When to plant watermelon: seeds and transplants

Sow or transplant watermelon after the soil has warmed, nights are warm and the danger of frost has passed. One sunny afternoon after a cold week is not enough. For an open home-garden bed, a practical guide is soil around 18 °C in the seed or root-ball zone, together with a favorable forecast. This is not a universal biological minimum for every cultivar and production system.

There is no single planting date for Ukraine. Combine local weather, the site, the available warm season and your growing method. Autumn or winter planning can prepare seeds, space and irrigation for the following season. It does not mean watermelon should be planted outside in November.

Choose the time for your own site

Use a soil thermometer where the plants will grow. Check conditions over several days and consider overnight cooling. A dry surface can feel warm while soil below remains cold. The air temperature in a weather forecast cannot replace a measurement in the actual bed.

In southern Ukraine, moisture for germination matters alongside warmth. In Polissia and the northern Forest-Steppe, a sunny, warm position and a cultivar suited to the available season deserve particular attention. A sheltered slope and an exposed plot can need different decisions within the same locality.

A raised bed can improve drainage and warming, but cannot guarantee a warm summer. Postpone planting into cold, wet soil. If colder weather is expected, assess the protection you can provide and maintain. Covering material stored in a shed does not protect plants already outside.

Direct sowing or transplants?

Direct sowing avoids moving the roots. It suits a cultivar and warm season that fit local conditions. Transplants allow growth to begin under protection, but do not guarantee an earlier harvest. Overgrown seedlings and damaged root balls can lose that advantage.

Do not start seedlings very early without knowing where they will wait for planting. Compact young plants with a few true leaves are easier to handle than intertwined vines. Work back from a realistic outdoor planting opportunity, allowing for a weather delay instead of assuming an exact day will be suitable.

Select seeds and allow space for vines

Check the cultivar or hybrid name, maturity information, recommended growing method and spacing on the seed packet. Earlier maturity matters where the warm season is shorter. Days to maturity help compare choices; they are not a promise of harvest on an exact date regardless of weather.

Reserve room for vines and access to irrigation. Spacing depends on vigor, cultivar and growing system. Do not crowd the bed because the seedlings are currently small. Mark the planting positions before removing plants from their cells so you will not have to move them again.

Seedless watermelons need a compatible seeded watermelon as a pollen source. Check the seed supplier's instructions and what is included in the packet. A cucumber or another kind of melon nearby cannot simply replace that plant. In a small garden, allow space for both types when planning the purchase.

Prepare the bed and seedling containers

Choose a sunny site with soil that drains freely. Clear weeds and prepare space for sowing or for the root balls. Before deciding on fertilizer, assess the soil. Dark color or a good crop last year does not reveal its precise nutrient supply.

For transplants, use individual containers and a suitable seedling growing medium. Avoid a system that requires pulling tightly intertwined roots apart at planting time. The aim is to move each plant with its own intact root ball, rather than raise as many seedlings as possible in one small pot.

Sow into the final growing position

Prepare a moist seedbed and follow the sowing depth appropriate to the purchased seed and soil. Do not sow into cold, saturated ground and try to compensate with fertilizer. Label the row and cultivar. Water gently without washing out the seeds or leaving the sowing position flooded.

After emergence, assess crowding and give the plants the space required by the chosen system. Avoid disturbing neighboring roots while dealing with excess seedlings. If no plants emerge, check warmth, moisture and seed condition before repeating the sowing in unchanged unfavorable conditions.

Harden and plant young watermelons

Gradually introduce seedlings to outdoor light, wind and changing temperatures. Begin with short periods in a sheltered position and increase exposure. Hardening off does not make watermelon frost hardy. Several previous outings are not a reason to leave young plants outside in cold conditions.

Check root-ball moisture before planting. Release the container carefully, support the root ball from underneath and move it without tearing the roots. Do not pull the seedling by its stem. Prepare a hole that accommodates the root ball, fill the surrounding gaps and water the root zone. Inspecting the plant afterwards is more useful than automatically adding several treatments.

Water, covers and subsequent feeding

After planting, monitor moisture around the roots rather than judging the dry surface alone. Apply water to the soil without washing it away. Weather, rainfall and actual soil moisture determine the next watering. An established watermelon's drought tolerance does not mean a newly moved seedling can be left with a dry root ball.

Monitor temperature beneath covers and ventilate when needed. At flowering, allow insects access to the flowers. Straw and black plastic affect soil warming differently: avoid insulating still-cold ground with a thick organic layer. Plan watermelon feeding separately from choosing the planting day.

Fertilizer for seedlings and planted crops

This liquid product applies through its vegetable-crop group, with separate requirements for seedlings. Fertilizer does not warm the soil or protect against frost. Consider the young watermelon’s stage, growing medium and previous feeding before preparing a solution.

Used throughout the entire period of plant development and growth. For root feeding into the soil/substrate, dilute 50 ml of fertilizer in 10 L of water (100 ml of solution per 1 plant) and use at intervals of 10-12 days. For foliar treatment (spraying), dilute 25 ml in 10 L of water and apply with a sprayer, ensuring even coverage.

For treating seedlings, halve the concentration of the working solution!

Feed plants with fertilizer in the morning or evening, avoiding hot weather. Fertilize the seedling substrate for the first time 10-14 days after pricking out or at the stage of 4 true leaves.

Remember that the solution for seedlings should be half as concentrated as the solution for mature plants. Do not use products whose instructions specify the same dosage.

The 5 L pack is the volume of concentrate in the canister, not the quantity of prepared solution for plants. Count the planned plants and check your measuring equipment before buying. My Garden can help plan a zone, crop, measurements and products; record sowing and feeding dates in your own notebook.

View the fertilizer in a 5 L canister · Plan your purchases in My Garden