to wait until autumn or the follow spring to get your first artichoke harvest and it’s a three-year wait before you can pick asparagus!
Once the soil has warmed to 12°C, you can start planting beetroot, cabbage, carrots, cauliflowers, celery, fennel, all the lettuces, rocket, soft salad greens and silverbeet.
Labour weekend in late October is usually the cue to plant tender summer crops such as basil, beans, chillies, cucumbers, eggplants, potatoes, pumpkins, tomatoes, peppers and zucchini. These need ground temperatures of over 15°C to survive and thrive (chillies, eggplants and peppers actually like it to be 18°C) and any chance of frost will see them curl up and die. But you can get them started earlier by germinating seeds in trays or pots indoors, so they’re ready to transplant when the soil warms up. Seedlings usually need to be about six to eight weeks old before they are ready to be planted out.
Nothing is more frustrating than finding that everything is going to be ready to pick right at the time when you’re away on summer holidays, so it’s essential to consider how long it takes from planting a seed or seedling until harvest. When considering planting-to-harvest timings, remember that different species take differing amounts of time from germination to harvest and hotter weather makes for quicker growth.
Bok choy, radishes and rocket are the speediest – you will have something to pick in 30 to 40 days. Parsnips, which take 150 to 300 days, operate at the other end of the spectrum. Garlic takes roughly six months – it goes into the ground on the shortest day (although in Wanaka I have to wait until late August when the ground unfreezes) and comes out on the longest. In colder areas, anything that dislikes frosts has to be able to mature in the growing season between spring and autumn frosts. So even though beans take 65 to 100 days, if you leave it too late in the season to get them into the ground there just isn’t enough time for them to mature before the days get too short and temperatures drop. That means that early January is fine to get a late crop of beans in but mid-February just won’t cut the mustard.
Coriander and spinach like it cool so spring and autumn are the best times for planting these – as the days lengthen towards summer they will bolt and form seeds. Any crop that has sat happily in the ground over winter growing ever so slowly will suddenly go to seed as soon as the days start to get longer, prompted by the increasing hours of daylight.
If you are growing from seed, check out the days-until-harvest information on the seed packet and work backwards from when you want to harvest to find out when to sow them. If buying seedlings at the garden centre, check the maturity details on the tags and time your purchases and plantings accordingly.
As soon as one crop has been harvested you can get the ground ready to plant the next. I like to do a big plant before we head away at Christmas so that when we come back in late January we have lots of vegetables coming into harvest rather than being at the end of their cycle.
For a winter garden you need to get plants into the ground by late February or early March so they can get established before the end of summer. In our family we eat loads of broccoli so every four or five weeks I plant another six to 10 plants. Use the seasonal planting guide below to stagger plantings of vegetables you eat often. Every third or fourth round give the soil a rest by leaving it fallow or planting a winter crop such as mustard.
There is a lot to be said for growing heirloom varieties if possible. Not only will you get to experience new flavours and help to maintain the diversity of the plant gene pool (which is under major threat from the monoculture of industrial agriculture) but research suggests that heirloom varieties deliver better nutrition than their highly bred counterparts. They also often give better yields and longer harvests and tend to be better adapted to backyard gardens. If you can remember come autumn, leave a plant to go to seed then dry and save the seeds to use next year and share with friends.
Make sure you get your soil well prepared and your compost bin and worm farm up and running now and you’ll be set to enjoy the wonderful sense of connection that growing some of your own food delivers. Happy gardening!
To download a seasonal sowing chart in printable pdf format (305KB) click here.