Problem with a forsythia

[BoscoeJayhawk]

Hello, I planted two Spring Glory forsythia and two French Hybrid Lilacs in a new bed in April of this year. All four did extremely well early on, and although the forsythia went into mild shock (droopy for a few days, but didn't lose any leaves) all four started growing vigorously through spring and early summer.

I live in Eastern Kansas (Kansas City area), so August is very dry and hot. I watered the shrubs pretty deeply about twice per week, and I never saw any loss of turgor or any other problems until about three weeks ago.

The lilacs are doing great. One of the forsythia looks great. The other, however, has gotten droopy, lost its color, and its leaves have a papery feel to them. Watering doesn't seem to help, and I'm beginning to suspect some kind of disease.

As far as the soil goes, the soil was somewhat clay when I first dug up the bed. I tilled down about 12", and added 600 pounds of good dirt and 400 pounds of compost along with mixed-in time release fertilizer. This raised the bed about six inches from ground level, and I have about an inch or two of wood chip mulch on top (aged, not fresh). I haven't fertilized since the end of spring.

The plants are all along the south side of my house, in full sun. The area is a little bit dry, but I've been watering deeply and the soil holds water very well.

Anyone have any suggestions? I've attached two pictures. The first is from the sick plant, the other is from the healthy plant eight feet from it.

Thanks in advance.

http://jayhawks.net/~watts/P8230097.JPG
http://jayhawks.net/~watts/P8230098.JPG

 

[treeseer]

600 pounds of good dirt and 400 pounds of compost along with mixed-in time release fertilizer.

Half a ton of soil amendment for 4 shrubs? :help:

Get the dirt off the stems, and let the soil dry out a little between waterings. Looks more like root rot than water stress to me.

 

[BoscoeJayhawk]

1000 pounds of dirt and compost really isn't that much. As I said, I wanted to raise the bed by six inches. 21 feet x 2.5 feet x .5 feet = 26.25 cubic feet, or just about three cubic yards. Three cubic yards weighs a lot.

These shrubs will end up being about four feet wide and six feet tall (and that's pruned height/width), so they need lots of space.

The reason I wanted to raise the bed is that side of the house has had chronic problems retaining moisture, so deep, good soil was a must.

Anyhow, if it's root rot as you think, would you suggest one deep weekly watering? There's no dirt on the stems or anything.

 

[Ed Roland]

A cubic foot of top soil weighs in the neighborhood of 75 - 100 pounds. There are 27 cubic feet in a cubic yard. So a cubic yard of top soil should weigh in around 2000 lbs. 1 yd of soil to amend a bed for 4 large plants sounds about right.

Me thinks Mr. Seer is more concerned with how much of that soil is on top of the root system. Without enough oxygen, plant roots suffocate and die. Plant parts above ground exhibit symptoms of this stress: wilting, yellowing, and drying foliage, leaf drop and twig dieback may all occur. Constant overwatering kills most plants.

So, make sure the plants are at the correct planting depth and the soil is not holding too much water. These plants may be back next Spring barring some other issue. Protect the root ball from freezing temps this winter.

 

[Urban Forester]

It's possible that w/the topsoil compost mix and watering twice a week, you've created an anerobic soil situation, where beneficial soil organisms have been reduced to such a point that anerobic organisms have taken over. These "bad guys" have the ability to degrade roots (google Phytopthora - i.e. root rot from post above). At the very least anoxia (lack of o2) has set in stagnating root development. It's also possible that this is transplant shock, and the shrub will come back, forsythia is pretty tough. Either way rule of thumb dictates in most soil conditions watering trees and shrubs is "once a week in absence of natural rainfall" is a pretty safe bet to maintain health. DISCLAIMER: I KNOW THERE ARE VARIATIONS OF THIS DEPENDING ON SPECIE, SOIL, DRAINAGE, Etc. Etc.

 

[BoscoeJayhawk]

Thanks for the suggestions. This is a new bed, the soil and compost were tilled in, then the plants were added. The sick plant was planted with the top of the roots at the same level as the top of the soil. The only thing above the soil is some mulch, I'll clear some away from the base to see if that helps.

The other three plants are vigorous and growing, and have been throughout the summer. Overwatering is possible, but it doesn't somehow seem right though. I'll move to once a week deep watering though to see.

If that is the case, will I see immediate improvement, or will it be a next Spring kind of thing? Thanks again for the advice.

 

[Ed Roland]

Next Spring kinda thing, for sure.

 

[S Mc]

I realize I am several days late on this thread, however, I will join in nevertheless.

A couple more questions. What kind of compost did you purchase? I am picturing well-aged, professionally produced kind of product obtained from a nursery or such? Did you make sure to blend it very, very, very well with the soil? (No pockets to create problems.)

Where in the line up of shrubs is the ailing forsythia? On an end? In the middle? Were they bare root or container plants? Do you remember if the roots were as vigorously healthy as the other shrubs? or even as well developed?

The weak plant does look like it has set buds. Keep an eye on those to see if they remain viable or start shriveling.

Sylvia

 

[BoscoeJayhawk]

Hello Sylvia.

The compost I purchased was a blend of several kinds (and some loamy dirt) from a local, well respected nursery that specializes in landscaping supply. I mixed it with a bunch of dirt from the same place, very black and loamy, no clay clumps, no sand. Both seemed to be good product.

I then used a large rented tiller (26" width) to till it in. I first tilled the existing dirt down about a foot, then I applied half of the amendments, tilled them in, then applied the other half and tilled it again. I was very thorough, the soil was very well mixed and aerated. The original soil was more on the clay side, and rather compacted.

Once it was tilled I edged the bed with limestone blocks, and I then planted the shrubs. I removed the 5 gallon shrubs from their containers, scored the ball with a small hand spade vertically to loosen the roots, and planted them so that the top of the soil level was even with the top of the planter bed. The two lilacs (which are thriving) didn't have overgrown roots, the two forsythia were a bit overgrown in the container, but they weren't too bad. The roots looked healthy as far as I could tell. Once all were planted, I put down about an inch or so of (seemingly) aged mulch throughout.

The odd thing is that the down-slope forsythia, which is near a gutter spout (and thus would be the most-wet of the two) is the one that's thriving. The up-slope one is the one that's having a harder time. The affected forsythia is the westernmost shrub, at the highest elevation. There's probably a two foot drop over 20 horizontal feet in this bed. The shrub order is (highest to lowest): sick forsythia, healthy lilac, healthy lilac, healthy forsythia. This bed is along the southern wall of my house, and gets full sun and limited moisture (as weather in Kansas tends to come from the NorthWest).

After the comments from the folks here I checked the mulch depth at the base of the affected plant. The depth under the plant is at most a half-inch, so there's not much if any mulch there. However, that plant is on the side that I watered them from, so it's possible that I was inadvertently overwatering that shrub - especially since I was watering them twice a week throughout the very harsh Kansas August drought (for those not familiar, Kansas gets about a full month of 90+ degree days and almost no rain during August).

I think the folks that have been responding are probably right. I probably inadvertently overwatered that shrub during the drought, and once it started looking poor I watered it even more, exacerbating the situation. I've since stopped watering that shrub (and now the rains have started back up).

Is there anything I can do to help the soil dry out? Should I use my finger or some other implement to make some air holes in the soil? Or should I just leave it alone, only watering it in the case of an extended drought until Spring next year?

I'm obviously a neophyte in the gardening area, but I'm trying hard to learn. I'm a bit disappointed with this as I spent a lot of time working on improving the soil. I picked hardy plants that can handle full sun and Kansas' rather harsh summer weather, but it looks like I probably should have paid less attention to their watering once their transplant shock was over and they started growing and thriving.

I'm hoping that the forsythia will bounce back in the Spring. I've heard they can be very hard to kill.

 

[BCMA]

Get your shovel and a pocket knife and head out the ailing shrub. First of all, make sure the plant is not planted too deep. Even on multi-stem shrubs you need to be able to find the buttress roots. They should be exposed and above ground. Once you have the planting depth issue identified, take your pocket knife and carefully cut into one of the stems at ground level that shows signs of wilting. If you find rotting bark or brown staining in the xylem- bingo, there's your problem...root crown rot. Too much water or planted too deep. The xylem should be creamy white with green colored phloem. If the xylem and phloem is good, take your shovel and dig up some roots. If the roots are rotting and staining brown, root-rot; too much water.

 

[S Mc]

You say that the ailing shrub is "on the side that you water from". So then you are hand watering from a spray nozzle or such? I'm just trying to fully understand because I am surprised that the uphill plant is the one we are assuming is being overwatered. I would think that the water would be flowing off soon enough not to be a problem. However, to check this probe down to the original depth of the root ball, along side of it, to see what the texture of the soil is. Is it soaking; holding water too much? Possibly the clay underneath is producing a perched water table then. Or is it too dry? Is the root ball the same dampness as the soil surrounding it? Sometimes interfaces in the soil can preclude water uptake. (I would not think that necessarily in this case as you prepared all shrubs the same.)

It is always a good idea to feel the ground prior to watering to get an idea of how much is needed in any new planting situation. (I can attest to this from experience...I did a number on some Rocky Mtn junipers last year by thinking they needed water when they didn't. Talk about chagrin!)

BCMA gave some good diagnostic instructions. However, for myself I would rather look at the roots first before cutting into the root crown to prevent injury if not absolutely necessary. If the roots look like they have suffered from too much water, then back off and let things dry out. (If the rains are a problem you could possibly shield that area to direct rain away from the plant.)

You are right in that forsythia are tough little guys. As I mentioned before, if the buds stay viable, you should come out ok.

Sylvia

 

[BoscoeJayhawk]

Thanks for the tips folks.

BCMA: I'll do that tomorrow or Friday and tell you what I find out.

Sylvia: I have a hose a few feet away from the bed, so I use a hose attachment that does a rather gentle shower spray. I've been watering into the mulch to the sides of the plants (though occasionally spray the leaves with it to dislodge any pests). The water does not run off, the soil seems to drain well. (total tilled depth of probably 18").

The possibility of the clay underneath forming a barrier to drainage is a possibility. I've been doing finger-pokes of the soil at the surface and it hasn't seemed dry. I'll remove the mulch and dig down on the sides of the plants.

I'll try looking at the roots to see what I can see. I suspect overwatering, and I'm hoping it's just from my overzealousness during the drought combined with the fact that the plant is still not fully established.

Thanks again.