Best Plants for Kratky Hydroponics Kits
The best plants for Kratky systems grow quickly, stay fairly compact and do not drink more than a container can hold. Leafy greens and herbs fit that description perfectly; larger fruiting plants can work, but ask more of the setup.
What makes a plant suit the Kratky method
- Short time to harvest. The solution only has to last weeks rather than months.
- Modest water use. Smaller plants drink less, so one fill can carry them through.
- Compact size. No heavy fruit or tall stems to support.
- Harvested for leaves. Leafy crops grow well on the higher-nitrogen nutrients sold for greens.
The Kratky method guide explains why a single batch of solution makes these traits important.
Easiest: leafy greens
- Lettuce. The classic Kratky crop and the one Dr. Kratky's research focused on. Loose-leaf and butterhead types are especially easy. See the article on a Kratky lettuce kit first crop.
- Spinach. Grows well in cooler conditions; can bolt in heat.
- Kale. Productive over a long period if you harvest outer leaves.
- Bok choy and other Asian greens. Fast and forgiving.
- Swiss chard. Large leaves, steady harvests; needs a bit more room.
- Arugula. Quick to harvest, though it can bolt in warm conditions.
Also easy: herbs
- Basil. Loves warmth and light; pinch the tips to keep it bushy.
- Mint. Vigorous; give it its own container.
- Parsley. Slow to germinate but steady once growing.
- Cilantro. Prefers cooler temperatures and can bolt quickly in heat.
- Chives, oregano, thyme and dill. All worth trying in small containers.
The article on a Kratky herb kit for the windowsill covers herbs in more detail.
Possible with more room: fruiting plants
Peppers, tomatoes, cucumbers and strawberries can be grown with the Kratky method, but they are a bigger project:
- They need much larger containers, often several gallons per plant.
- They stay in the system for months, so the solution may need topping up to a lower level partway through.
- They usually need staking or a trellis.
- Indoors, many need hand pollination to set fruit.
Choose compact varieties and read the Kratky containers guide before starting one. A fruiting nutrient formula suits them better once they flower; see Kratky nutrients.
| Plant | Difficulty | Container per plant | Harvest style |
|---|---|---|---|
| Loose-leaf lettuce | Easiest | Quart to half gallon | Pick outer leaves, or whole plant |
| Head lettuce, bok choy | Easy | About a gallon | Whole plant |
| Kale, Swiss chard | Easy | A gallon or more | Pick outer leaves over weeks |
| Spinach, arugula | Easy in cool rooms | Quart to half gallon | Pick leaves; bolts in heat |
| Basil | Easy | Quart to half gallon | Cut above a leaf node |
| Mint | Easy, vigorous | Its own container | Cut stems |
| Parsley, cilantro, chives | Easy | Quart to half gallon | Cut outer stems |
| Peppers, tomatoes, cucumbers, strawberries | Harder | Several gallons | Pick fruit over months |
| Root crops, melons, squash | Not suited | — | — |
The Kratky harvest guide explains each harvest style.
Best avoided
- Root crops such as carrots, potatoes and beets, whose harvest grows in the root zone.
- Large vining or sprawling plants such as melons and squash.
- Trees, shrubs and large perennials.
Some of these can be grown in specially designed systems, but they are not a good fit for a typical Kratky kit.
Matching plants to your kit
Look at the volume of solution each planting site gets, and how far apart the sites are. A small countertop kit with closely spaced holes suits herbs and loose-leaf lettuce. A large tote suits a tray of lettuce heads. A single bucket suits one larger plant. The guide on how to choose a Kratky kit covers this in more detail.
Starting the plants
Most crops are started from seed in rockwool cubes or plugs and moved into the kit once they have a few true leaves. Some herbs, such as basil and mint, can also be started from cuttings rooted in water. See starting seeds for a Kratky kit.
Frequently asked questions
What is the easiest plant to grow in a Kratky kit?
Loose-leaf lettuce is usually the easiest. It grows quickly, stays compact and drinks little, so one fill of solution often carries it to harvest. Basil and other leafy herbs are close behind.
Can I grow tomatoes or peppers in a Kratky kit?
Yes, but they need far more solution than a small countertop kit holds, usually several gallons per plant, plus support for the stems and often hand pollination indoors. Choose compact varieties and a large container.
Can I grow different plants in the same Kratky container?
You can, as long as they like similar nutrient strength, pH and light. Lettuce with other greens, or several leafy herbs together, usually work. Mixing a fast leafy crop with a long fruiting crop is harder, because one batch of solution has to suit both.
How many plants can one Kratky kit grow?
That depends on the solution volume per planting site and the spacing. Plant fewer than the number of holes if the plants will be large, so each one has room and enough solution.
Do Kratky herbs keep producing after harvest?
Many do. Cutting basil above a pair of leaves, or taking outer leaves from parsley and kale, lets the plant keep growing. Watch the water level: a plant that keeps growing keeps drinking.
Key points
- Lettuce, leafy greens and herbs are the easiest Kratky crops.
- Fruiting plants need bigger containers, support and more patience.
- Avoid root crops and large sprawling plants.
- Match the plant to the solution volume and spacing in your kit.