One of the most common causes of necrotic (dead) leaf tips and margins is over-watering. The mechanism by which this occurs arises from the fact that soggy soil reduces the oxygen essential to root function and metabolism, so roots are not efficient enough to move water to the plant's most distal parts - leaf tips and margins. The TWO most common causes of poor foliage are over-watering and a high level of solubles (salts from fertilizer and tap water) in the soil. Both of these maladies are exacerbated by heavy soils that are watered in sips to prevent root rot. Sunburn shows up as grey or silver areas on the foliage as the chlorophyll is bleached (oxidized) by the same free oxygen radicals found in hydrogen peroxide, also a powerful bleach/oxidizer. Following the short period of gray/silver blotches, foliage will turn brown, or sometimes black in plants with succulent foliage. 'Red' isn't in the realm of possibility because these oxidants would destroy the pigments that cause red coloration in plants. I use soils that require very frequent watering - usually daily in the summer months, and I can't remember the last time I had a plant with poor looking foliage. Fast soils allow me to water copiously and flush accumulating salts from the soil each time I water w/o any concern about root rot or suppressing root function because of soggy soil. I can also fertilize frequently at reduced rates with no worries about the level of soluble salts in the soil interfering with water and nutrient uptake. I wouldn't put much faith in the idea that letting your water rest for 24 hours is going to play a significant role in correcting your foliage issues - it won't. It's possible that chlorine (an element necessary for normal plant growth) and fluoride might be marginally contributory to your issues, but the fluoride in drinking water isn't volatile (doesn't dissipate) and nearly all municipal water suppliers are using a non-volatile form of chlorine as well. Almost all causes spoiled foliage issues can be found within the triangle formed by soil choice, watering habits, and nutrition. Unless your plants are next to a heat source (register/radiator, under hot lights, on top of a TV .....), most other cultural conditions like low humidity, chlorine, fluoride .... will be marginally contributory. Most growers take a giant step forward in their ability to produce consistently healthy plants with the least amount of effort once they've come to understand the importance of soil choice to their success. Getting your plants into a healthy, fast draining soil that holds little or no excess water provides a foundation you can build strong plants on. Heavy soils that support excess volumes of water are inherently wrought with issues that find you fighting the soil constantly instead of letting the soil work FOR you. More on that if you wish. I would abandon the use of any fertilizer for plants in containers that have the middle number (phosphorous) higher than either the first or third numbers (nitrogen and potassium respectively). No plant uses more P than either N or K, so it makes no sense to supply it in excess because an excess is limiting. When all the calculations are done, fertilizers in the 3:1:2 RATIO (RATIO is different than NPK %s) come closest to providing nutrients in the ratio plants actually use. This is very important when growing plants with temperamental foliage because it allows you to supply nutrients at the lowest level possible w/o nutritional deficiencies. LOW levels of soluble salts in the soil greatly increase your chances of producing plants with healthy leaves. Questions? Al

I'm incline to agree with Arthur here. This isn't salt damage. This plant want higher light than what you are providing. This damage is consistent with what I've seen in other plants: little too much water in too little light. It's not a rot, but rather the plant saying "ouch". Side note: this plant is a tough one. You can feel free to use tap water with it. Spring water really is unnecessary.

Mine did that too in the summer time and we're in similar growing zones (7). I attribute it to the heat, thought I've never though much about it. Many of my oncidium alliance plants suffer from those spots. I suspect its the heat, because growths that occur during the winter (when my plants are indoors and under lights) don't develop the leaf spotting. There's nothing you can do to get rid of the spots that are already there, aside from cutting away the leaves, but that's not a good idea. Basically, they're just cosmetic damage, the leaves are otherwise healthy and productive. As far as the leaf tip damage, you may be letting the plant dry out a bit too much between waterings OR you might be over watering (and killing off the roots). Sounds kind of odd doesn't it? Anyway, increasing the humidity would probably help with the spotting and leaf tip die back. I'd also suggest checking the roots to see if they are white and healthy with lots of green growing tips. If they look bad, don't worry too much, but cut back on watering for a bit and consider repotting the plant. Personally I wouldn't divide the plant when you repot. It actually looks fairly young and there aren't all that many growths (for a Twinkle). Give a another year or two before you consider breaking it up...really let it get large and healthy unless it's completely over grown the pot. Your plant is at least another growing season or two away from that point, though.

Hi Prairie_north: I check on Pro-Mix HP (65 to 75% peat moss, perlite, lime, wetting agent) http://www.pthorticulture.com/en/products/pro-mix-hp-mycorrhizae/ "PRO-MIX® HP MYCORRHIZAE™ HP - high porosity PRO-MIX® HP, with its high perlite content, provides a growing environment which benefits growers looking for significant drainage capacity, increased air porosity and lower water retention. The added benefit of a fibrous peat moss and coarse perlite ..." I notice on the last picture, the pot is sitting against a black saucer, which means water won't drain fast enough. Rugosa HATES WET FEET. Rugosa is known as "beach rose" since it thrives on DRY & SANDY SOIL. The Pro-Mix-HP has fibrous peat moss, which doesn't drain well like sand, plus peat moss when gets too wet, become acidic. Tip-wilting is indicative of acid-burns ... years ago I had the same problem with one of my band in an acidic too wet potting soil. How to fix that? Take the saucer at the bottom out, and use 2 wooden planks to elevate the pot, to air out the bottom. If possible, drill extra holes at the sides around the bottom, to drain off excess water. pH-test the soil with red-cabbage juice. The best potting soils I used become "clear" in red cabbage juice, which means it's a good buffer & neutral pH. The exception is MG-regular-potting soil (green bag for indoor plants) with a higher % of peatmoss, means more water-retention capacity, that became light pink in red-cabbage juice I still have problems with the over 65% to 75% peat moss content. I would add more perlite. When I root roses, I use 1/2 perlite to 1/2 potting soil (already has perlite), yet that doesn't drain fast enough, I have drill extra holes at the bottom of the pot. Rugosa doesn't like fertilizer, so aim for fast-draining, that way you won't get minerals-accumulation either from your tap, or excess fertilizer. I really think the saucer at the bottom is the culprit. That's why stores put their rose-pots on wooden-planks, for best drainage and airflow to the bottom.