PlantAlong
Photo: Markus Spiske / Pexels

Carrots

When to start, transplant and harvest carrots, as 6 university extension services put it, and what that means in each zone.

Family
Apiaceae5
Type
Root
Rules
8
Last reviewed
Garden experts do not always agree, so I show every rule side by side.

Five digits. The calendar is computed on your device.

Spring timing, source by source

Every rule counts from the last spring frost, so the same rule gives different dates in different gardens. Here are the rules themselves before any dates are worked out.

  1. Colorado StateSow outdoors
  2. Utah StateSow outdoors
  3. Oregon State, eastern ORSow outdoors
  4. Texas A&M (E-502)Sow outdoors
  • Plant outdoors
Figure 1. How each extension source times carrots in spring, in weeks before or after the last frost. Sources disagree; each bar is one publication's rule, shown as written.

Fall timing, source by source

Fall rules count from the first fall frost.

  1. Texas A&M (E-502)Plant for fall
  • Plant outdoors
Figure 2. How each extension source times carrots in fall, in weeks before or after the first frost. Rules written for warm states sit weeks earlier than those for cold ones.
Table 1. Planting rules for carrots, as published.
SourceWritten forWhatWhen
Colorado State1COSow outdoorsFrom 2 wk before to on the last frost
Utah State2UTSow outdoors2 weeks before last frost
Oregon State, eastern OR8eastern OregonSow outdoors4 weeks before last frost
Texas A&M (E-502)6TXSow outdoors4-6 weeks before last frost
Texas A&M (E-502)6TXPlant for fall12-14 weeks before first frost
Purdue (HO-66)3INPlant for fallCount back days to maturity from the first frost
Nebraska (G1343)4NEPlant for fallCount back days to maturity + 14-day fall factor (+14 for tender crops) from the first frost

Carrots by hardiness zone

Applied to the frost records of every ZIP in each zone. The zone median is a starting point; your own station can be weeks earlier or later.

Table 2. Outdoor planting for carrots by zone, using the Colorado State rule. Linked zones have their own page.
ZoneWhatZone medianAcross most of the zone
4aSow outdoorsApr 28 – May 12Apr 21 – May 24
4bSow outdoorsApr 24 – May 8Apr 17 – May 25
5aSow outdoorsApr 19 – May 3Apr 12 – May 20
5bSow outdoorsApr 17 – May 1Apr 7 – May 17
6aSow outdoorsApr 14 – Apr 28Apr 2 – May 10
6bSow outdoorsApr 8 – Apr 22Mar 27 – May 3
7aSow outdoorsApr 2 – Apr 16Mar 21 – Apr 28
7bSow outdoorsMar 22 – Apr 5Mar 16 – Apr 17
8aSow outdoorsMar 15 – Mar 29Mar 6 – Apr 7
8bSow outdoorsMar 3 – Mar 17Feb 21 – Apr 1
9aSow outdoorsFeb 17 – Mar 2Feb 2 – Mar 18

Growing facts

Table 3. Each value as one source states it. Sources measure differently, so values are not averaged.
FactValueSource
Frost tolerancesemi hardyColorado State1
Frost tolerancesemi hardyUtah State2
Frost tolerancesemi hardyPurdue (HO-66)3
Frost tolerancehardyNebraska (G1343)4
Minimum soil temperature40°FColorado State1
Best soil temperature80°FColorado State1
Days to germinate10-17 daysColorado State1
Days to maturity70 days from seedColorado State1
Days to maturity70-120 days from seedUF/IFAS Florida5
Days to maturity60 days from seedPurdue (HO-66)3
Days to maturity70-80 days from seedTexas A&M (E-502)6
Days to maturity60-100 days from seedArizona (AZ1005)7
Spacing2-3 in apart each wayColorado State1
Spacing1-3 in in the row, rows 10 in apartUF/IFAS Florida5
Spacing2 in in the row, rows 14-24 in apartTexas A&M (E-502)6
Spacing2 in in the rowPurdue (HO-66)3
Heat limit90°FColorado State1

Companions, and how sure anyone is

  • Onions · Helps Tested in a study

    Intercropped onions reduced carrot fly (Psila rosae) attack on carrots, probably because onion volatiles disrupt host finding; onion thrips on the onions were also reduced.999101111

    Conditions (Uvah & Coaker 1984, abstract only): effect greatest with young onions and higher onion:carrot plant density ratios, and virtually ineffective once onions began to bulb. Matters only where carrot fly is a pest. WSU EM128E separately advises pairing taproot carrots with shallow-rooted onions to limit root competition (guidance, no study cited for this pair).

  • Marigold · No clear effect Tested in a study

    Claimed: French marigold protects carrots from carrot fly. Tested: mixing carrots with French marigold (Tagetes patula) did not reduce carrot fly.9

    Single field study (Uvah & Coaker 1984), abstract only read. The UC tradition chart does not list this pair.

  • Lettuce · Helps Extension guidance

    Deep-taprooted carrots paired with shallow, wide-rooted lettuce use different soil layers, so their roots compete less.101111

    WSU EM128E recommends this root-depth pairing as practical guidance; no study of this pair is cited. The UC tradition chart lists each as the other's companion.

  • Dill · Avoid together Traditional pairing11

  • Tomatoes · Helps Traditional pairing11

  • Peas · Helps Traditional pairing11

  • Garlic · Helps Traditional pairing11

    The chart says "onion family"; garlic is an onion-family (Allium) crop. The carrot fly study tested onions, not garlic.

Traditional pairings come from a UC Master Gardener chart that traces to the UC Davis Edible Landscaping Handbook and ATTRA. The chart gives no reasons, and we found no trial of these pairs; treat them as garden lore.

All carrots companions, with sources · The full companion chart

Sources

  1. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 2024. Retrieved 2026-11-02.
  2. Utah State University Extension, Suggested Vegetable Planting Dates for Utah, January 2018; revised May 2025. Retrieved 2026-11-02.
  3. Purdue Extension, The Fall Vegetable Garden (HO-66-W), reviewed September 2019. Retrieved 2026-11-02.
  4. University of Nebraska–Lincoln Extension, Fall Vegetable Gardening (NebGuide G1343), Revised March 2012. Retrieved 2026-11-02.
  5. University of Florida, IFAS Extension (Department of Horticultural Sciences), Florida Vegetable Gardening Guide (SP 103 / VH021), Original December 1999; revised October 2015, January 2016, May 2018, September 2020, September 2021, and June 2025. Retrieved 2026-11-02.
  6. Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.
  7. The University of Arizona Cooperative Extension, Vegetable Planting Calendar for Maricopa County (AZ1005), reviewed This information has been reviewed by University faculty.. Retrieved 2026-11-02.
  8. Oregon State University Extension Service, Eastern Oregon seed-starting schedule, Revised April 2025. Retrieved 2026-11-02.
  9. Entomologia Experimentalis et Applicata 36(2):159-167 (John Wiley & Sons); abstract read via FAO AGRIS, Effect of mixed cropping on some insect pests of carrots and onions, 1984. Retrieved 2026-11-02.
  10. Washington State University Extension, Gardening with Companion Plants (Home Garden Series), EM128E, December 2023. Retrieved 2026-11-02.
  11. University of California Agriculture and Natural Resources (UCCE Master Gardener Program), Companion Planting Chart: Companion planting in the vegetable garden, File dated 2023-09 in URL path; no date printed. Retrieved 2026-11-02.