9 Tips to Keep Your Summer Annuals Thriving
Vibrant-colored annuals have a way of bringing summer to life. Use these easy tips to make them last all the way until first frost.
1. Lots of Water
As summer advances and annuals start to fill out their containers, it’s essential that you provide them with enough water to feed their growth. In fact, by midsummer most plants need a daily soaking. If you have containers with drainage holes, consider placing a dish or saucer underneath to hold any overflow from watering or rainfall. Potted plants that are especially big, like hibiscus or pineapple sage, may need watered twice a day, particularly in higher temperatures.
2. Shorten Plant Height
Trimming the stems of potted tropicals or perennials in early summer will bring them into flower at a shorter height. You can cut the stem height by up to half. The benefit? Plants will not only flower a bit later, but also won’t need to be staked due to their tall, delicate stems — quite a chore. Consider trying this with tall varieties like joe pye weed, butterfly bush, asters or Mexican bush sage.
3. Trim & Feed Petunias & Supertunias
If your petunias only show flowers at the end of stems and the stems are covered in seedpods, they need to be trimmed to promote new growth. Cut the stems back almost to the container edge and then remove any seedpods left on the trimmed stems. When you’re done, water and fertilize the plants with slow-release fertilizer.
As for Supertunias, they should be growing over the pot edges by midsummer. Prolong their life by trimming every fifth stem, cutting them back so that they’re even with the bottom of the container. Then go through and lightly trim the other stems, cutting them back just a few inches. Repeat this process again in late summer if your Supertunias look ratty.
4. Harvest Blooms
Feel free to cut your flowers all summer long for drying. Easy air-drying choices include wheat celosia, strawflower, gomphrena and tall ageratum. Simply harvest flowers throughout the summer as blooms are ready. Although it may seem counterintuitive, cutting blooms frequently will push the plants to produce more flowers.
5. Stake Taller Plants
Tall annuals, such as cosmos, hollyhock and old-fashioned cleome, must be tended to or they can fall over or break off during high winds and summer thunderstorms. Staking them early in the summer will prevent damage. Half-hoops work well to lend support to a group of plants, or use single stakes for individual stems.
Similarly, protected growing areas are a good idea for annuals with brittle stems that damage easily, including begonias, shorter Clemon and ivy geraniums. This is especially true in windy locations. Consider staking these types of plants with half-hoops or installing pieces of wire garden fence.
6. Prevent Mildew
Although zinnias are known for vibrant color, their leaves are susceptible to powdery mildew — an affliction that is too late to treat once visible. This means you have to take care of it before you see it. Different mildew treatments can be found online and include baking soda sprays, neem oil, and traditional fungicides. To prevent mildew in the future, choose disease-resistant varieties and avoid planting zinnias too close together.
7. Trim Back Cool-Season Annuals
You can give cool-season bloomers like snapdragons and sweet alyssum new life by simply trimming them back by half, fertilizing them, and keeping them well hydrated throughout the heat of summer. By doing so, you may even be surprised with a second flowering as the cool air of fall sets in.
8. Deadhead Weekly
Remove any spent blooms on your annuals once or twice per week, depending on the number of plants you have. Cut or break the stems off as close as you can get to the base. Dispose of the blooms in a yard waste bin or a compost pile, but never leave them lying on the ground. They can develop mold (botrytis) as they decay which can spread to blooms that are healthy.
9. Watch for Mold
When summer rains set in, mold becomes an issue for many plants, particularly those in crowded conditions (think packed container gardens). Certain annuals, such as geraniums, zinnias and begonias, are more prone to mold than others. As mentioned earlier, mold can develop on dying or decaying flowers and easily spread to healthy leaves and plants. Deadheading your plants is one way to help control the mold issue.