ADVERTISEMENT

ADVERTISEMENT

This is why an indoor rubber plant might be starting to yellow

"Fielding Questions" columnist Don Kinzler also answers readers' questions about zinnias for cutting and dividing Boston ferns.

021222.F.FF.FIELDINGQUESTIONS.png
There are several reasons this indoor rubber plant might have a yellowing leaf.
Contributed / Special to The Forum
We are part of The Trust Project.

Q: What causes a leaf on this houseplant to become yellow? — Jeff J.

A: Your plant, which has the botanical name Ficus elastica, has several common names, including rubber tree, Indian rubber plant and rubber fig. All plant parts contain a milky white latex, which has been tested for use in the manufacture of rubber, but without results. Commercial rubber products come from a different tree species.

In its native tropics, this houseplant becomes a large tree, well over 100 feet high. Its natural instinct indoors is to become treelike. Some shedding of lower leaves is common, as the rubber tree develops typical tree trunks.

There are other causes of leaf yellowing, though, on rubber plants. They’d prefer the humidity of the tropics, and our dry winter indoor air isn’t their best environment, and winter yellowing of leaves on Ficus can be common.

In studying the photo of the soil, a repotting into fresh, high-quality potting mix might be wise. A white crust is evident, and repotting will remove salt buildup, which can also cause yellowing leaves. Wash leaves and stems with insecticidal soap to limit possible insect and mite activity.

ADVERTISEMENT

Rubber plants often become tall and leggy indoors as they strive to become trees. If such a houseplant is less appealing than desired, I always suggest a dramatic cutback to less than 12 inches above soil level accompanied by repotting to stimulate fresh branching from the lower trunks. Providing higher light promotes new shoot development.

A drastic cutback isn’t 100% foolproof, but it’s worth a try if a huskier houseplant with better branching is desired.

Q: Do you have any recommendations for a shorter version of Cut-and-Come-Again zinnias that could be planted from seed? — Robyn W.

A: Cut-and-Come-Again zinnias are an heirloom variety, likely dating back to at least the early 1900s. They bloom in a rainbow of colors, with plants reaching 24 to 36 inches high. The flowers are about 2.5 inches in diameter, and the plants are well-known for prolific production, yielding plenty of blooms for cutting.

Most zinnias are highly productive, and the blossoms last well as cut flowers. Some of the newer hybrids have larger, more uniform flowers than Cut-and-Come-Again with shorter, more manageable plant heights.

For a shorter zinnia, try the cultivar Magellan. It’s a colorful mix, and the flowers are larger — up to 4 to 5 inches in diameter. Plants grow to a manageable height of about 14 inches, making Magellan a colorful addition to flowerbeds. With its hybrid vigor, the cultivar continues producing masses of flowers, even after harvesting some for bouquets. It’s available from seed companies such as Parks.

Another similarly sized zinnia is the Dreamland series, also with great hybrid vigor. Zinnias are easy to start from seed, and will bloom earlier if started indoors from seed, rather than direct-seeding outdoors. Because zinnias grow rapidly indoors, delay seeding until around April 1-15 for plants that will be transplanted into the flower garden around May 20.

Q: My large old Boston fern loses lot of leaves, and has many dry, dead branch stubs from when I cut back stems that have dropped their leaves. Can I separate the fern and get rid of some of the dry. dead stuff? — Pam L.

ADVERTISEMENT

A: Boston ferns are notorious for dropping leaves. It’s a good thing they’re beautiful, because they’re certainly one of the messier houseplants, especially in winter when indoor air is dry.

Ferns divide nicely, and the older inside parts with dead stem remnants can be discarded, and the fresher vigorous sections repotted. To divide a fern, remove it from its pot and slice through the root system with a sharp knife, pruning shears, or hacksaw blade.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at donald.kinzler@ndsu.edu. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.

What to read next
A listing of area meetings and events in the Brainerd lakes area.
Calendar of events at The Center in Brainerd.
"Fielding Questions" columnist Don Kinzler also advises a reader on the best time of year to divide and share rhubarb.
"Growing Together" columnist Don Kinzler says measures taken on a hot, windy day can save plant lives.