Caring For A Petunia

Petunias are well known for being low-maintenance flowers. They also stay beautiful from spring to fall and come in a variety of styles and colors. Growing petunias is relatively simple and the pay-off is a rewarding spectacle. You can start seeds inside or out, though it tends to be easier inside since you can keep a better eye on them and cater to their needs. Professionals suggest buying fully-grown petunias from a gardening store and re-planting them wherever you desire. This will give immediate results, but you will find that there are just as many problems with re-planting as with seeding.

Petunia Problems

Choosing the right petunia is key in successful growing because some are susceptible to disease, making all of your work ruined. Grandifloras are petunias that you have to pay close attention to. The have the largest bloom, 3 to 4 inches in diameter, but in hot and humid summers you will notice that this specific variety will get damaged much easier and it runs the risk of rot (fungal infection). Actually, if you are in a hot and humid climate, you probably know that fungus will form on most any type of plant, so look for this. Petunias are also susceptible to iron deficiencies. If you notice the leaves turning yellow and new leaves are yellow, don't ignore these signs.

Fertilizing and Watering

Before we delve straight into fertilizing, you most know how to read the fertilizer label. You will generally find three numbers. In the case of petunias, you want to use 8-8-8, 10-10-10 or 12-12-12 fertilizer. These numbers are telling you the amounts of nitrogen, phosphorus and potassium measured by percentage by weight. In other words, you want a balanced fertilizer for your petunias. Easy enough!

Work some of this balanced fertilizer into the soil (generally around 2 lbs. per 100 sq. feet). It is best to add fertilizer soon after planting, which will be early spring after the last frost. Around mid-July you should start using a liquid fertilizer. For boxed petunias, or those in small containers, use a time-release fertilizer as well as liquid, and water the plants often, sometimes every day, to replace lost moisture. For ground cover petunias, use liquid fertilizer every week and water a few times each week. It is no surprise that this variety is quite stingy with nutrients. For all other petunias, liquid fertilize every 2 weeks and set a sprinkler out to water them once or twice a week. The ground should be wet on the top 6 inches of the soil. 


If your petunias are planted in the ground and not in a movable container, they will die with the first frost. If they are in a container, you can take them inside where they can live for another month. They will not be able to withstand much more of the cold temperatures or survive with small amounts of sun. Remember to remove your plants after they've died because rotting petunias can adversely affect the soil for next year's plants.