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Spring Bulbs Chilling Guide


Chilling Facts

  • Only Tulips and hyacinths require any chilling

  • If your winter has at least five or six frosts then you don’t need to chill before planting.

  • Start chilling any time from late March to mid May for planting up to the end of June.

  • Chill for four to eight weeks in a paper bag in the fridge - not the freezer

  • Try to keep fruit out of the fridge if bulbs are in it

Should I chill my spring flowering bulbs is one of the questions we get asked most frequently here at NZ Bulbs. Along with, do I put them in the freezer? When do I start chilling? And, what do I do if my bulbs aren’t arriving until later?

Never fear, with over 60 years experience growing bulbs in New Zealand, we’ve got the answers to all your spring bulb questions.

Should I chill my spring flowering bulbs?

Yes - you may need to chill your spring flowering bulbs - but only tulips and hyacinths. And it’s only essential if you experience fewer than five frosts a winter.

In saying that, even if you do get enough natural chilling in winter, fridge chilling can still give benefits - taller stems and earlier flowering.

Tulips and hyacinths are native to areas which experience quite cold winters and they need this cold period for the bulb to complete the development of the flower bud deep inside. Sure signs you should have chilled your bulbs are if they produced unusually short stems or the bulbs failed to flower at all.

Do different types of tulips require different chilling?

Some tulip varieties require less chilling and are more suitable for planting in warmer areas like Auckland. Darwin Hybrid tulips are the most suitable types for warmer areas. If you are in a warmer area and want to grow all the colours available in the Single tulip range, the flamboyant Parrot and Peony types, or the graceful Lily tulips, then we strongly recommend chilling as long as possible.


Don’t start chilling until late March – too early and you’ll stunt the flower bud development. Any time from late March up until around mid/late May is a great time to start chilling.


Place your bulbs in a paper bag. It’s very important the bulbs can breathe and plastic bags cause sweating and rot may develop.

Keep the bulbs to the side of the fridge , not at the back where the cooler plate may ice up and damage them, or where condensation may cause mould to develop.

Never put bulbs in the freezer! The freezer is too cold and will kill your bulbs. The average fridge is at approximately 4 degrees celsius and this is an ideal temperature.

Keep fruit out of the fridge while you’re chilling your bulbs. Ripening fruit (and to a lesser extent vegetables) releases a gas called ethylene which can cause severe damage to the developing flower bud in the bulb. We make use of this sometimes by getting kiwifruit to ripen more quickly by putting them in a bag with apples or bananas, which are higher ethylene producers. However, ethylene has a down side as well. It can cause severe damage to the developing flower buds in bulbs, often resulting in complete loss of the flower.

If you can’t keep fruit out of the fridge, include an Ethylebe Absorbing Sachet in the bag with the bulb. This will prevent ethylene damage and suppress mould growth (they’re actually really good in the vege compartment too, to make your veges keep longer).

Alternatives to chilling

A number of things may help you get good tulip and hyacinth flowers without chilling:

All tulips should be planted later in autumn when the soil temperatures are cooler, ideally below 12°C. Mid May is an ideal time in warmer areas. Plant the tulips 15-20cm deep, and hyacinths 12-15 cm deep as the soil is cooler at that depth. The bulbs cope very well as long as the soil has been well cultivated below the planting depth so they can easily push their roots out.

Avoid planting tulips and hyacinths in pots - pots warm up very quickly, even in winter, when the sun is on them. Bulbs really don’t like this fluctuation with warm days and cool nights, they much prefer the steady cool conditions in the garden soil. Use a mulch to help keep the soil cooler.

When to plant

Ideally, chill for a minimum of four to eight weeks. But up to 12-16 weeks is fine. Once they’re chilled, and the soil temperatures are cooler, it’s time to start planting. They can go in the ground any time up to around early June.

For those of you in warmer areas waiting for your bulbs to arrive, remember the Manawatu, (where we are) is cooler and the natural chilling process will be under way already at the nursery before you get your bulbs. Just pop them in the fridge for the rest of the required time when you get your order.

Article Posted: 31/01/2024 19:13:54

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