Q: I've heard that asparagus plants can tolerate a lot of salt and that they actually need salt to grow well. I have some asparagus plants that aren't growing well.Should put salt on them?
A: Asparagus tolerates fairly high levels of soil salt, but it does not need added salt to grow well. Asparagus growers once applied salt to asparagus beds in order to help control weeds. The asparagus plants tolerated salt, but the weeds couldn't. Commercial growers now use weed killers and not salt. Home gardeners should not use salt either; a vigorous but careful hand-weeding early in the season, followed by occasional touch-ups through the summer, should control weeds.
If your asparagus plants are not growing well, you should evaluate their soil. Asparagus tolerates a fairly wide range of soil types, but it will perform best in loose, well-drained soil that has been amended with lots of compost or well aged manure.
Fertilize asparagus lightly each year with 5-10-5 or 10-10-10 fertilizer. I also like to mulch my asparagus bed with several inches of well-rotted manure each year. This adds nutrients and also has the added benefit of conserving soil moisture. Stop cutting asparagus spears when they are less than a half-inch in diameter; the end of June is usually the end of asparagus season here.
Q: We have what I think is a Toka plum in our yard. It blooms but then it never seems to produce any fruit. Is this because it blooms early and it's too cold outside? The tree must be at least 8 years old.
A: Many fruit trees, including plums, need cross-pollination in order to set fruit. This means that your tree's flowers need to receive pollen from another plum tree in order to set fruit. If there are no other plum trees in the area you won't get fruit on your tree.
Your best bet is to plant another plum tree in your yard. 'Alderman' is an excellent plum variety that has large juicy, red fruits. Other good varieties include 'Superior,' 'Pipestone' and 'La Crescent.' Wild plums (Prunus americana) are also good pollinators, but they have small, tart fruits.
Plums are pollinated primarily by bees, so weather during bloom time can affect how heavy a crop is set. Extended periods of cold, wet, windy weather discourages the bees from foraging, which can lead to reduced flower pollination. You can encourage bee visits by growing a diverse assortment of flowering plants in your yard. Be sure to include early-spring-blooming bulbs and flowers that will coincide with plum flowering.
Q: It was so cold in May that I had to keep the tomato plants I bought inside. Now they're tall and spindly and look a little yellow. Should I still plant them or do I have to get new plants?
A: There's still hope for your tomato plants. They do need to go outside in a protected spot now so that they get accustomed to outdoor conditions before you plant them in the garden. When you plant them in the garden, you can then take advantage of tomato's unique ability to produce new roots along its stem. Most vegetable plants must be planted at the same soil level as they were growing in containers, but tomatoes can have much of their stem covered with soil with no ill effects. In fact, the new roots that will develop from the stem will rapidly help the plant get established.
Rather than just digging a deeper hole and setting the tomato plant straight down, dig a shallow, angled trench. Put the root ball in the deepest end, then lay the tomato stem in the trench, gently bending the leafy top section up at the other end. Fill in the trench and water thoroughly with a diluted fertilizer solution. You may want to stake the top of the plant to direct its growth upward. Keep the plant well-watered and lightly fertilized and it should do just fine.
--Nancy Rose is a research horticulturist at the Minnesota Landscape Arboretum. She spends her spare time gardening, inside or outside, depending on the weather. Please address gardening questions to her at the Minnesota Landscape Arboretum, PO Box 39, Chanhassen MN 55317. She will answer questions in this column only.