Garden asparagus fern (Asparagus densiflorus) is susceptible to yellowing due to care issues and unsuitable growth conditions. The outdoor fern plant normally turns yellow during the winter. Common problems that result in them turning yellow include underwatering, low light, poor nutrition and low temperature.
NOTE: This fern is not a real asparagus plant.
How do Yellowed Asparagus Fern Look like? (Images)
Asparagus densiflorus yellowing and browning (Images Credit: Reddit)
Reasons for Yellowing Asparagus Fern
If you’re kind of, ‘why is my asparagus fern turning yellow?’ Here are common issues and problems.
1. Low (Poor) Lighting
Potted asparagus fern tend to turn light green then yellow when they enter dormancy in winter. Lighting is essential for any plant to thrive. However, when caring for asparagus fern indoors, duration and light strength should be considered.
You give your asparagus more than 5 hours of direct sunlight, and the leaves get burnt! The scorched areas of foliage will turn brown. A few of them then start turning yellow a few days afterward. You’re likely to see them in yellow spots.
Asparagus grown in greenhouses become sensitive to sunlight. Therefore, sudden exposure to light might threaten to kill them.
If you want to grow and to care for asparagus outdoors to be a success, plant your asparagus in small pots. After transplanting, start by moving them to under a slightly open shade. Allow them to stay for 1 – 2 hours under shade in the first week. Then gradually start exposing them to 1 hour of morning light in the second week.
Examine their physical health every day. If they look strong and are getting stronger, increase sunlight hours to two.
In summary, to fix the light problems:
- First, harden the fern plant you want to grow outdoors
- Then transplant them to smaller, manageable raised beds
Also, remember to protect them during strong winds and stormy weather.
Invest in light meters to help you in identifying the best location for planting
2. Overwatered Fern
Another common cause of yellow asparagus fern is overwatering. Whether you have grown them in the outdoor garden or indoors. Here are things that may lead to overwatered fern:
- Planting in poorly drained soils
- Using pots without proper drainage
- Strictly following a routine throughout the growing season
A healthy asparagus fern plant needs to be watered twice a week at most.
You can successfully water once a week on a carefully drilled water need basis. To solve and stop overwatering your asparagus fern, first withhold water once you notice the yellow leaves start to fall off. Then cancel your current water schedule and carry out the diagnostic test below.
- Check for signs of fern and stem wilting
- Determine for how long your fern roots have been sitting in water:
- A very damp pot means there could be a stale (rotting) odor from the pot
Start repotting your asparagus fern right away to save them. Clean the roots with running water. Remove soft roots and stems. Dip them in a rooting media and leave them to dry in a cool area.
3. Soil Drainage Issues
If you do control and correct watering but still find your pots flooded, there is something wrong with soil drainage.
While watering regularly can lead to flooded pot soils, a problem with the drainage systems can only worsen it. This poor drainage can either be of the pot or soil or both.
You can solve this soil drainage problem by selecting a quality pot mix. Alternatively, you can opt for DIY soil treatment. Simply add a little amount of perlite. Perlite makes the flowing of water out and through the drainage holes of your pot easy (pay attention to the drain holes in the pots as well).
Another simple step is to place some small rocks or stones.
Go for terracotta or containers with holes for draining excess water. Terracotta pot materials are usually made from clay. This quite helps evaporate water. However, this does not mean that you keep flooding your terracotta.
4. Under Watering
Underwatering your fern plant consistently can yellow them. It is easy to confuse signs of underwatered and overwatered ones. Notably, crisp-like dry fern are typical of under-watering. To identify these signs begin observing them from the tips.
Fixing the underwatering problem may be easy. Only make them drink water when they seem to want it (thirsty). First, check the dampness in ¼ the topsoil. You can either use your finger by poking or work with moisture meters for more reliable results. If you correctly identify clear signs of thirst, water yours lightly every week.
Growing fern plants often require consistent but little amounts of water. If you want to solve the problem, continue watering lightly for around three weeks. Stop watering them the moment you realize a new growth.
Ensure that you also snip off any affected parts to help better track their progress health-wise.
5. Nutrient Deficiency
Poorly fed asparagus fern can turn from green to light green or yellow or brown. Two nutrient elements that are important in keeping plants’ green matter are nitrogen and magnesium.
Over time, your soil will lose the amount of these nutrients. They may use all of the fertilizer nutrients or get washed away. If you have planted them in pots, besides leaking, your plant can also use all of it with time. Yellowing fern leaves can therefore be a sign of nitrogen deficiency.
Fixing this problem is quite easy if you have well taken care of the rest of the issues discussed. Sometimes it becomes difficult because detecting nutrition deficiency early is impossible. Nevertheless, you can still solve the problem.
- Check for signs of roots growing out of the pot
- If the length of the stems and soil level is way above the pot, then you need to re-pot
- Remove the old soil from their pots
- Divide up your asparagus fern plants
- Use a houseplant fertilizer with a more balanced N:P:K (reduce the recommended rate to half)
- Add well rot organic compost manure to your new mix
After your fern plant has rejuvenated/formed new growth, you need to considerately start feeding it.
Trim any climbing fern lightly in spring. Then apply a ¼ cup of a balanced slow-release fertilizer. To avoid over-fertilizing, keep a half-strength rate.
6. Extreme Cold Conditions
Like many indoor plants, the asparagus fern will thrive in locations that are a bit warm.
Low temperatures can have detrimental growth problems over time. Persistent cold temperature, particularly winter frost is the worst. Additionally, incessant cold drafts from openings can have similar effects.
Keep them away from open (unshielded) windows, ventilation and other air inlets. You can also acquire a digital thermometer and hygrometer to help you track temperature vs humidity changes. This way, you will be able to give your fern plant the best conditions indoors.
It is normal for them to turn yellow as long they look healthy and sturdy. Don’t panic if you notice those potted turn a bit yellow during the winter.
Indoor variety of asparagus fern
Yellowing Fern Leaves After a Transplant
After having been transplanted, your asparagus fern can experience a transplant shock. Leaves normally turn light green. The leaves may wither a bit but normally recover on their own.
For a quick recovery, transplant when it’s cloudy and cool. For example, by ensuring the new soil is moist your plants should recover from transplant shock more quickly.
Also read: Stages of Growing Asparagus (With Care) From Seed & Crowns
- Asparagus fern, Asparagus densiflorus. Wisconsin Horticulture. Division of Extension. Accessed online 11 Sep 2022
- How to grow asparagus ferns. BBC Gardeners’ World Magazine. https://www.gardenersworld.com/how-to/grow-plants/how-to-grow-asparagus-ferns/. Accessed online 11 Sep 2022