Hello gardening friends! My name is Ella Earth and I’m an expert gardener with over 20 years of experience. For today’s blog post, I will be discussing the different growth stages of watermelons.
I understand that many of you are new to growing watermelons this season. Determining what stage your watermelon plants are currently at can be tricky but important for providing them with the proper care. Through this post, I aim to address that problem by giving you a complete understanding of each distinct stage of watermelon growth.
To prepare this informative guide, I reviewed materials from multiple extension services and agriculture departments. I also drew from my own experiences successfully growing dozens of watermelon varieties over the past two decades.
By the end of this blog, I’m confident you’ll be able to identify what stage your watermelons are in and know exactly how to nurture them every step of the way.
Growth Stages of Watermelon
Watermelons are a delicious and refreshing summer treat enjoyed by many. However, did you know they go through many complex growth stages from seed to harvest? Let’s take a deeper dive into the growth stages of watermelons.
Key Takeaways
- Germination requires suitable soil temperature (70-85°F ideal), moisture, and oxygen.
- The radicle emerges first, followed by the cotyledons breaking soil.
- Most watermelon varieties will germinate within 5-10 days under optimal conditions.
- Scouting regularly is most effective for early problem detection
- Maintain optimal growing conditions to best defend plant health
- Watermelons are true annuals that complete cycle in one season
- Growth rate timing is useful for planning and assessment
- Understanding lifespan optimizes production practices
Watermelon Seed Germination
The first stage begins with watermelon seed germination. Once planted and conditions are suitable, the seed will absorb water and the embryonic root (radicle) will emerge. Soon after, the seed leaves (cotyledons) will break through. This stage typically takes 5-10 days depending on soil temperature and moisture levels.
Seedling Development
Next, the seedling will focus its energy on developing its root system and growing its first set of true leaves. The cotyledons provide nutrients to fuel this growth. Strong root establishment helps the plant uptake water and nutrients as it transitions to its vegetative stage.
Cotyledon Growth
The cotyledons, or seed leaves, are the first leaves that emerge from the germinating seed. They contain stored starches and proteins to nourish the developing seedling. As true leaves form, the cotyledons will yellow and drop off.
True Leaf Formation
Once the radicle and cotyledons have developed, true leaves will emerge. These oval leaves have a distinct petiole (leaf stalk) and are the plant’s first “real” leaves. Typically 2-4 pairs will form by the end of the seedling stage.
Stem Elongation
As the seedling matures, stem elongation occurs to lift compound leaves and develop vines above soil level. Internodal length increases dramatically at this stage. Auxins, a plant growth hormone, stimulate stem elongation and upward growth.
Root System Establishment
During stem elongation, the root system expands to gather water and nutrients. A vigorous root structure is essential to support fruit development later on. Fibrous roots branch out extensively in the top 12 inches of soil.
Moving past seed germination and the seedling stages, watermelons enter a crucial vegetative growth phase. During this time, the plant focuses on building a strong foundation through vigorous leaf and stem growth before flowering.
Vegetative Growth Phase
The vegetative phase is characterized by rapid vegetative growth through compound leaf and vine development. Longer internodes cause vines to sprawl along the ground. By mid-summer, a healthy watermelon plant will have 15+ leaves and 10+ feet of leafy vines. Maintaining optimum growing conditions like temperature, moisture, fertility and airflow is important during this stage.
Pruning to control vine growth and direct energy upward may be implemented, such as trellising vines. Growth rate is influenced by environmental factors and cultivar. Most varieties complete their vegetative cycle within 45-60 days after emergence.
Flower Bud Initiation
Once the plant has reached a sufficient size through ample vegetative growth, flower bud initiation begins. Auxins produced at leaf tips and growing points stimulate flower development. Male and female flower buds form in leaf axils along the stem and vines. Flowering typically occurs 60-90 days after seedling emergence.
Flowering Stage
As flower buds continue developing, colorful blooms emerge. Watermelon flowers are small (1/2-1 inch), yellow with a dark center. They open in the morning and wilt by evening. Flowers must open for successful pollination by bees or manually.
During flowering, both male and female flowers may be present. Male flowers contain only stamens and pollen, while female flowers have a miniature watermelon ovary below 3 slender styles. Cross-pollination is needed between flowers to set fruit.
Pollination Process
For pollination, insect pollinators like bees transfer pollen grains from the male flowers’ stamen to the female flower’s stigma. This allows the female flower’s ovules to be fertilized by male plant sperm. Once pollinated, the fertilized ovary begins to swell and develop into a tiny watermelon.
Proper pollination requires bees or manual pollination. Weather conditions affecting bee activity can impact yields if insufficient cross-pollination occurs. Up to 3-5 female flowers may be pollinated per day during peak bloom season.
Fruit Set and Development
Within a few days of successful pollination and fertilization, the developing ovary or “fruit set” can be observed. Cell division and rapid enlargement occurs as the miniature watermelon grows. At this early fruit development stage, proper care like irrigation, weed control and pest monitoring is important.
Cell Division and Enlargement
Inside the developing fruit, cell division and enlargement drive rapid growth. Cells multiply through mitosis and expand in size to form the various fruit tissues. Mesocarp (flesh), rind and seed tissues differentiate during this stage over 1-2 weeks after pollination.
Sugar Accumulation
As the fruit enlarges over 2-4 weeks, sugars like glucose and fructose accumulate within flesh cells. Total soluble solids (TSS) levels gradually increase, impacting the fruit’s eventual sweetness. Proper fertility and irrigation support high sugar content which typically peaks at harvest.
Rind Coloration
Around 4 weeks after pollination, rind color transformation begins signaling maturity. Watermelon rind colors range from light to dark green or striped depending on cultivar. Color change is a visual indicator used by experienced growers to time harvest.
Fruit Expansion
Entering the final 4-6 weeks, fruit sizes expand rapidly through cell enlargement until reaching maturity. Internal cavity or “heart” space grows along with developing seeds. Irrigation must be increased during peak sizing to meet high water demands. Proper support avoids fruit breakage on vines.
As the watermelon fruit nears physiological ripeness, certain physical signs emerge to indicate maturity and optimal harvest window according to the below table:
| Stage | Signs of Maturity |
| Initial | Rind hardens, shape rounded |
| Mid-point | Well-rounded shape, ground spot changes color |
| Mature | Ground spot yellow-tinged, full slip color formed |
| Overmature | Ground spot dries, slight yellowing of inner rind |
Using multiple maturity signs together gives the best indication of ideal harvest time. Let’s explore these key watermelon maturity indicators in more depth.
Related Article: Citrus Tree Plant Growth Stages
Watermelon Maturity Indicators
Rind Hardening
As cell walls lignify in the rind, it becomes firm to the touch. Early cultivars may be harvested once the rind hardens.
Well-Rounded Shape
Flesh filling out causes sides to round out into a symmetrical globe shape under the rind. Some flat shapes remain if picked too soon.
Ground Spot Color Change
The pale spot where the fruit rested develops from white to yellow as natural plant pigments develop in final sizing.
Full Slip Color Formed
Referring to the remnant portion of the fruit stem left after detaching. Its color deepens to match the fruit as internal sugars peak.
Avoids Overmaturity
After peak ripeness, interiors may start yellowing and rinds over-dry if left on the vine too long. Seeds may also darken.
Using 2-3 of these signs in combination helps accurately time harvest at optimum fruit maturity. Let’s explore harvesting considerations next.
Harvesting Time
Depending on variety and conditions, watermelons typically reach maturity 80-100 days after planting seedlings. They are ready for harvest:
- When physical signs indicate (as noted above table)
- In the morning for ease of detaching ripe fruit from vines
- Avoid bruising melons during harvest and transport
- Cut, don’t pull to detach from vines and leaves intact
Some growers may begin harvest once the first few melons on a vine ripen, then continue daily picking over 1-2 weeks as additional fruits reach maturity. Overripe melons may be harvested last.
Post-Harvest Handling
Proper post-harvest handling preserves watermelon quality until consumption. Steps include:
- Field-sorting ripe melons from greens
- Transporting carefully in ventilation to avoid heat injury
- Pre-cooling immediately to remove field heat
- Grading and packing in cartons for market or storage
- Ripening on-farm in warm humid conditions if needed
- Storing at 55-60°F and 90-95% humidity short-term
Pre-Cooling
Removing field heat through pre-cooling helps prevent condensation damage during cooler transportation and storage. Methods include:
- Hydro-cooling in chilled water bins for 20-30 minutes
- Forced-air cooling in cold rooms within a few hours of harvest
- Passive cooling by stacking in shade with good ventilation
By dropping melons to around 65°F core temperature before cooling the chain, shelf life significantly extends while avoiding chilling injury.
Grading and Packaging
Careful handling during sorting and packing protects skin integrity critical for marketability and storage:
- Inspecting for defects, damage or disease issues
- Sizing uniformly into standard carton sizes
- Cushioning with tissue or shredded paper between layers
- Sealing boxes for transport durability and ventilation
Proper containers like vented cartons balance breathability with protection especially important for long-distance shipping.
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Nutrient Requirements
Watermelons are moderate feeders requiring a balanced diet to fuel their growth. Key nutrient needs include:
- Nitrogen – supports lush foliage growth, apply in multiple applications
- Phosphorus – aids root and fruit development, apply pre-plant and at flowering
- Potassium – builds disease resistance, regulates water balance
- Calcium – strengthens cell walls in fruits and flowers
- Micronutrients – small amounts of boron, zinc, copper, manganese support growth
Soil testing determines existing nutrient levels to create a customized fertilization plan. Slow-release formulas supply steady releases throughout the cycle. Proper fertility combined with suitable growing conditions is a winning recipe for high yields.
Disease and Pest Management
Protecting watermelon crops from diseases and pests requires integrated management strategies:
- Scout regularly to detect issues early and monitor for pests
- Practice crop rotation to disrupt pest and pathogen life cycles
- Choose resistant cultivars when available for key problems
- Maintain good sanitation by removing weeds and refuse that harbor pathogens
- Apply biological or chemical controls judiciously per labels if thresholds reached
- Maintain optimal growing conditions to best defend plant health
Key diseases include fusarium wilt, powdery mildew and gummy stem blight. Common pests are squash beetles, aphids, and cucumber beetles. Taking a preventative, whole-farm approach keeps impacts at bay.
Pruning Techniques
Pruning vines redirects energy to fruit production and enables accessible harvest. Common methods include:
- Training onto trellis or fencing to lift foliage off ground
- Removing excess laterals and side shoots above 4 leaves
- Heading back runners that spread too far from the main stem
- Pruning regularly to encourage bushy growth on cultivars meant for vining
Pruning typically begins after setting initial fruit to balance growth with harvest needs. Timing and severity depends on individual variety growth habits.
Watermelon Growth Stages Timeline
With watermelon growth stages understood, let’s explore how growers implement practices over the production cycle’s timeline. Well-orchestrated plans optimize yields.
Here’s an example timeline showing how key management practices overlap and progress throughout the growth period:
| Stage | Weeks After Planting |
| Site Prep/Planting | 0-1 |
| Fertigation | 1-6 |
| Weed Control | 1-12 |
| Scouting | 2-15 |
| Trellising | 3-6 |
| Irrigation | 3-15 |
| Flower Thinning | 6-8 |
| Fruit Thinning | 8-10 |
| Harvest | 12-15 |
Proper planning, records and flexibility adapting to weather enables growing success following nature’s build-up from planting through harvest cycle. Now we’ve covered the many growth stages involved in bringing watermelons from seed to our plates! Let me know if any part needs more explanation.
Now that we’ve covered watermelon growth stages in-depth, let’s dive into some best practices growers employ during the production cycle.
Related Article: Bougainvillea Growth Stages
Irrigation Strategies
Watermelons require frequent, even moisture to thrive. Drip irrigation is commonly used to deliver water directly to the root zone, minimizing foliar diseases. Some key strategies include:
- Applying 1-1.5 inches per week, splitting into 2-3x/week as vines fill in
- Monitoring soil moisture with tools like tensiometers for precise scheduling
- Avoiding over-saturation that leads to root rot in heavy soils
- Allowing surface to partially dry between waterings for aeration
Proper irrigation is especially critical during flowering, pollination, fruit set and sizing periods for maximum yields.
Fertilization Schedule
A balanced organic or chemical fertilizer program supports growth needs throughout the season:
- Pre-plant – incorporate compost or slow-release pellets
- At emergence – sidedress with balanced fertilizer
- At flowering – phosphorus boost aids pollination and fruiting
- During sizing – nitrogen top-ups every 2-3 weeks
Soil tests annually help tweak rates and timings tailored for each grower’s conditions. Foliar feeds may also supplement key periods.
Trellising Methods
For vining cultivars, trellises or cages are often used to keep foliage and ripening fruits off wet soils prone to diseases. Common systems include:
- woven-wire or twine on stakes, posts or high fences
- plastic or welded-wire cages supported by conduit frames
- netting suspended overhead or on tall trellis systems
These allow adequate air flow, sun exposure and easier harvesting when vines are trained vertically versus sprawling.
Pruning Techniques
We discussed basic pruning methods earlier, here are some additional tips:
- Remove lateral vines as they emerge to focus growth up trellis
- Prune selectively – don’t strip all leaves which impact photosynthesis
- Head back vines 3-4 leaves from developing melons to improve air flow
- Cut leaves that touch the ground which risks disease splash-up
- Pinch off new growth tips periodically to encourage bushier habit
Proper vine management allows sunlight penetration down rows for lower fruits to ripen. Developing a consistent pruning schedule optimizes production.
Fertility Management
Let’s look more at developing a balanced fertility program:
- Soil test every 2-3 years and adjust phos/potash accordingly
- Sidedress nitrogen at 1 lb/100 sqft at emergence and flowering
- Supplement with weekly foliar feeds at peak bloom/fruit set
- Apply compost or organic amendments in fall for minerals and tilth
- Activate amendments with compost teas for microbiome stimulation
Maintaining optimal nutrient levels supports the watermelon’s lengthy vegetative stage through harvesting period for high quality yields.
Common Pest & Disease Prevention
Key strategies for protecting crops include:
- Rotating crops families (cucurbits, tomatoes, brassicas etc) yearly
- Planting barrier crops along borders like marigolds to deter pests
- Removing crop residues after harvest to reduce overwintering sites
- Scouting every 3-5 days and controlling issues early if detected
- Applying bio fungicides or Bacillus sprays weekly at first sign of pressure
Being proactive helps avoid severe pest/disease outbreaks that impact quality and quantity at harvest time.
References & Citations
Frequently Asked Questions on Watermelon Growth Stages
Q. How long does it take for watermelon to grow?
A. On average, it takes watermelons around 80-120 days from seed planting to reach maturity, though some varieties may be faster or slower depending on conditions. Peak growth periods are flowering (60-90 days) and fruit development/sizing (80-100 days).
Q. What is the life cycle of watermelon?
A. Watermelons are annual plants that complete their full life cycle within one growing season. This includes germination, vegetative growth, flowering, fruit set and development and vine senescence typically by early fall after the first frost.
Q. What is the best fertilizer for watermelon?
A. A balanced, all-purpose fertilizer high in nitrogen, phosphorus and potassium applied in multiple applications supports watermelon growth needs. Organic options include composted poultry manure or fish emulsion. Inorganic options could be 10-10-10 or 12-4-8 applied at planting, bloom and fruit set.
Q. What watermelon grows the fastest?
A. Miniature or “personal” watermelon varieties often mature quickest in 65-75 days. Some top sellers that crop fast include ‘Sugar Baby’, ‘Blacktail Mountain’, and ‘Young and Tender’. Larger varieties average 80-100 days but may push over 100 days in cooler regions or with poor growing conditions.
Q. Do watermelons need full sun?
A. Yes, watermelons require a minimum of 6-8 hours of direct, unobstructed sunlight per day for healthy growth and maximum fruit production. Lack of adequate sunlight will delay maturity and reduce yields. Full sun exposure is essential during flowering, pollination and fruit development periods.
Q. What is the best month to plant watermelon?
A. The ideal planting window varies regionally depending on your climate zone’s final spring frost date. As a general guideline, plant 2-3 weeks after last expected frost once soils have warmed to at least 65°F. This timing allows plants sufficient growing degree days to establish and set fruits prior to summer’s end.