Note this is a general guide. If you are in Hobart you may start earlier than the Huon Valley for instance. When in doubt, wait a few weeks. Note seasons are not always the same, some Springs are warm, some are nasty. View failures as part of the fun of Gardening. The best calendar is the one you create for your garden over years of experience. Some of the below is from my experiences. I can be wrong!!
For areas outside of Tasmania, refer to local resources. I am not an expert in Canberra, Sydney etc so no point me trying to list what to sow when.
June (winter is here, frosty)
Rest up, maybe add some compost to you beds so they settle in before the planting season ahead. Organise your seeds for the coming season (especially the Tomato, Capsicum, Chilli, Eggplant and Onions which go in next month on a hot bed). Watch a good movie, enjoy good coffee!
Ok to sow is spring onions, shallots, spinach, have a go add some asian greens, chervil, radish, Broad beans (note some of these will be short crops. will grow slowly and bolt in spring).
GET YOUR CERTIFIED POTATO SEED before they sell out
long day onions (best started indoors to plant out in Sept in cold wet soils)
mid to late in month can start Tomato, Chilli, Capsicum and Eggplant on a heatmat (ideally around 22 degrees C – find them on ebay for $30 ish ) – These are for those that will be grown in a hothouse (Tomatoes plant out in hothouse mid to late Sept, Chilli, Caps and eggplant late Oct to Nov).
August
(still cold soils, some of the below is better delayed in cooler parts of Tasmania as cold periods stress seedlings into bolting – start indoors or protect with fleece outside, some frosts)
*Some of these best sown under agricultural fleece or indoors and planted out after risk of frost has past. This is due to frosty nights on some of these young seedlings germinating can cause them to bolt prematurely.
Asian Greens * Some are best planted out after risk of frost has passed
an start Tomato, Chilli, Capsicum and Eggplant on a heatmat (ideally around 22 degrees C) – These are for those grown in a hothouse or for Tomato planted outside in mid to late October under fleece.
IN THE GARDEN: Note veggies growing such as Carrot, parsnip, Beetroot and others will begin their journey to flowering as the soil begins to warm. Harvest them an any sign of a flower!
September
(starting to see some warmer days, soils warming, still get bleak cold fronts, winds and some frosts in many parts)
Swedes (from mid September, best are autumn/winter maturing in my onion)
Tomato/Tomatillo (start on a heat mat, plant out around 8 to 10 weeks old – best to use fleece to protect after planted out in lateOct/Nov for protection on cold nights and days)
Zucchini (start indoors mid/late month on depending on your frost risk, can plant in hothouse, quick to grow so allow 3 weeks from sow to plant)
*Note: Frosts are the limiting factor for a variety of veg in Sept. Lettuce can handle a light frost but a hard frost will set them back. Many Brassicas may go to flower if frost hits them (I use fleece to cover). Old bed sheets are handy to throw over on forecast frosty nights or simply wait. It depends on how much food you want to grow. Market Gardeners around the world use fleece in order to keep food growing. Silverbeet best delayed and sown mid October on as cold nights (and frost) can tell them to go to flower (same for Kale).
October
(warming up but cold fronts and wind can still wreak havoc, often end of average frost risk mid month)
Tomato/Tomatillo (start on a heat mat, plant out at 8ish weeks old) or plant out seedlings late in month (protection important on cold nights and days to reduce setting back the plants from cold strees)
Watermelon/Rockmelons (Start on heat mat indoors late in month from experience unless in warmest parts)
Zucchini (start indoors – possible to plant out late in month if warm).
November
(tricky month, some warm periods and possible cold periods – protection needed over cool periods to protect summer plants, winds can be gusty at times).
Note: We still get many cold nights or cold fronts along with warmer days/nights during November. I highly recommend you at least use those plastic tree guards if planting outside (Mitre10/Bunnings have them) around your Tomatoes, Chilli, Capsicums, Eggplant, Cucumber to offer additional protection from cold nights (>5C for Toms, <10C for others) to give your the greatest chance of success and yields. Laying some black plastic down will also help keep soils warmer (great for storage pumpkins) which is an issue when we have cool springs. We aimto provide maximum days to maturity but that first 30 to 45 days can be a challenge.
Summer lovers that experience cool soils are set back thus the most you can do to provide protection and warmer soils the better.
Tomato/Tomatillo (try sowing or plant out seedlings – protect on cold days or nights<5 degrees C) Note where I am in the Huon, Around Nov 15-20 has been on avg the best time to plant out tomatoes)
Turnips
Watermelon/Rockmelons (Start on heat mat indoors – plant out on black plastic later part of month)
Tomato/Tomatillo (try sowing or plant out seedlings (aim to sow no later than first week and seedlings in by mid month latest, this is getting late for ripening (March) – protect on cold days or nights<5 degrees C)
Turnips
Watermelon/Rockmelons (plant out on black plastic, really want to have started seed by now)
Zucchini
January
(A fairly stable month as Tasmania goes, one of the warmest months)
(warm but some colder nights, Tomato picking should be going strong, last chance for many sowings for winter – do earlier in month except for Spinach, Asian Greens)
Asian Greens (Choi Sum, Gai and Kai Lan, Chinese Cabbage, Hon Tsai Tai, Mizuna, Mibuna etc) This is a great month for sowing these.