Tuesday, July 7, 2020

July 7, 2020 The Heat Is On


Hi Gardeners

The garden of M. Hodgson 
As I sit here it’s clouding up and I am hoping like heck for rain. Storms are popping up here and there around us, but it’s hit and miss. Radar is showing we are just at the edge of storms and it’s frustrating to see it so close.  Like many of you we have had very hot miserable weather here and it’s been dry, so any rain is welcome at this point. 

The grass is brown and crunchy now, but at least I don’t have to mow.  I have been watering every day, half of my gardens in the morning and half at night. One hose burst in the heat and I had to replace it. I know the water should be turned off at the house but it’s hard to get to, and I tend to forget to do it.

My plants are for the most part, hanging in there, but some things are starting to go despite watering. The ostrich ferns are browning, some hostas have scorched areas. The daylilies are just starting to bloom but I notice I have big buds on some of my mums already. That’s way too early! What will be left for fall bloom?

Asiatic lilies are shorter and the flowers smaller this year. The orienpet lilies are also getting ready to bloom and are shorter and smaller this year. By this time the martagon lilies have generally bloomed already, but this year I have yet to see any blooms and only small buds.

The rocket ligularia and joy pye weed are starting to bloom. I have a few nasturtiums in bloom, but my zinnias and cosmos are just sitting there, not growing much. The dahlia’s are way behind this year too.

My corn is more than knee high and so far, the deer haven’t gotten to it this year.  I’m hoping for some good eating.

I’m going to write about hot weather issues today, hoping that will make the hot weather disappear.




Plant Problems in hot weather

With a heat wave over much of the country, plants everywhere are experiencing some problems. If you understand what problems in the garden are being caused by hot weather, you may be less anxious about what is happening.

Every plant species has a temperature threshold that can trigger dormancy, death or delays in growth or fruiting. In general though, temperatures over 95 degrees F for several days in a row are stressful to most plants.

Some plants like pansies and calendula will stop blooming and go into dormancy when it gets too hot. Dianthus, snapdragons, diascia, delosperma, and sweet alyssum are other plants that don’t like heat.  Some plants like ostrich ferns, will turn brown and die back if it gets too hot, especially if it’s also dry. Perennial plants may also bloom early and then go dormant quickly. Some seeds won’t germinate at high temperatures.

Photosynthesis slows down or ceases in very hot weather.  Dry conditions make this even worse, because vast amounts of water are needed in the photosynthesis process. Without as much food being produced plant growth will stall and blooming could be delayed. On the other hand, heat will cause plants like lettuce, spinach, broccoli, and cauliflower to rapidly go to seed and make them unsuitable for eating.

Leaves turning yellow and dropping off the plant are common in high heat as are browned leaf tips and scorched looking areas.  All you can do is make sure plants have adequate water and perhaps some shade.  

Bees may die or stop working in very hot weather and this will affect plant pollination. Some plants like tomatoes and peppers like warm weather for growth, but warm weather at night can cause pollination failure.  No fruit will set until conditions improve. Partial pollination and imperfect pollination caused by heat can lead to deformed fruits and early fruit drop in tomatoes, peppers, melons, squash and other fruiting plants.

In fact, warmer than normal temperature at night is usually more harmful than hot weather in the daytime for plants. Just like people, being able to cool down at night reduces plant stress and allows normal life processes to continue. Temperatures above 75 degrees F at night can trigger problems in many plants.

For tomatoes blossom end rot may appear in hot weather. This is caused by fluctuations in watering, getting very dry then being watered heavily. It is not caused by lack of calcium. Very warm soil along with less water can inhibit the uptake of some nutrients and cause deficiency symptoms in plants.  Fertilizing at this time is not helpful.

Cucumbers, eggplant, and summer squash harvested in very hot weather may taste bitter. This is caused by plant stress. If you want potatoes to produce well in hot weather make sure they get plenty of water.

Some plant diseases are favored by either hot dry weather or hot humid weather, but many fungal diseases are less likely in dry weather. Some insects are less likely to be present in hot weather but some, like spider mites and aphids are more likely to build up large populations in hot weather. Plants stressed by heat are more vulnerable to insect and disease damage.

As the climate warms, we may see more of these long stretches of high heat. We may have to adjust what we grow and how we grow it. This summer is practice, I guess.

More reading
 
Diascia stops blooming when its too hot
Watch those pesticide sprays in hot weather

Every pesticide has a label that gives directions on it’s use. Some pesticides should not be used when the temperature exceeds a certain point.  If they are used, they may harm your plants. Read the label.  If the label is gone, look the pesticide up online, if you list the brand name, you can find a website and most of those have a way to look up labels for your product.

Many homemade sprays should not be used in hot weather either. Dish soap-based sprays are one of them.  Many oil-based concoctions are also harmful in high heat.  I would avoid homemade sprays, even of things like garlic and hot pepper, when temps exceed 90 degrees.

Watering Tips

When the weather is hot like it is over much of the country the landscape and our gardens suffer. Most people will need to water their gardens if they have been without substantial rain in a week. Some things like hanging baskets and containers may need to be watered even if you have had rain this week. Some of you have irrigation systems or soaker hoses installed, but many of us still do hand watering.

It’s an old wives’ tale that you cannot water when the sun is high. Water droplets will not burn plant leaves because they are a “prism”. The sun often comes out right after a rain when droplets are on plants. Nature wouldn’t “plan”(evolve) things this way. If you want to test this theory, simply water a plant in the noon sun and see what happens.

That being said, watering in the early morning or evening wastes less water due to evaporation.  More water gets into the soil.  It’s also easier on you. One exception is watering tomatoes and any plants that are prone to powdery mildew. They should be watered several hours before sundown, so the foliage dries before the sun sets. When foliage stays wet for a long period of time many fungal diseases have an easier time infecting the plants.

Water when you have the time to do it. When you see badly wilted plants it’s time to water, not wait until a perfect time. When it’s really hot, the cooling effect of watering can help plants survive.

Overhead or at the base?  Type of water?

Most plants won’t be harmed by overhead watering in hot, dry sunny weather.  As mentioned above it won’t cause leaf scorch and because plants will dry quickly it probably won’t help any fungal diseases. It’s always better to water at the plant base if you can, but if that’s impractical water the plants in any way you can manage.

In very humid, but dry, sunny weather watering at the base of plants is recommended if you can do it. Also, if you water in the late evening when plants might not dry off quickly watering at the base is preferable.

Rainwater is always preferred by plants but if they had rain, we wouldn’t be talking about watering them. If you store rainwater use it.  Well or city water being used outside shouldn’t be a problem for plants, even if it’s “hard” or “soft” water.  Cold water won’t harm them but do be careful if a hose is left on and sits out in the sun. That water can heat up to very high temperatures and if used on plants, could burn the leaves.  Let it run until it cools down before watering plants.

You can use “gray” water or pond or lake water in most cases, to water plants.  Dyes or bt for mosquito control in ponds won’t harm plants.  Stagnant, algae filled water won’t harm them either.  If a pond or lake was treated for weeds, however, don’t use that water on your garden.
You can use water from a swimming pool on plants if it hasn’t been chlorinated in several days.  Because it could contain bacteria, don’t use it on edible plants.

Gray water is water from laundry, sinks, tubs, anything but a toilet. It can be used on all but food plants. The soaps in this water generally aren’t harmful if used at plant bases. However, water with bleach or strong cleaners shouldn’t be used.  Because there can be bacteria in gray water it shouldn’t be used on food plants.

Baskets and containers

By this time of year most containers and hanging baskets are quite full and the plants mature. These baskets and containers will dry out very quickly, especially those in full sun. They may need to be watered twice a day, especially those in sunny spots.  Water carefully so the water gets to the potting medium. The foliage in full baskets or containers may shed water over the sides if watering from above.

If watering twice a day and the plants still wilt, check the soil.  If it’s dry you may need to deep soak the pot in a bucket or let a hose trickle on it until the pot is saturated. Taking a hanging basket down and putting it in the shade until it’s cooler may also help. Some containers or baskets without good drainage could be overwatered even in hot weather so check the soil before watering.

Plants in containers that sit on cement, asphalt or metal or that are against a reflective surface like a white house wall are prone to scorching from the heat. Leaves may brown on the edges and curl or the leaves could look bleached out. Elevate all containers off such surfaces by an inch or so. Small pieces of wood or rocks will work.  Don’t block drainage holes.

If you can’t move these plants away from the hot areas, you may want to provide some kind of light shade for them until the weather cools. Don’t restrict the airflow though, that will make things worse.  An umbrella could work, or some light cloth suspended on a frame over the plant might help.

Annuals

Most bedding annuals require watering to bloom well. Depending on your site conditions and plant species that could be every day or once a week.  Watch annual beds carefully. If there are signs of wilting, get them watered. Plants in sunny spots will need more watering.

Don’t let the annuals dry up and expect them to revive when it rains. Most won’t do that and if they do, it will take a while before they bloom again.  Some plants will wilt in the heat of the day and then perk up in the evening. When you see wilting in the day the plants probably do need water. They may be able to hold on for a day or two longer with this water conserving strategy but get to them soon.



Do I need to water perennials?

If temps are over 90 and it hasn’t rained at least a ½ inch in a week, I would consider watering some perennials.  Anything with buds or blooms should probably be watered.  Anything that is wilting should be watered.  Plant species that like moist soil should be watered.

You can wait to water perennials that have finished blooming, or that like dry conditions. However, if the temps and drought continue another week, I would consider watering most perennials except the most drought tolerant ones.  After 3 weeks without rain I would water even the drought tolerant plants.

If you need to water annuals in the same bed don’t worry about watering perennials with them.

Grass- lawn

Personally, I don’t water lawns.  I can tolerate brown crunchy grass.  I don’t care if grass doesn’t grow because I won’t have to mow, which gives me more time to water important plants. Grass can go dormant and then revive later in cooler wetter weather. If you must conserve water, or watering time then don’t water the grass.

But if you like a green lawn and don’t have an irrigation system you’ll need to give the lawn an inch of water once a week.  Watering once deeply is better than watering lightly every day. Put a rain gauge or a simple can out in the lawn so you can measure how much water you applied.

Trees and shrubs

In a long period of hot dry weather trees and shrubs also suffer. If the tree or shrub was planted this spring it needs at least weekly watering.  If it’s wilting water more often.

It’s a judgement call on established trees and shrubs as to whether you water or not. Sometimes it’s simply impractical to water and you’ll need to let nature alone.  If it’s been hot and dry for 2-3 weeks and you can intervene with watering, water at the base of a shrub or under a tree canopy by letting a hose trickle water there for at least an hour. 

There are devices that you fill with water and the water slowly leaks out to water trees and shrubs. You could use a 5 - gallon bucket with a few tiny holes to water them.

Now is not the time to plant or transplant

Across most of the country right now it’s hot and in many places it’s also very dry. Many people are still asking about planting things, however.  While emergencies may come up, now is not the time to plant new things in the garden or to dig up and transplant things.

Hot weather puts a lot of stress on plants and it’s not a good time for them to be trying to establish a new root system in this heat.  Even if you water everyday the stress may be too much for many plants. If you can’t water frequently and it isn’t raining a lot in your area, it’s definitely not time for planting.

Hold off on all planting, transplanting, dividing, repotting and so on until the weather is cooler. In late August and September, we usually have more favorable weather for those tasks. Plants also vary by species as to what the best time for planting and dividing is for them.  Some prefer spring planting.

Here’s an article that gives the best times for dividing and planting perennials.


One exception to not dividing now is for bearded iris, which should be divided just after blooming- unless you have a re-blooming variety. If you haven’t done this already you could still do it. You can hold the divided sections for a better planting time if needed.  Here’s a page where you can learn about dividing iris.

If there is an emergency reason for planting or transplanting now, try to do it in early morning or late evening. Make sure to keep the root systems moist when they are out of the ground. However, leaving them with roots submerged in a bucket of water for more than an hour or so is not recommended.  After planting, water the site well. Provide some shade for the new plant, even if it’s a sun lover, for a few days. You could put a beach umbrella over the plant, a lawn chair, paper tent or other item to provide shade.  Check the plant daily and water if the soil looks dry.

July almanac


The full moon in July this year was on the 5th.  It’s called buck moon because the buck deer’s antlers begin to show this month. Its sometimes called the Hay moon too.  The moon perigee is the 25th .  Moon apogee is the 12th.

This month’s flower is the sunflower- very appropriate and the birthstone is the ruby. It’s National Blueberry, Eggplant, Lettuce, Mango, Melon, Nectarine and Garlic month as well as National Hotdog and Vanilla Ice Cream month.  Why isn’t it National Cherry month?  The second week of July is nude recreation week. That’s this week.  Have fun.

The Delta Aquariids meteor showers begin mid-month and peak on July 27-30th.  These meteors continue into mid- August and overlap with the Perseids meteor shower. Best viewing will be around 2 am for most of the US. Look to the south. 

"Our fear of death is like our fear that summer will be short, but when we have had our swing of pleasure, our fill of fruit, and our swelter of heat, we say we have had our day."

-  Ralph Waldo Emerson


Kim Willis
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