Northern New Zealand: mild frost, plentiful rain and what to plant when
Frost and rain
| Frost | Light frost some years |
|---|---|
| First autumn frost | May to June |
| Last spring frost | September |
| Note | NIWA publishes the average number of frosts in each month rather than dates, and these months are where frosts appear in most years, mainly as ground frosts: air frosts are rare in most of Northland and Auckland, and sheltered inland sites such as Henderson and Dargaville have the most. |
| Rainfall | Rain all year |
Northland, Auckland and the warm north of the North Island have the lightest frosts of any part of New Zealand on this site. NIWA calls Auckland subtropical, with summers that are warm and humid and winters that are relatively mild, and Northland a mild, humid and rather windy region. Frost is light and the season starts earliest and runs latest. For a gardener the year is long, the limits are wind and the summer dry spell rather than cold, and the question is less when to start than when to stop.
Frost
NIWA records two kinds of frost. An air frost is a reading below 0 °C in a screen 1.3 m above the ground, and a ground frost is a reading of -1 °C or lower at the surface of clipped grass. Air frosts are rare in most of Northland and Auckland, and the ground frosts that do occur are often confined to a very shallow layer that does not seriously affect plants. Kaitaia has about half a ground frost a year, Auckland Airport about nine and Kerikeri about 11, mostly from June to August. Sheltered inland sites are colder. Henderson, in the west of Auckland, has about 27 ground frosts and nine air frosts a year, and Dargaville has about 15 and five.
Because NIWA gives averages by month, the first and last frost are best taken as months. Ground frosts at these sites begin to appear in May and are over by September, with a few in April and October. Air frosts, where they happen at all, come in June, July and August.
Frost is a local event and forms on calm, clear nights, in flat ground and in valleys where cold air cannot drain away. Protect citrus, young tomatoes and tender cuttings in a sheltered inland garden with fleece before dusk, and leave frost-damaged growth in place until the weather warms.
Rain and watering
Rain falls all year, with a clear winter maximum. NIWA gives Northland 1,000 mm in low-lying coastal areas and about 2,000 mm at higher elevations, with 35 to 40 percent of the year’s rain in June to August in the north and east and 18 to 20 percent in December to February. Auckland gets about 32 percent of its rain in the winter months and about 20 percent in summer, with eastern areas such as Leigh and Waiheke Island averaging about 900 mm a year.
Summer and early autumn bring dry spells, though in Auckland they are usually not long lived. In Northland there is usually at least one, and often two, between December and March, lasting about 20 days on average, so plan to water deeply, mulch and keep a hose ready. In the house the humid summer keeps compost damp for longer, so check before you water, and give plants a little less water from June to August.
Month by month
Each month below adds the local frost and rain timing to the matching southern hemisphere page, which has the general list.
January
Midsummer, warm and humid, with the dry spell building. Sow beans, cucumbers, courgettes and basil, and sow carrots, beetroot and lettuce for autumn. Water deeply and mulch. The general list is on January, south of the equator.
February
Late summer. Sow the winter vegetables, with brassicas in trays, and sow beans and basil for a last picking. Sow sweet peas, and divide agapanthus after it flowers. The general list is on February, south of the equator.
March
Autumn. NIWA says cold climate vegetables planted in autumn will mature in early spring if the ground is well drained, so sow broad beans, spinach and onions now. Plant spring bulbs. The general list is on March, south of the equator.
April
Mild, with frost still some weeks away. Sow lettuce, spinach, onions and carrots, and plant strawberries. Make the most of the warm soil. The general list is on April, south of the equator.
May
The first ground frosts may appear in sheltered inland gardens. Plant garlic, and plant hardy hedging and perennials. Cover tender plants on clear, still nights. The general list is on May, south of the equator.
June
Winter, with the most rain and the first regular ground frosts. Plant garlic, prepare planting holes for bare-root roses and fruit trees, and sow broad beans. Drain heavy ground. The general list is on June, south of the equator.
July
The coldest month and the peak for ground frosts. Prune roses, fruit trees and vines, and keep planting bare-root stock. Protect citrus and any young plants. The general list is on July, south of the equator.
August
Late winter, with the frost easing. Sow potatoes in the open, and start tomatoes and capsicums under cover. Plant lavender, rosemary and thyme. The general list is on August, south of the equator.
September
Spring, with the last ground frosts in the cold inland gardens. Sow beans and tomatoes under cover, plant potatoes, and sow the summer annuals. Keep fleece handy. The general list is on September, south of the equator.
October
The soil is warm and the frost is gone. Plant out tomatoes, capsicums, cucumbers and courgettes, and sow beans and basil. Mulch after watering. The general list is on October, south of the equator.
November
Early summer. Sow beans, courgettes, cucumbers and basil, and stake the tomatoes. Start watering regularly before the dry spell arrives. The general list is on November, south of the equator.
December
The dry spell may begin. Water deeply, mulch, and pick beans and courgettes often. Sow broccoli, cabbage and cauliflower in trays for autumn. The general list is on December, south of the equator.
Plants that belong here
- New Zealand broadleaf comes from coastal and lowland New Zealand forest and takes salt-laden wind, which suits an exposed northern coast.
- Lemon wants bright light and a cool but frost-free winter rest, which a light-frost garden gives it.
- Agapanthus flowers in summer and takes a light frost.
- Hydrangea wants dappled light and soil that stays damp all summer, so water it through the dry spell.
- Tomato is killed by frost, so plant it out after the last ground frost.
- Peppers and chillies need a long warm season, which this zone has.
- Beans are tender and wait for warm soil, and can go in from spring and again in late summer.
- Basil sulks below about 10 °C and runs to flower in a heatwave.
- Garlic is planted in autumn and needs the cold months, so plant it in May or June.
Questions from the margin
Does it frost in Auckland and Northland?
Lightly. NIWA says Auckland frosts are generally light and infrequent and that Northland has air frosts only rarely. Ground frosts are more common, about nine a year at Auckland Airport and about 11 at Kerikeri, mostly from June to August, and sheltered inland sites such as Henderson have up to 27 ground frosts and nine air frosts a year.
When is the summer dry spell in Northland?
NIWA records dry spells of 15 days or more with less than 1 mm of rain on any day as not uncommon in Northland in summer and early autumn. There is usually at least one, and frequently two, each year between December and March, lasting about 20 days on average, so plan to water in that stretch.
When should I plant tomatoes in Auckland?
From September under cover and from October outside, once the last ground frosts have passed. Frost is light and the soil warms early here, so the season starts earlier than in most of New Zealand, but a sheltered inland garden can still have a late ground frost in September.
Checked against
The figures and the advice on this page were checked against the sources below, and where they disagree the page says so.
Read on
- Planting almanac for this region
- Opens the almanac with this region and its hemisphere already chosen.