Why Did My Watermelon Stop Growing?

Soil in hand for planting

Melons have a reputation for being fast growers that are easy to cultivate, so why did your watermelon stop growing, and why are your watermelon plants producing mean little golf balls rather than big juicy melons? No matter how hard you stare at those hard little balls there’s just no progress. 

Watermelon might stop growing due to temperatures that are too high or too low, planting too early or too late, too much or too little water, poor soil quality, root damage, poor pollination, an insufficient or poorly timed care regimen, plant diseases, fungi, and pests, and the wrong variety in the wrong place.

There’s no need to hide your failure from your expectant family and inquisitive neighbors, or to pretend you forgot to plant them this year because prompt action might save your harvest, so read on for some watermelon first aid tips, and what to do next year to get a bumper crop from your watermelon patch.

Temperature and Sun Exposure

Watermelons love the sun and higher temperatures, and cannot tolerate frost at all. If you have a sunny patch with a minimum of 4 to 6 hours of direct sunlight every day, with average daytime temperatures between 70 to 90 degrees Fahrenheit, you’re well on your way to your first melon harvest.

However, too much sun can damage or kill your crops. Most plants, including melons, can suffer from heat stress and sunburn and will stop growing when temperatures exceed 95 degrees Fahrenheit for a few days.

Successful experiments in arid or semi-desert areas have shown that melons do very well when they have at least partial protection against extreme heat during midday. Also, keep in mind that wild temperature swings of around 20 degrees Fahrenheit can also produce tasteless or even bitter fruit.

Too Much or Too Little Water

Thirsty watermelon plants will stop growing. They need a regular supply of water, but it’s not quite as simple as installing an automatic sprinkler system because soil texture plays a critical role in water retention and drainage. Be sure to add generous amounts of organic matter before you plant or sow, and use a good organic mulch to cool down the soil and prevent excessive moisture evaporation.

Experts recommend that you allow the top 1 to 2 inches of soil to dry out before you water again and that you water early in the day to ensure that the leaves are dry before the sun sets to help prevent fungal diseases. Trickle or drip irrigation is a great idea to deliver moisture to the soil without risking fungal diseases.

The critical period for your watering regime starts just after flowering when the fruits begin to develop until the fruits are slightly bigger than half-size. Over-watering at this stage could cause the plant cells to collapse and produce fragile, droopy leaves and few flowers or fruits.

When the melons reach about half their full size, you should slowly and judiciously cut down on the watering to allow the melons to develop a good sugar level. Excessive watering at this stage may cause your melons to develop hollow centers, and it won’t do much for the taste, either.

Soil Quality

Melons are greedy feeders because they grow so fast and produce such massive fruits. While they have a reputation for growing in almost any soil, they don’t produce much under adverse conditions or when they have to compete for nutrients. 

The right soil texture with a pH of 6.0 to 6.8, loads of well-rotted compost or organic matter, and the correct fertilizer will reward you with spectacular results. Melons can take over a substantial surface area of your garden, so it makes sense to get all the produce you can from that section.

Root Damage

If you prefer to transplant seedlings rather than planting the seeds in situ, be careful not to damage the roots during transplantation. Generally, the bigger the seedlings by the time you transplant them, the bigger the damage to the roots. In the case of melons, the best solution is to use individual peat pots, which will allow you to start your seedlings earlier and transplant much larger seedlings for the best shot at healthy fruits.

The other important cause of damaged roots, especially in areas with sandy soil that lacks organic matter, is nematodes. Nematodes are microscopic worm-like creatures – some good, some bad – that infest the roots of host plant roots and prevent them from taking up nutrients. Signs of nematodes in your veggie patch include visible knots, swollen beads or galls on the roots, wilted leaves, and poor yield.

Poor Pollination

No pollination means no juicy, delicious melons. ‘Good’ insect populations are becoming increasingly stressed in certain areas due to the indiscriminate use of insecticides, climate stress, and even invasive insect species. There may not be enough bees and other pollinating insects in your area to overcome a prolonged bout of poor weather during flowering.

It’s the perfect excuse to spend a few hours out in your veggie patch: you can hand-pollinate the flowers using a very small paintbrush. Since you’ll be leaving the bee food intact they probably won’t mind the helping hand!

Insufficient or Poorly Timed Care Regimen

While your melons are growing gangbusters, give them some extra care. Add fertilizer when you plant and repeat the process at monthly intervals. Feed with manure tea and a follow-up feed after two weeks, or feed with a good fertilizer (4 parts Phosphorus to 1 part Nitrogen) every month to encourage good foliage and better fruiting. 

Add a side dressing with mature compost at any stage during the growing phase. If you prefer to feed only once, it should be when they are setting fruit.

Plant Diseases, Fungi, and Pests

Well-fed, well-watered melon plants are more robust than stressed plants, but melons are susceptible to many common vegetable garden pests, plagues, and conditions. Always keep a close watch on those aphids, spider mites, whiteflies, and cucumber beetles.

Since melons have large leaves and dense foliage you may not spot a condition before the damage has been done. It’s a great idea to do a regular close-up inspection of the leaves to catch early signs of mildew, leaf spot, or mosaic virus, and to prevent further spread to the rest of your garden.

Inappropriate Cultivars and Incorrect Positioning

Melons are generally robust and very amenable to experimentation with trellising and potting. As a general rule, the more exotic melon varieties need more specialized care and may not do too well in your no-nonsense back garden.

Follow the instructions on the seed package to prepare the soil and provide each plant with optimum space. Cramming your melons into tiny spaces is for them the proverbial equivalent of sharing a small camping tent with your noisy, competitive neighbors. Your plants will suffer from either poor air circulation or inefficient pollination and will produce more foliage than fruits.

In Conclusion It’s Also Just Common Sense Gardening

Most veggie gardeners start with the basic staples like lettuce, spinach, onions, and the like, and only start thinking about cultivating melons once they have an established home gardening track record. That’s an unnecessarily cautious approach, because melons grow readily, fast, and can deliver great results even for novice gardeners.

When in doubt stick to the basics of good soil, ample water and feeding, and a watchful eye, and you’ll reap the benefits in your first melon planting season.


I enjoy all things outdoors and I love plants! I've never considered myself to be one with a green thumb, but it's my mission to learn, so I figured I would bring you along for the ride. :) Happy planting!

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