Save Your Seedlings! 7 Ways to Prevent Damping Off

We've all had it happen: You sow a tray of seeds, use a good potting mix, keep it watered and warm, and then rejoice to see the little seedlings emerge from the soil. They grow up and up, stretching for the sun, and then--disaster! You awake one morning to find them stricken, stems discolored, leaves wilted, perhaps an entire crop of seedlings collapsed on top of the soil. You've just encountered the dreaded "damping off" disease.

In fact, damping off is not one disease but a general term applied to the affliction of any of a number of fungal diseases, including Botrytis, Fusarium, and Phytophthora, that affect seeds and seedlings. For a look at how damping off affects seedlings--in nature as well as in greenhouse settings--check out this video:




There's no cure for damping off, so prevention is best course of action. If you want to give your seedlings the best possible odds of avoiding damping off and surviving those tender early days, here are 7 tips to follow:

1. Start with as sterile an environment as possible. That means using a sterile potting mix; cleaning pots or seed trays with a diluted bleach solution; treating tools like trowels, soil blockers, hand seeders, and labeling stakes with disinfectants; and using seeds that have been properly stored in a cool, dry, air-tight container.
2. Improve the drainage of the potting mix by adding perlite, vermiculite, or clean horticultural sand.
3. Avoid overwatering and if possible, avoid watering from above. A better approach is to set the pots or trays in a tray of water long enough to moisten the soil completely. Then empty the bottom tray of excess water.
4. Do not add fertilizers to the potting mix when you sow the seeds. Excess nitrogen can encourage growth of fungal diseases and besides, seeds can't utilize it. Seedlings will not really benefit from fertilization until after the first set of true leaves has emerged.
5. Good air circulation is necessary so putting a fan on a low setting over the seed trays can be helpful. A light breeze on young seedlings can also strengthen the stems.
6. Proper light from above and heat from a heating mat below will also keep moisture under control and encourage healthier seedling growth.
7. Avoid touching seedlings unnecessarily, especially when wet, as that can spread fungal spores, if they are present. But once you seen signs of damping off, dispose of any affected plant material as well as the soil right away before it spreads further.

With these precautions your young seedlings should have an excellent chance of growing up strong and healthy.

Wrapping Up Propagation Month

After taking a couple days off from the trials and tribulations of trying to propagate something different every day, I thought I'd post some conclusions I've come to:

1. Of all the different seed-growing methods I tried, one stood out as a clear favorite. If you're going to plant anywhere but directly in the ground, then soil blocks are definitely the way to go. Jiffy plugs suck. They really do. Forget about them. And sowing in flats is convenient for storing on a greenhouse shelf, but it makes transplanting the seedlings more time-consuming and traumatic for all the little roots. Seed blocks on the other hand make transplanting a breeze, plus you can control the soil mix, plus you don't have to worry about having a bunch of little pots or cell-packs laying around. More control, less stuff, happy seedlings. What's not to like?
2. It really does seem that just about all of my seed-starting adventures would have been greatly helped if I'd had a heating mat or two. Heat can really make seeds pop.
   
3. Those gel-rooting cups I tried to root salvia and catmint cuttings in? Don't waste your money. Every one of the cuttings got funky, and even though the package says you can just take out a cutting that isn't rooting and put in a new one, there's no point in putting a fresh cutting into what's supposed to be a sterile gel when it's obviously contaminated.
4. Actually, I had a hard time with almost all of the cuttings I tried to root and I think the problem is that they just weren't staying hydrated enough. It's just so much easier to root cuttings with a mist house. I did some searching on the Internet and found a couple of sites describing small mist houses that people built for under $100 using a set of shelves, some plastic sheeting, and some inexpensive misters and a timer. I'd like to try putting something like that together one of these days.
5. There are a couple things I didn't get around to doing that I still hope to get done. One is to air-layer the camellia at the side of my house (or maybe the really pretty white one at my friend Mark's house). The other is to do some budding on my cherry tree.
   
6. Lastly, I have to say that I had a lot of fun doing all this propagating and I look forward to doing it again next year.
   

I'm afraid that May, however, will have to be Weeding Month. That I'm not looking forward to.

Propagation Month, Day 30: Rooting Sedum Cuttings

Something I hadn't gotten around to trying in all my propagation adventures is succulents, although I've heard they can be pretty easy to do. The basic process is to remove an offset or a leaf, leave it in the open air for a few days to callus over, and then place it to root on a well-draining medium. When I was at the IPPS conference last year I even heard a speaker talk about rooting sedums for green roofs by just chopping up a bunch of plants, sprinkling the pieces over a layer of soil and then, once they had rooted, they could roll it all up like sod and transplant it.

Working on a much smaller scale than that, I pulled off a handful of little "beans" from my Pork & Beans sedum plants to try rooting them. I left them to callus for about five days, then today I potted them up in a 50/50 mix of perlite and potting mix. I moistened them just a bit and covered the pot with plastic wrap. They should start to root within a couple weeks.

Propagation Month, Day 29: Sowing Amaranth Seeds

Last year I bought an amaranth plant. I can't remember what kind it was, but it was sold as an edible. It never got more than about 18 inches high, but it had great red leaves and tassel-like flowers. It also re-seeded freely and I've got a number of new sprouts already growing.

But I got some seeds a couple years ago for the old-fashioned Amaranthus caudatus, better known as Love Lies Bleeding. I tried sowing them but nothing came up, and once again I'm suspecting that it's because I didn't keep them watered well enough. So I'm giving it another try. I'm planting them against the south fence, where I think they'll get enough sun. The seeds are very tiny and I sprinkled them about with a pretty liberal hand. Hopefully, something will grow. I love that this plant is both ornamental and edible. Double-duty is a very noble thing for a plant to do.

Propagation Month, Day 28: Planting Garlic

While I wasn't looking, a bulb of organic garlic decided to sprout on my kitchen counter. I think August is actually the best time to plant garlic around here and I hadn't really planned on planting garlic anyway, but sometimes opportunities just present themselves. I grew some garlic last year, but the bulbs came out very small--perhaps I didn't water or feed them enough. Time to give it another try.

I only planted the cloves that had sprouted (about nine of them) and I planted them at the same depth you would normally plant bulbs--about three times the height of the bulb.

Propagation Month, Day 27: Scaling Daffodil Bulbs

Most people know that daffodil bulbs will "naturalize," meaning that they will multiply in the ground, each bulb adding one or two more each year. But there is another way to increase your bulbs--a process called scaling in which you slice the bulb into sections that will then form bulblets. Bulbs produced through scaling will take two or three years to flower, but you can potentially produce more bulbs through scaling than through naturalizing.

To scale a bulb, begin by clipping off the roots, taking care not to damage the bottom of the bulb, which is called the basal plate. Using a sharp paring knife, cut off the stem tips of the bulb. Then, starting your cuts at the basal plate, cut the bulb into sections lengthwise. Depending on the size of the bulb (I'm using the small tete-a-tete daffodil bulbs here), you can usually cut them into quarters or eighths. Make sure that each piece has some of the basal plate attached. If the basal plate becomes detached, throw out that piece--it won't form bulblets without it.

Pull out the center part of the bulb section--this is the actual flower stem and it will be discarded. Then, using the knife, separate the remaining part of each bulb section into two-scale sections, each with a piece of basal plate attached. If the scales are so thin that you can't separate all of them, that's probably OK, but you want to get as many two-scale sections as you can. The bulblets will grow between the two layers of scales.

Put the scales into a Ziploc bag filled with moist vermiculite. Gently distribute the vermiculite around the scales so that they're well-covered. Seal the bag and put it somewhere warm. You'll need to check it every so often for rot--if any of the scales look funky, discard them. The bulblets should form in about 8 to 10 weeks. The bulblets can then be potted up with each scale tip just above the surface. The bulbs should leaf out the following spring, but will need another year or two to flower.

Propagation Month, Day 26: Washing Cyclamen Seeds

I almost missed it, but my white cyclamen developed a seed pod and I found it just in time. It is best if you can catch them just before they're ripe enough to pop. When I brought this one inside, I found that I could easily crack it open with my finger, exposing the seeds clustered around the white fruity substance inside.

Soft-centered seedpods often contain germination inhibitors, which means you have to wash the seeds really, really well if you expect them to ever sprout. I learned a trick for doing this in my propagation class that makes seed-washing very easy.

Once you've collected all the seeds, put them in the foot of a nylon stocking and tie a knot in the end. Hang the stocking over the edge of the toilet tank with the the foot of the stocking containing the seeds dangling in the water. Put the lid of the tank back on to hold the end of the stocking securely in place. Every time you flush the toilet, fresh water will rinse the seeds. After a week or two, the germination inhibitors should be leached out and you'll have clean seeds to sow.

Linus the cat inspects my work.

Following the advice of various sources on the Internet, after the seeds have been thoroughly washed, I'll sow them in some potting soil, cover them with vermiculite, put them somewhere warm, and keep them in complete darkness until they germinate (30-60 days).

Propagation Month, Day 25: Rooting Rose Cuttings

This beautiful rose is in my neighbor's yard and it is sending gorgeous blooms over the top of my fence. I'm not sure what rose it is--it looks like Double Delight, but that's a guess. It is incredibly fragrant and the scent pulls me over to it every time I'm out in the yard. I couldn't resist the temptation any longer, so today I clipped two long stems for cuttings to root. (The bush is over 6 feet tall and covered with flowers, so the cuttings from my side of the fence won't be missed.)

I haven't tried rooting roses before so I did a few Google searches to see what techniques work. I found suggestions for everything from sticking the cuttings directly in the ground and covering with a Mason jar, to rooting them in loose, moist potting soil in a ziploc bag. I chose a middle path--rooting them in a pot of 50/50 potting soil-perlite mix sealed into a ziploc bag. I used cuttings about 5 inches in length with the ends cut on the diagonal and the end of the stem wounded slightly to expose more tissue. I also dipped the ends in Dip 'N Grow gel. I left on very few leaves, mostly because I wanted to make sure that I wasn't bringing any black spot or rust into the rooting environment. With any luck, roots should start to form in about four weeks.

Propagation Month, Day 24: Sowing Pansy Seeds

I'm still planning a small black-and-white garden so whenever I find some kind of black flower, I want it. These black pansies (Viola x wittrockiana) caught my eye and would work really well to border the bed. I love the tiny little purple and yellow throat with just a dot of white.

Today I sowed a flat of the pansy seeds, using an old wooden crate that some clementines came in. It's a great size that fits well on my greenhouse shelves. The seeds should germinate in 10-20 days.

Propagation Month, Day 23: Direct-Seeding Nasturtiums

I'm still craving more color in the front yard, so today I planted a few Whirlybird nasturtium seeds. I really like nasturtiums for their bright color, their re-seeding ability, and their generally easy maintenance. What I don't like about them is that they often end up looking scraggily, with long shoots going off in all directions. This variety, however, is supposed to stay in compact mounds. We'll see.

I soaked the seeds for a few hours before planting. They probably should have soaked overnight, but...

Propagation Month, Day 22: Direct-Seeding Sunflowers

What better way is there to celebrate Earth Day than sowing sunflowers? I had these seeds left over from a couple years ago--hopefully, they're still viable. If they are, I'll have, after thinning, maybe a half-dozen yellow Mammoth sunflowers (8-10') and maybe a full dozen of these reddish-brown Velvet Queens (about 5').

Propagation Month, Day 21: Sowing Salvia

In my continuing efforts to ingratiate myself with the local hummingbirds, I'm trying to plant some of their personal favorites. This Violet Blue salvia should keep them happy and it will make a great shot of color in both the front and back yards.

I sowed two six-packs, which should be enough to keep even the most gluttonous hummingbirds quite busy.

Propagation Month, Day 20: Sowing Herb Seeds

It would make a lot of sense if I could have all the edibles in my garden conveniently located next to my back door, but there's really not enough sun there for most of the veggies that I want to grow. As a compromise I've moved a big pot of mesclun there, with another one to follow. Then it occurred to me that the other thing I could probably grow there--right on the back steps, in fact--is a couple pots of herbs. By far, the two herbs I use most often are basil and thyme, so I sowed one pot of each to go on each step. I may plant some additional basil plants elsewhere in the garden since it takes a lot of basil to make pesto, but these pots should provide enough for a pinch of seasoning here and there.

Propagation Month, Day 19: Direct-Seeding Cosmos and California Poppies

I've been neglecting my front yard lately while I've been working in the back yard. I took out the lawn in the front last year and replanted with a variety of drought-tolerant plants and three dwarf citrus trees and although there are some things in bloom right now (some apricot-colored poppies, white Pacific coast iris, purple and white tulips, orange gazanias, and white calla lilies), overall it's lacking in color. More orange, I'm thinking, is what's needed. So today I spread around liberal amounts of California poppy seeds and less generous amounts of Cosmos seeds. These Cosmos, called Little Ladybirds and Cosmic Orange, only grow to about 1 1/2 feet tall but if they're anything like the other types of Cosmos I've grown, the butterflies and bees will love them.

Propagation Month, Day 18: Direct-Seeding Zucchini

An easy task for today: I planted zucchini seeds in four spots in my flower garden. This hybrid variety from Burpee is supposed to produce high-yielding but compact, bush-like plants in about 50 days from seeding to harvest. Zucchini are one of my favorite vegetables and I love that they are so versatile you can even bake desserts with them. Four plants should give me plenty to eat, with some more to freeze and give away.

Propagation Month, Day 17: Sowing Snapdragons in Soil Blocks

I've been reading good things about using soil blocks for sowing seeds and I have to admit I like the idea of not having to buy all those plugs. I also like being able to control the soil mix. I was just about ready to order a soil block maker, but then I decided to experiment with some improvised soil blocks and see how they work before I invest in yet another gadget.

It only took a few minutes to put together a dozen soil blocks using a small, square plastic pot as the form. The trick is to get the soil mix (I used a basic potting soil with just a little perlite added) fairly moist and then pack it into the form very tightly until the moisture is oozing out. That way, the soil block will slide out of the form and still hold its shape.

I used a plastic deli container to hold the soil blocks; they fit pretty snugly, which should keep them from drying out too fast. The snapdragon seeds I was sowing are really tiny so they just needed to be sprinkled sparingly on top and then pressed down to make good contact with the soil. I'll move them to the mini-greenhouse tomorrow. Seedlings should start to appear in one to two weeks.

Propagation Month, Day 15: Stratifying Siberian Iris

I'm really loving the irises that are in bloom in my garden right now and it's just making me crave more. I gathered some Siberian iris seed last autumn and I probably should have stratified them then, but I'm finally getting around to it now.

I mixed the oh so tiny seeds with moist vermiculite and sealed them in a plastic container. They'll stay in the refrigerator now for at least six weeks, then I'll sow them in flats by just spreading the vermiculite mix onto some moist potting medium.

Everything I've read says that iris seeds can be very slow to germinate and even then, the germination rate is not terribly high. I've also read that it can take anywhere from two to four years for plants to go from germination to bloom. That may seem like a long time to wait, but for something that looks as great as this Tiger Eye Dutch Iris, I think it might be worth it.

Propagation Month, Day 14: Rooting a Fig Scion

I've heard some people say that rooting fig scions is incredibly easy. But as with many other things that I've heard are incredibly easy to do, I seem to be having a hard time with this.

I started about two weeks ago with a Desert King fig scion that I'd gotten at the California Rare Fruit Growers' scion exchange in January. I'd kept the scion wrapped in a moist paper towel in a ziploc bag in the refrigerator. When I took it out of the fridge, there were a couple of buds just starting to turn green, so it was apparently beginning to break dormancy.

One suggestion I'd read on the Internet said to soak the scion in a dilute rooting hormone dip for 24 hours and then pot it up. I did that, although I thought it might be better to pot it just in perlite and keep it in a plastic bottle to keep the humidity in. It seems to have kept too much humidity in, however, because it was starting to get a little furry and there were still no roots forming. It's still alive, though, because the buds are green and growing.

Today I took it out, wiped it down with hydrogen peroxide to kill the fungus, and repotted it in a 50/50 mix of perlite and potting soil. I also rubbed it down again with some rooting hormone, although this time I used a gel form that should stick a bit better. Tomorrow it goes out in the greenhouse for its last chance to put on some roots.

Propagation Month, Day 13: Direct-Seeding Zinnias and Baby's Breath

Sometimes the direct approach is the best.

After I moved the hostas out of this small corner bed last week, something was needed to fill in the empty spots, preferably something fast-growing since the irises won't last much longer. These lime-green zinnias called 'Envy' interspersed with some baby's breath seemed like a good combo.

Now that the temperature is warming up, sowing the seeds directly in the ground is a good option, and it couldn't be simpler: sprinkle, press, and water. The zinnias should start to appear in a week or so.