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Dracaena leaves turning black - any help?

Posted by ah97 (My Page) on
Fri, Aug 6, 10 at 3:08

Hi,

I've had the Dracaena plant for a year with no problems. I give it 500 ml of tap water, once every week.

Lately, the leaves started getting black areas and the tips turning black as well.

Any help is appreciated!


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RE: Dracaena leaves turning black - any help?


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RE: Dracaena leaves turning black - any help?

  • Posted by tapla z5b-6a MI (My Page) on
    Fri, Aug 6, 10 at 9:39

While it could be fungal (doubtful), or from over/under-watering, simply adding a pint of water weekly absolutely guarantees a steadily progressive build-up of soluble salts in the soil. This is the main reason such a high % of hobby growers think houseplants 'only last a year or two' before you have to buy another that doesn't look so ratty.

You haven't given us anything to go on, as far as cultural conditions and your fertilizing/watering habits, but based only on odds, my first guess is you need to take steps that will eliminate both soluble salts AND the possibility of root rot if you DO water properly.

Al


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RE: Dracaena leaves turning black - any help?

Thanks Al. Can you or someone please advice on
- what is the correct watering habit for such a plant?
- how often should I add a fertilizer?
- how often should I replace the soil?
- how to eliminate a soluble salts and root rots.

Thanks.


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RE: Dracaena leaves turning black - any help?

  • Posted by tapla z5b-6a MI (My Page) on
    Sat, Aug 7, 10 at 10:50

Here is a synopsis of the easiest route to long term good vitality in your plants, and for plants you can pass down to your children if they want them:

If you cannot water so that you fully saturate the soil every time you water, and a fair % (at least 10-15%) of the total volume of water you applied exits the drain hole - your soil is inappropriate. OR, you need to take steps to ensure salts do/can not accumulate. Flushing the soil on a regular basis (at least every 2-4 weeks) is very helpful in keeping salt levels at a reasonable level, but flushing the soil doesn't address the aeration/compaction associated with soils so water retentive you cannot water properly w/o risking root rot.

The best way to water is to apply enough water so the soil is thoroughly moistened. Then, return a few minutes later and apply enough water so that at least 10-15% of the total volume you applied in both applications flushes through the soil and exits the drain. During this watering, your pot should be where it can drain freely or it should be above a saucer so the soil never comes in contact with the effluent after it has exited the drain hole.

How often you fertilize depends on where the plant is in its growth cycle, what your soil is like, and your watering habits, so no one can tell you how to fertilize w/o knowing something about these things. Because I use soils that drain freely, I fertilize weekly at half to full strength in the summer. Those plants I over-winter under lights get fertilized every time I water, but at low dosages. I usually add 12 drops of Foliage-Pro 9-3-6 fertilizer to a gallon of water (winter) and fertigate with that solution. The plants always have a low dose of the proper ratio of nutrients available in the soil. Coming full circle to the fact that we WANT to keep salt levels low, you can see how frequent low doses of fertilizer and a soil/watering regimen that flushes salts from the soil before they accumulate is very beneficial.

Plants vary, but most plants are physiologically constructed so they can be bare-rooted and repotted on a regular basis. When to repot sort of depends on your goals or your vision for the plant, but base your decision on the fact that when the root/soil mass becomes congested to the point that you can lift it from the pot intact, growth has already been negatively affected and the growth rate/vitality will continue to decline. Even if you pot up (as opposed to repotting) you will see only the plants temporary return to a growth rate a little closer to its potential, but you will never see its full growth potential restored unless you correct the original root congestion.

I would suggest you repot at the point the root/soil mass can be lifted intact, or the year after that milestone in the month before your (house)plant will exhibit it's most robust growth. I repot all my houseplants & tropical/subtropical trees in late Jun to early Jul, unless I fall behind, which often occurs because of the number of plants I have.

You asked about how to avoid root rot. Very important is to keep your plants growing robustly - a plant that has good metabolism is manufacturing plenty of the bio-compounds that allow the plant to resist these fungi. Second, avoid the cultural conditions that allow these fungi to grow/multiply. Avoiding soils that support a soggy layer of soil at the bottom of the pot ("drainage layers" do not help) is key. Proper watering habits and avoiding high soil temperatures is also helpful.

Once you understand a few basic principles that apply to an extremely high % of plants, maintaining your plants so they always exhibit good vitality and a healthy appearance is easy. When all is said and done, the source of what binds most people down and prevents them from being able to realize the full potential of their containerized plants is the soil. Usually, watering issues, appearance, even disease and insect infestations can all be traced to low vitality levels that have their roots in the growers choice of soil.

Admittedly, light, fertility, temperature ..... also play major parts in whether or not your plant will realize its potential, but each of these conditions are easily changed by the grower in an instant, but the effects of a poor soil persist, setting you down slope from an uphill battle from the outset.

Al



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