Lima Bean (Phaseolus lunatus)

The lima bean (Phaseolus lunatus) is an annual bushy or creeping, perennial herbaceous plant whose stems can reach lengths of 2 to 4 meters. The petals are usually light green, sometimes purple. The beans contain protein, fiber, minerals, and antioxidants; however, you must cook them to neutralize the cyanide, oxalates, and saponins in them.

I. Appearance and Characteristics 

A lima bean (Phaseolus lunatus), also commonly known as butter bean, sieva bean, double bean or Madagascar bean, is a legume grown for its edible seeds or beans.

Phaseolus lunatus is found in Meso- and South America. Two gene pools of cultivated lima beans point to independent domestication events. The Mesoamerican lima bean is distributed in neotropical lowlands, while the other is found in the western Andes. They were discovered in Peru and may have been the first plant that was brought up under civilization by the native farmers.

Lima beans, also known as butter beans or chad beans, grow much like green beans but take a little longer to mature, about 60 to 80 days. Lima beans have three oval leaflets about 2 to 3 inches long with loose clusters of white or yellow flowers. Lima bean pods are curved and flatter than common green beans.

Lima bean plants grow fast when started in the spring, requiring soil temperatures consistently 65 degrees Fahrenheit or warmer.

The most abundant mineral in the raw lima bean is potassium, followed by calcium, phosphorus, magnesium, sodium, and iron. When lima beans germinate, there is increased bioavailability of calcium and phosphorus. Additionally, it is a good source of vitamin B6.

Like many beans, raw lima beans are toxic (containing e.g. phytohaemagglutinin) if not boiled for at least 10 minutes. Canned beans can be eaten without having to be boiled first, as they are pre-cooked.

The lima bean can contain anti-nutrients like phytic acids, saponin, oxalate, tannin, and trypsin inhibitor. These inhibit absorption of nutrients in animals and can cause damage to some organs. In addition to boiling, methods of roasting, pressure cooking, soaking, and germination can also reduce the antinutrients significantly.

II. How to Grow and Care

Sunlight

You will need a spot with full sun, meaning at least six hours of direct sunlight on most days, to get the most yield from your lima beans. In addition to light for growth, full sun exposure will help keep the vines dry and less prone to fungal problems.

Temperature and Humidity

Lima beans can be a bit temperamental about temperature. They don’t like extremes and grow best in climates between 70 and 80 degrees Fahrenheit for several months. However, they can handle warmer temperatures better than prolonged cool temperatures and aren’t frost-hardy. Humidity isn’t an issue as long as adequate soil moisture is maintained.

Watering

Keep the soil evenly moist but not soggy until germination. After sprouting, the plants should get at least 1 inch of water weekly. In hot, dry weather, mulch around the roots to keep them cool and to retain soil moisture. Pay extra attention to watering once the plants are flowering and starting to set pods; they will drop the flowers and pods if they experience any drought at this point.

Soil

The soil should be well-draining and moderately rich in organic matter. Heavy clay soil can pose problems because lima beans have deep, expansive roots and don’t like to sit in wet soil. The soil pH should be slightly acidic to neutral.

Fertilizing

Legumes generally don’t need extra fertilizer, especially if the soil is already rich. However, because some lima bean varieties have a relatively long growing season, it can help to give them a side dressing of compost or composted manure mid-season. These slow-releasing sources of nutrients will help the plants continue for the rest of the season.

Growing in Containers

If you don’t have garden space or the right soil conditions, container growing can be a good option. Choose a container that’s at least a foot wide and similar in depth, and make sure it has ample drainage holes.

An unglazed clay container is beneficial because it allows excess soil moisture to evaporate through its walls. Water when the top inch of soil feels dry, but make sure the soil doesn’t get waterlogged. If the container plant is a vining variety, add stakes or another type of support structure for it to climb.

Pruning

Pruning isn’t essential, but pinching back the top couple of inches of growth as the plant begins to flower can help promote a bushier habit and potentially more flowering and fruiting.

Propagation

Most gardeners grow lima beans from seed. You can save seeds from a mature plant to grow the following year. This method is an easy and inexpensive way to get new plants, and it will allow you to duplicate plants that were excellent producers or had good taste. Here’s how:

• Allow the pods to dry out on the plant. Cut them off when they are brittle.
• Arrange the pods in a single layer and continue to dry them for at least two weeks indoors in a cool, dry spot with good air circulation.
• Remove the seeds from the pods. Put them in an airtight container, and store the container in a cool, dark, dry spot.

How to Grow From Seed

Lima bean seeds take seven to 18 days to germinate. If your growing season is long enough, you can succession-plant seeds every two to three weeks to extend your harvest. You can also consider planting varieties that mature at different times to stagger your harvest.

Here’s how to grow lima beans from seed:

• If your growing season is short, you can start seeds indoors three to four weeks before your projected last frost date in the spring.
• Use biodegradable pots that you can plant directly in the ground or a larger container so you don’t have to disturb the seedlings’ roots.
• You can warm your outdoor soil faster in the spring by putting a black sheet of plastic over it before planting seeds.
• Plant seeds about 1 inch deep, spacing the rows about 2 feet apart. Each seed should be at least 2 to 4 inches from the next.
• Thin seedlings if they are within 4 inches of each other. Keep the strongest or more vigorously growing seedling.
• Water regularly, ensuring the plant has at least 1 inch of water. During periods of heavy rain, especially if the plant is in a container, bring it inside or cover it.

Potting and Repotting 

Use a quality all-purpose potting mix that drains well for potting lima beans. Select a container that will accommodate their mature size to avoid having to repot your bean plants, as they typically don’t take well to having their roots disturbed.

Overwintering

As lima beans are annuals, meaning they complete their life cycle in one growing season, no overwintering will be necessary.

Pests and Diseases

All the usual bean pests will seek out your lima bean plants. They commonly include bean beetles and aphids. Many rodents also love tender, young bean seedlings, so fencing is recommended to keep them out of your garden. The biggest disease problem is root rot, which you should be able to avoid with well-draining soil and proper watering. If you have a particularly rainy spell, be sure to turn off any automatic irrigation.

III. Uses and Benefits 

• Medicinal uses

The high fiber content in lima beans prevents blood sugar levels from rising too rapidly after eating them due to the presence of those large amounts of absorption-slowing compounds in the beans, and the high soluble fiber content. Soluble fiber absorbs water in the stomach, forming a gel that slows down the absorption of the bean’s carbohydrates. They can therefore help balance blood sugar levels while providing steady, slow-burning energy, which makes them a good choice for people with diabetes suffering with insulin resistance.

• Culinary uses

Lima beans, like many other legumes, are a good source of dietary fiber, and a virtually fat-free source of high-quality protein.

Lima beans contain both soluble fiber, which helps regulate blood sugar levels and lowers cholesterol, and insoluble fiber, which aids in the prevention of constipation, digestive disorders, irritable bowel syndrome, and diverticulitis.

IV. Harvesting and Storage

Harvesting 

Lima beans are ready to harvest within 60 to 90 days. Each variety has a different maturation point, varying by a few days to a week, depending on climate conditions. However, mark on a calendar roughly when your variety is due to mature for a successful harvest. Next, look for signs of maturation at the shelling or dry stages.

• Shelling Beans: Lima beans are ready for shelling when the pod changes color; the beans inside plump up, but before the pod and seeds dry.
• Dried Beans: If you want to harvest the beans to store as dried beans, leave the pods on the vine until they are dry and brittle, with the beans inside dry and hard. Hold the vine end when pulling off the pods to prevent damaging the vine.

Storing 

Keep unshelled beans in the refrigerator for up to a week—or shell and blanch beans to freeze for up to three months. Dried beans can be stored in an airtight container in a cool, dry spot for several years. Allow the beans to dry directly on the plant until the seeds are hard and the pods are brittle.