“Can watermelon vines be grown in containers?” Question from George of Hagerstown, MD
Answer: Watermelons can be grown in large containers if you choose a compact variety. Here are my recommendations regarding potted watermelon culture.
Growing Potted Watermelons
First, choose a more compact, short-vine watermelon variety suited for container growing. ‘Cal Sweet Bush‘, a 2019 AAS award winner, has excellent melons and vines that do not take over, and ‘Bush Sugar Baby‘ is another small-vined type with tasty melons. Next, choose a large container that’s between 18 to 24 inches. There must be holes at the bottom for drainage. Plastic or glazed containers hold water better in the heat of summer. Fill the pot with quality, porous potting soil that holds water well. I would choose Black Gold Natural & Organic Raised Bed & Potting Mix. Place the pot in a spot where it gets full sun, and the vining stems can hang down and spread a little. Patios or open garden areas work well for large potted vegetables like this.
Plant one or two watermelons in the pot in spring after the threat of frost has passed. Keep the soil moist. When the vines have reached a good size in summer, water daily in the absence of rain. Fertilizer well from the beginning. A good slow-release fertilizer formulated for vegetables is ideal. Be sure to follow the manufacturer’s application instructions.
Melons should start to appear by late July or August.
“I have a small plot and planted two tomato plants and several watermelon plants. As they grow I’m realizing my plot is quickly running out of space. Can tomato plants be trimmed back? Will watermelon plants take over my yard? How do I trim them back or space them out wide enough?” Question from George of Hagerstown, Maryland
Answer: Both plants can be pruned (please watch the video below about how to prune cherry tomatoes). Both indeterminate (vining) tomatoes and long-vined watermelons will completely take over a garden space in no time. Here are some solutions for managing these gregarious plants this summer and in the future.
Space-Saving Solutions for Tomatoes
Choose determinate, or bush tomatoes. They stay small. The only downside is that they do not produce fruit for as long as indeterminate (vining) tomatoes. If you want more fruit, you have other options.
Cage indeterminate tomatoes with tall, strong, robust cages. I recommend Titan tomato cages or any of comparable size and quality. This way, the vines will grow upright and be easier to prune.
Prune indeterminate tomatoes. Please watch the video below to learn how.
Space-Saving Solutions for Watermelon
Choose short-vine watermelons, such as ‘Cal Sweet Bush‘, a 2019 AAS award winner that has excellent melons and vines that do not take over.
Train melons on a trellis. Small-fruited types, like ‘Little Baby Flower‘, a personal favorite, are the best for trellising.
Trim back select watermelon vine branches that have outgrown their area. Keep in mind, some will need to reach a long length to properly fruit.
Watch the video below for more watermelon-growing tips.
“I lost all of my watermelons to black rot. How can I prevent this next year?” Question from Tina of Holley, New York.
Answer: I am so sorry! The excess moisture of the season has caused extra problems for fruit and veggie growers out East. Black rot on watermelon (more commonly called “gummy stem blight” (GSB)) is a nasty disease caused by the fungus, Didymella bryoniae. Not only does it attack watermelon, but it infects all cucurbits (cantaloupe, squash, cucumbers, etc.). Thankfully, there are several steps you can take to managing it in the future.
Clean up: Remove all vines and debris infected with GSB, and bag and dispose of them in a sanitary manner. Never compost them. GSB will hang out on any old infected crop litter, ready to infect more veggies.
Rotate: Refrain from growing melons for at least three years in the spot where you experienced GSB.
Seed: Purchased seed can be infected with GSB without you knowing it. Be sure to buy seeds from good seed companies that will ensure their seed is GSB-free.
Nursery seedlings: If you buy your watermelon as seedling starts from a nursery, inspect them first. Seedlings with GSB will show several telltale symptoms: dead areas on leaf edges, and oozing-water-soaked areas on the stems. Basically, if seedlings don’t look perfectly healthy, something’s wrong.
Raise planting areas: Raising your planting area can help keep roots from becoming waterlogged and plants drier. Also, plant them in full sun and areas with high air flow. This may help them better resist the disease in the field.
Keep beds well weeded: Some weeds are carriers of GSB, so clean beds are better beds.
Monitoring: Monitor plants for any signs of GSB. Look for oozy, gummy stem lesions, leaves with dead edges and spots (with concentric circles in the spots), and the beginnings of fruit lesions. (Click here for images.) Remove plants immediately if they have GSB.
Fungicide application: Several fungicides can manage GSB, but all are highly toxic. (Learn more here.) Sadly, no organic options work, yet.
Post-harvest storage: GSB infection can also occur on the skin of just-picked watermelon that look okay. Avoid damaging melon skins after harvest, and store fruits at 45°F–50°F to prevent black rot after harvest.
Work is being done to find resistant watermelon varieties, but none have hit the market so far. Good luck, and keep us posted on your melon growing next year.