There’s a point in spring when you start looking at every empty patch of garden and imagining flowers.
A few cosmos here. Something colourful in that pot. Perhaps some amaranthus for picking later in summer. Before you know it, the seed trays are out and the growing list has doubled.
October is a lovely time to get warm-season flowers underway, but there’s still one thing worth remembering: a warm afternoon doesn’t necessarily mean warm soil, and it certainly doesn’t mean the last frost has passed everywhere.
The trick is to start what you can grow comfortably now, while giving the more tender plants a little protection until your local conditions catch up.
Let Your Garden Set the Timetable
October looks different around New Zealand.
A sheltered northern garden might be ready for planting, while an inland or southern garden is still having chilly nights and the occasional frost.
For warm-season seeds, pay attention to the temperature of the growing medium, not just the sunshine through the window. A tray can feel beautifully warm during the day and become surprisingly cold overnight.
If you’re starting seeds under protection, make sure you also have somewhere bright for the seedlings to grow afterwards. Warmth helps get them started, but light helps turn them into sturdy plants.
Cosmos for Summer Colour and Picking
Cosmos is a wonderful place to start if you want flowers for both the garden and the vase.
Its airy growth brings movement to a planting, and there’s something very satisfying about picking a handful of fresh stems on a summer morning.
Sow under protection if your nights are still cold, or direct sow once the soil is suitably warm and frost risk has passed. Don’t start more than you have room to look after: cosmos can grow quickly once it gets going.
Give young plants good light, harden them off before planting outside, and leave enough room for their mature growth.
Amaranthus for Texture or Colourful Foliage
Amaranthus appreciates warmth and can be slow to get moving in cold conditions.
Flowering types, such as ‘Autumn’s Touch’, bring textured heads to summer arrangements. Joseph’s Coat offers something different, with colourful foliage rather than the same showy flower crop.
Start seed in a warm, bright position and keep the young plants growing steadily. If frost is still possible, leave them protected a little longer.
It’s worth deciding what you want from the plants before planting them out. A substantial central flower head and several smaller branching stems need slightly different management.
Portulaca for Sunny Pots and Edges
For a sunny, well-drained spot, Portulaca can bring cheerful summer colour without taking up much height.
It’s a good candidate for pots, edging and those warm places where a low-growing plant makes more sense than another tall flower.
The seeds are tiny, so surface sow carefully and keep them gently moist while they germinate. This is not the stage to test their drought tolerance!
Once established, the plants cope with drier conditions much better, but young seedlings still need attention. Give them warmth, good light and drainage, and avoid leaving trays constantly wet.
Many forms open their flowers best in sunshine, so choose their position with that in mind.
Purple Bells Vine, If You’re Happy to Be Patient
Rhodochiton is one for growers who enjoy watching a plant find its way along a support.
At Chbotanics, it really comes into its own in late summer. It’s lovely in a pot beside a pergola, with growth guided along wires or twine, upwards, downwards or sideways.
If you haven’t started it yet, a protected October sowing is an option, but expect a later display rather than instant results. Germination can take time, and the young plants need a chance to establish.
This is one to enjoy as a living climber, not to cut for a vase.
More Warm-Season Flowers to Have a Go At
- Zinnia
- Sunflower
- Celosia
- Gomphrena
- French Marigold
- African Marigold
- Tithonia
- Nasturtium
- Nicotiana
- Ageratum
- Salvia splendens
- Annual Phlox
- Dahlia
- Petunia
- Gazania
- Rudbeckia hirta
- Annual Vinca (Catharanthus roseus)
- Cleome
- Torenia
- Impatiens
- Balsam (Impatiens balsamina)
- Four O’Clocks (Mirabilis jalapa)
- Moonflower (Ipomoea alba)
- Morning Glory (Ipomoea tricolor)
Check local suitability before choosing climbing species, and start tender plants under protection while frost is still possible.
A Few Well-Timed Trays Are Enough
You don’t need to sow the whole summer garden in one afternoon.
Start with the plants you have space and suitable conditions for. Keep your trays labelled, check them regularly, and leave yourself room to pot seedlings on.
Where the season allows, another small sowing later can be more useful than one enormous batch now. It spreads the work and gives you a chance to learn from the first lot.
Most importantly, don’t rush tender seedlings into cold ground simply because the calendar says spring.
There’s plenty to look forward to. A little patience now can mean stronger plants, less juggling, and a lovely garden to wander through with the snips later in summer.
Happy sowing,
Cathy 🌱😊
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