Mid‑Summer Seed Starting: What You Can Still Sow for Late Harvests (Greenhouse Friendly)
Mid-summer in Australia can feel like the season where the garden either takes off or taps out. The sun is intense, hot northerlies can dry pots in a blink, and pests seem to appear overnight. It is also the time many gardeners assume seed starting is finished until autumn.
We do not see it that way. With smart greenhouse seed starting, a bit of shade, and reliable protection from birds and insects, mid summer sowing can set you up for a seriously satisfying late harvest. It is also a great way to keep your patch productive without wasting water or constantly replanting seedlings that got scorched.
This is our practical, greenhouse-friendly guide to what you can still sow now, how to raise strong seedlings in the heat, and how to use simple covers and netting to protect your work.
Why mid summer sowing is worth it (even when it’s hot)
Mid-summer seed starting works because you are not trying to fight the whole season. You are aiming for the back half of it.
A few reasons we keep sowing through summer:
- Fast growers still have time. Plenty of vegies mature quickly enough to harvest in late summer and early autumn.
- You can stagger crops. Succession sowing means you do not end up with everything ripening in the same week.
- Stronger late crops. Seedlings started now can hit the ground running once the weather settles, especially as nights begin to cool.
- You stay ahead of gaps. When one crop finishes, you have the next ready to transplant.
The key is protecting seedlings from heat stress early, then giving them a smooth transition into the garden.
Greenhouse seed starting in mid-summer: the rules change a bit
A greenhouse is brilliant, but in summer it can also overheat quickly. Our biggest tip is to think of your greenhouse as a controlled nursery, not a sealed hot box.
Keep it cooler than you think
For greenhouse seed starting in summer, airflow and shade matter more than extra warmth.
- Vent early in the morning, not once it already feels stifling.
- Use shade to soften harsh midday sun.
- Water in the morning so foliage dries through the day.
Use covers and netting to protect seedlings outdoors too
Not every seed tray needs to live inside a greenhouse. In mid-summer, many seedlings do better in bright shade with protection from pests and wind.
This is where our Garden Covers range can really help, especially if you are trying to keep seed trays safe from cabbage moths, grasshoppers, birds, and curious pets.
You can browse our covers and tunnels here: Maze Garden Covers
What you can still sow for late harvests (greenhouse friendly picks)
What you sow in mid-summer depends on your climate zone, your microclimate, and how quickly you can get seedlings established. Instead of giving a single rigid list, we like to group crops by how they behave.
1. Quick wins for late summer picking
These are great for mid summer sowing because they germinate fast and mature quickly.
- Beans (dwarf and climbing)
- Cucumbers
- Zucchini and summer squash
- Sweetcorn (best if you can get it growing strongly straight away)
- Basil and warm-season herbs
Greenhouse seed starting tip: cucurbits do not love having their roots disturbed. We recommend sowing into individual pots so you can transplant with minimal disruption.
2. Leafy greens that handle warm starts (with protection)
Some greens struggle in heat, but you can still have success if you provide shade and consistent moisture.
- Silverbeet
- Perpetual spinach
- Asian greens (choose heat-tolerant types where possible)
Summer growing tip: raise these in bright shade, keep moisture even, and protect seedlings from pests. A netted cover can be the difference between thriving and being skeletonised overnight.
3. Late harvest roots and salad staples
A lot of roots are still on the table if you manage the germination phase carefully.
- Beetroot
- Carrots (best sown where they will grow, keep surface consistently damp)
- Spring onions
- Radish (some types can get pungent in heat, so pick quickly)
Greenhouse seed starting tip: for carrots, we often skip seed trays and sow directly into a prepared bed, then use a cover to maintain humidity and protect the surface from drying out.
4. Brassicas for the transition into autumn
Depending on where you live, mid to late summer is also the on-ramp to autumn crops.
- Broccoli
- Cabbage
- Cauliflower
- Kale
These can be fantastic late harvest crops, but seedlings need protection early because brassica pests are relentless in many Aussie backyards.
Our go-to strategy: start brassicas in trays, harden them off in bright shade, then transplant and protect with netting.
Walk-in greenhouse setup: a simple mid-summer seed raising routine
If you have the space, a walk-in greenhouse is one of the easiest ways to keep seed raising organised, especially when you are sowing in batches.
A simple routine we like:
- Sow in the evening or early morning so trays are not sitting in peak heat right after watering.
- Label everything immediately. Mid-summer sowing often involves lots of small batches.
- Keep trays elevated for airflow and to reduce pest access.
- Vent and shade so the temperature stays stable.
- Water consistently and avoid letting trays fully dry out.
If you are specifically looking for a walk-in option, you can check our collection here: Maze Walk-in Greenhouse.
The Maze covers we use to make summer seed starting easier
When we are sowing through summer, protection is not optional. It saves seedlings, reduces rework, and supports more sustainable gardening because we waste fewer seeds, less water, and fewer growing weeks.
From our Maze Garden Covers collection, these options suit mid-summer seed starting and seedling protection:
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NET Garden Tunnel options (2m, 2.5m, 3m)
Great for protecting young plants from insects and birds once they are planted out. -
2m POLLINATOR-FRIENDLY Garden Tunnel and POLLINATOR-FRIENDLY Crop Protection Cage - Large
Handy when you want coverage but still want to be mindful of pollinators in the garden. These are especially useful around flowering crops. -
NET Crop Protection Cage options (Slim, Medium, Large) and ARCH NET Crop Protection Cage (Compact, Medium, Large)
Ideal for creating dedicated protected zones, which works well when you are succession sowing and always have something young and vulnerable in the patch. -
2m SHADE Garden Tunnel and SHADE Crop Protection Cage - Large
Very useful for summer growing when seedlings need light but not brutal midday sun. -
3pk Pop up SHADE Cover - 0.92m2 x 1m High
A flexible option for quick shade over small sections, including new transplants. -
Pop-up Tall Greenhouse - Extra Large
A handy small-scale greenhouse-style cover when you need a protected spot for seedlings and young plants without committing the whole greenhouse space.
We like these tools because they support organic-style, low-intervention gardening tips. Instead of chasing pests after damage is done, you prevent the problem upfront.
Compost and sustainability: the best seed starting “boost” is healthy, finished compost
Seed starting is one of those moments where sustainability really shows up in the small choices.
A few compost-friendly habits we recommend:
- Use mature compost, not “hot” compost. Fresh compost can be too strong for seedlings.
- Screen compost if you are adding it to mixes. Seedlings prefer fine texture for even moisture and good root contact.
- Go easy. Seed raising mix is designed to be gentle. A small amount of finished compost can help, but too much can hold excess moisture or be nutrient heavy.
If you are building your compost system, our collections include composting categories such as Compost Bins and Compost Tumblers. You can start browsing here: Maze Collections.
Common mid-summer seed starting mistakes (and what to do instead)
Overwatering in the heat
It sounds backwards, but overwatering can happen quickly, especially in humid conditions or if trays are shaded all day.
Do instead: water deeply, then let the surface begin to dry slightly before watering again. Ensure airflow.
Starting seeds in full sun
A seed tray in full summer sun can cook seeds before they even germinate.
Do instead: bright shade, morning sun only, or a shaded tunnel.
Transplanting straight into harsh conditions
Seedlings raised gently can collapse if transplanted into extreme heat without hardening off.
Do instead: harden off over several days. Increase sun exposure gradually, and transplant late afternoon with a thorough water in.
FAQs people are asking
1. What can we still sow in mid-summer in Australia for late harvests?
Plenty, especially fast growers and transition crops. Beans, cucumbers, zucchini, basil, beetroot, spring onions, and many leafy greens can still work well. In many areas, mid to late summer is also a good time to start brassicas for autumn harvests, particularly if you protect seedlings from pests and harsh sun.
2. How do we stop seed trays drying out too fast during greenhouse seed starting?
The most effective fixes are shade, consistent watering routines, and reducing wind exposure. We also recommend moving trays into bright shade during the hottest part of the day. For plants that are already in the bed, a shade tunnel or shade cover can reduce stress and water loss.
3. Do we need insect netting for summer seedlings?
If pests are active in your area, netting is one of the simplest, most reliable protections you can use. It helps stop insects, birds, and other garden visitors from damaging seedlings, which means you re-sow less often and waste less water and seed. Our Garden Covers range includes net tunnels and crop protection cages designed for this kind of protection.
Final thoughts: keep sowing, just sow smarter
Mid-summer is not the end of seed starting, it is a pivot. With the right approach to greenhouse seed starting, good shade management, and dependable protection, mid summer sowing can deliver late harvests that make the whole season feel longer.
If you want to build a more resilient summer setup, start with protection. Browse our netting, tunnels, cages and shade options here: Maze Garden Covers. And if you are planning a bigger nursery space, keep an eye on our Walk-in Greenhouse page.
