Hi Daniel. Right off hand my first thought is an issue with watering. Too wet or too dry are both detrimental to the plant's health and so is irregular watering. here is some info about Dieffenbachia leaf curl problems. Additionally, too much fertilizer can cause leaves to curl and yellow and a lack of humidity can cause leaf tips to brown.
You are very welcome Daniel. I do think it may be humidity/water related. Make sure that the container is draining well and always do a "finger test" before watering . Poke your finger down into the soil as far as it will go...if you feel moisture, wait a day or two and check again...if it is dry, water the plant. Make sure that the plant does not sit in the drained water.
If the plant is too close to a cold window, or sitting in a drafty area, that can cause problems, and also if it is sitting where a heater vent blows. Sudden changes in light and temperature can also cause problems. If the house is kept warm, there may be a lack of humidity. two things you can do are to mist the plant with a spray bottle each morning, or set the container on a tray with pebbles so the water drains into the tray, away from the roots, but slowly evaporates around the plant to raise humidity.
House plants do well with a little fertilizer to replace nutrients. For Dieffenbachias, a general purpose houseplant fertilizer mixed at 1/2 strength and applied once a month is usually enough to keep the plant healthy. Always remember to soak the plant thoroughly when you water and then allow it become almost dry before watering again.
I know the trick with the finger test and stuff to water it,but sometimes it's kinda dry every 2 or 3 days,is it normal to water it every2-3 days?and it stays near the window and I open that window daily.
If it's dry after 2-3 days then there are a few possibilities...it could be that the plant is getting rootbound, or maybe you have potting mix that drains well, or you're not sticking your finger down far enough when you check, or you're not watering thoroughly enough when you do water (you don't want to just give the plant little "sips" of water every few days, it's better to do a more thorough watering less often). As far as the window--I have no idea where you live, but if there's a cold draft coming in from the window that can stress out plants. If you're in an area where it's warm outside now then of course that wouldn't be an issue.
Hi DaniŽl, the first picture is definitely not a problem. I work at a dieffenbachia plantation and we see a lot of these signs.
The second picture is probably damaged by a bug. These are mostly white flies. They lay their eggs on the bottom side of the leaves and the larves feed on the leaves. Otherwise it is probably a problem with watering. Dieffenbachia must always be in a moist enviroment. You can easily check the plant for drought by finding a part of the roots. Wet roots will be relatively strong and have a healthy white look, while dry roots are very weak and almost fall of by themself. Dry roots have a darker white colour.
The third picture doesn't have to be a problem. Normally the leaves of a dieffenbachia curl and finally fall off to make space for new leaves. But since the leaves are also damaged like in the second picture, I think this is also due to bugs or drought.
I hope you didn't threw your dieffenbachia away, it is a beautiful plant if cared for right.