I recently started gardening and this is one of my first plants. Can you help me understand what's wrong with it? Location: Souther California (warmer weather). Plant location: In a pot, outside (5th floor if that changes anything). Soil used is : Organic potting mix. Watered once I see some dry soil on top.
Unfortunately, it is not an easy question to answer. There are many, many things that can cause leaves to yellow and die: overwatering, nutrient deficiencies: (magnesium nitrogen or iron), low light, diseases, viruses... you get the idea.
It really comes down to a process of elimination. What are you doing correctly and what aren't you doing? I think your watering routine is probobly fine. You live in sunny California and the plant is outside so low light is probobly not the problem. It is hard to tell based on the single picture but the plant looks rather large it might be time for a new pot, a larger pot. If your not fertilizing the plant I would suggest you start.
After giving the root system more room to spread out (larger pot) and fertilizing a bit the plant should come back.
The first point I'll make is that container gardening is completely different to gardening in soil in the ground. This fact alone took me years to understand properly. Once you can grasp that concept, pot plant and other container gardening becomes a lot easier to manage.
I'll make a strong distinction from this point onwards... soil is in the ground and growing media is used in pot plants.
Container gardening demands more time and effort and here are the reasons why...
- Water - growing media in pot plants and other containers drys out far quicker than soil in the ground. In warmer climates and exposed conditions, such as your fifth floor balcony Southern California, this means a lot more water is required to maintain a healthy medium and therefore healthy plant;
- Sun - balcony gardening means you often don't have a choice as to how much sun your plants are exposed to, so you may need to provide temporary or permanent shading, ESPECIALLY to the sun side of the pots (note that, space permitting, this can be achieved with other pot plants);
- Direct and radiant heat - Concrete, tiles, render are all building materials that heat up during the day and then release that heat overnight, increasing the temperature variations in the growing media and increasing the top/high temperature, such that the growing media in pot plants can heat up and literally cook the roots of your plant.
The second point I'll make is that a healthy growing medium equals a healthy plant. So to bring your plant back to health, let's look at making sure you provide it with a healthy growing medium.
A good growing medium needs moisture. Container gardens need constant watering. Probably daily in your climate, especially in summer. Once the growing medium in any container has dried out completely and for more than one day, most of the soil biology is dead or dormant.
A good growing medium needs microbiology to facilitate the absorption of nutrients by plant roots. Container gardens need special attention to biology. Those essential organisms that normally "appear" in soil must be encouraged to "appear" in container growing media. Let's look at how you might achieve this...
Organic based fertilisers are essential. Well rotted / decomposed cow manure is excellent for this purpose. Spread across the top surface of the growing medium to a depth of about 0.5cm / 0.25 inch. A light sprinkling of pelletised chicken manure is also good, once the plant is well established and growing strongly (but remember not to do this when you have visitors - the smell is unpleasant).
Soil amendments help. A light sprinkling of granular potassium sulphate is valuable for plant cell growth.
A thick layer of mulch is essential. If you can procure some pea straw or lucerne / alfalfa hay, use a 2.5cm / 1 inch layer of this material across the surface of the potting mix as a mulch. At worst, a thinner layer of lawn clippings will suffice. Mulch is like our skin - just as our skin protects us from the elements, mulch protects the microbiology in your growing medium from the elements.
Liquid tonics are essential. Every two weeks in summer and every four weeks in winter, apply a liquid seaweed mixture as tonic for your container growing media. This tonic will help feed the soil microbiology, which will in turn help feed your plants. If you can procure worm castings (worm poo), this material mixed into the liquid tonic will make a substantial difference.
As Rob mentioned, a larger pot also helps because the larger volume of soil:
- retains essential moisture for longer periods of time;
- takes longer to heat up and cool down, thereby providing a more consistent soil temperature;
- provides greater volume for root growth in the growing medium, which in turn can support a greater amount of plant growth above the growing medium.