Spring GreenHouse Gardening

Spring is one of the most exciting times of the year for greenhouse gardening! The days are getting longer, temperatures are warming up and it's finally time to start thinking about all those delicious summer crops.

New Zealand's spring runs from September through to November, and while we're all ready to embrace the warmer weather, spring conditions can still be unpredictable. Warm sunny days can be followed by chilly nights and late frosts, which is exactly where your greenhouse comes into its own.

A greenhouse gives you the opportunity to get your summer growing underway earlier, protect young seedlings and create a more controlled environment while you wait for outdoor temperatures to catch up.

Here are some of our tips for spring greenhouse gardening in NZ:

1. Choose the Best Crops for Spring

Spring is the perfect time to start many of your favourite summer vegetables from seed or seedlings.

Some of our favourites to grow in the greenhouse during spring include:

• Tomatoes: Get your tomatoes established early in the greenhouse and you'll be well on your way to that first homegrown summer tomato!
• Capsicums & Chillies: These heat-loving plants benefit from the extra warmth and protection a greenhouse provides during spring.
• Cucumbers: Cucumbers love warmth and can grow incredibly quickly once conditions are right. Give them something to climb to maximise your growing space.
• Courgettes & Pumpkins: Start these in pots or seed trays before planting outside once the risk of frost has passed.
• Beans: Beans can be started under protection for an earlier crop.
• Leafy Greens: Lettuce, spinach, rocket and other leafy greens are perfect for filling gaps while your summer plants are still small.
• Herbs: Basil, parsley, coriander, chives and other herbs are great additions to your spring greenhouse.

You can also start flowers such as marigolds in your greenhouse. They're a fantastic companion plant to have ready for your summer vegetable garden.

Remember, New Zealand has a huge range of growing conditions, so what can be planted outside in Northland may still need protection further south. Use your local temperatures and frost dates as your guide rather than the calendar alone.

2. Make the Most of Your Greenhouse Warmth

One of the biggest advantages of greenhouse growing during spring is being able to create warmer growing conditions before the outside temperature is quite ready.

Your greenhouse will warm quickly on a sunny spring day, helping seeds germinate and encouraging faster growth from young plants.

However, don't forget about nighttime temperatures!

Close your greenhouse doors and vents later in the afternoon to help retain some of the day's warmth when cold nights are forecast. Young tomatoes, capsicums, chillies and cucumbers in particular will appreciate the extra protection.

A Polycarbonate Greenhouse can be particularly useful during changeable spring conditions, with the polycarbonate panels providing good thermal efficiency while diffusing the sunlight entering your growing space.

Keep an eye on the forecast too – a beautiful warm week doesn't necessarily mean the last frost has been and gone!

3. Ventilation is Just as Important as Warmth

It can be tempting to keep your greenhouse shut up tightly during spring to maximise warmth, but good ventilation is essential for healthy plants.

A sunny spring day can send the temperature inside your greenhouse soaring surprisingly quickly.

Open doors and roof vents during warmer parts of the day to allow hot air to escape and fresh air to circulate around your plants.

Good airflow can help:

• Regulate temperature
• Reduce excess humidity
• Reduce the risk of fungal disease
• Encourage stronger plant growth
• Improve the overall growing environment

An Auto Roof Vent Opener is a handy addition during spring, particularly when you aren't home during the day to manually open and close your vents as the temperature changes.

If you're growing in one of our Tunnel Houses, make good use of your doors and ventilation options on warmer days to keep that fresh air moving through.

4. Keep an Eye on Pests & Disease

Warmer spring temperatures don't just wake up our plants – unfortunately, they wake up the pests too!

Aphids, whitefly and other unwanted visitors can multiply quickly in the protected environment of a greenhouse.

Check your plants regularly, paying particular attention to:

• The underside of leaves
• Fresh new growth
• Around flower buds
• Any curled or discoloured leaves

Catching a problem early is much easier than trying to deal with a full infestation later.

Keeping your greenhouse tidy and allowing plenty of airflow between plants can also help reduce problems with pests and fungal disease.

Avoid overcrowding your greenhouse in your excitement to get everything growing – we know, it's hard!

5. Feed Your Plants for the Growing Season Ahead

Spring is all about growth, which means your plants are going to need plenty of nutrients.

Before planting your main summer crops, add good-quality compost or well-rotted organic matter to your greenhouse beds.

Once plants become established, crops such as tomatoes, cucumbers and capsicums will benefit from regular feeding throughout their growing season.

It's also a good idea to think about crop rotation if you grow directly into your greenhouse soil. Where possible, avoid growing the same plant family in exactly the same spot season after season.

Healthy soil = healthy plants = a better harvest!

6. Adjust Your Watering as Temperatures Rise

Your greenhouse watering requirements will start changing quickly during spring.

Plants that needed very little water through winter may suddenly begin drying out much faster as temperatures rise and growth takes off.

Rather than watering on a strict schedule, get into the habit of checking your soil regularly.

Water deeply when required and, where possible, water earlier in the day. This allows plants to take up the moisture they need while giving the greenhouse environment time to dry before temperatures cool overnight.

As you move towards summer, you may find yourself watering much more frequently.

If you have an irrigation or automatic watering system, spring is the perfect time to get it set up and working before those hot summer days arrive.

7. Harden Off Seedlings Before Planting Outside

One of the great benefits of owning a greenhouse is being able to start your summer vegetables earlier – but don't forget that greenhouse-grown seedlings have been living a fairly sheltered life!

Before moving young plants permanently into your outdoor garden, gradually introduce them to outdoor conditions.

Start by placing seedlings outside in a sheltered position for a few hours during the day, then slowly increase the amount of time they spend outside over a week or two.

This helps them adjust to direct sunlight, wind and cooler temperatures and reduces the shock when they're finally planted into the garden.

Don't rush this process. A little patience now can result in much stronger plants later.

8. Plan Ahead for Summer

Spring growth can happen incredibly quickly.

That tiny tomato seedling sitting neatly in the corner of your greenhouse can become a rather large plant before you know it!

Think ahead about:

• Where your tomatoes and cucumbers will grow
• Adding stakes, strings or supports before plants become too large
• Keeping pathways accessible
• Leaving enough room for airflow
• Where taller plants may shade smaller ones
• Which plants will eventually move outside

Making use of vertical growing space is one of the easiest ways to maximise the amount you can produce from a smaller greenhouse.

And if you're still deciding which type of protected growing space is best for your backyard, our Glasshouses, Polycarbonate Greenhouses and Tunnel Houses all offer different benefits depending on your space and how you like to grow.

Enjoy Your Spring Greenhouse!

Spring really is when greenhouse gardening starts to get exciting.

Seeds are germinating, seedlings are taking off and you're laying the foundations for months of fresh, homegrown produce.

Your greenhouse allows you to get ahead of the outdoor growing season, protect vulnerable young plants from New Zealand's unpredictable spring weather and create the ideal conditions for your favourite summer crops.

Start with Tomatoes, Capsicums, Chillies, Cucumbers, Courgettes, Beans, Lettuce, Spinach, Basil, Coriander and Parsley – then experiment and find out what loves growing in your own greenhouse.

And don't forget to check out our Spring GreenHouse Chores Guide for all the cleaning, maintenance and preparation jobs you can do to get your greenhouse ready for the busy growing season ahead.

Have you got some great Spring greenhouse growing tips and tricks? We'd love to hear them! Comment below and share your greenhouse gardening knowledge with other Kiwi growers.

If you're thinking about getting started with your own greenhouse, glasshouse or tunnel house, have a browse around Urban Backyards or get in touch with us – we're always happy to help you find the right option for your backyard.

We look forward to helping you get growing this Spring!

Happy Growing!

Urban Backyards – Helping You in Growing, Living and Loving Your Backyard.