User avatar
Gary350
Super Green Thumb
Posts: 7392
Joined: Mon Mar 23, 2009 1:59 pm
Location: TN. 50 years of gardening experience.

Re: How do I know when I've watered my herbs sufficiently?

williamthomas wrote:
Mon Jul 27, 2020 4:23 am
I just purchased Rosemary and Basil that I'm gonna plant outside. How do I know when I've watered enough? When I Google it, I see stuff like "1 inch of water per week". How do I know how much an inch of water is?!
I have learned that my rosemary & basil both like well drained soil. I have better luck planting these in the garden, not in pots. Plants don't seem to like uneven soil moisture in pots. My plants do better in my garden if I buy a bag of child play sand to mix into garden soil so it drains better. Rosemary does very well for me in full sun all day. Basil will bolt in 90 degree hot weather I have very good luck planting basil on the north side of a bush or tree so it gets early morning sun until about 11 am then full shade the rest of the day until dark. I have no problem giving basil lots of water every day plants seem to do much best with 2 quarts of water every day. My rosemary does very well with 1 quart of water 2 times a week. Both plants do good if I feed them 1 tablespoon of 5-5-5 fertilizer once a week after plants have gotten larger. Small plants need small amount of fertilizer & larger plants need more fertilizer. Our TN summers are very hot and humid and often dry as desert June to Oct.

User avatar
digitS'
Super Green Thumb
Posts: 3923
Joined: Sun Sep 26, 2010 1:10 pm
Location: ID/WA! border

My herb, vegetable and flower gardens are entirely watered with sprinklers. Here at home, that is me moving a hose and sprinkler around. In the distant garden, that is a field sprinkler system.

I have measured the water by setting cake pans at different distances from the sprinklers, measuring, and keeping track of the time.

Gary is right that different species benefit from different amounts and frequencies of irrigation. And, soil type makes a difference. The nearest weather station will help you with rainfall.

An inch of water comes close to a gallon on every square foot: 231 cubic inches in a gallon. 144 cubic inches will cover 1 square foot, 1 inch deep.

Steve

imafan26
Mod
Posts: 13947
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Water is always as needed. It is better to group plants according to water needs. Some plants need to be watered more often than others. Watering is also dependent on how fast your soil dries out.

HInts:
Look at plants' orgins and try to mimic that environment.

Plants with gray or gray green and small leaves usually need less water.

Plants that store water like cactus,suculents and plants with "wet stems" like pelargoniums, like to be watered well, but need to dry out between.

Air plants like tillandsia, orchids, anthuriums grow on trees in wet locations, but they have roots and leaves that can absorb water from the air. They can take frequent watering if they are allowed to dry out. Don't water until the color or the roots or leaves change. If roots are not in the air, and in a pot instead, they need to be watered less frequently and need good air circulation

A porous soil with perlite, vermiculite, sand, or rocks has more air spaces. Water displaces air. Roots need air.

Soils with more organic components hold on to water longer. Your finger is the tester. If it is still damp a couple of inches down, it can wait a bit longer

Plants will tell you when they need water. They leaves will turn over, droop, or fall off if you wait too long. If you don't need to water daily, at least check the plants every couple of days. Water meters can help if you have a hard time deciding.

User avatar
digitS'
Super Green Thumb
Posts: 3923
Joined: Sun Sep 26, 2010 1:10 pm
Location: ID/WA! border

Good and well written advice. (It's interesting that the original post was deleted. I wonder why.)

I'm not sure that beginning gardeners have a feel for beneficial soil moisture. There is less of a problem with potted plants, if the pot can drain easily, but plants can certainly be overwatered. I often look at a picture someone posts, suggesting that there may be a disease problem, and think that the plant would look much the same in waterlogged soil. But, what is waterlogged? Yes, plants generally need air in the soil. We aren't usually growing swamp plants in our gardens, patios and windowsills.

For plant starts, I once tried to pay careful attention to how dry I could allow the soil - no wilting! I don't want to see a seedling with only a few leaves begin to wilt. Anyway, at the point when I decided that another 12 hours might cause undue stress, I weighed the flat. It then went into a basin of water. I wanted the soil to soak up every drop of water that it could but in shallow containers and standing water deep enough to reach the soil surface, that won't take an hour.

Then, the flat of containers was allowed to thoroughly drain for a couple of hours. I then weighed it a second time. The weight had doubled. This was a fairly standard potting soil. Now, do I do this every time that I water? Of course not! A gardener gains experience moving containers with plants around but until one does, perhaps the experience of setting a thoroughly moistened pot on a scale, then waiting to water until that same potted plant is nearing one-half of that weight would be useful to some folks.

Rain during the growing season isn't quite an unknown here but July provides an example of what is common. There were two "sprinkles" that together amounted to less than 1/4 of an inch of rain, for the entire month. I claim that my garden soil is 50% gravel. It only might be an exaggeration but I must have been gardening over 40 years in this valley where there is hundreds of feet of glacial moraine sitting on the valley floor. Wells are 200 to 500 feet deep, here.

Water on the surface drains quickly. What remains may quickly evaporate when afternoon humidity levels drop below 20%. Impossible growing conditions? Not at all. There is mountain snow each winter, lakes and rivers, and an amazing aquifer. Irrigation!

Cereal grain and alfalfa are commonly grown on valley farms. When I arrived here 50 years ago. Strawberries, melons, sweetcorn, and green beans were commercial crops. Interstate transportation and housing has changed that but gardening has always been possible and rewarding.

Steve

User avatar
digitS'
Super Green Thumb
Posts: 3923
Joined: Sun Sep 26, 2010 1:10 pm
Location: ID/WA! border

Too subjective.

:wink:

What's dry? What's wet?

:D Steve

imafan26
Mod
Posts: 13947
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

For orchids, which are really easy to over water in pots, weighing the pots on a scale was the objective way to tell when to water. The usual advice is to water the plant thoroughly. It is important to water well when you do water to flush out toxic salts as much as possible. Weigh the watered pot. Wait until you think it is dry and weigh the pot again. That would be the empirical way to do that. Usually, people are told to pick up the pot when it is fully watered to get a sense of the weight. Pick up the pot again when you think it is dry and see if the weight feels different ( you can put it on a scale as well). Wait one more day (weigh it if you want), and then water.

Dryness and wetness is subjective. It is also determined by a lot of factors, including what the plant needs. Some plants need to be dry between watering like cacti and succulents. They are designed by nature to be natural sponges and absorb water until their cells burst. Other plants like water lilies really can't live long in a dry environment and are adapted to living with their roots totally underwater. Most plants are in between, they need to keep their roots moist but also need air.

The type of container matters as well. In the ground, plants can go longer without watering. The roots will be able to spread out to seek moisture and nutrients. Not so, with plants in a pot. The soil and the pot are all the roots can work with.
Solid containers like the decorative painted ceramic, metal, or other non-porous pots with either small or no drain holes need to be watered very carefully. Porous pots like unglazed terracotta, cement; wood, plastic or wire baskets, rafts, specialty orchid pots with additional holes in the sides of the container, lose water faster. Pots that are too small for the plant or pot bound will dry much faster. A small plant in a large container can also be at risk if the media in the container stays wet too long because the plant can't use all the water stored in the media in a timely fashion.

Soil and media should be chosen to fit the pot as well. Plants need air as well as water. Some plants, like water plants are adapted to live in a submerged environment, they are able to extract oxygen from the water. Some air plants don't like to be wet at all. If they get wet, they absorb so much water their cells burst and they turn to mush. Most plants like something in between. Plants that live in an arid environment are usually adapted to collect and store moisture on their leaves, stems (hairy leaves and stems). They can collect even the morning dew. Plants like adenium and many bulbs collect water. Plants that are adapted to wet environments either have mechanisms to dry out quickly or roots that don't like to dry out at all.

Unfortunately we don't see the roots of most plants, unless they are orchids on a tree. Dead roots do not absorb nutrients or water. The result is the same, the tops of the plants will either rot or wither and die. Roots die when there is either too much or too little water at the wrong time.

My rule of thumb has always been to try to mimic the natural environment of the plant as much as possible. Plants can tolerate dryness longer than being too wet, so I prefer an airy potting mix and a pot that breathes and allows for 1-2 years of growth. Soil becomes sour over time, and should be changed if the plant is to be kept in a pot for a long time, or choose a media that does not breakdown easily. Plants should dry out in 3 days, if they are staying wet longer, they are at risk of rotting, and either the pot and media need to be more porous, the plant needs better air circulation, and or the pot needs to be smaller.

Empirically, a healthy plant will have firm roots that are not soft, or black. Leaves will be firm and flexible, not soft, wilted, yellow, dropping off, withered, and branches will not be dying.
Media will be well drained and not have a sour odor or fungus gnats flying around. When you feel the media it should have some texture and should not be mushy or have fungal or algae growth.

Pots with a lot of salt build up will show the salt stains around the drain holes. Terracotta pots will turn white over time from accumulated salts.

Watering should be thorough and allow the water to flush through a pot or for the surrounding soil to be able to be damp 4 inches deep. How much water depends on the water holding capacity of the media which is variable. Pots and plants in the ground ideally should be dry enough in three days to be watered again. If it isn't dry, it depends on if the plant looks stressed. If it is then, I need to change something. If it is not, then I need to hold off watering a few more days. I don't use any pot saucers. It is the first thing I take off a pot and I either throw them away or turn it upside down and use it as a pot stand. Holes in the sides of the pots are a bonus. It does not block the outflow of water. How much water is subjective. There is no specific amount as small plants need less than big plants with larger roots systems.

User avatar
digitS'
Super Green Thumb
Posts: 3923
Joined: Sun Sep 26, 2010 1:10 pm
Location: ID/WA! border

imafan26 wrote:
Fri Aug 14, 2020 12:25 pm
... In the ground, plants can go longer without watering. The roots will be able to spread out to seek moisture and nutrients. ...
And, that spreading and seeking moisture is important. As you point out, nutrients also become more available.

If one waters many plants too frequently, the roots do not spread. The plant is being "set up" for problems. Perhaps, the gardener is out there every day with the water but leaves home for a weekend. The plant may not survive the sudden change in water availability.

It may seem that I am obsessed with this subject and to an extent, I am 8) . In this gardening environment, I consider inadequate soil moisture the most limiting factor for plant growth. More than fertilizer or sunlight, under usual situations. But then, water here at home costs money and I should also be able to justify the use of a natural resource. In the distant garden, the property is a part of an irrigation district. Charges for water use is included with property taxes and is allocated on the basis of acreage. "Overage" requires an additional charge at the end of the year. The property owner and I have never had additional charges levied. So, that's one concern to set aside but another is finding the time to get the valves turned on and off - for me, it's miles away.

The last few weeks, the garden has been watered 3 times each week. This week, I skipped a day because of cloudiness and the high temperatures dropping back into the low-80's and 70's. The water was on 2 times. Next week, the Weather Service says we are returning to 100°f afternoon temperatures and irrigation will be back to 3 times. Most of the plants are not seedlings and they are maturing. They are shading the soil around them. Certainly, these common garden plants can handle 2 or 3 summer days in a row without water. (Common - except for my Cucamelon! This is the 3rd time I've grown it over the years and I still don't know what it's up to :D !)

Steve

imafan26
Mod
Posts: 13947
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

- I skip a few days too if it rains all night. But, I found that even if it rains, it may not be enough. A pot is a small target and there has to be enough rain to thoroughly get the pot media soaked all the way through.

I agree that plants that are watered frequently and shallowly don't send down "survivor roots". Some places only have to water a couple of times a week. My plants in the pots can't go that long, maybe a day and a half. The pots that are pot bound will go less and the ones that have more root space can go longer. I just repotted some citrus trees in larger pots so they actually are going a day longer now before they start to wilt.

Right now in August, the temperatures are hovering around 89-90 degrees so there is a lot of transpiration loss during the day. Mulching would help in retaining soil moisture and limit losses to the top layer drying.
I plant my garden intensively so there is minimal spacing between the plants and I actually try to plan it so the leaves of the plants will almost touch. Sometimes, like with the komatsuna, I still planted it too close. Close planting not only maximizes the space in the garden, it also shades the soil. It is mainly for weed control, but it also helps to retain moisture that way. I do hand water the garden. My sprinkler valves need to be replaced and I am dreading that task. Hand watering is never going to deep water as long as a soak. Most people, including me don't stand around long enough or run the water slow enough to do a thorough deep soaking.

If I actually did deep watering and mulching, at least some of the plants would be able to be trained to go longer without water. Training is required. Plants adapt to the existing conditions. If they can't adapt, they are dead. In the cooler months, I can actually go up to three days between watering some of the plants without problems. Potted plants are usually watered about the same no matter what time of year it is since they can't really store water or reach out unless they have already escaped the pot. I did try the polymers before, it does work in summer to extend the watering period but it bubbles out of the soil and becomes a gelatinous mess when the rainy season comes, so it is not practical if it is not in a controlled environment.

The bigger plants I have in the garden like the tomatoes, and cutting celery have fairly large root systems. The tomatoes, bitter melon, beans, and sunflowers look pretty good even if I miss watering for 2 days. The cutting celery, chard, and komatsuna with their larger leaves that lose water faster are usually wilted. The potted citrus trees usually start showing signs of drought (leaves yellowing, turning over, curling and dropping) on the fourth day.

The orchids can actually stand to be watered once or twice a week. It rains enough at night and the humidity is 90%. Orchids are good at extracting moisture from the air.

My grass is mostly weeds. I rarely water it. It lives mostly on rain. It was pretty brown a few weeks ago, but since it has been raining almost every night it is getting green again. Once in a while I will feel sorry for it and actually feed it. It should be dethatched, aerated, and top dressed twice a year. My thatch is way beyond what it should be. It is almost 2 inches thick. I rarely feed the lawn since it tends to pay me back by needing to be weed whacked more often. It is not unusual for warm season grasses to brown out and go dormant in summer. Most people here do not renovate or water grass enough and we keep the grass for over 20 years. The grass in the front yard is close to that now.

I haven't watered my front yard for a while. The roses do o,k, they just don't grow as fast or have as many leaves. The gardenia and pelargoniums are unhappy, there are more yellowing leaves than usual on the gardenia and it also has white flies so it is under stress. The pelargoniums have a lot of brown branches on the bottom, but I also cut it because it was drifting out onto the grass more than I like. It is looking better after we got more rain and I have deep watered it a couple of times. I really should water it more than once or twice a month. The weeds, of course don't need much to grow.



Return to “Herb Gardening Forum”