Cucumbers are one of the most popular, carefree, and easiest vegetables to grow in your garden. They can be grown in garden beds, containers, or grow bags and thrive on sunny balconies and decks. The summer garden – and your salad plate – simply isn’t complete without delicious cucumbers fresh off the vine.
Did you know that cucumbers are actually fruits?
Even though we call a cucumber a vegetable, botanically-speaking, it’s a fruit. A fruit is the mature ovary of a plant, developing after the flower is fertilized and containing the seeds of the plant. Cucumbers are just like cantaloupes, tomatoes, squash, peppers, apples, pears, and eggplants (all are technically fruit).
A vegetable is the edible portion of the plant itself, such as leaves (lettuce and kale), stems (celery and rhubarb), roots (carrots and beets), tubers (potatoes and yams), bulbs (onions and garlic), and flowers (broccoli and cauliflower). Seeds such as beans and peas are also considered vegetables.
Types of Cucumbers
Cucumbers are of 2 kinds: pickling (for making pickles and canning) and slicing (for fresh eating). Both can be grown as vining types or bush types.
Vine-type cucumbers have large leaves and vigorous vines that can be left to ramble through the garden or trained up and across trellises, cages, or fences. Bush-type cucumbers form a sturdy, compact plant that’s easier to contain and preferred for small gardens and container growing.
Growing cucumbers in containers
Vining cucumbers are big plants that need to spread, so if you’re growing one of these types, choose a large container so the plant has plenty of room. If the container is too small, root growth will be restricted by mid-summer and the plant may become more susceptible to disease due to stress, with a dropoff in yield. Each plant requires at least 2.5 gallons of soil, so plant a max of 2 cucumbers in a 5-gallon pot. You can use a tomato cage fitted to the container as a trellis.
You’ll get the best results in containers with a bush-type cucumber (which might also be referred to as “compact”. Bush varieties offer good disease resistance and produce high-quality fruit in much less space. As you might suspect, these varieties have a bushy, round shape instead of a vine. Bush cucumbers have less space between leaves, branch quicker, and set fruit earlier and closer to the base of the plant. Some bush varieties will even produce yields comparable to standard-sized vines.
If you live in a cool climate, place the containers in a south-facing area if possible. This orientation gives them maximum sunlight all day and keeps them warmest if things cool off. In areas with high heat – over 90 – avoid black plastic containers and give them shade in the late afternoon to save them from the hottest part of the day. Containers subject to high heat should be elevated at least four inches off the ground, especially on concrete and brick surfaces.
For container growing, do not use garden soil, whether bagged or native. This is too dense and won’t provide enough air for the roots and may become waterlogged. Only use a high-quality potting soil, which is looser, allowing for root growth, and air and water circulation. And remember that your container must have holes in the bottom of it to allow water to drain. The types of containers without holes are generally meant to hold less decorative, functional containers. The preferred type for cucumbers are those with 4 holes on the edges of the container, not one central hole.
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How to plant cucumbers
In the garden, cucumbers require a generous amount of organic material in the soil – it must drain well and never be waterlogged. If your garden is heavy clay soil, improve it with 2-3 inches of compost before planting cucumbers. After the plants germinate, add 2-3 inches of compost around the root zone to feed the plants all season.
When to sow cucumber seeds
Cucumber seeds can be started indoors 2-4 weeks before last frost. They grow quickly so don’t start them any earlier or they’ll quickly outgrow the starter pot.
Sow seeds or set out transplants no earlier than 2 weeks after the last frost in your area. Cucumbers are a tropical plant and are extremely sensitive to cold temperatures, so don’t risk planting them out any earlier. A late cold snap in spring may kill them.
Cucumber seeds will not germinate in cold soil, so there is no use in trying to plant them early. When the soil has warmed to at least 65 degrees (generally, when air temps are between 70 during the day and 50 at night), sow seeds every 5 inches and plant about 1″ deep. Keep the soil damp but not soaked until seedlings appear. Seeds will germinate in 3-10 days, depending on soil temperature. When seedlings are 5″ tall, thin them to stand 12″ apart. If the cucumber is a bush variety, you can space plants 12-18″ apart.
Like melons, cucumbers can also be planted in “hills”. Create mounds about 6-8″ high and 5 feet apart. Plant 2-3 seeds in each mound. When plants reach 4 inches in height, thin to one plant per mound.
Keep cucumbers damp but never waterlogged
After the plants emerge, water deeply at least once a week, keeping the soil damp but not drenched. Don’t allow the roots to dry out, as fruit production will quickly slow, flower development will slow or terminate, and leaves will curl to conserve moisture.
Trellising cucumbers and mulching
If you’ve chosen a vining variety and have lots of space, you can let the plant ramble through your garden. If space is limited, or to make harvesting easier and reduce the possibility of disease, grow the cucumber on a trellis. Trellises are the superior way to grow cukes as the improved air circulation and access to direct sunlight vastly improves fruit yield.
Use a mulch such as straw, bark, or wood chips around cucumbers to suppress weeds, insulate the soil, and preserve moisture. If the vines are left to sprawl in the garden, fruit should be positioned on top of the mulch to keep it dry and away from pests and disease.
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When to harvest cucumbers
Cucumbers can be harvested as soon as the fruit reached mature length, which depends on the variety you’ve planted. Early harvests, about 1 week early, is the best time to harvest, as the fruits are their sweetest and fewer seeds have developed. Late harvests turn the fruit soft and bitter.
Cucumbers are ready for harvest in roughly 45-70 days from planting, depending on the variety. Harvest cucumbers by cutting the stem 1/4″ above the fruit (do not tear it from the stem or the entire plant may come with it). Cucumbers taste best when harvested before full maturity – they should not be allowed to reach the stage at which they start to yellow as they become bitter. Frequent picking of cucumbers is essential – waiting until cukes are the maximum size reduces the quality of the fruit and makes the plant less productive.
Because of their high water content, cucumbers will only store for about 1 week in the refrigerator, so eat them fresh, in salads, or stir fry recipes. Some varieties are specifically developed for canning and pickling to be enjoyed all winter long.
Cucumber growing tips
- When the cucumber plant has developed 7 leaves, pinch out the growing tip. This encourages sideshoots that grow laterally, which can be left to trail over the ground or trained up a trellis.
- Cucumbers are a sub-tropical plant and need lots of light, warm but not hot temperatures, and a liberal amount of water, but never wet feet.
- Water cucumbers around the roots, and not the leaves, to avoid fungal diseases. Providing adequate moisture consistently improves the flavor, but inconsistent moisture can result in bitter fruit.
- Cucumbers need 6-8 hours of direct sunlight to thrive. Early day sunlight is ideal to dry the plant’s foliage quickly after rainy nights.
- If left to grow on the ground, place mulch like cardboard or straw under the fruit to protect from it from pests and disease.
- Squash bugs and cucumber beetles are frequent pests – monitor and trap them with yellow sticky traps to avoid using chemical insecticides.
- Cucumbers like slightly acidic soil with a pH of 6.0-6.5.
- Keep the soil around cucumber seedlings free of weeds, but be careful not to disturb the roots that grow close to the soil. When plants are mature, the leaves will shade out most weeds. An organic mulch or straw keeps down weeds and insulates the soil.
- Cucumbers mature in 45-70 days depending on the variety.
- Practice crop rotation and do not plant cucumbers where you planted them in the last 2 years – they are very susceptible to disease.
- Cucumber seeds can be planted 2-3 weeks apart for a steady supply of fruit all season.
Wisconsin Vegetable Gardener has a good video on growing cucumbers on a trellis or in a homemade container.
Sources: Texas A&M Agrilife Extension; University of Minnesota Extension; University of Georgia Extension; Michigan State University Extension.