What to plant this week in Denver, CO
Denver gardeners should protect Daikon radishes and garlic from the current chill, as temperatures can still dip near -10°F before our average last frost on April 21st. This week marks a critical holding pattern where outdoor sowing or transplanting must wait for warmer soil, though early spring greenery is finally emerging.
The next 7 days
Denver, COGrowing in Denver right now
- Our high-altitude freeze-thaw cycles are cracking winter cover; ensure row covers are secured tightly against the wind before any overnight drop below freezing.
- Soil in the Front Range often remains compacted from winter snowpack; aerate heavily if you plan to prepare beds for next week's potential sowings.
- Spring dust storms can carry alkaline particles into wet soil, so water your transplants with clean rainwater or filtered tap water to prevent salt buildup on leaves.
- Be patient with seedlings; Denver's rapid temperature swings often shock young plants that were acclimated indoors but are now facing full sun.
Sow this week
No direct sowing windows open this week.
Transplant this week
Nothing is due to go out this week.
Harvest soon
2 crops- Daikon Radish
- Garlic
Seasonal tips
- Apply fresh mulch now to retain soil moisture as temperatures rise.
- Test soil pH before adding any compost or amendments for new transplants.
- Keep a close eye on emerging seedlings to protect them from late spring fluctuations.
Pest & disease watch
- Late-season aphids and soft-bodied flies may cluster on emerging brassica greens seeking tender new growth as temperatures rise above 40°F.
- Powdery mildew is starting to appear on spinach and lettuce leaves due to the combination of high humidity in morning fog and dry afternoon air.
- Cutworms are active along fence lines and garden edges, ready to sever stems once plants reach a vulnerable height.
Watering this week
Water deeply but less frequently now that the soil is warming up, encouraging strong root development.
Harvest Daikon Radish promptly before the heat sets in to ensure the best crunch and flavor.
Denver gardening questions
3When can I finally start sowing my cool-season seeds outdoors in Denver?
Wait until after April 21st when the risk of a hard freeze drops significantly, though you can use cold frames for a few weeks before then to extend your season.
How do I protect my garlic and Daikon radishes from a sudden -10°F snap frost?
Cover them immediately with heavy row fabric or straw mulch to insulate the roots; these crops are hardy but will suffer if the soil freezes solid overnight.
What causes the grayish-white powder on my lettuce leaves right now?
That is powdery mildew, common in our dry Denver climate when plants sit wet from morning dew or irrigation in the early hours of the day.
Other cities in zone 6a
12See the full zone 6a guide → · Plan your Denver garden in SproutGuide →