The Complete Spring Planting Guide: When to Plant What (By Zone)

More than 122 million US households garden, spending over $52 billion a year on plants, seeds, and tools [11]. And most of them, in late winter, are asking the same question: when exactly can I start?

The honest answer isn’t a date on a calendar. It’s a number on a soil thermometer. Frost dates tell you when cold air stops being a danger. Soil temperature tells you whether your plants can actually grow — and the gap between those two things can be two weeks or more. This guide gives you both: a clear framework for timing each stage of spring, plant-by-plant guidance for everything from strawberries to zucchini, a companion planting section grounded in actual science, and a protocol for the late frost that inevitably shows up after you’ve planted everything out.

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Why Soil Temperature Beats Frost Dates

Frost dates are a starting point, not a planting trigger. Once your last frost date passes, the air is safe — but if the soil is still sitting at 50°F, warm-season crops like tomatoes and zucchini will barely move. Roots can’t absorb nutrients efficiently in cold soil, germination slows, and seeds planted below their threshold are as likely to rot as to sprout [1].

Here are the thresholds that actually drive planting decisions:

• 45–50°F soil — bare-root strawberries, bare-root roses, peas, spinach, lettuce, onion sets
• 50–55°F soil — lavender transplants, forget-me-not seeds, hardy annuals
• 60°F+ soil — tomatoes (transplants), zucchini (direct sow), cucumbers, peppers, basil, marigolds (direct sow)
• 65–70°F soil — optimal range for tomato transplants to take off [2]

A soil thermometer pushed 2–3 inches into the ground costs a few pounds and gives you a far more reliable answer than any frost date chart. Push it in during the afternoon when soil is warmest, and check it over a few days — soil temperature fluctuates more than people expect, particularly in spring.

Oregon State University’s guidance on soil temperature thresholds is clear: planting warm-season crops before 60°F doesn’t give them a head start — it sets them back [1]. By the time the soil warms up, the early-planted seedlings have often been overtaken by ones planted at the right time.

One more thing worth checking before you finalise your spring plans: in November 2023, the USDA updated its Plant Hardiness Zone Map for the first time since 2012. Around half of the US shifted to a warmer half-zone, based on temperature data from 1991–2020 [3]. If you haven’t looked up your zone recently, you may be planning around outdated information — more on this at the end.

The Three Phases of Spring

Spring doesn’t arrive all at once. For planning purposes, it helps to think in three phases, each defined by soil temperature and frost risk rather than a calendar month. The exact dates shift by zone, but the sequence is the same everywhere.

Zone offsets (rough guide): Zone 4 — shift each phase 3–4 weeks later than Zone 6. Zone 7 — shift 2–3 weeks earlier. Zone 8 — shift 4–6 weeks earlier.

If you don’t know your last frost date, the Old Farmer’s Almanac frost date lookup uses your postcode for a local estimate. Use it as a reference point, then verify with a soil thermometer before any warm-season planting.

Early Spring Planting: Cool-Season Stars

Early spring — when soil is workable but still cool — is prime time for a specific set of plants that actually prefer cold feet. Don’t wait for warm conditions to plant these. Their advantage is the cold.

Strawberries

Bare-root strawberry crowns go in as soon as soil temperature reaches 45–50°F — earlier than most people expect. The reasoning is straightforward: cool spring temperatures encourage root establishment before the plant has to divide its energy between foliage, flowers, and fruit. University of Minnesota Extension’s strawberry guidance puts it plainly — early planting in cool soil produces stronger plants than waiting until it warms up [6].

The single most important detail with bare-root strawberries is crown depth. The crown (the dense central knob where leaves emerge) must sit exactly at soil level — not above it, not below it. Too shallow and the crown dries out; too deep and the emerging leaves can’t push through and the plant rots. I’ve seen entire rows fail in a single week from crowns planted just an inch too deep. It’s worth taking the extra minute to check each plant individually.

For full growing and care guidance, see our complete strawberry growing guide.

Roses

Bare-root roses are planted before they break dormancy — ideally in early spring while the canes are still dormant but the soil is no longer frozen. The timing varies by zone: Zone 7 gardeners plant in early March; Zone 6 in late March; Zones 3–5 just after hard freeze danger passes. Potted roses are more forgiving and can go in throughout spring.

The advantage of bare-root planting is that the root system establishes itself before the plant has to support leaf growth, producing a stronger first-year plant. Soak bare roots in water for 12–24 hours before planting to rehydrate them, then set the bud union just at or slightly below soil level depending on your zone.

Everything you need for planting, feeding, and year-round rose care is in our complete rose care guide.

Forget-Me-Nots

Forget-me-nots (Myosotis) are a spring staple that most gardeners underprice. Sow seeds directly from early spring through to August — those started in early spring often flower by autumn; later sowings bloom the following spring. If starting indoors, begin 4–6 weeks before your last frost date. Seeds germinate in 8–14 days in consistently moist, cool conditions.

What makes forget-me-nots particularly useful in a spring garden is their role as a companion plant for roses. They grow to about 2 feet and naturally cover the bare, thorny lower canes of rose bushes — softening the look of the bed and suppressing weeds at the same time. The blue flowers complement every rose colour, and the combination has been a staple of English cottage gardens for exactly this reason.

One cultural note that catches new growers out: forget-me-nots are biennial (or very short-lived perennials). They’ll bloom for one season and then die. But leave the spent plants in place until late summer and they’ll set seed prolifically — the colony re-establishes itself year after year without any intervention from you.

See our forget-me-nots care guide for sowing, spacing, and care details.

Another cool-season annual worth planting out at this stage is diascia (twinspurs). These South African natives produce abundant small flowers in pink, coral, and salmon from May through July, then rebloom in September after a midsummer cutback. They excel in containers and window boxes alongside osteospermum and forget-me-nots.

Mid-Spring: The Transition Window

Mid-spring is the bridging phase — soil is warming past 50°F, the last frost is approaching (or just behind you), and the warm-season plants you started indoors need to begin transitioning to outdoor conditions. It’s the busiest, most decision-intensive part of the spring calendar.

Lavender

For gardeners in Zones 1–6, spring is the preferred planting season for lavender. The combination of softened soil, mild temperatures, and natural spring rainfall gives newly planted lavender the best possible start — it can establish roots before it has to deal with summer heat stress. Aim for April or early May, once the soil has warmed above 50°F but before the spring rains wind down.

In Zones 7 and 8, lavender can also be planted in autumn — autumn planting actually gives it a longer establishment window before summer. But wherever you are, spring-planted lavender grown in full sun and well-drained soil will often bloom in its first year.

For variety selection, soil preparation, and pruning guidance, see our complete lavender care guide.

Peonies

There’s something important to say about peonies and spring planting: autumn is better. Peonies planted in late September and October have time to establish root systems before winter, fulfil their chilling requirement naturally, and bloom reliably in their second year. Spring-planted bare-root peonies are playing catch-up — they typically lag a full growing season behind autumn-planted specimens and may not bloom until year three.

You might also find planting spring bulbs helpful here.

That said, potted peonies bought from a nursery in spring are a more viable option than bare-root spring planting. They arrive with established roots and can transition outdoors once frost risk has passed.

Whether you plant in spring or autumn, the planting depth rule is non-negotiable: the buds (eyes) must sit no deeper than 2 inches (5 cm) below soil level. Peonies planted too deep — even 3 or 4 inches — may produce foliage for years without ever flowering. The RHS’s guidance on herbaceous peonies is emphatic about this [15]. And patience is required regardless — consistent, full peony blooms typically take 2–3 years from planting.

Full planting and care guidance: our peony care guide.

Hardening Off: The Step Most People Skip

Tomatoes, peppers, and zucchini seedlings started indoors have been living in stable, sheltered conditions — no wind, no temperature fluctuations, no direct UV. Transplanting them straight outdoors is a shock to the system. The result is transplant stress, wilting, and sometimes outright failure even in perfectly warm conditions.

The solution is hardening off: a two-week process of gradual outdoor exposure that allows the plant to build the physiological resilience it needs. Penn State Extension’s guidance on hardening transplants explains what’s actually happening inside the plant: cell walls thicken, carbohydrate reserves build up, and extra root growth is stimulated [7]. None of that happens without the gradual exposure process.

The protocol is straightforward. Week one: set plants outside in a sheltered spot (no direct sun, protected from wind) for a few hours each day, bringing them in overnight. Week two: extend outdoor time to most of the day, introduce direct sun gradually, and continue bringing in if frost is forecast. By day 14, they’re ready for the ground.

I made the classic mistake in my first years of growing tomatoes — put them out on a warm, sunny day without hardening, watched the leaves bleach white from UV exposure within hours. They recovered, but lost two weeks of growth in the process. The two-week protocol is genuinely worth it.

If you have clay soil, it’s also worth pre-warming planting beds during mid-spring. Clay holds water and warms more slowly than sandy or loamy soils. The RHS recommends covering planting areas with black plastic or a cloche from early spring onward to help clay reach target temperatures before your planting window arrives [8].

Late Spring: Warm-Season Planting

Once overnight temperatures are reliably above 50°F and soil temperature is reading 60°F or above, warm-season planting can begin. This is the most productive period of the gardening year — and also where the most common planning mistakes happen.

Tomatoes

Tomatoes are the most-grown food crop in the country — the National Gardening Association’s 2024 survey found 86% of food gardeners grow them [11]. The 60°F soil threshold is the real planting signal. Below it, tomato roots can’t absorb phosphorus efficiently, growth stalls, and the plant is vulnerable to fungal issues. At 65–70°F, the same transplant will establish within days and produce visible growth within a week [2]. That timing only works if your seedlings are already at the right size — which is why having a solid seed starting schedule matters.

Blossom drop is the other late-spring risk to be aware of: if overnight temperatures dip below 55°F or rise above 75°F after the plants are flowering, blossoms fall without setting fruit. This is temporary — once temperatures stabilise, the plant resumes fruiting — but it’s worth knowing that a cool spell in early summer doesn’t mean something is wrong with your plants.

Full growing guidance, staking, feeding, and variety selection: our tomatoes plant care guide.

Zucchini and Summer Squash

Zucchini is one of the easiest late-spring crops to direct sow. Wait until soil is 60°F+, sow seeds 1 inch deep after your last frost date, and zucchini will germinate within 5–10 days. The plants grow fast and take over significant space — give each plant at least 3 feet in every direction. If you’re short on space, a single compact variety in a large container is genuinely viable.

Zucchini is also one of the best plants to include in a companion planting scheme — it works well alongside tomatoes, lavender, and marigolds in the late-spring garden. More on that below.

Full care guidance: our zucchini plant care guide.

Marigolds and the Science of Companion Planting

Marigolds are one of the most widely recommended companion plants in vegetable gardening — but the advice is often vague. “Plant marigolds near tomatoes” doesn’t tell you why it works, when it works, or which variety to use. The science is actually quite specific.

French marigolds (Tagetes patula) produce a compound called alpha-terthienyl in their roots, which inhibits the development of root-knot nematode eggs in the surrounding soil [12]. Separately, the compound limonene in marigold foliage deters glasshouse whitefly — research showed French marigolds grown next to tomatoes significantly slowed whitefly population development [12]. Both mechanisms are well-documented, which puts marigolds in a rare category of companion plants with genuine peer-reviewed support behind them.

Two practical notes that matter:

1. Timing is everything. Marigolds must be planted simultaneously with their companion crops for the benefits to apply. They don’t retroactively eliminate existing infestations. Plant your marigolds the same day you plant your tomatoes and zucchini.
2. Variety selection. French marigolds work for nematode and whitefly control. African marigolds (Tagetes erecta) are larger but take longer to establish — start them indoors 4–6 weeks before your last frost date. French marigolds can be direct sown after last frost and will bloom within 5–6 weeks.

Marigolds also deter squash bugs and cucumber beetles — both common pests on zucchini and other squash. Lavender planted nearby pulls in pollinators, which boosts zucchini fruit set. And the traditional Three Sisters approach — planting corn, beans, and squash together — uses zucchini as living mulch to insulate soil and suppress weeds below the other crops.

See our marigold growing guide for variety selection, sowing times, and care throughout the season.

Sunflowers

Sunflowers are one of the easiest late-spring direct sowings. Wait until soil temperature reaches 55°F (13°C) and sow seeds 1 inch deep in full sun. Giant varieties like ‘Mammoth’ can reach 3–4 metres, while dwarf types like ‘Teddy Bear’ stay under 90 cm and work well in pots. Succession sow every 2–3 weeks through to early July for flowers from midsummer into autumn.

What to Do If a Late Frost Hits

A late frost after you’ve planted out warm-season crops is a genuine possibility in most zones — and it’s one of the most anxiety-inducing moments in the gardening year. The damage looks alarming: blackened or water-soaked leaves, wilted stems, discolouration. Here’s a four-step protocol that applies to most situations.

1. Assess, but don’t panic. Light frost damage (brown or black leaf edges, some wilting) usually resolves in 7–14 days [9]. The plant is damaged, not dead. Check the stems — if they’re still firm and green at the base, the root system is likely intact and recovery is possible.

2. Don’t prune immediately. This is the most common mistake. It’s tempting to cut off the damaged parts, but doing so too early removes tissue that may be protecting the still-living growth beneath. Iowa State University Extension advises waiting days or even weeks before pruning frost-damaged plants — and for woody plants, waiting until spring new growth appears to fully understand the scope of damage [9].

3. Don’t fertilise. A damaged plant doesn’t need food — it needs to stabilise. Fertilising immediately after frost damage stimulates tender new growth that is highly vulnerable to any subsequent cold. Use a balanced slow-release fertiliser only once the plant is actively growing again [9].

4. Water and mulch. Stable soil moisture and a layer of mulch around the root zone helps moderate soil temperature swings and supports recovery. The roots, insulated by the soil, are often undamaged even when top growth looks severe [10].

For tomatoes with significant frost damage — more than half the plant affected — replanting is often faster than waiting for recovery. Seedlings in mid-May can catch up quickly in warm conditions.

The Old-Wood vs New-Wood Pruning Rule

Spring pruning guidance is everywhere, but most of it skips the one distinction that actually matters: whether your plant blooms on old wood (growth from last year) or new wood (growth from this season).

Prune an old-wood bloomer in spring and you cut off the flowering stems that were already set last autumn. You’ll get foliage but no flowers that year.

Old-wood bloomers — prune immediately AFTER flowering, not in spring:

• Lilac, forsythia, weigela — prune in late spring right after flowers fade
• Roses (most types, on old canes) — light deadheading only in spring; structural pruning after flowering
• Rhododendron and azalea — prune immediately after flowers drop

New-wood bloomers — prune in early spring before new growth starts:

• Hydrangeas (paniculata and arborescens types)
• Buddleja (butterfly bush)
• Most roses grown for repeat blooming (cut back hard in early spring)

Fruiting plants — light tidy only in early spring:

• Strawberries — remove old foliage and dead runners before new growth emerges
• Blueberries — minimal pruning in spring; wait until established plants are 3–4 years old for structural work

If in doubt, look up the specific plant before you cut. Getting this wrong costs you a full season of flowers.

Check Your Zone: The 2023 USDA Update

Before you finalise any planting decisions, it’s worth confirming your current hardiness zone. In November 2023, the USDA updated its Plant Hardiness Zone Map for the first time since 2012 — based on temperature data from 13,412 weather stations covering 1991 to 2020 [3]. Roughly half of the US shifted to a warmer half-zone.

What this means practically: plants you previously considered borderline for your zone may now be reliably hardy. Conversely, plants that were solidly hardy may face occasional winter conditions they didn’t used to. The zone change doesn’t shift your planting calendar significantly — frost dates are what drive timing — but it does affect what you can successfully overwinter.

Check your current zone using the USDA’s interactive Plant Hardiness Zone Map [4].

Spring Planting: Key Takeaways

Spring gardening rewards gardeners who work with the season’s rhythm rather than against it. A few principles to carry forward:

• Measure soil temperature. A $10 thermometer gives you more useful information than any frost date chart.
• Early-spring plants like cold. Strawberries, roses, and forget-me-nots go in while soil is still cool — don’t wait for warmth.
• Harden off everything. Two weeks of gradual outdoor exposure before transplanting saves weeks of recovery time later.
• Plant marigolds on the same day as tomatoes. The companion planting benefits require simultaneous planting — they don’t work retroactively.
• Peonies are better in autumn. Spring potted peonies work; spring bare-root peonies lag a full season behind.
• Late frost is survivable. Don’t prune, don’t fertilise, do mulch and water — and wait.
• Check your zone. The 2023 USDA update changed zones for around half of the US.

Check your frost dates with our free Frost Date Calculator to get personalized results for your garden.

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Sources

1. Oregon State University. Let Soil Temperature Guide You When Planting Vegetables. OSU Extension Service. news.oregonstate.edu
2. UC Agriculture & Natural Resources. Soil Temperature Conditions for Vegetable Seed Germination. UC Cooperative Extension. ucanr.edu
3. USDA Agricultural Research Service. USDA Unveils Updated Plant Hardiness Zone Map. USDA ARS, 2023. [linked inline]
4. USDA Plant Hardiness Zone Map. Interactive Zone Lookup. USDA ARS. [linked inline]
5. University of Minnesota Extension. Planting the Vegetable Garden. UMN Extension. extension.umn.edu
6. University of Minnesota Extension. Growing Strawberries in the Home Garden. UMN Extension. [linked inline]
7. Penn State Extension. Hardening Transplants. Penn State Extension. [linked inline]
8. Royal Horticultural Society. Warming Soil for Planting. RHS. [linked inline]
9. Iowa State University Extension. Cold and Freeze Damage in Garden Plants. ISU Extension. [linked inline]
10. Royal Horticultural Society. Frost Damage. RHS. rhs.org.uk
11. National Gardening Association. National Gardening Survey 2024 Edition. Garden Research. [linked inline]
12. The Dallas Garden. The Scientific Evidence That Marigolds Repel Tomato Pests. thedallasgarden.com. thedallasgarden.com
13. Penn State Extension. Growing Strawberries. Penn State Extension. extension.psu.edu
14. Old Farmer’s Almanac. Frost Dates by ZIP Code. Almanac.com. [linked inline]
15. Royal Horticultural Society. Herbaceous Peonies: Growing Guide. RHS. [linked inline]