Choosing the best crops for raft systems
So you’re starting a farm. You’ve got a basic business plan, a mentor to help you, and a growing facility. You’re not entirely sure what crops to plant in your raft system (deep water culture system), but you’ve got some ideas.
To help you make those decisions, we’ve put together a recommended list of crops for your raft system.
Before you choose, remember that crop choice depends not only on climate, technique, and facilities but on your local market. If you don’t have demand for your produce, you won’t make money. Period. Do market research before choosing crops!
Once you have market research done, you can consider other factors.
We’ve grown dozens of crop types and had our share of failure. We’ve put together this guide on deep water culture (DWC) to help you learn from our mistakes, and make the right choice of crops from the get-go.
What is DWC?
For the uninitiated, deep water culture (DWC) or raft systems use a tank with nutrient solution (fertilized either with fish waste or a hydroponic fertilizer). A raft floats on top of the water, and plants on the raft dangle their roots into the solution below. Plants are supported on the raft with net pots or other tools like Grow Grips.
Check out our course on Upstart University for more information on managing an aquaponic DWC system.
This guide will walk you through a number of the best crops for deep water culture growing. Each kind of crop possesses a number of positive and negative qualities and offers unique possibilities for each growing situation. After reading this guide, you’ll be on track to make the best selection for your deep water culture operation, no matter how large the scale.
Factors for choosing DWC crops:
Selecting crops is a complex choice based on your individual growing situation. Instead of recommending crops without any context or clear methodology, consider the important qualifications for your crops:
Rafts are usually quite durable and affordable, but they can only support so much weight. The best crops for deep water culture are small and lightweight. Lettuce, for example, is a popular DWC crop and the perfect size to fit on rafts. Larger crops like tomatoes grow top-heavy. Without the root anchoring provided by a dense media, top-heavy plants can fall over or break at the stems.
2) Footprint (volume)
DWC systems function on a single horizontal plane since they are typically too heavy to stack. This means that you have a 1:1 volume to growing area ratio. If you have limited space, consider a technique that can facilitate denser growing. If you have abundant space, this won’t be as big of a problem.
This does mean, however, that you want to fill that horizontal plane efficiently. Be sure to match your plant site spacing on your rafts to your plant size. (For instance, don’t leave 12 inches of space between sites if you’re growing romaine lettuce. You’ll waste a lot of space between plants.)
Drought loving plants and herbs (like rosemary) that prefer “dry feet” don’t do well in DWC systems. On the other hand, thirsty plants like lettuce will thrive in DWC systems, so pick seed varieties that love water.
4) Yield (harvest potential)
If you’re growing for commercial sales, you’ll want to ensure that the plant will provide you with a profit!
Make sure that you: a) have a decent margin on the crop and b) have a place to sell the crop. Don’t forget opportunity costs in your analysis. (If Crop A can offer you a decent income, don’t forget that there might be a Crop B that can offer you more.)
6) Breeding (hybridity)
Durability and vitality make hybrid plants more viable in deep water culture than selectively bred heirloom plants. Although heirloom varieties are appealing, the more well-known and studied hybrids are a more consistent bang for your buck.
Best crops for raft systems
With these qualifications in mind, here are a few recommended crops that can make your DWC operation great.
Growth time: 8–10 weeks from seed
The most labor intensive of our recommended DWC crops, basil is a unique plant. Clipping specific stems can change the growth direction of the plant from primarily vertical to bushier. This allows growers to get higher yield and better plants for displays but can take some practice.
Basil is a product that restaurants and groceries prioritize. A steady stream of basil means fresh pesto, caprese salads, and happy customers. While we don’t recommend basil for the newest growers, consider choosing basil as your second or third rotation of crops.
Grow time: 5–6 weeks from seed
The globetrotting lettuce is certainly one of the most popular crops in the world and makes a great addition to any deep water culture farm. Lettuce is one of the most easy-growing plants in any farming operation, and DWC is no different. With a short growing cycle and high market demand, we encourage any growers new to deep water culture to consider lettuce as an option for their farm.
There are hundreds of varieties of lettuce; favorites of the Upstart Farmers include green or red romaines, Amish Deertongue, Salanova, and mesclun mixes. The flavor in these brands can be crisp, buttery, or tart. Lettuce is a great first pick for new DWC growers.
Grow time: 7–9 weeks from seed
The beautiful and delicious okra is a common sight on tables and in gardens in the American South. Planting okra is a bit unique, requiring soaking the seeds a few hours before planting.
Okra also has beautiful flowers and is sometimes used as an ornamental in public gardens. Okra is another great crop to wow your potential restaurant and grocery clients.
Grow time: 5–6 weeks from seed
Everyone’s favorite superfood, kale is a great match for the DWC approach to indoor growing. Kale prefers cool temperatures and can be harvested either fully or partially by taking 30% of the plant at once. Kale and lettuce together make for a great first growing operation.
Grow time: Broccoli 7–8 weeks, cabbage 7–8 weeks from seed
A staple of many dinner tables, collard greens are affordable, healthy, and delicious additions to any deep water culture operation. The collard green family refers to either cabbage or broccoli. Both of these plants are durable.
These crops are likely to present little competition from other local growers in your community. The investment required to support crops for greater than three months can be intimidating, but it means that you can likely charge a premium for these rare local crops. Don’t forget that both crops will grow rather large and heavy. Both will require a healthy amount of space on the rafts to thrive.
Grow time: 4–6 weeks from seed
Sorrel is a unique crop that remains unfamiliar in most households. Like collard greens, sorrel in the outdoors is a cold growing crop, thriving in fall and winter conditions. Deep water culture offers the opportunity to grow this temperature-sensitive crop year round.
Slightly bitter, sorrel is commonly used in cream- or sauce-based dishes where the slight acidity of the plant can be managed by dissolving. Sorrel not only makes for a great addition to many dishes, but its beautiful flowering adds a lovely touch to any growing operation.
Grow time: 4–5 weeks from seed
Chard is a French green we recommend for its consistent demand. Our favorite variety is the Swiss “rainbow” chard. Chard is more susceptible to powdery mildew than some other crops, so look out for the white powder and take care of it proactively.
With a little temperature regulation, chard will produce delicious, buttery-tasting leaves. Like kale, chard can be harvested either fully or partially. Chard makes for a durable, tasty, and easy-to-grow crop in deep water culture operations.
Grow time: 8–11 weeks from seed
Bok choy (and its cousin Tatsoi) is a popular Chinese cabbage that is a great choice for deep water culture. Bok choy’s various strains show remarkable variation between seed varieties, so be sure you’re selecting the right plants when purchasing.
We recommend the basic mustard bok choy variety, tatsoi (aka Broadbeak mustard), or Napa cabbage. Bok choy is a little heavier than the rest of the crops on our recommended list for DWC. Be sure your rafts are sturdy and ready to handle the potential weight and don’t overload your operation with too many bok choy plants.
What are your fellow farmers growing?
Our friend Brandon Youst writes on his deep water culture success,
“I’ve grown a wide variety of lettuce, but I mostly stick to the larger heads. Butterhead (Sylvesta), bibb (Breen, Rhazes), romaine (Ridgeline), kale (Olympic Red, Toscano).
The only spinach I’ve found to work is tatsoi. Last year I grew bok choy and collards very well.”
Rob Torcellini of Bigelow Brook Farm writes on his DWC experience, “We mostly grow lettuce in our DWC. We’ve had very good luck with an heirloom variety called Crisp Mint which we buy from Seed Savers. I also will grow some green and red oakleaf but the primary is Crisp Mint.
Once the water temps go back over 62 or so, I will do a batch of basil which also does very well. We will harvest some fresh during the summer, but once the water goes back down to the low 60’s it dies fairly quickly so we will harvest and dry the remaining.
This year we grew some celery in the fall through the winter which is about ready to be harvested. It did very well in the cold temps so next year I’ll probably do a lot more.”
Picking crops for hydroponics?
Choosing crops? You can quickly reference the information you need for sixteen of the most popular hydroponic crops in the Best Crops for Hydroponics.
Use the eBook to discover:
- Which crops are compatible with others
- Special harvesting and planting considerations
- Crop timelines and turns