Plant Life-Saving 101

Soggy soil and rotting roots

It's an understatement to say that spring rainfall has been more than adequate. This year even the River birches and willows are looking longingly toward higher, drier soil. While you can't stop Mother Nature there are actions to take to save plants after the recent downpours:

1) It seems obvious, but do override the in-ground sprinkler system. When air spaces in soil are full of water rather than oxygen, roots become stressed, roots may die. Even lawns, with their comparatively shallow root systems, have had enough for the time being. Save the water, save the money, save the plants.

2) Consider pulling mulch away from root systems to encourage surface drying. This might be a particularly keen idea for any soft-stemmed annuals, perennials or veggies. It may prevent rotting at the soil line. Pots of succulents should probably be brought under cover.
  
3) Water-compromised plants may show symptoms that include yellowing of lower, older foliage. Leaves may show unusual colors at the edges, or between the veins, which might indicate a nutrient deficiency. Compromised root systems don't transport nitrogen and "minor" elements efficiently.

4) Don't be surprised if plants with big soft leaves (Hydrangeas, for example) wilt even when you know soil is saturated. Yes indeed, your plants may wilt in both cases, whether they're too wet or too dry. So, be sure to check soil moisture levels before adding water to wilted plants that may already be floating.

5) Remember that plants in containers have more positive drainage than plants in beds. Most potting mixes are "soilless" and contain large amounts of bark or coarse peat to promote positive drainage. The minimal nitrogen content these mixes provide can be leached out of the bottom of the pot with heavy rainfall. You can apply: water solubles (Dyna-Gro), earth-friendly naturals (Dr. Earth, Espoma) or timed-release (Osmocote) to maintain optimal growth and beauty.

6) If you have hanging baskets or containers with saucers (either attached or otherwise) be religious about pouring off the drainage water within 30 minutes. After that, roots are drowning.

Drain those saucers

7) Slug populations will be exploding soon. Protect hostas, lettuce, spinach, cabbage and other slug favorites with Sluggo, which is indeed safe around edibles. Slugs will eat the bait, lose their appetite, stop feeding and die within a few days!

Slugs in the rampage

8) Fungal problems (black spot on roses, tomato blights, powdery mildew, leaf spots) will undoubtedly blossom with the abundant rainfall, heat and humidity. Remember that fungicides must be applied ahead of an infection. They will not reverse symptoms that are already present.

9) As the summer wears on we will reach a time when the soil is dry again. Rainfall is not cumulative. So,be sure to do regular checks of newly installed trees and shrubs even after measurable precipitation. Any plant that was container grown or had a small root ball will dry out more quickly than an established plant. Don't be lulled into thinking you don't have to water "new" plants for the rest of the summer. You will at some point in time.

10) Few plants tolerate standing surface water for long periods of time. If your garden has areas that flood and you aren't planning to correct the drainage (for whatever reason) research and use plants that are "flood tolerant". Even if those areas are bone dry later in the season you must plan and plant for worst case scenario. Baldcypress, River birch, Swamp white oak, 'Huron' gray dogwood, winterberry and a number of hardy ferns will endure challenging moisture conditions.

Rain, rain, it will go away. In the meantime, are any of these actions you can take right now to save lives in your garden?

Rain sodden, down-trodden gardens

When the surface water is an inch deep for a full day in my delta “garden” I know the soil is saturated. (If you saw it, you would understand why garden is in quotes).  While my dwarf River Birch (Betula nigra ‘Fox Valley’) loves periodic flooding, few plants do. Landscape plants recovering from 2012’s  historic heat and drought  needed rain- no doubt. But the extreme flipflop to saturated soils is equally dangerous.

What are the immediate symptoms of too much water? 

Surprisingly, plants may wilt even though the mulch or soil surface is wet. Roots need oxygen to transport  water so they wilt in saturated soils.

Nitrogen (responsible for leaf color, vigorous growth) is highly mobile in soil and may be leached by heavy rain. Nitrogen deficient leaves will be pale throughout, including veins. New leaves of water-stressed plants  may be smaller than normal. Older leaves will show yellow first. It’s possible that even lawns may start looking lighter-than-normal green.   

Water-induced nutrient deficiency 

Unusual colors that might  otherwise be interesting may start showing at the edges or throughout the leaves between the veins. Yews, a landscape staple, are poster plants for wet soil damage. Their needles turn rusty-orange – all the way to the branch tips. Also, keep your eyes peeled for black, purple or discolored bands (cankered) stems on deciduous trees and shrubs.

Is there a difference between wet and flooded?

Absolutely. Areas that often have standing surface water for a day or more require  flood tolerant plants (or a great landscape firm to change the drainage!). For example, trees such as Bald Cypress, Swamp White Oak and River Birch (have you seen the cool dwarf cultivars like ‘Fox Valley’?) are perfectly happy with periodic flooding. While it seems logical please understand plants are not Wet-Dry vacs that will pump an area dry. Select flood-tolerant plants for these sites. 

'Fox Valley' River Birch

What about containers?  

Plants in containers with holes in the bottom drain better than plants in the ground. Most potting mixes are “soilless”, being coarse peat or bark-based, to promote drainage. The downside is minimal nutrient value. So, be sure to fertilize throughout the season (more frequently in sun, less for plants in shade) in years with heavy rain. Be sure that containers with saucers (attached or otherwise) are emptied religiously. After 30 minutes the soil will have absorbed all the moisture it can hold. After that, roots die.                                        

What about insects and disease?

Pestilence is most certainly in our immediate garden future. The jury is out on how this moisture will affect Japanese beetles. Slugs should be rampant. Protect hostas, annuals and other perennials whose foliage  rests on the ground. Earth-friendly baits, like Sluggo, contain iron phosphate and are safe even around edibles. Slugs eat the bait, get a tummy ache and crawl away to die in a few days. It’s alright. Chances are, you’ll never run across the proverbial slug graveyard.

Fungal diseases will abound. The usual suspects, black spot on roses, tomato blights, powdery mildew and a jillion leaf spots are a sure bet as we move into heat and humidity. Remember, fungicides must be applied ahead of the infection. They will not reverse symptoms that are already present.

Can I forego watering new plants?

Sure can’t. Rainfall is not cumulative. Do regular checks of newly installed trees and shrubs even after measurable rainfall. Water appropriately. Don't forget to overrride your irrigation system on days it's raining heavily and for a few days after substantial rainfall. Your plants will thank you!!!