How to grow arugula in pots: staggered sowing, flavor and heat

Arugula does well in a pot of at least 3 gallons, sown thinly in cool weather and picked young. NC State Extension puts the minimum depth at 4 to 6 inches and says plants mature within 40 to 50 days. The one thing that ends a pot early is heat: arugula flowers, the leaves turn sharp, and the planting is over. Staggering your sowings and shading the pot in warm weather are what keep it going.

Arugula is a fast annual, grown like lettuce or radish. That makes it a natural fit for the rhythm in the succession planting guide. If you want the water-only version, with reservoirs and nutrient targets, see hydroponic arugula.

The pot, the mix and the spacing

NC State Extension says to use a minimum pot size of 3 gallons and a minimum depth of 4 to 6 inches. UF/IFAS Extension is less demanding for transplants, suggesting a 1 to 2 gallon container with drainage holes. If you are choosing between the two, NC State’s 3 gallons is the larger option, and it gives the mix more room to hold moisture, which matters in warm weather. Since NC State’s minimum depth is only 4 to 6 inches, extra width gives you more plants per pot than extra depth does.

Use a loose, well-draining potting mix with some compost. UF/IFAS Extension says to add compost before planting, avoid heavy clay soils and mix in a balanced, slow-release fertilizer at planting. The feeding schedule for container vegetables covers what to do after that.

Sow seed 1/4 to 1/2 inch deep, according to the University of Delaware Extension. Seeds germinate within a few days even in cool soil, says Wisconsin Extension. Then thin, and the sources differ on how far:

• Wisconsin Extension: 3 to 6 inches apart for individual plants, or leave denser plantings for cut-and-come-again picking.
• NC State Extension: 6 inches apart.
• University of Delaware Extension: 6 inches in both directions, thinning as plants begin to touch.

For a baby-leaf pot you cut often, go close. For plants you want to grow big, use the wider spacing. Wisconsin Extension also notes that arugula is quick enough to tuck between slower crops. For how many plants a pot of a given size can carry, see plants per container.

Sun, temperature and when to sow

Arugula is a cool-season crop. UF/IFAS Extension gives 50 to 65°F as the best range and 4 to 6 hours of partial to full sun. Wisconsin Extension says it tolerates frost, so it can go in several weeks before the last spring frost. UF/IFAS adds that it can take light freezes, and suggests frost cloth, row cover or a cold frame below 32°F. To find your own dates, start with the frost date guide for balconies.

That makes the best sowing windows early spring and early fall. UF/IFAS Extension suggests planting from early fall through late spring in its region. The fall salad greens guide covers sharing a pot with lettuce, spinach and mizuna as the weather cools. Wisconsin Extension also says arugula can be grown in containers through winter on a bright windowsill.

Staggering the sowings

One pot sown all at once will give you a short burst of leaves and then a bolting mess. Sow a small section on a rhythm instead. The sources give slightly different intervals:

• NC State Extension: every one or two weeks.
• UF/IFAS Extension: every two weeks.
• Wisconsin Extension: every 2 to 3 weeks, from early spring to fall.

Pick the interval that matches how much you eat. In a wide planter, divide the surface into three or four sections and sow one each time, refilling the one you just cleared. Wisconsin Extension says you can also cut a whole plant back to an inch or two above the soil in as little as 3 to 4 weeks and harvest from the regrowth, which is a second reason you may not need to resow as often as you think.

Water and feeding

UF/IFAS Extension says to water when the top inch of soil feels dry to the touch, and to give deep, even watering. It also notes that arugula prefers slightly drier conditions than other greens, so keep the mix damp rather than soaked. Dry soil is not a safe way to save water, though: Wisconsin Extension lists dry soil, along with long days and high temperatures, as a trigger for the plant to send up a flower stem. In a small pot in warm weather, check that top inch often, since it dries faster than a bed. The container vegetable watering guide explains how pot size and plant stage change the interval.

Heat, bolting and flavor

Arugula that has started to bolt sends up a single, branched flower stem 2 to 3 feet tall, according to Wisconsin Extension. NC State Extension says bolting in hot weather changes the flavor and stops leaf growth.

What you can do in a pot:

• Move the container where it gets afternoon shade. UF/IFAS Extension says to keep arugula in afternoon shade when temperatures are above 85°F.
• Use shade cloth. UF/IFAS gives around 30 to 50 percent shading.
• Keep the mix evenly moist, since dry soil adds to the stress.
• Pick regularly. Wisconsin Extension says regularly harvesting the small leaves helps keep the plant from going to seed and from developing older leaves.

A heatwave in the middle of a planting is a different problem; the heatwave guide for container plants covers it. Wisconsin Extension also describes wild arugula (Diplotaxis tenuifolia) as heat tolerant, with a similar flavor, and a hardy perennial. If summer is your main season, that is the plant to look for.

Flavor follows the same logic. Wisconsin Extension describes young leaves as nutty-peppery, mustard-like or horseradish-like, and older leaves as stronger and more bitter. It adds that drought and summer heat intensify the leaves’ flavor. NC State Extension advises picking young leaves for the same reason. A hot, sharp pot is usually an old, dry or overheated one.

Once a plant has bolted, it is not wasted. NC State Extension says the flowers and seed pods can be harvested as well, and Wisconsin Extension says the flowers are edible and milder than the leaves.

Picking

Start when leaves are around 2 to 3 inches long (UF/IFAS Extension), picking the outer leaves first and leaving the inner ones to keep growing. Wisconsin Extension puts it at “a couple of inches”. Check your seed packet for the days to harvest of your variety.

Two approaches work in a pot. Take the outer leaves and keep the center growing, or cut the whole plant an inch or two above the soil and let it regrow. The University of Delaware Extension says to harvest any time up to maturity, preferably before the plant flowers, and that you can clip flowers for an extended harvest.

Pests

Arugula has few pests, according to Wisconsin Extension, but flea beetles can damage leaves or completely devour small plants when numerous. Shot-holed leaves are still edible. Row covers help, but Wisconsin warns that the beetles overwinter in the soil and can emerge under a cover put on too early. NC State Extension also lists aphids, and UF/IFAS mentions aphids and caterpillars.

Sources

• UF/IFAS Extension Leon County, Arugula: Planting and Care
• University of Wisconsin-Madison Extension, Arugula, Eruca sativa
• NC State Extension Gardener Plant Toolbox, Eruca vesicaria
• University of Delaware Cooperative Extension, Grow Your Own: Arugula