Weathering drought

This May I posted about my suspicion that I was over-watering my garden, and why that was environmentally unsound. The post prompted me to cut back drastically on watering via our sprinkler irrigation system. Until this summer, I had the system programmed to deliver water twice weekly to each of twelve irrigation zones.

    I was aware that most of my established trees, shrubs, and perennials were well adapted to dry spells during New England summers. They needed frequent watering in their first two years while they got settled and developed a generous network of roots. After that, they should be able to thrive without supplemental watering, except at the driest times. 

Established plants should be able to cope with dry summer conditions

    So why didn’t I cut out the watering after plants entered their third year in the garden? One excuse is that I was continually adding new plants, so often a bed with older plants also contained newcomers. But I think the real reason was that in my heart, I didn’t really believe that my babies could make it through the summer without a regular soaking two or three times per week.

Would the balloon flowers perish without watering?

    After challenging myself with that blog post, I decided to focus on watering areas where I’m growing vegetables, annuals, and newly planted and perennials. In the rest of the garden, I’d stop irrigating. If individual plants needed water, I’d water them by hand.

I'm still watering a bed of vegetables and pollinator plants

     Overall, I’m surprised and pleased at how well the garden is looking this year with about a third as much irrigation as I gave it during the last few summers. My area is experiencing a mild drought. This weekend we were 5 inches behind our average precipitation for the year, despite heavy rains this week. Yet the garden is chugging along, not noticeably daunted by the dry conditions.

Doing fine without watering

    Over the years I did reduce watering in some of the irrigation zones that contained only mature plants. A red-leaved Japanese maple (Acer palmatum ‘Atropurpureum’) and mostly evergreen shrubs in a bed of vinca (Vinca minor) in the front yard got less and less irrigation. This year this zone is getting none, which highlights an issue with my planting plan.
     
     Two mountain hydrangeas (Hydrangea serrata) that I planted in the front yard don’t tolerate dry spells the way the other denizens do. The hydrangeas wilt dramatically after three days without rain or irrigation. 

Lacecap hydrangea starting to wilt

This year, instead of taking that as a cue to irrigate the whole bed, I’m watering the hydrangeas with a watering can. That seems to suit them fine. 

     I could have avoided this complication if I’d thought to group plants that need lots of water together in one irrigation zone, as a Xeriscape gardener would do. That way I could have lavished water on one section close to the house and let the rest of the yard fend for itself.

     By taking parched conditions in stride, the garden is teaching me a lesson. I’m seeing that it’s OK to let my plants live as they would naturally, including tolerating some dry times. 

Coneflowers unfazed by summer weather

What's to be done indoors?

What’s a sustainable gardener to do when it’s too hot to work outside? Skulking indoors on a 90-degree day, I found my thoughts turning to indoor gardening.

African violets are stalwarts among my houseplants

     A lot of the very forgiving houseplants that survive in my house, such as a venerable monstera (Monstera deliciosa) and resilient African violets (Saintpaulia ionantha), hail from tropical regions near the equator where they grow in the shady understory of the rainforest. They’re equipped to handle low light. On the brightest windowsill, plants can’t get more than 6,000 lux, in contrast to 100,000 lux outdoors in full sun.

This orchid gets enough light to bloom in an east-facing window

    As in the garden, I’ve come to recognize that many kinds of plants aren’t going to grow inside my house. Better to enjoy the houseplants that thrive here than try to pamper the ones that don’t. Conditions that prevail in my house—dry air with human-friendly temperatures--aren’t right for all low-light plants. For example, I’ve failed several times to keep gardenias alive indoors. They need high humidity and low temperatures, around 60 degrees during the day and 55 at night. That I’m not willing to provide.

Gardenias like Houston, not Massachusetts-photo ljmacphee

    I try to exclude leaf-eaters from the house by keeping plants healthy and ruthlessly discarding any that look wan or infested. My houseplants have to be able to survive without pesticides, just like my garden plants. Insects aren’t the only menace. I recently moved an African violet upstairs from the basement because something was chewing mammal-sized holes in its leaves while it was reconditioning under LED grow lights. 

Chewed by mice?

     I suspect this was a member of the mouse lineage that had previously gnawed on my young succulents. So far mice haven’t chewed the leaves of amaryllis plants (Hippeastrum cvs.) that I’m fattening up under the same LEDs, coaxing them to rebloom next winter. They must not taste as good.

With no cat in the house, mice keep showing up

    Some of the houseplants—easy orchids, a treasured streptocarpus, a crown of thorns (Euphorbia milii) and a some anthuriums--are summering on wire shelves on the driveway that runs along the north side of the house. The monstera I’m trying under the roof of the front porch. These plants soak up the indirect rays to store energy for the cold months—and they also get chewed on by insects they wouldn’t encounter indoors.

Monstera summering on the front porch

     Meanwhile, I’m stuck inside in the air conditioning, my outdoor gardening enthusiasm extinguished by the heat. This could be the time to learn how to make seedling pots out of newspaper.

     I’ve had no luck starting bush beans in the vegetable garden this year. Something chews the leaves to bits as soon as they emerge, possibly Mexican bean beetles (Epilachna varivestis). 

     Maybe I can fool the leaf-chewers by planting now, out of sync with their life cycle, and still have 60 days for beans to ripen before the cold sets in. I’d like to give the bean seedlings some protection by starting them indoors and planting them out when they have a few leaves. During the heat wave, they and I can enjoy moderate temperatures indoors.

Letting it go

This 4th of July weekend has been a sad one. We’re already grieving for all the things we can’t do because of COVID-19 and mourning for Black victims of police violence. 

Black Lives Matter protest in Times Square on June 7-photo

Anthony Quintano

The holiday adds the overdue realization for me that not all Americans can be proud and happy on Independence Day. Uncritical endorsement of the Declaration of Independence and the founding fathers feels hollow this year. On top of that, there’s the new information that particulates and metals from fireworks damage the environment. 

Polluting the Black Hills on July 3rd-photo National Park Service

It seems an old era is ending. We might be starting a new one that entails further loss of comforting illusions. Let’s hope it also brings gains in equity for the whole community.

    In this setting, I admired the local oak trees’ response to heavy thunderstorms. 

Oaks let branches go in storms

In the last few days, humid weather (and increased energy in the atmosphere because of climate change?) produced high winds and tropical downpours. The rain was very welcome after weeks of drought, but a number of trees lost branches large and small.

    We were lucky that no major limbs came down on our house or cars, as happened elsewhere in the neighborhood. But lawns and sidewalks showed the fallout in smaller branches broken off from maples and oaks, the most common trees on local streets.

Branch from a Norway maple

    I can’t tell whether these tree parts were torn off by the heavy winds, previously weakened by chewing animals or insects, or jettisoned by the trees. Oaks are prone to a phenomenon that arborists call summer branch drop, in which limbs of 4 inches in diameter or more suddenly fall to the ground. What I’m seeing is branches of less than an inch in diameter but well furnished with leaves and side twigs.

    Trees do engage in a self-pruning process called cladoptosis, or shedding of branches, in response to senescence or drought. In plant senescence, a shoot that isn't producing enough sugars to support itself and a root of equivalent size may be cast off.

     The tree “decides” to drop this under-productive part and direct resources to more successful areas. The same can happen to roots that aren’t taking in their share of water and minerals from the soil. This process of abcission is currently understood as directed by a hormone cascade that triggers the death of the cells that attach the unwanted part to the body of the plant.

The same process in an aloe leaf?

    Imagine if the human body could decide to rid itself of diseased or painful parts and go on to develop useful and beautiful replacements! Plant stem cells are located in shoot and root tips and the lining of trunks and stems. These stem cells are pluripotent and totipotent, i.e. they can regenerate freely throughout the plant’s lifetime and can form any kind of plant cell.

    Right now I wish I could drop unwanted and outdated schemata just as easily and grow some new ones better suited for an uncertain future.

I won't be posting next week while I deal with a deadline at work. See you on two weeks!