Summer & Autumn Seed Sowing

Published On: July 23rd, 2021


Summer and early fall can be an ideal time to sow seeds, whether it be vegetables, lawns, or cover crops. Extend your vegetable garden longer into the season and enjoy multiple harvests into the fall.

Sowing Cool-season Vegetables in Mid-to-late Summer

Cool-season vegetables can be planted in the earliest spring for summer harvest but can also be planted in summer, for fall harvest. Aim to sow your summer seeds so that plants will start to mature when the weather cools off in the fall.

Cool-season vegetables are able to withstand a light frost. In some cases, such as kale, carrots & Brussel sprouts, the flavor improves after a frost!

Summer and autumn seed sowing is part of the greater topic of planting cool season vs. warm season vegetables in your garden.

seed packets for summer and cool season sowing vegetables

Single Seeding / Single Harvest Crops

Crop Days to Harvest Cold Tolerance
Beets 50-60 days High 20s
Broccoli 50-70 days Tolerates light frost
Brussel Sprouts 90-100 days Down to 20°F
Cabbage 50-90 days Down to 20°F
Carrots 50-70 days Down to 15°F
Cauliflower 60-80 days Tolerates light frost
Garlic Harvest following summer Winter hardy
Green Onions 60-70 days High 20s
Kale 40-60 days Down to 20°F
Kohlrabi 50-60 days Tolerates light frost
Leeks 70-80 days Down to 20°F
Lettuce 40-60 days Down to 20°F
Parsley 70-90 days Down to 20°F
Parsnips 100-120 days Down to 15°F
Peas 70-80 days High 20s
Spinach 30-40 days Tolerates light frost
Swiss Chard 40-60 days Tolerates light frost
Turnips 50-60 days Tolerates light frost
a lettuce trial bed for summer and fall vegetable garden late season plantings
swiss chard is a single seeding one harvest crop that can grow in late summer and autumn

Multiple Seeding / Multiple Harvest Crops

Fast maturing plants which are not cold tolerant can also be summer-sown to produce multiple crops in a single season. For continuous harvest, sow a fresh crop every 3-4 weeks.

Crop Days to Harvest
Arugula 40-50 days
Basil 30-60 days
Beans 40-60 days
Cilantro 60-70 days
Lettuce 40-60 days
Mustard Greens 30-40 days
Radishes 30-60 days
seed packets for fast growing vegetable gardens cold tolerant multiple harvests

Summer & Fall Lawn Seeding

Mid-August to late September is the ideal time to seed a lawn in Wisconsin.

  • Conditions are favorable for germination & growth
  • Fewer weed seeds are germinating
  • There is ample time for young grass to get established before winter

Dormant seeding can also be done in early to mid-November. The seed will remain dormant through the winter and germinate in spring. This technique is best suited for areas of consistent snow cover.

best premium grass seed for summer and fall lawn yard seeding emerald park at Heyden's Gardens

Cover Crops / Green Manure Crops

A cover crop is essentially a living mulch – a fast-growing crop that is grown on empty soil to prevent soil erosion and keep weeds from growing. Most cover crops produce flowers that are valuable to beneficial insects, although these crops should be cut before they produce seed to avoid self-seeding. Cover crops are also known as Green Manure because they are tilled into the soil, providing organic matter and nutrients.

Cover crops can be sown in early spring to prepare a newly cleared garden area for the first planting. They are also utilized after the summer harvest to replenish the garden for the next season. For this application cover crop seed should be sown 4 to 8 weeks before the average first frost (September 27th in Cedarburg, Wisconsin).

seed packets for summer cover crops green manure living mulch

The foliage will be killed by the frost and the dead plant material will provide winter mulch before being tilled into the soil in spring. Legumes are especially valuable as green manure crops because of their ability to capture atmospheric nitrogen and hold it within their own plant tissues. This nitrogen is then returned to the soil, where it can be used by other plants, when the legumes die, decompose, and are tilled into the soil.

Buckwheat (Fagopyrum esculentum)

  • Frost sensitive annual
  • Days to Maturity: 30-40 days
  • Adds phosphorus. Grows very quickly and breaks down quickly in the soil, allowing for planting in the same area just 3 to 4 weeks after incorporating it into the soil.

Crimson Clover (Trifolium incarnatum)

  • Frost-tolerant annual
  • Days to Maturity: 60-90 days
  • Showy red blossoms invite beneficial insects, Fixes nitrogen. Grows well in cool weather.
crimson clover trifolium incarnatum cover crops green manure crop Heyden's Gardens

Fava Bean (Vicia faba ‘Sweet Lorane Improved’)

  • Frost-tolerant annual
  • Days to Maturity: 30-60 days
  • Highest nitrogen-fixing rate. Large, deep roots break up heavy clay & compacted soil. Germinates in soil temperatures as low as 35°F, and plants are fast-growing and very cold hardy.

Peas & Oat Combination (Pisum sativum & Avena sativa)

  • Frost-tolerant annuals
  • Days to Maturity: 50-70 days
  • Pea plants fix nitrogen and flowers attract beneficial insects. Oats provide organic material and suppress weeds. When sown in the fall, peas and oats grow well in the cool weather but are killed by winter weather.