The Tricks for Growing Watermelon In Cooler Areas

Growing watermelons has always delighted me in the garden.

The main trick to being successful with this plant is to pick early varieties if you live in a cool climate area.

Too Big = Too Long

Pick a larger, long-day variety and you'll still be waiting for fruit to ripen when the snow is on the ground.


Red juicy watermelon

Growing Watermelon

Start your seed indoors around the middle of April. Do not bother sowing after the first of May as you won't have time to ripen a crop with even the early varieties.

Each seed gets its own pot because you don't want to disturb the roots when you transplant. Use two to three seeds to each four inch pot because you'll thin out the weakest seedlings once the plant gets to the three leaf stage. (three true leaves, not counting the first tiny seedling leaves) Figure you'll get (realistically) three ripe growing watermelons from each vine.


Soil temperature is critical for success with this plant. Ensure the soil is at least 72F. 75 is even better. Only use lukewarm water on the seedlings – never cold water. If you lower the soil temperature with cold water, the seeds will not be happy and will not germinate.

Once the seeds are up, grow them at an air temperature of 70 to 72F with good air circulation and high light levels. Feed with a regular, balanced house plant food (10-10-10 etc) to keep the seedling growing.

Harden Off

Harden those growing watermelons off before you put them outdoors. If you move them from high heat to outside temperatures, you'll stunt them and set them back. This will lower or eliminate getting a good fruit ripening.

Put the melons outside after all danger of frost and when the soil has warmed up enough for melons. In my zone 4-5 garden, this is normally the middle of June. You can stretch black plastic mulch (garbage bags work well) over the planting area to warm it up as soon as the ground is workable. Then when the air temperatures are high enough, the soil under the black poly will be quite warm enough for melons. Weight the plastic edges so they don't fly away in the wind. Some gardeners leave the black plastic in place for this crop and merely make a slit in the plastic to plant the potted watermelon in the ground under the poly.

Trying to rush a growing watermelon will only result in poor garden performance. I'd make comments about rushing spouses having the same effect but I think I'll just let it slide by. :-)


Once planted, remember that watermelons are mostly water and you do have to provide them with enough to both grow the vine and fruit. They are also very shallow rooted plants and weeding next to the vine has to be done carefully or you'll chop up the roots. So, don't move the vines – they resent this big time.

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Try to feed them some compost tea and/or fish emulsion every few weeks to keep them healthy and growing.

Once they are large, how do you know they're ripe? Ask them! If they don't talk back, then look for when the rind on the bottom of the watermelon turns from white to pale yellow. Pale yellow means this baby is done.

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