To grow watermelons in a raised bed, first select a small watermelon variety, such as Sugar Baby watermelons, since they can be grown on a trellis. Then, pick a full-sun location for your watermelon bed. Once your raised bed is filled, install a tall, sturdy trellis. Now, you’re ready to plant watermelon seeds every 24 inches along the base of the trellis. Once the watermelons sprout, provide them with 2 inches of water per week until they begin producing fruit. Once fruit appears on the vines, reduce watering to 1 inch per week. Finally, as your melon vines grow, train them to climb your trellis and provide support for the melons so they don’t break off the vine.
How Many Square Feet Does a Watermelon Plant Need?
If you allow watermelon plants to sprawl on the ground, they can take up well over 20 square feet. However, if you trellis your watermelons in a raised bed, you can grow them in 10 square feet of space.
- Watermelons grown along the ground can easily take up 20 square feet.
- Trellised watermelon vines in a raised bed can be grown in 10 square feet of space.
- Training watermelons to grow on trellises maximizes the amount of fruit you can grow in a raised bed.
You can truly maximize watermelon growing space in a raised bed by trellising. With this system, you can fit 3 watermelon vines in a single 8-foot-by-4-foot raised bed. You can grow anywhere from 60 to 120 pounds of watermelon in this space, which is a sizable harvest for such a small footprint. A raised bed can also help keep certain animals at bay.
How Deep Should a Raised Bed be for Watermelon?
Watermelons grow best when the soil depth is at least 24–36 inches. However, you may not need a raised bed that is this tall. If your raised bed is constructed so that there is no barrier between the bottom of the raised bed and the soil below, watermelon roots will be able to dig down into the soil as deep as necessary. So, you can grow watermelon in a very shallow raised bed, as long as the roots can dig deeper than the raised bed.
- Watermelons need 24–36 inches of soil to grow.
- If there is no barrier that prevents watermelons from sending roots deeper than the walls of your raised bed, you can grow watermelons in a shallow raised bed.
- If the raised bed has a barrier between it and the soil below, it must be 24–36 inches deep for watermelons.
If you place landscape fabric or another barrier between your raised bed and the soil below, your raised bed should be at least 24 inches deep for watermelon. 36 inches is better. The majority of watermelon roots are in the top 12 inches of soil, but additional soil depth allows for deep taproots and evenly moist soil. Deep soil contributes to a drought-resistant watermelon bed.
7 Steps for Growing Watermelon in Raised Beds
Growing watermelon in raised beds is an incredibly space-efficient way to get a big harvest. Even if you have a relatively small raised bed garden, you can still grow an incredible crop of ripe watermelon. Here’s how:
Choose a Small Type of Watermelon
Because growing watermelons in a raised bed requires trellising and supporting growing watermelons, it is essential to pick a variety of watermelon that produces 5–10-pound fruit. Heavier melons can break off the vine while growing or put a lot of strain on a trellis.
- Growing watermelons in a raised bed requires trellising the vines—the trellis must also support the weight of the growing fruit.
- Choose a small (5–10-pound) watermelon variety. This prevents the melons from breaking off the vine as they grow on the trellis.
- Sugar Baby and Blacktail Mountain are popular watermelon varieties for raised beds.
Varieties like Sugar Baby, Mini Yellow, and Blacktail Mountain are ideal for growing on a trellis in a raised bed. There are several other mini watermelon varieties with flesh ranging from pink, to yellow, to white. You can pick one variety or try several to see what grows best in your region.
Pick a Sunny Location
Watermelon vines love sun. They require at least 6–8 hours of direct sunlight per day, but you can offer them even more if you live in a cooler climate. Whether you are growing watermelons in an existing raised bed or building a new one, choose a spot with all-day sun exposure, if possible.
- Watermelons require 6–8 hours of full sunlight daily, at minimum.
- Planting locations that receive morning sun and some afternoon sun are ideal for watermelon.
- You’ll get the best fruit from watermelon vines grown in sunny, warm areas of your garden.
In extremely hot weather (over 100℉), watermelons can be damaged by too much sun, but this is generally not a concern. Warm soil and plenty of sunlight fuel watermelon growth and promote the best fruit. So, grow watermelon in sunny garden beds.
Fill Your Raised Bed With Non-Acidic Soil
Watermelons grow best in sandy, loam soils with relatively low acidity. Select a rich, well-draining topsoil to fill your raised bed. Then, test your soil pH with a soil meter. pH between 6.0–6.5 is perfect for watermelons. To prevent raising the soil acidity, do not mix peat moss into your raised bed. You can mix compost into the soil or apply a balanced fertilizer for a growth boost.
- Fill your raised bed with sandy, loam soil to encourage healthy watermelon vines.
- Test the soil pH with this soil tester.
- Watermelons thrive with soil pH between 6.0–6.5.
- Correct low pH by mixing agricultural lime into the soil.
- Avoid mixing peat moss into the soil since it will raise soil acidity.
If the pH is under 6.0, the soil is too acidic for watermelons to thrive. The plant may grow yellow foliage and fail to produce fruit. To reduce soil acidity, mix calcitic or dolomitic lime into the soil. With the correct soil pH, you set your vines up for success.
Install Heavy Duty Trellises
Growing watermelons in a raised bed requires heavy-duty trellises. The trellis must support the weight of the vine, as well as the heavy watermelons. For a truly sturdy trellis, select livestock panels as the trellis material. Then, follow these steps to construct your trellis:
- Use these livestock panels.
- Set the livestock panel so that it is standing vertically, as tall as possible.
- Support the panel by driving one of these T-posts into the soil on either side of the panel.
- Secure the panel to the T-post with wire or heavy-duty zip ties.
Because livestock panels are typically 2 feet wide, they’re the perfect size for growing watermelon. A pair of 2-foot-wide, 8-foot-tall panels provides ample space for a single watermelon vine. Just add more panels to your raised bed for additional watermelon plants.
Plant Your Watermelons
With your trellises securely in place, it’s time to begin planting. Select a location 24 inches from neighboring plants and the walls of your raised bed. Plant 3–4 watermelon seeds ½-inch deep at the base of your trellis. Continue planting 3–4 watermelon seeds every 24 inches. Once the seeds sprout and produce their first true leaves, remove the weaker plants, leaving one strong watermelon vine every 24 inches.
- Plant watermelon seeds and plants with 24 inches of clearance on all sides from the raised bed walls and neighboring plants.
- At each location, plant 3–4 watermelon seeds ½-inch deep at the base of the trellis.
- When the seeds sprout, remove the weaker vines until only one plant remains every 24 inches.
- In colder climates, it’s best to start watermelons indoors, then transplant them to raised beds after the danger of frost has passed.
In warm climates, it’s best to grow watermelons from seed once the soil temperature rises to 70℉ in spring. However, if your area has short summers, it’s best to start plants from seed indoors 2 weeks before the last spring frost. Then, transplant the seedlings into your raised bed 4–5 weeks later.
Water Your Plants for Success
Watermelon plants need a lot of water. Before they set fruit, watermelons require 2 inches of water per week. This can be delivered with 1 hour of watering with a soaker hose, split into 2–3 weekly sessions. Two 30-minute watering sessions per week would be ideal, for example.
- Give watermelon plants 2 inches of water per week until they set fruit.
- 2 inches of water can be delivered with 2 weekly soaker hose waterings for 30 minutes each watering session.
- Cut watering in half when your melon vines set their first fruits—this encourages sweeter fruit.
- You may need to adjust watering due to drought or rain.
Once your watermelons begin to produce their first baby melons, cut the watering in half. This produces sweeter, higher-quality fruit. So, if you’re watering twice per week, water for 15 minutes at each session. However, environmental factors can affect how much water your plants need. Provide more water in times of hot, dry weather. Reduce watering when there is natural rainfall.
Train and Support Watermelon Vines
As your watermelon vines grow, it is essential to train them to grow on your trellis. Unlike trellised cucumbers, watermelons will not climb a trellis on their own. Instead, use soft twine or surveyor’s tape to loosely tie the vine to the trellis. Because watermelon vines grow quickly, you will need to tie new portions of the vine to the trellis throughout the season.
- Watermelon vines will not climb a trellis on their own.
- Use this inexpensive surveyor’s tape to gently tie the vine to the trellis as it grows.
- Support watermelon fruit with slings to prevent melons from breaking off and falling to the ground.
- Use these melon hammocks to support each watermelon.
- Tie both ends of the sling to the trellis, then rest each melon in its own sling so it can grow safely.
Once your watermelon vines begin to produce fruit, you will need to add extra support. A watermelon vine growing on a trellis cannot support the weight of a growing melon. The fruit will snap off the vine and fall, ruining your harvest. To prevent this, use bird netting, net bags for oranges, or similar material to make a sling for each melon. Tie each end of the sling to the trellis and place the melon itself in the sling. This will allow you to grow 10-pound melons on a trellis without losing a single fruit.
Do Watermelons Grow Well in Raised Beds?
Watermelons can grow very well in the limited space of a raised bed, provided you grow them on a trellis. It is simple to grow watermelons this way. Just follow these steps:
- Plan to grow a small type of watermelon, such as Blacktail Mountain or Sugar Baby melons.
- Choose a raised bed location that gets at least 6–8 hours of direct sunlight daily.
- Fill the bed with sandy, loam soil with a pH between 6.0 and 6.5.
- Construct a tall trellis made from livestock fencing and T-posts.
- Plant watermelons every 24 inches along the bottom of the trellis.
- Provide young watermelon plants with 2 inches of water per week.
- Reduce to 1 inch of water per week once the first fruit appears on the vine.
- Train your watermelon to grow up the trellis by gently tying the vine to the trellis.
- Use netting or melon hammocks to support individual watermelons on the trellis.
This system will provide you with an abundance of fruit in the smallest space possible. You can grow up to 3 watermelon vines in a single 4-foot-by-8-foot bed.