Summer Squash

Cucurbita pepo var melopepo

Introduction: The squashes originated in the Americas and have been cultivated for over 5000 years. The summer squash are a group of varieties that are eaten while the fruit is immature and soft skinned. They are called summer squash to differentiate them from the longer lasting winter varieties.

Summer squash are one of the most popular crops for home gardeners. Just a couple of plants can produce more fruit than the average family can eat and they have a reputation for being so productive that it’s hard to keep up with them. They are actually something of a gardeners joke and countless magazine articles about them open with some ostensibly humorous variation on the theme that everyone eventually has so many they have to resort to desperate measures to get rid of them.

Ease of growing: In warm weather summer squash are productive, fast growing and very easy to grow. They are not so easy if the weather is cold, or if they are attacked by hordes of squash vine borers, squash bugs and cucumber beetles. These pests can make life difficult for the unsuspecting squash grower.

You always see summer squash seedlings for sale at garden centers, but there is little point in buying them. The plants will be happier if grown from seed and it will cost a lot less.

Nutritional content: Summer squash aren’t particularly nutritious, they contain vitamin A, folate, potassium and a small amount of manganese. They don’t provide many calories either, only about 75 per pound (any time a food grows very quickly it will be low in calories).

About Summer Squash  
Seed facts Germ temp: 60 (65 – 85) 100°F
Germination time: 3 – 10 days
16 days / 59°F
6 days / 68°F
4 days / 77°F
3 days / 86°F * Optimum
Germination percentage: 75+
Viability: 3 to 6 years
Weeks to grow transplants: 3 – 4
Planning facts
Hardiness: Tender
Growing temp: 60 (65 – 75) 90°F
Plants per person: 1
Plants per sq ft: ⅓  

Start: 2 wks before last frost
Plant out: 3 wks after last frost
Direct sow: 2 wks after last frost
Succession sow: Every 4 – 6 weeks  

Harvest facts
Days to harvest: 50 – 120
Harvest period: 12 weeks
Yield per plant: 15 – 20 fruits
Yield per sq ft: ½ – 2 lb  

Crop value: Summer squash can be very productive, but they take up quite a bit of space and aren’t very nutritious. All of this means they rate fairly low on the self reliance scale.

Climate: Squash originated in the tropics and need warm weather. They can’t tolerate any frost.


pH 6.0 – 7.0

Summer Squash is a hungry and fast growing crop that produces a lot of biomass. To do this it needs a fertile soil with lots of organic matter, so that it retains moisture, but drains well. It doesn’t do well on acid or saline soils.

Soil preparation: Squash have a very vigorous root system, which may go down 6 feet in its search for nutrients. Add 2˝ of compost, or aged manure, to the top 8˝ of soil, to supply nutrients and to increase its ability to hold moisture.

If the soil is poor you can plant into individually amended holes (you won’t need many).

The traditional method of sowing squash in hills probably originated to help the soil warm up faster and to provide good drainage. Prepare a hill by digging a hole 12˝ deep by 18˝ wide and half filling it with compost. Return all of the soil to the hole to form a small mound or hill. Generally these should have a slight depression in the top to aid in water absorption otherwise they can be hard to water.

You might try growing squash on the site of an old compost pile.


Where: Squash are large plants that take up a lot of room, but make up for it by being very productive. You may only get one row (or two offset rows) of plants in a wide bed. I like to put them at the edge of the garden, where they act as a buffer zone with the rest of the garden. This is definitely the place for the vining types, as they can be allowed to wander off into vacant space.

All of the squash must have full sun for good growth.

Rotation: Don’t plant squash where any other member of the Cucurbitaceae (cucumber, melon, pumpkin, winter Squash) has grown within the last 3 years.

When: Summer squash are quite frost tender, so can’t be planted until all danger of frost has passed and the soil has warmed up (at least 3 weeks after the last frost). If the weather is very variable at this time, cover them with cloches to keep them warm.

Don’t sow squash seed before the soil has warmed up to at least 60°F and preferably 75°F). If it’s too cold they may simply rot in the ground before they germinate. You can use black plastic to warm the soil if necessary.

Succession sowing: You may want to make at least one succession sowing 4 – 6 weeks after the first one, so you can replace declining plants. If your growing season is long enough you might even do a third sowing 4 – 6 weeks later.


Direct sowing: Plant 2 seeds at each location and when both have germinated thin to the best one

They germinate and grow fast in warm soil and soon produce vigorous young plants.

If the soil is only marginally warm enough, you could pre-sprout the seed (take care not to damage it). Such extra effort is rarely worth it however; it’s better to be patient. You can warm the soil with black plastic to get them off to a faster start and protect them under cloches until the weather gets warmer.


Starting inside: Summer squash grows quickly when direct sown into warm soil, so this is the preferred method of growing them. Starting indoors is usually only worthwhile if the growing season is short and spring growing weather is less than ideal. By doing this you may be able to save a few weeks. You may also find that a direct sown crop planted a month later, actually catches them up (and that you wasted your time).

Squash dislike transplanting, so should be started in individual containers. Plant two seeds in each pot and after they have both emerged, you remove the inferior one (pinch it off to avoid disturbing the other one).

I like to use 4˝ pots as they allow some time before the fast growing seedlings must be planted out (you don’t need many of them). If containers are smaller than this you may have to pot them up before planting out, which is an additional chore.

Planting out: Plant your squash out as soon as they have 3 leaves, as they will quickly outgrow their pots and get root-bound (if it’s too cold outside then plant into a bigger pot).

To plant them make a large hole, add a shovel of compost and a handful of fertilizer mix and plant as deep as their first true leaves.

Hills: They can also be planted in hills as described under Winter Squash.

Protection: If cold weather threatens to return after you have planted, you can cover them with cloches. In many areas it’s a good idea to protect the young plants with row covers, to keep pests from attacking the young plants.

Spacing: Squash grow into big plants that need a lot of space.

Beds: In intensive beds they are spaced 18˝ – 24˝ – 36˝ apart, depending upon how large the particular variety gets.

Rows: You could plant your squash in a row down the center of the bed, spaced 18 – 24˝ apart, and fill in the rest of the space with a fast growing crop. You could also use 2 offset rows, to fill the bed more completely. Normally you don’t usually need very many plants, unless you are growing for sale.

Hills: The hills (which are clusters of plants) are usually spaced 36 – 48˝ apart in the row, with 48 – 72˝ between the rows.


Weed: Once squash get going they grow so rapidly that weeds generally aren’t a big problem. They should be weeded while small however. It’s always a good idea to keep weeds to a minimum in the beds, if only to prevent them setting seed.

Watering: The plants should have evenly moist soil all the time. The leaves wilt readily in the hot afternoon sun to slow down water loss. Normally they will recover quickly in the evening as the temperature drops. If they don’t they either need water or (bad news) you have a disease or pest problem.

The best way to water squash is with soaker hose, as wet foliage can lead to fungus diseases.

A low tech way to water and feed the plants is to bury a one gallon pot alongside the plant and half fill it with compost. Then fill it with water a few times a week.

Fertilization: If your soil is poor give the plants a liquid feed of compost tea every 2 – 4 weeks.

Mulch: This is helpful with these widely spaced plants, to keep down weeds and conserve moisture. You can also use a living mulch of annual clover or hairy vetch.

Pollination: The first few squash flowers to appear will be males and won’t produce any fruit. These will soon be followed by female flowers, which have what look like a tiny fruit behind them. If these are fertilized, the fruit will swell within 4 – 5 days. If the temperature is very cool (below 50°F) the females may not be pollinated and the tiny ‘fruit’ will drop off. It is easy enough to hand pollinate (see Seed Saving below), but this is rarely necessary.


Pests: Depending upon where you live, squash aren’t much bothered by pests, or they may be so badly affected that they may be impossible to grow.

Squash vine borer: Many pests simply do some damage (often not serious), but this one will usually kill the plant unless drastic measures are taken. If you aren’t very observant, by the time the damage is apparent the plant is wilting and close to death.

If a plant starts to wilt, the commonest course of action is to cut the plant open and pry out the worm like caterpillars (I don’t like killing things but it’s hard not to feel satisfaction when removing these). The borers give away their location by the sawdust-like frass that comes out of little holes in the stem. After digging out 8 or 10 borers the plant may be pretty well shredded, but you might save it if you bury the stems in soil, so they can send out new roots. Another course of action is to inject B.T into the stem.

It would be much better if you could prevent the borers from entering the plant in the first place. One idea is to lay a sheet of aluminum foil ‘mulch’ under the plant, apparently it is supposed to fool the parent moth so she doesn’t find the stems. You might also wrap the stem with aluminum foil. I moved away from the area (and left this pest behind) before I had a chance to try this.

Squash Bugs: These small brown bugs can be a big problem if they get out of hand. Hand pick adults and nymphs and remove egg clusters.

Cucumber beetles: These attack the plants at all stages and are a problem not only because they eat the plants, but also because they spread bacterial wilt disease.

If you manage to avoid the vine borers and the squash bugs, you may be faced with a variety of other pests, including aphids, mites and pickleworms.

Diseases: Potential problems include angular leaf spot, alternaria blight, bacterial wilt, downy mildew, mosaic and powdery mildew.

You can often avoid many of these problems by keeping the foliage dry and providing good air circulation. Also succession plant, so you can simply remove old plants before they succumb to disease.

Blossom end rot isn’t a disease, but is caused by an irregular water supply. See Tomato for more on this.


When: Harvest the fruit when they are 4 – 8˝ long, which should be about 4 – 6 days after pollination. Generally it’s better to harvest them when still fairly small (4˝ is good), though often they are still good when twice this size. If you pick them while they are small it’s easier to consume all that are produced, so less are wasted.

Whatever the size you like it is very important to pick the fruit regularly and not let any mature on the vine. Those jumbo fruits take a lot of energy and can stop the plant producing altogether.

Gather the edible flowers on the day they open, ideally in early morning while they are still cool. Put them straight in the fridge and use them the same evening. Usually you use the males for food, leaving a few to pollinate the females.

How: Cut the fruits from the plant with a sharp knife to minimize damage to the vine. Leave a small section of stem on the fruit to prevent moisture loss and so improve storage life.

Storage: The fruits are best used fairly promptly. They will keep in good condition in the refrigerator for 2 weeks, but by that time you will have many more new ones. I don’t know of a good way to preserve them.

Seed saving

Squash are cross-pollinated by insects. They will not only cross with other varieties of summer squash, but possibly also with some kinds of winter squash too. This means you have to have only one type flowering at one time. If you have more than this you can try hand pollinating them. As with most Cucurbits you should save the seed from at least 5 plants to ensure enough genetic variability (which is a lot of seeds). Fortunately they are quite long lived (and you can always eat some of the seeds too.)

Hand pollination isn’t as difficult or complicated as you might imagine. Go out in the evening and find some male and female flowers that are about to open the following day and tape them shut with ¾˝ masking tape. It doesn’t matter if they are on the same plant.

The next day you open a male flower and remove its petals. You then carefully open the female flower without damaging the petals, brush the pollen-laden anthers from the male on to the pistil lobes of the female and then tape it closed again (to prevent further pollination). This procedure should work 50 – 75% of the time. It works even better if 2 males flowers are used to pollinate each female.

You will soon know if the above procedure has worked because a successfully pollinated flower will swell rapidly. If it wasn’t successful the flower will soon wither and fall off. Mark the hand pollinated fruit prominently so it isn’t accidentally harvested and leave it to mature fully on the vine. This will slow down further fruit production, or may even stop it altogether.

When the fruit is fully ripe it will get woody like a winter squash. It takes time for the fruit to ripen fully, so allow plenty of time before frost – at least 60 days). You then clean the ripe seed, dry it thoroughly and store in a cool dry place.

Unusual growing ideas

Volunteers: You will often find healthy young squash seedlings popping up in your garden (especially around compost piles). Unfortunately you don’t know what they were pollinated by (though you may have an idea if you only grew one kind) and may end up with some strange and inedible fruit.

In mild climates some people sow squash seed in the fall, in the belief that only the most vigorous and hardy seeds will survive until the spring.

Containers: The bush varieties do quite well in containers, so long as they are large enough and you keep them well watered.


Most summer squash have a bush habit, though a few are vines. There is considerable variation in the kinds of fruit they produce, in both shape and color (green, yellow, white).

There are now a lot of hybrid varieties, especially disease resistant ones. I don’t think they offer a huge advantage though, certainly not enough to give up being able to save the seed (squash are already pretty vigorous anyway).

The main groups are:

Zucchini – These produce the familiar long, green fruit you see in stores (though some are yellow – mostly F1 hybrids).

Black Beauty


Black Zucchini


Gold Rush F1

Crookneck / Straighneck – Yellow and bulbous with a crooked or straight narrow neck.

Summer Crookneck

Cougar F1

Zephyr F1

Round – These resemble a small green melon.

Ronde De Nice

Eight Ball F1

Pattypan – A round and flat with scalloped edges. Some people consider them among the best flavored types, though I’m not sure there is much difference.

Bennings Green Tint

Peter Pan F1

Scallopini F1

Sunburst F1

Vining types – These aren’t very common, as most gardeners now grow the more compact bush types. The only one of these I have grown wasn’t really a vine in the same way as a winter squash, it was more like a bush type that just kept getting longer and longer (to 10 ft or more).

Costata Romanesco

Long Green Trailing

Tender and True


Trombocino – This is actually a variety of C. moschata, that grows as a vine and is more pest resistant than other types.

Kitchen use

Squash are quite versatile in the kitchen. My favorite ways of cooking squash include frying in tempura and making vegetarian “burgers” from them. Tender young ones can also be eaten raw in salads.

Squash flowers may be fried in batter, stuffed and baked, added to soups and eaten in quesadillas.

Vegetarian burgers  

1 cup grated squash
1 cup oats
1 cup grated onion
Salt and pepper
Oil for frying
Herbs for flavoring  

This is the basic recipe. Just mix all the ingredients together and shape
into patties for frying. You can flavor them with a variety of herbs and
spices (basil, coriander, jalapeno, etc) according to your tastes and
whatever you have available.