Q: Can I use plastic milk jugs as frost protectors for my tomatoes and peppers?
A: Yes, but they will offer very little protection. Any plant cover is designed to hold the soil warmth instead of allowing it to dissipate into the colder night air. Some substances are better at holding heat than others. Glass slows down heat dissipation well; thus there are glass greenhouses. The standard weight of white row cover will hold temperatures all night at least three degrees above the outside air. The heavyweight row cover, often called "Frost Blanket," keeps temperatures eight or ten degrees higher.
Plastic, unfortunately, does not slow heat transfer at all. That is why plastic garden structures like greenhouses and cold frames have double walls. Two layers of plastic with a dead air space between are good at heat retention. If you wanted to construct a double walled milk jug, it would work equally well.
Plastic milk jugs are good at protecting plants from wind, though, and wind protection can double the growth rate of tender plants. Peppers, for example, showed a 40 percent improvement in production when grown with wind protection. If you use plastic jugs for anything, be sure to prop up one side of the bottom, allowing air circulation, on every sunny day. Without ventilation the plants would cook within an hour or two.
Q: I have an old rose that is getting very tall. It has a few blooms, but the flowers are six or eight feet in the air. They are on big, old, bare stems. There is some small, young growth in the center, but it has no flowers. What can I do?
A: You can fix the situation quickly and easily. Cut all the big, old stems as close to the ground as you can. That will stimulate the growth of the existing small stems and will encourage new ones to start from the base. Eventually you may need to thin some of the young stems, but only if they get too crowded. Old roses seldom need pruning except for old or dead canes.
This is exactly the right time to be pruning roses. I have just severely cut back a hardy rose. Although it should not need pruning, either, it does not seem to understand that it was supposed to be a ground cover. Every year it grows tall enough to cover a window; every year I cut it back to eighteen inches. If that example proves anything, it is that plants are living organisms. They do not always and everywhere grow to the same size, and they are never under our control.
Q: Last year I bought poppy seeds and scattered them just the way the package said. None of them came up. What did I do wrong?
A: Nothing at all. The package directions were written for places with much more spring rainfall than we get, even in a wet year. Poppy seeds of any kind need to be scattered on the soil surface and not covered. They require light to germinate.
Like all other seeds, poppies will die if they dry out during the germination process, which takes about a week. Presumably that is what happened to your seeds. It is very hard to keep seeds damp on the soil surface on sunny days. With some success, I have persuaded poppy seeds to grow by covering them with row cover scraps and watering them twice a day.
My preferred method is to sprout poppy seeds (on top of the potting soil, of course) in little pots, in the house. As soon as the seeds germinate, I move the pots to a protected place outdoors. When the seedlings have four leaves, and before roots appear in the drain holes, I plant them in the ground, about a foot apart. I do not thin the seedling clumps but allow them to thin themselves.
The best news is that, once started, annual poppies are very good at reseeding themselves. It will be several years before it is necessary to think about poppy seeds again.
Master gardener Molly Hackett, whose motto is “Never trust a gardener with clean fingernails,” welcomes your questions. Send them to 1384 Meridian Road, Victor, MT 59875; call 961-4614; or email firstname.lastname@example.org. Please include a garden-related subject line in emails. Hackett writes a twice-monthly Dirty Fingernails opinion piece for the Missoulian.