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Garden Help Desk: Adequate light and fertilizer lead to healthy orchids

By USU Extension - Special to the Daily Herald | May 18, 2024
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Orchids should be placed where they can get bright, indirect light for at least a few hours every day. A bright windowsill can provide enough light to meet their needs.
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Orchids will produce aerial roots that can collect moisture from the air if the room conditions are right. There is no need to remove them.
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Orchids in bloom are more readily available now than they were just a few years ago. With good care, they can provide a flush of indoor color every year.
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Root weevil adults aren't easily seen, but ragged damage along the margins of leaves is a reliable indicator that they're active in your garden.
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Root weevil larvae feed on the roots and crowns of heuchera and many other landscape plants. Their feeding damage can leave plants looking drought-stressed even though the soil is moist.
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Heuchera, heucherellas and coral bells are popular plants in shade gardens. They are also popular with root weevils.

We have a happy little orchid, which appears extremely healthy and active. The leaves are vibrant and the spikes are prolific as you can see. We water fertilizer about every two weeks. The problem is some of these spikes have been growing for the best part of a year or more and we don’t see any real promise of flowers.

The orchid has bloomed twice before with beautiful flowers and has been repotted in a larger pot once. At this point we are wondering if these are flowering spikes or just roots growing up into the air? How do we manage this odd growth and encourage flowering?

The “spikes” in your photo are aerial roots, not flowering spikes. Roots like this are normal for your orchid and the green tips are a sign of healthy root growth. The aerial roots absorb moisture from the air. They don’t need to be down in the potting bark mix to do their job if there is enough humidity in the room. In dry settings, the roots in the bark mix will absorb moisture from the mix.

Depending on the species of orchid (yours is a phalaenopsis) and the conditions in the room (light level, temperature and humidity), a healthy orchid will usually bloom about once every year, give or take a few months. You may see a new flowering spike emerging in the next few months.

Your orchid looks fine. If it has been more than a year since you’ve seen blooms, the problem may be either too much fertilizer or too little light.

Inadequate light is the most common cause of delayed blooming. Your orchid doesn’t want to be in bright, direct sunlight by a window at midday or afternoon, but if you can give it another hour or two of indirect light, that might be helpful. You said you’re keeping it in a bathroom that gets some morning sun. Perhaps leaving the bathroom light on for an hour or two in the late morning will help. That said, the leaf color in your photo looked fine, so there’s enough light for healthy leaves but maybe not enough for flowering.

Stop fertilizing at full strength when you water and make sure you don’t fertilize if the potting media and roots are dry (water first and then fertilize). It’s also a good idea to leach out the old fertilizer salts by watering very heavily about once or twice a year and then returning to your usual weak fertilizer every two weeks.

Did you remove the flower spike once the flowers had all faded? It can be helpful to cut it back all the way, or at least back to the couple of nodes at the base of the spike. A phalaenopsis will sometimes rebloom in a few months if the spike is cut back part way and the general conditions are good.

Unclip the roots that you’ve fastened to the small stake. Just let the aerial roots do their own thing and reserve the stake and clip for the new flowering spike as it gets tall enough to need a little support.

One of my heucheras popped right out of the soil when I was raking out my perennial beds. It looks like the roots rotted away. What can I do to prevent my other plants from getting the disease?

Root rot diseases are often the result of frequent watering, poor drainage, chronically wet soils near leaking sprinkler heads or downspouts, or shaded soils that get watered along with sunny spots. Proper watering is the No. 1 management strategy for reducing root disease problems in the landscape.

This doesn’t look like a root disease problem, though. This looks like an insect problem. The damage in your photo looks like the damage seen when there has been root weevil activity. There are several root weevil species in our area, and they feed on a variety of plants. Root weevils spend part of their life underground as larvae, feeding on the roots and lower crown of a plant. The adults are small black, gray or brownish snout beetles. They may feed on leaves, leaving the margins of the leaves ragged or notched. Bristly or hairy leaves seem to avoid this damage.

There are a couple of things you can do to reduce or avoid root weevil damage in the future. First, water deeply but not frequently. This will promote healthy plants that better tolerate weevil feeding and make your garden soil less hospitable to root weevils. You can also try a systemic insecticidal soil application with imidacloprid. Parasitic nematodes are also an option.


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