Eerie White to Golden Flowers, with Some Fungi Helping Out

/3 Comments/in , , /by

White Indian pipes, mycorrhizae, and a golden flower

I do occasionally tear myself away from the farmden. So into the woods I went last Friday and as I was hiking along and glancing down at the trail, I came upon one of my favorite flowers. It’s a favorite not for its beauty but for what it hints at of goings-on beneath the soil surface.

The flower was indian pipes, Monotropa uniflora, an eerily white plant that looks like a upright tobacco pipe whose stem has been poked into the ground. Yes, it’s white. All white. You might rightly wonder how the plant synthesizes carbohydrates for energy and for structure. Photosynthesis, which makes carbohydrates,  requires chlorophyll, which is green. Indian pipes don’t need chlorophyll because they get their carbohydrates from neighboring trees.Indian pipes growing in woods

Join me while I go below ground. Stopping for a look at the roots of indian pipes, we see that they are infected with the fine threads of fungal hyphae. Now, if we follow the fine threads of the fungal hyphae out of the roots and through the soil, we eventually come to the roots of a nearby tree whose roots also are infected by one and the same fungus. A continuous connection exists from the tree to the fungus to the indian pipes.

The tree does have green leaves and, as with other plants, some of the products of its photosynthetic labors are channeled down to its its roots. Some of those products travel out the roots and into the fungal hyphae, and some of that is drawn out of the hyphae into the indian pipes for the latter’s sustenance and growth. Sounds like a one-sided relationship, a pretty good deal for the indian pipes. It is. The plant is a parasite, taking but offering nothing in return. 

The relationship between the fungus and the tree, however, is symbiotic and called mycorrhizae (my-co-RYE-zay, which means fungus-root). Yes, the fungus sucks up some of the tree’s photosynthates, but in return it sucks up nutrients from the soil, then channels them back to the tree’s roots. The network of fungal hyphae in the soil is much more extensive than that of the roots, so, with fungal hyphae as “extenders,” the effective volume of soil “grazed” by roots is increased. Mycorrhizae are especially important for uptake of nutrients such as phosphorus, which roots (or their fungal extenders) must go out and find because it moves but little in the soil.

Myco . . . say what?

Wouldn’t mycorrhizae spur growth of garden plants? Yes. But look out your window; most of the plants you see are naturally mycorrhizal already. Still, deliberate inoculation might benefit young transplants. You can purchase inoculum, but the problem is that purchased inoculum often is not of fungal species best adapted to a particular location.

Fungal hyphae coiled in blueberry root cell

A better approach would be to keep your indigenous fungi happy. Limit tillage, which discombobulates the hyphae, grow a variety of plants, especially those that form mycorrhizal associations, and avoid pesticides. Also limit phosphorus fertilizers because they suppress mycorrhizae.

Another approach would be to grow your own mycorrhizal inoculant of local fungal species. Basically, you mix up a big batch of potting soil that has some indigenous soil in it and is not too high in nutrients. In this potting soil you grow a suitable host plant. (Not spinach, beets, or any plant in the cabbage family, none of which ever form mycorrhizae.) After the host plant dies at the end of the season, what’s left in the pot is indigenous fungal inoculum that can be added to a potting soil for growing seedlings. For more details, see http://rodaleinstitute.org/a-complete-how-to-on-farm-am-fungus-inoculum-production/. I use garden soil and compost in my potting mixes and assume there’s sufficient inoculum already present.

Grow Some Gold

As I rounded the bend at the back of my garden after my woodland hike, I came face to face with a flower I had planted temporarily back there, giant knapweed (Centaurea macrocephala), also known as Armenian basket flower, globe centaurea, and yellow hardhat. Plants with too many common names are usually suspect to me, and none of this plant’s names have a particularly nice ring to them — yet this plant is a showstopper.Golden buds of Armenian basket flower

From the whorl of rather coarse leaves at the base of the plant rises a sturdy flower stalk. At almost 4 feet high, a big fat bud forms atop the stalk, a bud that looks like a globe artichoke that has been gilded. Nice enough even then, but a couple of weeks later — which is now — a bottlebrush of lemon yellow petals spills forth from the top of the bud.

Globe centaurea, the name most euphonious to my ears, tolerates heat and cold (USDA Hardiness Zones 3 to 8), and is relatively carefree. No need to prop the flower stalk up with a stake. The blossoms put on their show for about a month, not counting the gilded opening act, and hold up well as cut flowers, or can be dried. 

Yellow blossoms of Armenian basket flowerGlobe centaurea deserves more attention over much of the country, except perhaps in the Pacific Northwest, where it’s considered invasive. I grew it years ago, and it disappeared. Nice to have it back.

Peas Please Me

/1 Comment/in , /by

In some gardening circles, a gardener’s worth is measured by how well he or she grows peas: how soon the first pea gets to the table, the crop’s abundance, and, of course, the flavor.  Sad to say, I haven’t been able to grow peas well for about 10 years.

Pea pods on vinePeas require a humus-y, moisture retentive soil and early planting, all of which I provide. But about 10 years ago, just as the crop was coming on strong, vines began to turn yellow, leaves would flag, and plants would die. The probable cause was fusarium wilt disease (caused by Fusarium oxysporum). This soil-borne fungus invades plant roots and then clogs up the vascular system.

(You may have heard of fusarium wilt of tomatoes and other vegetables. Fear not spread of fusarium among these vegetables, because different vegetables have their own fusarium subspecies. Cucumbers have F. oxysporum f.sp. cucumerinum, canteloupes have F. oxysporum f.sp. cubense, and peas have F. oxysporum f.sp. pisi. How cozy.)

Fusarium wilt probably never made it past my garden gate. It was probably already in my soil at some low level. Over the years, I’m guessing that it built up to a critical mass and was inadvertently spread — by me — on trowels, boots, and tellising. Which leads to one way to keep the disease in check: Clean trowels before planting peas; clean hoes before hoeing peas; and clean or torch the chicken wire trellises and metal support posts that keep the vines off the ground.

Some pea varieties are resistant to fusarium disease. But there are a few races of the disease. A variety resistant to one race may be susceptible to another race. Planting a resistant variety one year did not ratchet up my “good gardener rating.” The plants succumbed to the disease as in other years, and understandably so since I did not know which fusarium race I was up against, and variety descriptions for wilt resistant peas don’t always specify to which wilt race the variety is resistant.

Fusarium conquered(?)

This year I’m back in the game again with peas — and an excellent harvest it is: abundant, early, and flavorful! (These are shelling peas, which take longer to mature than snap peas or snow peas, but also taste better even if they do need shelling.)

peas on trellis

One thing that I did this spring — the thing that I’m touting as responsible for my good crop — was to plant the pea seeds in my south vegetable garden, where I haven’t grown peas for the past 6 years. My wan efforts over the years have been plantings in my north vegetable garden, and they have been consistent failures.

F. oxysporum f.sp. pisi survives from year to year in the soil as spores, very hardy spores. So hardy that the recommendation is frequently made not plant peas again, ever again, in tainted soil. Other recommendations are to wait 5 or 10 years before replanting. In either case, of course, it’s necessary to be very careful about spreading the disease again on tools, boots, or trellises.

And again, the ideal would be to plant disease resistant varieties.

Good rotations

People sometimes ask me if I rotate my crops each year. Crop rotation does not involve twirling plants; it’s moving certain plants — be they in a botanical family or part eaten — to different parts of the garden each year.

Sammy, the pup, guarding garden beds

Sammy, the pup, guarding garden beds

In the case of plant families, it’s a way to reduce pest problems because family members may host the same pest (clubroot disease of broccoli, cabbage, turnips, and radishes, for example). A pest that overwinters in the ground will eventually starve if a suitable host is not on hand on which to feed. A pest that flies or that shoots spores far and wide can travel some distance to find a host, but that, fortunately, is beyond the capacity of many pests.

In the case of rotating by part eaten, such as leaf, fruit, or root, the idea is to balance nutrient uptake. Leafy vegetables are hungry for nitrogen, root vegetables for potassium, and fruiting vegetables for phosphorus.

It’s generally safe to rotate vegetables on a three year cycle. That is, not to return a vegetable in the same family or with the same part eaten to the same place sooner than within 3 years. Planting in beds makes this easy because once the garden is planned out, you just move the crop to the next bed, or two beds away for further distance, each year.

Garden bedsDo I rotate my crops? You betcha’. With peas, I’ll try the 3 year rotation in the south vegetable garden. And I’ll wait at least another 5 years before planting them again in the north vegetable garden, then giving the south garden a “rest” from them. It’s good to again be unzipping green pods and scooping out the sweet peas within.