Eight summer plant-watering tips
Watering the plants sounds like a simple enough duty. Just get out the hose, turn it on, and what can go wrong?
Actually, a lot can go wrong with this important, trickier-than-you-think facet of plant care.
Getting the watering just right is a balancing act that isn’t always easy or apparent, especially in summer.
Here are eight common watering fakeouts that might help…
1.) Just because it rained doesn’t mean the plants are fine. Summer storms are sometimes fakeouts because heavy downpours often run off more than they soak in, leaving the root zone of the soil surprisingly dry.
Your goal is to keep the roots damp. A soil-moisture meter, a stick, or even your index finger are ways to gauge that.
2.) One plan does not fit all. Not only do different plants have differing water needs, different parts of your yard likely have different water-holding capacities.
Low-lying clay areas, for example, may be damp for weeks after a rain, while a raised area in sandier soil or a sunny area under a limbed-up big tree is bone-dry two days later.
3.) Forget general rules. You can’t go by generic advice on how long and how often to water. Timing and amounts of needed vary based on assorted factors, including the size of the plants, your soil type, the size of your hose or irrigation lines, and even your water pressure.
What counts is the overall goal of making the soil damp – but never to the point of sogginess – all around and to just under the plants’ roots. That might take you five minutes every other day in a flower bed but 20 minutes around a young tree two or three times a week.
4.) You can kill plants with too much water, even in a drought. If you’ve planted a tree in a small hole with lots of added, well-drained soil, water can back up when it hits the surrounding clay.
That can create a “bathtub effect” if you overdo it. That scenario makes it possible to rot roots in soggy soil while the surrounding soil is dry.
5.) Mulch makes a big difference. Two to four inches of organic mulch (bark, wood chips, pine straw, etc.) keeps moisture in the soil far better than bare soil.
On the other hand, if you stack mulch too deeply, it can take an inch or more of soaking rain just to get down to the soil surface.
6.) Weather also makes a big difference. Plants lose moisture much faster when it’s hot, dry, and windy than when it’s cooler, cloudy, and calm.
Adjust your watering frequency accordingly, and don’t water solely by the calendar.
7.) Watch the trees. Plants under trees often go drier quicker, not only because the tree canopy blocked rain in the first place but also because big tree roots out-compete flower and shrub roots for moisture.
You might have to water those plantings even more than ones in a sunny, open area.
8.) Green grass isn’t a good indicator… and neither is wilting. Just because the grass is still green doesn’t mean your tree and shrub roots don’t need water.
Frequent, shallow rains might be enough to keep shallow-rooted grass green, but it’s possible the soil is dry deeper.
Some people use wilted leaves as their cue of when to water, but that’s too late. Widespread wilting means plants already are suffering drought stress. When plants wilt, the best time to water was yesterday.
The exception is plants that are the very first to wilt, which can tell you it’s time to get out the hose before even more plants follow suit. Big-leaf hydrangeas and impatiens are two good early-wilting “indicator” plants.
Those puffy green balls
One oddity you might notice while out and about nature this time of year is little green balls about the size of Ping-Pong balls.
Sometimes they’re very light-weight and papery with white fibers inside. Other times, they’re spongy – almost like over-ripened, mini green apples.
People usually don’t know what to make of them. Are they some kind of seed pod? Maybe a weirdo fungus? Maybe some sort of fruit-like plant part? Droppings left behind by an alien life form?
Actually, these mystery balls are none of the above. They’re plant deformities called “galls,” grown by plants in reaction to an assault by bugs, most often tiny wasps or mites.
The little green Ping-Pong balls are a particularly curious gall known as the oak apple wasp gall.
They grow on oak trees, look like little green apples, and are caused by wasps (hence the name).
When they’re hanging on twigs, it looks like an oak tree is growing apples. In landscapes, people often don’t notice them until the tree drops them into the lawn or garden beds.
Another similar, wasp-caused gall – called the “hairy oak gall” for its fuzzy appearance – is more of a red-brown color and drops later in the season.
Both of these – and all galls, really – aren’t as bad as they look. Other than the occasionally large infestation, they’re fairly harmless to trees and require no spraying, no action, and no sleepless nights.
Entomologists haven’t nailed down exactly how bugs make these weird growths happen, but it’s some sort of hormonal and/or genetic reaction by the plant to secretions injected or deposited by the bug.
Galls can take on many shapes, colors, and forms, but specific bugs always cause the same kind of gall on specifically targeted plants and plant locations.
Oaks seem to be a favorite. They often get ball-shaped galls and other fleshy formations, including some really alien-looking ones that have finger-like projections.
Maples and many other species commonly get leaf galls, which look more like little blisters or pimples growing on the leaves.
In all cases, the point of gall-making for bugs is to create a shelter for the larvae to live in, along with a built-in food source – the fibers, spongy tissue, or similar plant material that the tree makes the gall out of.
In a way, the galls are like little benign tumor-houses that increase the survival odds of the bugs that trigger them.
When the larvae mature, they break out of the galls, and fly away to mate, lay new eggs, and/or overwinter for next year.
Ball galls drop and dry, and galled leaves drop when the trees shed them in fall – their job complete.
Flowers falling off the tomatoes?
A common problem with tomatoes in late June and July is when the plants produce plenty of little yellow flowers but then the flowers drop off before setting young fruits.
The problem, called “blossom drop,” is almost always related to too-hot temperatures when it happens this time of year. (Too-cold nights also can cause it in cold climates or if you’ve planted too early, i.e. under protectors in April.)
Tomatoes set fruit best when daytime temperatures are in the 70- to 85-degree range and nights are between 55 and 70 degrees.
When daytime highs hit the 90s – especially for several days in a row – the pollen in the flowers becomes less viable or even altogether infertile, causing unpollinated flowers to drop off at their stems. That means no fruits.
Some research has shown that shading the plants might help a little (about 30 percent shading is ideal).
Otherwise, since we can’t control the temperature, the solution is to wait for a cool-down and let the plants naturally solve the problem.
If blossom drop is happening other than in a heat wave, the cause could be poor pollination.
Tomatoes are self-pollinators that transfer pollen mainly via wind and the vibrating action of visiting bees, especially native bumble bees. In other words, you don’t need “male” or “female” tomatoes as with some fruiting trees and shrubs.
But even when pollen is viable, a lack of wind or bees can limit successful pollination.
To help spread pollen when the weather has been calm, try gently shaking flowering plants to move the pollen manually.
To encourage bees, avoid insecticides and plant a diversity of blooming plants, including native plants that bloom throughout the growing season.
Another option is to transfer pollen yourself by using a paintbrush to dab pollen from one flower to the next. Of course, if the pollen isn’t viable from high heat, you can dab all you want, and you still won’t get fruit.
A few other occasional causes/contributors of blossom drop include drought stress, excessive humidity, and plants that are “self-thinning” from too-heavy flower production.
Besides hand-pollinating, trying shade cloth, and being patient, keep tomatoes consistently damp at the root level and cover the soil surface with a couple of inches of straw or leaf mulch. Those can also help that other frustration of fruits that rot on the bottom before fully ripening – a condition known as “blossom end rot.”
- Read more on blossom end rot and nine other tomato troubles
If flowers aren’t forming at all in the first place, the problem could be a nutrient imbalance in the soil. Excess amounts of nitrogen can encourage lots of leaf growth at the expense of fruiting.
Cut back if you’ve been heavily fertilizing with a high-nitrogen fertilizer, and look instead for tomato-geared fertilizers that are generally higher in phosphorus and potassium (the last two numbers on the three-digit fertilizer-bag labels).
Avoid nitrogen altogether if you’re using high-nitrogen lawn fertilizers nearby that could be leaching into the tomato garden or if the bed was recently converted from lawn.
A DIY Penn State soil test – available for $9 or $10 at Extension offices, many garden centers, or online at Penn State’s soil-testing lab – can help sort nutrient problems.
- More when-to-do-what tips: George’s “Pennsylvania Month-by-Month Gardening” book