Readers ask: Seedlings, compost and overgrown orchids

  • Author: Jeff Lowenfels
    | Alaska gardening
  • Updated: March 8
  • Published March 8

Bok choy seedlings await transplant into vertical hydroponic grow towers at Alaska Seeds of Change on Wednesday, Jan. 11, 2017, in Midtown. (Erik Hill / Alaska Dispatch News)

The question of the week is: Can you use compost to start seeds?

I suppose this question originates from the not-so-long-ago standard advice to use only sterilized starting mixes when germinating seeds. This was to prevent "damping off" of the seedlings (a condition where the stems of seedlings rot, killing the plants). You can still probably buy electric soil sterilizing boxes. However, don't.

Using sterilized soil is not my preferred medium for starting seeds, though you can sure use it. For one thing, your seedlings can dampen off just as easily in a sterilized mix as not. Adequate air circulation is the key to prevention.

More to the point, if you follow this column at all (or read my books), you know I am the biggest believer in the power of soil microbes, or in this case, compost ones. Using compost ensures the right mix of microbes your plants need to feed them (except for the mycorrhizal fungus, which needs to be added or applied to your seeds before planting).

Just make sure it is good compost. It should smell good and you shouldn't be able to recognize the stuff it was made from. If you are buying compost, read the labels before you do.

Next: Can you use old seeds to start this season's plants? This is a "depends" question, as you can well imagine. It depends on how you stored them. If dry and cool, they should last for several years at least. They've found tomato seeds in ancient Chinese graves that still germinate.

Obviously, the only way to tell if seeds are still viable is to try and start a few. You can use the damp paper towel method, which entails rolling them up in a towel and watching them for germination. You can also try soil. Do not wait until the week they are to be planted to see if they are any good. Get your old seeds out now and test them all.

OK, how do you know when to re-pot an orchid and how do you do it? Orchid roots should not grow over the sides of their pots. If yours do, then it is repotting time. You can expect to re-pot a healthy plant every 18 to 24 months.

In addition to finding a pot that is 1 to 2 inches wider in diameter, you will need to replicate the type of growing mix, which will either be bark chips of one size or another or a mix of moss and finer material than the chips. You can locate these at nurseries and some of the chain stores. Do not use the stuff you may have saved from a plant that died as it may carry pathogens. Soak your purchase in water overnight as you don't want dry media pulling the moisture out of your plant's roots.

Gently dump the plant out of its existing container. If you have to, carefully pull and detach the roots which may have attached themselves to both the inside and the outside of the pot. Use your hands to remove any material stuck to the roots. Cut off anything that is mushy, as healthy roots are firm.

Finally, hold the plant so the roots are inside the new pot and fill in with the appropriate orchid potting mix and fill in between the roots, which should be spread out so that the plant will be able to support itself when you are done. Hold it so the crown will be at the "soil" line.

The last questions have to do with when to start gladiolas and dahlias. Let's start with the glads. Last year, I mentioned a reader who insisted there is no need to plant glads indoors as they can be planted outdoors at the end of April and will flower. He has done it for many years.

I think that this is surely worth of all of us trying a few glads at outdoor planting time, but I feel uncomfortable about waiting, not because I think our friend's advice is wrong, but because we can not yet (and I many be wrong here as global warming increases) guarantee how long our season might be. The choice is yours. You can wait or start planting glads now. I like to stagger starting them, so the flowering season can be extended. If you have any experience going all at once when the outdoor season starts, let me know.

As for the dahlias, the time to start yours depends on how much room you have indoors to grow them. These get to be big plants (as in wide as well as tall) and need big pots (with lots of soil). And remember, if you start them before the first week of April, they really need lights.

One thing is for sure, however, our good friend and local dahliaman Rob Wells is still around and has a good supply of dahlia tubers with over 200 varieties for sale. His website no longer works, but and at 907-982-7182 do. The Persistent Farmer Facebook page highlights this year's offerings and you can find him at the Sears Mall Center Market in March and April on Wednesdays and Saturdays with tubers and to deliver any preorders.

Do not let the snow get you you down! Spring is really here!

Jeff's Alaska garden calendar

Willow Garden Club: Pam and Ken Fennell will introduce their Garden Center products, plants and landscaping and lawn services, all conveniently located in Wasilla. 7 p.m. March 15, Willow Community Center.

Summer Camp at Alaska Botanical Garden: It is time to register! See for dates and more information.

Flower to start from seeds: lobelia, pansies, rhodochitons, fibrous begonias, foxglove and hollyhock. Later in the month, lupines, malvas, salvias, pansies, violas, verbenas, carnations, cosmos, seed dahlias and godetia.

Vegetables to start from seeds: Leeks and onions.

Stores plants: Get those fuchsias out and growing. Same with stored bulbs. Pelargoniums need to be potted up. Tuberous begonias should be exposed to light (concave side up). If in a container you like, leave them but wait a couple of weeks to pot yours. Buy some, however, if you need them.