Nemesia provide late season color for the garden

Autumn can sneak up quickly in New England, and it's often surprising to see just how close we are to the onset of changing foliage. But even as the days grow shorter and cooler, it's still possible to enjoy a few last floral blooms.

Nemesias are well-suited for this stage of the gardening season. The genus, native to southern Africa, includes a number of plants that prefer the cool temperatures of spring and autumn.

The plants can be grown as perennials, but only in certain regions. Judy Wolfe, writing for SFGate, says nemesias should be grown as annuals in areas outside of USDA zones 9 and 10. Connecticut and Rhode Island are in zones 5 through 7.

Nemesias usually grow about a foot tall, but may reach heights of up to 18 inches. The Missouri Botanical Garden says the plants produce lance-shaped leaves and two-lipped flowers in just about every color except green. Some flowers may produce a different color on each lip.

In mild climates, nemesias planted in the late summer can bloom throughout the winter. Costa Farms, a Florida gardening company, says the flowers will prove attractive to butterflies and hummingbirds. The plant will be killed off by cold temperatures in the winter or when hot, humid conditions arrive in the summer.

Since nemesias are somewhat sensitive to weather conditions, it can be useful to start them indoors. The Missouri Botanical Garden says seeds can be planted eight to 10 weeks before the last spring frost. Seedlings can be set out in the soil immediately after the last frost.

When sown outdoors, look for an area with full sun. The plants will also do well in sites with afternoon shade.

The soil should be raked thoroughly to break up clods and improve drainage. Wolfe says nemesias grow well in acidic soils down to a pH level of 5.5 as well as mildly alkaline soils.

Seeds should be scattered in the garden plot and lightly covered with soil. Add an inch of water each week. Costa Farms says you should dampen the soil whenever its surface starts to dry out, which will help keep the plants cool.

Once the second set of true leaves appear on the seedlings, start to thin out the plants. Wolfe says seedlings should be about six inches apart when you are through thinning. You can also pinch back the leaves after the third set appears to allow for bushier growth.

Blooms will continue as long as temperatures remain mild. The Mississippi State University Extension says temperatures should ideally stay in the 70s during the day and 50s at night. Wolfe says branch ends should be trimmed once nighttime temperatures hit 75 degrees, since this will help divert energy to the branches and promote new blooms once cool weather returns.

Nemesias can benefit from an application of slow release fertilizer. This can be added once in the spring, or twice a month when the plant is actively growing.

Once the plants die off due to warmer temperatures, they should be cut back or removed from the garden. The Missouri Botanical Garden says cutting nemesias back to the ground in late spring may allow the plant to bloom again in the fall.

Nemesias generally aren't susceptible to diseases or pests. However, their roots can rot if they are overwatered.

The plants have a gentle trailing appearance, making them a good choice for containers and window boxes. They also work well in rock gardens, borders, and grouped together in garden beds.

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