Dry Soil and the Cape Cod Garden

July 12, 2022 | CLFornari | Problem Solving

As I write this blog post, it’s a sunny 81 degrees and very windy. We haven’t had significant rain for sometime, and according to the latest Cape Cod landscape message from the UMASS Cooperative Extension, our soils are dry. “Precipitation fell on June 27/28 and July 2 amounting to just under an inch (0.91”). Soil moisture is short; there’s just enough precipitation to keep plants limping along,” they wrote on July 8th.

Unfortunately, that sea-breeze that is so delightful for us on summer days blows even more moisture away from plants in sunny weather. So it’s especially timely to do a post today about watering.

“I have an irrigation system, so my plants are okay, right?

The answer to this questions depends on how long your system runs, and how often. Unfortunately, many automatic irrigation systems are set to run for only 20 or 30 minutes at a time, and usually this only dampens the soil a couple of inches down. In fact, if a layer of mulch has built up in beds over time, this brief watering might not even reach where the roots are in the soil. Since irrigation equipment and water pressure varies, it’s impossible to give people a set time and frequency for their watering schedule. But it is possible for each homeowner to check for themselves to see if their system is doing the job. An hour or two after your irrigation has gone off, go out to your beds with a trowel or shovel. Move any mulch aside and then dig a hole ten inches deep. Look and feel the soil at the bottom of that hole. If it’s moist from your recent watering, you’re in good shape. But if it’s dry, your irrigation isn’t running for a long enough period of time. Set the system to run longer, but not as frequently. Ultimately you’ll be using about the same amount of water but it will be going down in the root zone where it can sustain your plants.

Be sure to test your soil moisture in this manner in two or three locations. Sprinkler heads might be soaking on one side of a shrub, for example, while the back part of the plant remains dry.

Remember that it’s usually the most breezy on Cape Cod in the afternoons, so watering in the morning makes good sense. Not only can the foliage dry off in those afternoon breezes, but the water won’t all blow away as you see happening in this photo.

“My perennial dried up! Will it come back?”

Most of the time perennials will recover even if the top foliage has wilted and dried. Cut off those dying and unattractive stems, and water the area well with a sprinkler. You could soak one plant temporarily with a hose or watering wand, but for over-all recovery water with a sprinkler so that the entire area gets a good, deep soaking. If you’re only soaking the individual plant, the dry soil around it will take that moisture away quickly, and the plant won’t be able to restore its drying roots.

This perennial might be able to be saved, if the dried tops are cut off and the ground is given a good soaking. A one to two inch layer of mulch would also help this plant in that mulch helps hold the moisture in the soil for a longer period of time.

“How do I know if my plants are drought-stressed?”

Plants that are thirsty often show signs of drought before there is actual dieback. Look for curled leaves, brown leaf edges, and drooping stems. Sometimes these are very noticeable and other times they are more subtle. Look at the tops of plants, and the parts that are most exposed to the sun, because that’s where you’re likely to see the symptoms of drought first.

This PJM Rhododendron is telling us that it’s thirsty with curling leaves. We know that in the winter rhody leaves curl in the below-freezing temperatures, but in the summer they do this when they are dry.

This is my witch hazel shrub. As I sat on my deck the other night and looked at this plant closely, I noticed that not only were the leaves on top curled and a bit wilted, but there were branches that were dying back. Needless to say, this shrub got a long soaking with a sprinkler. I may have to prune off those brown areas if they don’t show signs of recovery in a couple of weeks.

These poor plants died because they were at the very end of a too-long soaker hose. The homeowner thought that he could hook many soakers together and water the entire front and side foundation plants, but in this case the water never made it to the end because the soaker hose was too long. Use shorter sections of soaker hose and hook them up to the faucet independently.

“If my plant has dried up, will giving it some fertilizer help?”

If your plant has gotten really dry, do not fertilize in an attempt to make things better. If you’re using synthetic fertilizers this can cause more damage than good. The best help for a plant that’s in drought stress is water. Mulching bare soil, or covering the dirt with a layer of compost can also be of benefit. Water regularly while you wait to see if the problem areas come back or not. If they don’t show new growth by mid-August, prune them off. Apply an organic fertilizer in the spring.

These are Rhododendrons that had drought damage from the dry summer of 2021 on Cape Cod. Those dead branches aren’t going to come back, so removing them is recommended. If the plant looks too sparse after pruning, these plants could be cut way down next spring. That is called a “renovation pruning” and the time to do such a drastic cut is in late-April or early-May.

“My containers look dry by 4 PM, but I thought that I was supposed to only water in the morning.”

While morning watering is the preferred time, it’s best to water a thirsty plant when you notice that it’s dry, be it in the ground or in a pot. Containers dry more quickly, and in some situations you may need to water them twice a day. As long as they have a drainage hole, let your eyes and fingers be the judge of when pots or boxes need water. Additionally, if the soil in a container has gotten very dry, it’s best to water them twice. Water well once, wait a few minutes, and then come back and water them again. This will ensure that the entire root ball will be well soaked.

There are wands with long or short handles, and adjustable hose heads without the pole as well. They are perfect for watering containers and newly placed plants or seeds, but for the long-haul over the summer, use soaker hoses or sprinklers.

Posted in Problem Solving