Growing Watermelon In The Community Garden...

Surely part of every small gardener's rites of passage: to grow watermelons outdoors, under UK conditions and in a large wooden planter.

With an unofficial plot becoming available, and heeding good omens, I felt that it was time to embark on my own journey and partake of this rite.


Stage 1

The acquisition of seeds.

 

The watermelon was delicious.

Sixteen seeds planted, eight per pot. After twelve days only five germinated.

One pot was set aside as contingency for the "normal" method, the other for Plan A.


Stage 2

Plan A: Grafting onto pumpkin rootstock grown from seeds collected from last year's rather successful Dill's Atlantic Giant.














Now, it's just a waiting game.

 

About a day after the grafts were done, I noticed that the watermelon scions were floppy and had drooped over to one side. I immediately realized that the humidity was not high enough and so enclosed one plant inside a 2Ltr plastic bottle, and grafted a third and enclosed that also just in case.

For future reference, grafted watermelon seedlings need to be semi-active (grown in dappled sunlight rather than full sun) and be kept in humid conditions for the healing process to take effect. The seedlings should then be slowly introduced back to the surrounding atmosphere over a period of about seven days.

 

Incredible! I never thought growing watermelon outdoors in the UK is a viable idea. If you succeed I am definitely going to grow some next year.

 

Five consecutive days where both the night-time and day-time temperatures were at least 10°C meant that, in previous years, there would be no signs of frost and that it would be safe to head outdoors.


Stage 3

Planting outdoors after seven days in the cold frame.

21st May 2017 - Planter dimensions 100 x 120 x 28cm soil depth.


The middle plant did not undergo the high humidity treatment.


The scion died back but signs of regrowth remain.


Compare that to the plants that underwent the high humidity treatment.



Yes, there was a large snail lurking inside the cold frame.


Two of the best planted with plastic bottle cloches for protection against slugs, snails and cold winds.



The plants show signs of yellowing due to nitrogen deficiency since I do not feed them - I use this as an indicator for the next step.

 

When do I remove the cloches? When the leaves turn green again with obvious signs of growth.




I put a runner bean plant in the corner to get some extra mileage out of the planting space.

There is also a sweet potato slip planted next to it. This was propagated from a Morrisons sweet potato.

Sweet potatoes are known to produce masses of low growing foliage and I am hoping to use it primarily as ground cover to reduce surface evaporation, hence, prevent high humidity during late summer. Thus, reducing the chances of getting powdery mildew.

 

How's your melons doing? And sweet potatoes?

 

On every journey a little rain must fall..., and so it did!

Said rain was heavy and lasted for two consecutive days and, coupled with a dip in temperature, caused the roots to rot.

The symptoms included mushy brownish rootstock vines and sickly, fern-like leaves which I believe was caused by fungal disease (possibly, Fusarium Wilt).

To remedy this, I drenched the compost with aspirin solution (two aspirin tablets dissolved in 10L of water) every ten days and let it dry. If the compost became too dry in the intervening days then I drenched using plain water in an effort to wash out excess Nitrogen.


Before the rot took hold.



Undergoing treatment.



Half of the rootstock vine rotted away leaving a healthy recovering sliver.




Remedial action: buried the rootstock and a small part of the scion in the hopes that they will form more roots.







As you can see, one of the two watermelon plants did not make it so in its designated space I planted some beetroot and Swiss chard.

The watermelon, like the sweet potato plant, seems to be vining again.

 

Male flowers are starting to appear.