📅 Star, Idaho Year-Round Garden Calendar
Month-by-month for Treasure Valley — what to plant, what to harvest, what to prep, what to watch out for
How to Use This Calendar
Star sits in USDA Zone 6a with about a 140-day frost-free growing season. The critical dates that govern everything else:
- Average last spring frost: May 11–20
- Average first fall frost: October 1–10
These are 30% probability dates. For safety, treat May 20 as the earliest safe transplant date for warm-season crops, and plan to protect tender plants if frost threatens after September 25.
Everything in this calendar assumes a typical Star backyard garden — raised beds or in-ground vegetables, some perennials, fruit trees, maybe a few critters to deal with. Adjust as needed for your specific situation.
❄️ JANUARY
Temperature: Avg high 39°F, avg low 25°F. Snow likely.
Planning & Indoor Tasks
- Order seeds. Best selection now. Order from Johnny's, Botanical Interests, Baker Creek, High Mowing.
- Plan this year's garden. Crop rotation, layout, succession plantings. Sketch it on paper.
- Service tools. Sharpen pruners, oil hinges, clean and store winter projects.
- Inventory supplies. Soil amendments, fertilizer, seed-starting mix, row cover, drip parts.
- Read. This is the month to actually learn something new about gardening. Books, UI Extension publications, YouTube channels.
Outdoor Tasks
- Walk the garden after a snow. Check for animal tracks (deer, voles, rabbits) so you know what's been browsing.
- Brush heavy snow off evergreens to prevent branch breakage
- Check tree wraps on young fruit trees — make sure voles aren't girdling them under the snow
❄️ FEBRUARY
Temperature: Avg high 47°F, avg low 28°F. Still cold but lengthening days.
Indoor Seed Starting
- Late February: Start onion seeds indoors (if not buying sets)
- Late February: Start leek seeds indoors
- Late February: Start celery and parsley if you grow them from seed
Outdoor Tasks
- Prune fruit trees (late February through early March, before bud break)
- Prune dormant grapes
- Apply dormant oil spray to fruit trees on a calm day above 40°F
- Spread compost on perennial beds and around fruit trees
🌱 MARCH
Temperature: Avg high 56°F, avg low 33°F. Soil starting to thaw. First crocuses bloom.
Indoor Seed Starting
- Early March: Start tomatoes, peppers, eggplant indoors (8 weeks before transplant)
- Mid March: Start broccoli, cauliflower, cabbage, Brussels sprouts indoors
- Mid March: Start lettuce indoors for early transplant
Direct Sow Outdoors (Late March)
- Peas — snap, snow, shell. Trellis them.
- Spinach, lettuce, arugula — they germinate in cool soil
- Onion sets
- Radishes
- Carrots (if soil is workable)
Outdoor Tasks
- Finish pruning fruit trees before bud break
- Cut back ornamental grasses to 6 inches before new growth
- Cut back perennials that you left for winter interest (Russian sage, sedum, etc.)
- Apply pre-emergent to walkways and gravel areas if you have a weed problem
- Build new raised beds while the soil is still soft from winter moisture
- Set up your drip irrigation system before you actually need it
🌷 APRIL
Temperature: Avg high 64°F, avg low 38°F. Warming fast. Frost still possible.
Direct Sow Outdoors
- Beets, turnips
- More carrots, radishes, lettuce (succession planting)
- Swiss chard
- Kohlrabi
- Potatoes (mid-to-late April when soil is workable and 50°F+)
Transplant Outdoors
- Broccoli, cauliflower, cabbage transplants (mid-April)
- Onion transplants
- Bare-root fruit trees and shrubs (early April is ideal)
- Bare-root strawberries
- Bare-root asparagus crowns
Outdoor Tasks
- Apply Nolo Bait for grasshopper control (late April through May while nymphs are small)
- Mulch perennial beds
- Start hardening off indoor seedlings at the end of the month
- Begin watering perennials as the soil dries out
- Weed early — bindweed and cheatgrass are easier to pull when small
🌸 MAY
Temperature: Avg high 73°F, avg low 45°F. Warming fast. Last frost mid-month.
Early May (Before May 20)
- Plant potatoes if you didn't in April
- Continue succession planting lettuce, radishes, spinach
- Direct sow: beets, carrots, turnips
- Transplant: more brassicas, lettuce, onions
- Harden off warm-season seedlings (tomatoes, peppers) — gradually expose them to outdoor conditions over 7–10 days
After May 20 (Critical Date)
- Transplant tomatoes (cage them at planting time)
- Transplant peppers and eggplant
- Direct sow: beans (bush and pole)
- Direct sow: cucumbers, summer squash, zucchini, winter squash
- Direct sow: corn (late May)
- Direct sow: melons (late May, choose short-season varieties)
- Plant basil (transplant or direct sow once soil is warm)
- Plant flowers: marigolds, zinnias, cosmos, sunflowers
Outdoor Tasks
- Watch for late frost through May 20. Have row cover ready.
- Continue Nolo Bait for grasshoppers if needed
- Begin regular irrigation as temperatures climb
- Mulch warm-season beds after planting
- Train tomatoes to cages or stakes as they grow
☀️ JUNE
Temperature: Avg high 83°F, avg low 52°F. The garden explodes.
Plant
- Last successions of cucumbers and beans for fall harvest
- Sweet potatoes (slips) if you grow them
- Heat-loving herbs: basil, oregano
Harvest
- Spinach, lettuce (before they bolt in the heat)
- Radishes
- Strawberries
- First peas mid-month
- Asparagus (stop harvesting by late June)
Tasks
- Water deeply, infrequently — this is critical now. Daily watering creates shallow roots.
- Mulch everything you haven't yet
- Prune spring-flowering shrubs after they finish (lilacs, forsythia)
- Watch for squash bugs — crush eggs daily
- Check tomatoes for hornworms
- Set up shade cloth over lettuce if you want to extend it through July
🔥 JULY
Temperature: Avg high 92°F, avg low 58°F. Peak heat. Often 100°F days.
Plant (For Fall Harvest)
- Late July: Direct sow carrots, beets, kale, Swiss chard for fall harvest
- Late July: Start broccoli and cauliflower transplants for fall
Harvest
- Beans, peas, cucumbers, summer squash, zucchini — peak production starts
- Garlic (mid-to-late July when bottom leaves yellow)
- First cherry tomatoes
- Onions (when tops fall over)
- Berries — raspberries, currants
Tasks
- Water early morning only — evaporation kills daytime watering
- Watch for heat stress on tomatoes (blossom drop above 95°F)
- Mulch deeper to keep soil temps stable
- Pull bolted lettuce and spinach, save the seeds, replant the spot
- Stake tomatoes aggressively as they get big
- Pinch basil to prevent flowering and keep leaves coming
- Watch for grasshoppers — peak adult season starts
- Yellow jacket traps — start now before they get aggressive
🍅 AUGUST
Temperature: Avg high 91°F, avg low 56°F. Still hot but mornings cooling.
Plant (Fall Garden)
- Direct sow: spinach, lettuce, arugula, radishes (early August for fall harvest)
- Transplant: fall broccoli, cabbage, cauliflower, Brussels sprouts
- Direct sow: turnips, more carrots and beets
- Last chance: bush beans for late September harvest
Harvest
- Tomatoes — peak production. Can, freeze, give away.
- Peppers
- Eggplant
- Corn
- Cucumbers, beans, squash — still going strong
- Melons (late August for short-season varieties)
- First apples (early varieties)
Tasks
- Continue deep watering — heat stress is real
- Process the harvest — canning, freezing, drying. The kitchen becomes a factory.
- Order garlic seed for October planting
- Start collecting seeds from open-pollinated varieties you want to save
- Watch for tomato hornworms — they get huge this month
- Prune raspberry canes after harvest
🍂 SEPTEMBER
Temperature: Avg high 80°F, avg low 47°F. Cooling fast. First frost possible late month.
Plant
- Lettuce, spinach, kale for late fall harvest under row cover
- Cover crops in empty beds — winter rye, hairy vetch, crimson clover
- Spring bulbs (late September) — tulips, daffodils, alliums, crocus
- Perennials and shrubs — fall is the best time to plant trees and perennials in Treasure Valley (cool weather, fall rain, dormancy ahead)
Harvest
- Continue summer harvest — tomatoes, peppers, beans, squash
- Winter squash and pumpkins (when stems harden)
- Apples and pears
- Grapes
- Late corn
Tasks
- Watch the forecast after September 25 — first frost can come anytime
- Cover tender plants with row cover or sheets if frost threatens
- Pick all green tomatoes before the first hard freeze (they ripen indoors)
- Bring in tender herbs (basil) before frost
- Stop fertilizing trees and shrubs — let them harden off for winter
- Start reducing irrigation for established plants
🎃 OCTOBER
Temperature: Avg high 67°F, avg low 36°F. First frost mid-month. Garden winding down.
Plant
- Garlic (mid-October) — the easiest crop you'll ever grow. Plant cloves pointy-end up, 4 inches deep, mulch heavily.
- Shallots (same as garlic)
- Spring bulbs if you didn't in September
- Trees and shrubs — still a good month for woody plant planting
- Cover crops in cleared beds
Harvest
- Final tomatoes, peppers, eggplant before frost
- Pumpkins, winter squash
- Carrots, beets, turnips (these get sweeter after frost)
- Brassicas — cabbage, broccoli, Brussels sprouts (also sweetened by frost)
- Late apples
Tasks
- Clean up summer beds — pull dead plants, compost or burn diseased ones
- Mulch perennial beds for winter protection
- Wrap young fruit tree trunks with tree guards (vole protection)
- Drain and store hoses after final freeze
- Drain drip irrigation systems
- Shut off and blow out outdoor sprinklers before mid-November
- Apply compost to vegetable beds for next year
- Save seeds from your best plants
❄️ NOVEMBER
Temperature: Avg high 51°F, avg low 28°F. Hard freezes regular. First snow possible.
Tasks
- Finish irrigation winterization — blow out lines if you haven't
- Wrap young trees if you haven't (sun scald and vole protection)
- Apply final mulch on perennials and garlic beds
- Plant a few more spring bulbs (last chance)
- Clean and store tools for winter
- Drain rain barrels
- Start a winter compost pile with leaves
- Order a soil test for spring planning (UI Extension does them cheap)
- Begin planning next year's garden
❄️ DECEMBER
Temperature: Avg high 39°F, avg low 24°F. Cold and dark. Garden is asleep.
Tasks
- Knock heavy snow off evergreens after storms
- Walk the garden after fresh snow to spot animal activity
- Inspect tree wraps for damage
- Browse seed catalogs as they start arriving
- Sharpen tools
- Plan spring garden expansion — new beds, new fruit trees, etc.
- Take photos from windows of the winter garden — useful for planning structural improvements
- Rest. The growing season starts again in two months.
🗓️ Critical Dates Summary
| Date |
Event |
| Late February | Prune fruit trees before bud break |
| Early March | Start tomatoes/peppers indoors |
| Late March | Direct sow peas, lettuce, spinach, onions |
| Mid April | Plant potatoes, transplant brassicas |
| Late April / Early May | Apply Nolo Bait for grasshoppers |
| May 11–20 | Average last frost — danger window |
| May 20+ | Safe to transplant tomatoes, peppers, squash |
| Mid July | Harvest garlic when bottom leaves yellow |
| Early August | Plant fall garden (lettuce, brassicas, root crops) |
| October 1–10 | Average first fall frost — protect tender plants |
| Mid October | Plant garlic for next year |
| Late October / Early November | Wrap young trees, winterize irrigation |
Final Thoughts
The Treasure Valley garden calendar runs about nine active months and three quiet months. The active months are intense — there's always something to plant, harvest, water, or fight off. The quiet months are for planning, reading, and tool care.
The two dates that govern everything: May 20 (the safe transplant date for warm-season crops) and October 1 (the first-frost watch date). Build your year around those two and the rest falls into place.
And remember: every gardener in Star has a year where the late frost catches them, the early frost catches them, the grasshoppers eat the beans, the deer find the tomatoes, or the heat wave melts the lettuce. That's not failure. That's gardening here. The gardeners who succeed long-term are the ones who shrug, learn one thing, and start again next March.
Plant on time. Harvest on time. Watch the calendar. Watch the deer.