New Potted Roses Dying
I'll preface by saying I have never grown anything before - I wanted to try to give some color to my tiny south-facing balcony here in DC. The garden staff at Home Depot said roses could survive the winter, so I bought a hybrid tea rose plant. I re-potted it with fresh potting soil, fertilized it with miracle gro 24-8-16, and have been watering it daily. I've only had it on the balcony a week but I already noticed new blossoms after 2-3 days. Then the new blossoms immediately began browning and as of yesterday I noticed half the plant appears to be dying. I tried googling this and some said it could be a fungus and some said it could just need water, I'm not sure what I did wrong. I'm going to prune the brown/dying bits and see what happens. Even if this plant is un-salvagable, any help would be great so I know for the future!
District of Columbia County District of Columbia
Container life can be challenging for most plants, but we understand that you don't have the option of growing in the ground. Challenging conditions include some that can be helped and others that can't - temperature extremes (both heat and cold, since the roots are much less insulated than in-ground roots), moisture fluctuations, space constraints (room for the roots to grow), and nutrient limitations.
Daily watering sounds reasonable for a pot this size in the current weather. However, make sure it's getting enough water when it needs it - feel the soil for dampness about a finger's depth into the pot (not just the surface). If fairly dry, the pot could use a good soaking - use enough water that the excess drips freely out of the bottom drainage holes. If you use a saucer underneath, empty it when it collects water so it doesn't re-soak into the root zone and keep it too wet. If you water it over a sink and drip-dry before moving it back outside, this shouldn't be an issue. The key is to make sure it gets plenty of water each time so that all roots are moistened; otherwise, dry sections will suffer and can cause leaf loss as the plant tries to conserve resources. If this is a plastic pot, over time you may get used to how heavy the pot feels when freshly watered and how light it feels when it needs water, and be able to just pick it up to gauge wetness without probing the soil each time.
Nutrients are similar in that they are limited to what gets put into the container and what leaches out - there isn't a more steady supply as a plant in the ground would get from surrounding soil (mixed-up by insects, earthworms, etc) and decaying leaves and roots from surrounding plants. Therefore, what you add is important to both maintain the plant's health and to promote growth. Nutrient deficiencies can manifest as yellowing leaves, since some nutrients will wash out of the soil after being watered a number of times. (This is normal, so don't over-compensate...follow the instructions on the fertilizer label about dilution and frequency of use for container plants. If it doesn't mention containers, try the "indoor" directions rather than "outdoor" or "garden.") When nutrient deficiencies are corrected, already-yellow leaves don't always turn green again, because some nutrients only move into new growth. What will happen instead is that no new leaf yellowing appears and new growth looks normal. (Red color on new rose leaves is normal.)
A general-purpose fertilizer with micronutrients is best; yours should be fine if it has them, so just check the label. Micronutrients are the nutrients listed on the package beyond the top three, N-P-K, and they are called "micro" only because they are used in smaller amounts, not because they are less important. Some fertilizers have them (termed "complete" as a category) and others don't, but all nutrients included will be listed on the label. Hardy plants like roses need to "rest" and go dormant in winter, so since they are losing leaves and stopping stem growth in autumn, cease fertilizing until spring at that point.
We do not see signs of pests or disease on the rose, so the petal browning and leaf loss (yellowing, browning, shedding) may simply be a reaction to insufficient moisture. Transplant shock is what we call this adjustment period after being moved into another pot (or planted in the ground) because of the minor root damage that occurs in the process. Because of its temporary reduced ability to absorb enough moisture, the plant's most vulnerable tissues (flowers, new leaves) can "burn" and old leaves can be jettisoned as the plant conserves resources until enough new roots grow. All you can do is to clip off any spent flowers, pull off/out dead leaves, and wait for the plant to recuperate while making sure it stays watered as needed. If the soil is moist enough, don't over-water, just wait for the roots to be recovered enough to be able to use that moisture.
In general, this plant appears to be in good condition and is just suffering a temporary setback while adjusting to its new container and watering regimen. It's possible at some point it got too dry, which started the petal and leaf loss. If you see any different new symptoms, you can certainly send us photos. For long-term care, this plant will need a bigger pot, but that can be addressed at a later time (later this fall or next spring).