What can I plant this month, and when do I prune?

A band of average annual minimum winter temperature, 10 °F wide, split into a and b sub-zones of 5 °F each. It tells you which perennials, shrubs and trees can survive your winter. Zone 7a is 0 to 5 °F, zone 7b is 5 to 10 °F, and so on up and down the scale.

Almost everything else: summer heat, humidity, rainfall, soil, season length and the timing of your frosts. Coastal Washington and central Texas can share a zone number and grow entirely different gardens. For heat, the AHS Heat Zone map is the complementary tool.

Yes — the USDA published a revised map in 2023 using 1991–2020 climate data, and about half the country shifted half a zone warmer. If a plant tag or an article predates that, it may be quoting the older edition, which matters most for anything marginal in your area.

Often half a zone or more within a single garden. South-facing walls store heat and release it overnight; enclosed courtyards trap it; low-lying spots collect cold air and become frost pockets that are effectively a zone colder than the rest of the property. Marginal plants live or die on exactly this.

One colder, if you want the plant to survive an unusual winter rather than an average one. Zones describe the average annual minimum, which means roughly half of winters are colder than the number. Planting exactly to your zone is planting to a coin flip on the bad years.

Six to eight weeks before your last spring frost date, indoors, and transplant out one to two weeks after that frost date once night temperatures stay above 50 °F. Starting too early gives you leggy root-bound seedlings that a later-sown plant will overtake within a month.

Your county extension service publishes them, usually as a probability rather than a single day — a 50% and a 10% chance of frost after a given date. The 10% date is the one to use for anything you cannot afford to lose. Frost dates vary by weeks within a single state and by more than that across elevation.

Count backwards from your first autumn frost date. Take the days to maturity on the packet, add roughly two weeks for the slower growth that comes with shortening days, and sow that many days before the frost. Miss that window and the crop stalls at half size and sits there.

Late winter to early spring while the plant is dormant and the buds are swelling but have not opened: January–February in zones 9–11, February–March in zones 6–8, and March–April in the coldest zones. In cold areas the reliable signal is the forsythia coming into bloom, which tracks soil warmth rather than the calendar.

Because pruning stimulates new growth, and soft new growth is destroyed by a late freeze — frequently taking the whole cane with it. Waiting until the danger has largely passed costs you nothing; going early can cost you the plant.

No, and this is the mistake that costs a whole season of flowers. Repeat-flowering modern roses bloom on new wood and take hard late-winter pruning. Once-blooming old garden roses and ramblers bloom on last year’s wood, so pruning them in late winter removes every flower bud — those are pruned immediately after they finish flowering.

Dead, damaged, diseased and crossing canes, always. That is not really pruning, it is maintenance, and removing it improves airflow through the plant, which is the main defence against black spot and mildew.