Cucumber(Cucurbitaceae, Cucumis)

Place of origin: The Himalayas in India

Optimal temperatures for germination 75-80℉ (25-30℃)

Optimal temperatures for plant growth 65-75℉ (18-25℃)


Scientific name: Cucumis sativus

It is said that cucumbers originated along the southern foot of the Himalayas in northwestern India.

Cucumbers are popular for eating and pickling.  The pickling cucumbers are smaller and should be picked while still small.  The table varieties are larger and are picked when they are about 7-9” long.


Soil Conditions


The humus-rich, well-aggregated soil is best suited for growing cucumbers. Plants grown in sandy soil produces fruit that matures quickly and quickly ages.  On the other hand, plants grown in clayey soil,  produces cucumbers that mature late and age slowly. As cucumber flowers do not need to be pollinated by male flowers in order to produce fruit (parthenocarpy), cucumber plants can produce fruit with only female flowers. Therefore, cucumbers can produce high amounts of fruit.

※The fruit produced by parthenocarpy is not suitable for saving seeds.




Cucumbers like warm weather, and the optimal temperatures for plant growth are between 65-80℉ (18-25oC). When temperatures are around 50℉ (10-12℃), cucumber plants stop growing; however, plant growth also slows down when the average temperature goes above 80℉ (25℃). Therefore, even heat-tolerant cucumber plants don’ t grow well in hot climates during July and August. (Planted in a place that gets some tree shade, cucumber plants can grow better.) Also, in high temperatures that exceed 86℉ (30℃), pollens become short-lived and many flowers fall.


Sowing Seeds

Sow seeds when the soil temperatures reach 60℉ (16-17℃). Place seeds in water. Then,skim off and discard the seeds that float and select the good seeds from among those that have sunk.


Direct Planting


Drop three or four seeds in holes of ¾” (2 centimeter) depth.  The holes should be about as round as a soup can.If the space betweenseeds is too small, bolting occurs, so the space betweenseeds should be about 1-1½” (3-4 centimeters). Then, cover the seedswith about ¼” (one centimeter) of soil, and press the soillightly. If necessary, cover the soil with natural compost.Then, water after planting.

※To extend the harvest over a long period of time, it is better to grow the plants that are sown early separately from those that are sown later.


Inside a Greenhouse

Even though cucumber plants are vulnerable to transplanting, a few seeds can be sown in a pot of 4-5” (10-12 centimeters) in diameter. After seeds germinate, select and leave the best seedling in a pot by removing the other seedlings.  Another method is to sow the seeds in rows in a box, and when cotyledons emerge, transplant the seedlings to pots. While transplanting seedlings, be careful not to cut the roots.


When the temperatures for germination have just been reached, the time that the seeds germinate in is likely to be the same as it would be at higher temperatures. However, bolting occurs in the heat. Just after germination, let the temperature go down to around 77℉ (25℃), and later, let the temperature go down to 73℉ (23℃). (After bolting the plant will not be good.) Once germination has occurred, it is better to give the seedlings enough water once in the morning than to give seedlings a small amount of water many times a day.


Growing Seedlings

While seedlings are growing, bolting occurs when both the soil and the air contain a lot of water. Therefore, duringthe day, expose seedlings to a lot of sunlight. Also,when seedlings are too crowded, bolting occurs, so make sure that the pots have enough space around them. (After plants are in their permanent position, plants that have bolted become vulnerable to strong sunlight.) The time period to grow seedlings should be shortenedaccording to cropping patterns.  The seedling stage is basically for 40-45 days from germination, or ends after 4-5 leaves have appeared after the primary leaves (cotyledons).


Planting Seedlings in their Growing Location

It is important not to hurry.The seedlings need to be planted permanently when the soiltemperature reaches 60℉ (15-16℃) so that the plants cansteadily grow. The lowest temperature for planting seedlingspermanently is 55℉(13-14℃).


The top of the root clump should be planted at the same level as the surface of the ground. Then the top of the root clump should be covered lightly with the soil. For varieties of cucumber that produce female flowers on their main stem, the space between seedlings should be 15-18” (40-45 centimeters). With varieties that produce female flowers on secondary stems, since there a lot of secondary stems, the space between seedlings should be 20-30” (50-70 centimeters). With varieties that grow along the ground, the width of ridge should be about 6’ (2 meters) and the space between seedlings should be about 3’ (90 centimeters).


Mulching with Grass

Cover the surface of the ground with grass densely, in order not to leave empty spaces.As the roots of cucumbers like oxygen, it is necessary that thesoil allows air to pass through easily. Poorly drained soil during the rainyseason causes the roots to become weak andseedlings can easily get a disease. In poorly drained soil,make higher ridges and a drainage ditch around the field or garden. Asroots of cucumbers also become weak in high heat, mulchingwith grass is needed so that the soil remains cool.(When the soil temperature exceeds 77℉  (25℃), roots age quickly.) The materials suited for mulching aregrasses that dry easily. Cover the soil thickly with grass.




Water seedlings in the morning. When cucumber plants are watered properly, the tendrils grow straight from vines at an angle of 45 degrees. When the soil dries, these tendrils wither. Therefore, the seedlings need to be watered.


Cucumbers want a lot of water, but cucumbers are also vulnerable to excessive moisture. In cases where the width of ridge is not very large, water the furrows between the ridges.




In pinching out cucumber plants, don’t remove the leaves from the base of the fruit

that you want to keep.

※Be sure to remember where to pinch, for the position is very similar to other crops. You don’t necessarily have to pinch out plants. It is a good idea to compare a plant that has been pinched to one that hasn’t — especially while learning how to grow your variety.


Pinching of plants grown along the ground:

Pinch out a main stem at the 7th or 8th joint, and let side branches arising from the main stem grow. (Likewise, if you pinch off side branches at the 7th or 8th joint, the fruit enlarges.) Basically, let shoots from side branches grow, but it is good to pinch off the shoots growing thickly.


Pinching of plants grown with a net or trellis:


Basically, grow a plant with just a main stem. It is also good to grow a plant with a main stem and one or two side branches. (Leave vigorous side branches arising from the 5th or 6th joint on the main stem.) In cases where the net is not very high, pinch off the tip of the main stem before it grows over the net. Instead, grow the side branches. In cases where the net is high, pinch off the main stem at the 20th joint or so. Pinch off side branches at the third joint, arising from the 10th-20th joint of a main stem. Also, pinch off the second joint of the rest of side branches.


Grow plants in a way suitable for varieties: There are two varieties of cucumber. One is grown with nets or trellises. The other is grown along the ground. However, they don’t always have to be grown in the same style. Good fruit can be produced with the proper cultivation method. If you want to grow cucumbers with nets or trellises, it is good to use varieties which grows that way, and if you want to grow cucumbers along the ground, use varieties meant to be grown without support.




Harvest cucumbers frequently. As cucumbers enlarge rapidly, harvesting is needed at least once a day. If harvesting is delayed and mature fruit is left, plant vigor deteriorates, and the number of deformed fruits (such as bent fruit or fruit with fat bottoms or thin heads) increases.  In this case, harvest the cucumbers while smaller than the ordinary harvest size, so that the plant’s vigor recovers. Watering the plants is also an effective way to help them recover.


Depending on the variety, the optimal size of  the fruit for is about 7-9” (20-22 centimeters).In hot temperatures, fruits enlarge rapidly, so at times the fruits need to be harvested twice a day. Otherwise, the fruit becomes too large and loses its quality. Also if the fruit becomes hot after harvesting, its quality rapidly diminishes. Therefore, in order to maintain the fruit’s quality after harvesting, harvest in the morning or evening, keep in the shade, and refrigerate as quickly as possible. The optimal temperatures for preservation are between 44-48℉ (7-10oC).


Saving Seeds


Pick the fruits kept on vines until they are fully matured. Then, slice the cucumber lengthwise and push out the seeds and the jelly-like liquid with your fingers and place the seeds in a bottle. At normal temperatures, the cucumber will ferment in one day. Then wash the seeds in water, so any remaining residue can easily be removed, and then dry.


A wide-mouthed bottle is very useful for letting seeds ferment and for saving seeds. A bottle cap keeps the smell in. While the seeds ferment, never add any water to the seeds. If water is added, the seeds will germinate.

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