From planting ‘til first frost, petunias can stay in bloom. All summer flowering is the promise, and it’s true, to an extent. Pinch off fading flowers, new ones grow to replace them. That’s partly how to keep petunias blooming.
However, even with thorough care, nurturing, and following the expert advice, the flowers may still wither away.
7 Things To Do To Keep Petunias Blooming All Summer
1 – Give Them an Abundance of Sunlight
The minimum amount of sunlight petunias need for flowering is five to six hours. That’s low for a summer bloomer. To keep petunias blooming for longer, you’re going to want these getting full sun all day. 8-hours. Depending on your local climate, that may not be possible.
If you’re really struggling to find a location that can give petunias full sun for longer, switch to growing impatiens. Despite being completely different, they look very much similar. To onlookers, they’d need to in-the-know, and up close to notice the differences in the blooms.
Impatiens prefer shadier locations. If you lack the natural sunlight needed for the best in petunia care, grow their colorful cousin instead. It’s easier to fix impatiens not blooming than it is to keep petunias reblooming the entire season.
Not all’s lost if you really want petunias though…
Before giving up on petunias, know that they can be grown in containers too. If you’re struggling to keep yours blooming, relocation may be all that’s needed.
As an example, your goal may have been to open up the base of a shrub to plant some bright flowering annuals around it.
In that case, the canopy of the shrub could be the problem. Use impatiens around the shrub and plant the petunias at another location, either as a bedding plant in an flower bed that’s more in the open, or pot them up in a hanging basket and hang that where they will get more hours of sunlight.
Location matters!
2 – Use the Right Feed and From Planting
Petunias, being prolific bloomers, need hordes of energy, and from the get-go.
When you’re planting these, or potting them up, it’s beneficial to include a slow-release fertilizer to give them a kick-start.
If growing in containers, mix in slow-release fertilizer granules. If planting in flower beds in your garden, add in organic compost with the soil before planting.
Then, feed them with a liquid fertilizer that’s high in potash, every couple of weeks, minimum.
Given the high concentration of chemicals in fertilizers, when you do add it, directly afterward, water them to further dilute the concentration.
Too strong, or too frequent can burn roots, denting any chance of keeping petunias blooming.
Do take note though because how much fertilizer you use is dependent on how and where they’re planted, and the type of petunia you’re growing.
Spreading varieties and ground covering plants don’t need as much feeding. In containers, the more you add, and the more water is added through the season, lessens the effectiveness. The potting mix in containers, window boxes and hanging baskets can begin to lose its effectiveness.
3 – Seeds and Sowing
Typically, petunias are planted as annuals. They can, possibly, serve another season, possibly three if you’re super thorough with overwintering.
However, and here comes the big BUT. Past their first season, the blooms aren’t as vigorous nor as vibrant, and certainly not as long lasting.
To really get oomph into petunias, you need to be getting fast growth early in the season so that by the time the longer summer days come in, they’ve plenty of pent up energy to throw into blooming and reblooming consistently too.
That happens when you sow fresh seeds. Fresh – as in – buy fresh seeds.
Saving the seeds from last year doesn’t count. When you find a gorgeous variety you love, then search to find out how long do petunias last, delighted to discover you can have it another season, you go ahead and save the seed to sow.
Thing is, you’d be sowing a second generation plant. It’s never going to be identical to the flower you saved the seed from.
And when sowing from seed, don’t use rich soil. Keep the good nutrient rich stuff for transplanting.
To get the seeds off to the best start, a plain multipurpose soil is best. Exposing seeds and seedlings to too much nutrients early on, can damage them to the extent that they don’t bloom as often, or as profusely as you’d expect.
4 – Give Them Plenty of Space
An abundance of floral beauty grown close together does give splashes of color, no doubt. That comes at a premium though, and the cost is the length of the blooming cycle.
Petunias hate congestion. Crowded containers are not what you want. Particularly with cascading varieties as those need a more space for the roots to spread.
Less space equates to faster nutrient absorption.
Considering these bloom best when fed every 10 to 14 days with a potash-rich liquid plant food, if all those roots are soaking that up too fast, they won’t be getting regular feeding. They’ll soak in nutrients much faster, then spend the rest of the time struggling.
When planting multiple plants in containers, make sure it has the depth and width to accommodate all of the plants that’ll be in it.
5 – Pinch Faded Flowers Weekly
This is for the Grandiflora and Multiflora varieties, which are much higher maintenance than your Milliflora and Wave petunias. Pinching the bigger varieties back is how to make petunias fuller, and that, in turn, prolongs the blooming cycle.
For big, dense, and bushy petunias with the biggest of flower heads, make it a weekly ritual to pinch spent flowers. As soon as the colors of the petals begin to fade, remove them. Because even dead flowers consume energy to produce seed.
Pinch them off before they die and the plant won’t go to seed. Instead, it’ll throw the energy into producing more gorgeous flowers. And the cycle repeats. For every flower you remove, a new one takes it place.
The thing to remember is that the flowers on petunias are short-lived, but the bloom cycle isn’t.
Don’t make the mistake of removing only the seed pod though. Part of it will remain. The correct way to remove spend flowers it remove it in its entirety. Pod, petals, and the top part of the stem the flower grew on.
To be certain it doesn’t go to seed, cut the stem back to just above the topmost set of leaves.
When pinching, also be on the lookout for straggly stems. Any that are becoming leggy, pinch them back too. Straggly stems won’t produce terrific blooms.
Again, it comes back to where the plants energy is being directed. The healthier the stem, the better the flowerhead it’ll produce.
All petunia varieties should be short, and dense. Cascading or mounding varieties. If yours is putting out stem growth causing you to question how big do petunias grow in terms of the stem length, there’s likely an issue of neglect happened regarding the pruning.
These should be short, and dense so that the energy is concentrated on blooming. Not long stems with foliage. Flowers are the intention of growing petunias.
6 – Be VERY Vigilant for Diseases (And Pests Too)
There’s numerous diseases can inflict petunias and every one of them will lessen its blooming frequency.
Many a problem is related to watering. Too little, or too much. The majority of diseases are fungal or bacterial, infecting the soil. Fungus can feed on nutrients in the soil instead of reaching the plant. Overcrowded containers are more likely to succumb to something during the season.
If you do notice your flowers starting to peter out, inspect it closely for signs of pest damage. Particularly for petunias kept in window boxes. Sap-sucking pests make it look like your petunias are wilting and dying. The reality can be as simple as insects are draining the fluids the plants need to flourish.
Any bacterial, fungal, or insect problems need to be addressed promptly and treated, or your seasonal blooms from petunias will be short-lived.
7 – Adjust the Watering Frequency in Line With the Local Temperature
Petunias put on the best floral displays when they are watered on a regular basis and with consistency. They can be considered as drought-tolerant, but that only means they’ll survive in dry conditions.
When the weather warms, the heat intensifies in the soil, causing much of the moisture to evaporate. The soil dries out faster, so to get them enough irrigation to prolong blooms, you need to water it more.
Irrigation directly correlates to the fertilizing because in pots and hanging baskets, the more you water the soil mix, the more nutrients is flushed.
Fertilizers may need to be diluted further so that the plant can be fed more frequently in order to increase efficacy. If the nutrients are flushed before the roots absorb the plant food, it’s wasted.
You may think because you added fertilizer, it should be blooming. If it’s been heavily watered afterward, there’s likely to be little added nutrients to help the plant bloom.
Watering and feeding petunias can’t be done on a set schedule. There needs to be a degree of flexibility to account for temperature changes, watering fluctuations, and nutrient leaching from the soil because of the extra water.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.