Can You Plant In Summer? (3 Key Things To Remember)


Maybe you got a late start with planting the garden this year. Or, maybe you just want a second harvest, if possible.

So, can you plant in summer? Depending on your area, you can plant in summer to get a second harvest (succession planting). Cool-weather crops (like broccoli or peas) should be planted in spring or later in the summer. Warm-weather crops (like tomatoes) should be planted early enough in the spring or summer to avoid fall frost.

If you want to do summer planting, you will need to know some key facts (like your USDA hardiness zone or the cold tolerance and time to maturity for each of your plants).

In this article, we’ll talk about summer planting and what you need to know. We’ll look at some examples so you can get an idea of how to plan ahead for summer planting.

Let’s get started.


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Can You Plant In Summer?

You can plant in summer, but you will have to think ahead. This means knowing some key facts, including:

frost
Keep frost dates in mind (both spring and summer) when you think ahead to summer planting.

For example, some frost-sensitive crops (like certain tomato varieties) take a long time to mature (up to 100 days or longer).

If you plant too late, they won’t be ready before frost kills the plant (especially if you live in an area with a short growing season). You might need to start seeds indoors or buy established plants (called starts) to beat the cold.

You can get more out of your garden with succession planting. This means planting one crop in the fall (like radishes, which grow fast) and then another crop to follow in summer (like peppers).

turnip
With succession planting, you can get more out of your garden (for example, by planting peppers right after turnips in the same spot).

The University of Minnesota Extension has some good ideas for succession planting pairs, including:

  • Plant radishes first in spring, then follow up later with tomatoes or peppers (cool/warm)
  • Plant greens (lettuce or spinach) first in spring, then follow up later with broccoli for fall harvest (cool/cool)
  • Plant the same crop twice in succession, such as peas and a second crop of peas later.

What Can You Plant In Summer? (Crops For A Fall Crop Or Second Planting)

The crops you can plant in summer (or fall) will depend a lot on where you live and what the weather is like. Fall frost dates and days to maturity for your plants will play a big role as well.

spinach
You will need to know about frost dates and days to maturity before you can decide on which plants to grow in a summer planting.

The Farmer’s Almanac has some suggestions on what to plant (and when) for spring and summer planting. You can use their tool here by entering your zip code or city/state.

For example, I live in Massachusetts (Zone 7a), and the Farmer’s Almanac suggests summer plantings of:

  • Arugula
  • Beets
  • Carrots
  • Corn
  • Cucumbers
  • Green Beans
  • Kohlrabi
  • Lettuce
  • Okra
  • Peas
  • Potatoes
  • Pumpkins
  • Radishes
  • Spinach
  • Swiss Chard
  • Turnips
  • Winter Squash
  • Zucchini
pea plants
Peas are one crop that you can grow in a spring planting, a summer planting, or both.

Tomatoes transplanted outside after the end of June (July 1 and later) will likely not have enough time to mature before frost (around October 13th). After all, many tomato varieties require more than 75 days to mature after transplant.

You can also plant garlic in the late summer or fall. This is a special crop because it takes 8 to 9 months to reach full maturity – plant in fall, harvest the next spring or summer!

sprouted garlic
Garlic is an exceptional crop because it takes 8 to 9 months to mature – longer than most others.
Image from: https://commons.wikimedia.org/wiki/File:Garlic_with_Horns.jpg

The Iowa State University Extension has some suggestions for a second planting in late summer or fall:

  • Plant seeds in damp soil (after rain or irrigation), since hot, dry soil reduces germination rate.
  • Plant seeds deeper than you would during spring planting.
  • Water after planting.
  • Wait for a stretch of mild weather to plant lettuce seeds, which are extremely heat sensitive.

You can also plant deciduous trees in summer – but evergreens will not have enough time to get established if planted in late summer or fall.

In addition, you can plant some types of grass seed in summer, as long as you have time to water them enough. (You can also plant some types of grass seed in the fall – you can learn more here).

grass sprouting
You can plant grass seed in the summer or fall, as long as you water it enough.

Do Plants Like Hot Soil?

Some plants prefer hot soil (or at least warm soil) for seed germination and growth, while others need cooler soil temperatures.

For example: okra, pumpkins, and squash prefer soil temperatures of 85 to 95 degrees Fahrenheit (29 to 35 degrees Celsius) for ideal seed germination. They can withstand soil temperatures up to 105 degrees Fahrenheit, or 41 degrees Celsius, and still germinate!

okra pod on plant
Okra is one plant that likes hot soil – it can still germinate at soil temperatures of 105 degrees Fahrenheit!

On the other hand: lettuce, parsnips, peas, peppers, and spinach prefer soil temperatures between 65 and 75 degrees Fahrenheit (18 to 24 degrees Celsius) for ideal seed germination. Soil temperatures of 85 degrees Fahrenheit or 29 degrees Celsius is about the upper limit for them to still germinate.

pepper plant
Pepper plants prefer soil temperatures a bit cooler for germination: 65 to 75 degrees Fahrenheit is ideal.

(You can find more information about minimum, maximum, and ideal seed germination temperatures with this resource from the University of California).

Plants have different sensitivity to heat during various growth stages. According to the University of Nebraska-Lincoln, extreme heat and increased soil temperature limits plant growth and development.

Intense heat hurts plants in several ways:

  • Decreased photosynthesis (which leads to lower energy production and smaller plants)
  • Restrained root development (which leads to less ability to uptake water and nutrients – this is an even bigger problem for shallow-rooted crops, such as lettuce and onions)
  • Drier soil (hot air causes hot soil, and both of these lead to more evaporation from soil and transpiration from plants, ultimately meaning lack of water for plants)
lettuce seedling
Lettuce is a shallow-rooted crop. As such, it is more susceptible to dry, hot weather than other plants.

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What Temperature Is Too Hot For Planting?

As mentioned above, the ideal soil temperature for seed germination depends on the plant. However, most seeds will germinate just fine at a soil temperature of 75 degrees Fahrenheit (24 degrees Celsius).

(The exception is spinach, which has a maximum seed germination temperature of 75 degrees Fahrenheit).

A soil temperature of 85 degrees Fahrenheit (29 degrees Celsius) is the maximum for seed germination of lima beans, lettuce, parsnips, and peas.

peas sprouting
Peas have a maximum soil germination temperature of 85 degrees Fahrenheit.

At a soil temperature above 95 degrees Fahrenheit (35 degrees Celsius), several more seed types will stop germinating, including beets, broccoli, cabbage, carrots, cauliflower, Swiss chard, eggplant, garlic, leeks, onions, parsley, peppers, radishes, and tomatoes.

ripe tomatoes on vine
Tomato seeds have a maximum soil germination temperature of 95 degrees Fahrenheit.

At a soil temperature above 105 degrees Fahrenheit (41 degrees Celsius), almost all seeds will fail to germinate due to the intense heat.

The table below summarizes various soil temperatures and the effect on seed germination.

Soil
Temp
Range
F
(C)
Effect On Seed
Germination
below 32
(below 0)
Most seeds will not
germinate.
32-40
(0-4)
Garlic, leeks, lettuce, onions,
parsnips, and spinach will
germinate slowly.
40-50
(4-10)
Beets, broccoli, cabbage,
carrots, cauliflower, celery,
Swiss chard, parsley, peas,
radishes, and turnips will
germinate slowly.
50-60
(10-16)
Most seeds will germinate
(some slowly).
60-75
(16-24)
Just below ideal range for
most plants. Perfect for
lettuce, parsnips, peas,
peppers, and spinach.
75-85
(24-29)
Ideal range for most plants.
85-95
(29-35)
Above ideal range for some
plants. Lima beans, lettuce,
parsnips, and peas will not
germinate.
95-105
(35-41)
Above ideal range for most
plants. Beets, broccoli,
cabbage, carrots, cauliflower,
Swiss chard, eggplant, garlic,
leeks, onions, parsley,
peppers, radishes, and
tomatoes will not germinate
(in addition to those listed in
the 85-95 bracket above).
over 105
(over 41)
Most seeds will
not germinate.
This table shows the effect of soil
temperature on seed germination.

The temperatures for growth of established plants is a different story – and it varies by the type of plant.

Why Do Plants Stop Growing In Summer?

Plants stop growing in summer for a variety of reasons, including:

  • Lack of water – drought or intense heat in windy conditions can cause rapid evaporation of water from soil and transpiration of water from plants.
  • Lack of nutrients – this often occurs as a result of lack of water. However, plants can also use up nutrients during the growing season and run low in summer. In that case, try side-dressing with fertilizer to solve the problem.
  • Intense heat – above a certain temperature, a plant will stop growing. The threshold is different for each plant, and causes different problems. For example, tomato fruit will stop ripening at an air temperature above 85 degrees Fahrenheit (29 degrees Celsius). Potato tubers will stop forming at a soil temperature above 80 degrees Fahrenheit (27 degrees Celsius).
  • Pest pressure – certain pests really start to attack plants in the summer. For example, a summer generation of Colorado Potato Beetles can badly defoliate potato plants if their numbers are great enough.
potatoes soil
Potato tubers stop forming if soil temperatures reach 80 degrees Fahrenheit (27 degrees Celsius).

Do Plants Need More Water In Summer?

Generally, plants do need more water in summer. This is just a natural result of increased water loss from soil and plant tissues (caused by evaporation and transpiration with hotter air and soil).

Evaporation occurs when air and soil come into contact – water in the soil is converted to vapor in the air. This happens faster with hotter air or soil temperatures, more intense sunlight, and when soil has more contact with the air.

daylight
More intense sunlight and higher temperatures will increase the rate of evaporation and transpiration (soil and plants losing water).

To prevent evaporation of water from soil, put down a layer of mulch (you can learn about 7 good mulch options here). For intense sunlight, use shade cloth to protect plants during the hottest part of the day.

Transpiration occurs when plants move water through their tissues and some of that water evaporates through plant surfaces.

To avoid wasting water in dry climates (or during water bans), use drip irrigation and other water conservation measures. These methods deliver water to the root zone of plants, which is the only place they can absorb water from.

Drip Irrigation Guide Home Page Image
Drip irrigation conserves water and ensures that plants have water in the root zone, where they can absorb it.

When watering manually (hose, can, etc.), the best way to tell if you need to water is to feel the soil with your hands. If it feels dry and powdery, it is time to water.

If it is a little moist and cool, you can probably wait safely. If the soil is damp or soggy, you should not water.

When you do water, give the plants a good soaking. Don’t water shallowly often – rather, water deeply less often to encourage deeper, stronger, more extensive root systems.

Finally, remember that it is better to water early in the day (rather than at night). That way, you can avoid wet leaves at night (which promotes the spread of diseases, like blight).

Conclusion

Now you know what to consider if you want to plant in summer. You also know about succession planting and how to care for plants when summer heat and dry weather threaten their health.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

You can learn more about succession planting methods in this article from Johnny’s Selected Seeds.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon


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Join 500+ gardeners to get access to news, tips, and information.

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If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon


Jon M

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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