April is the first full month of spring in the garden. If this is the first month you have gotten out into the garden you will likely find that your garden plants have begun their spring growth. But in addition you may find that your weeds have been just as busy over the past few months. The last average frost can be as early as April 19th in the Puget Sound Region but it can be more than a month later depending on where you live in relationship to the Sound. (People in other parts of the country can find their frost dates on these Freeze/Frost Maps Don’t be tempted to put out tender plants until next month unless you plant to protect them with row covers or cloche’s. Even if our last frost is early most heat loving plants will not make much growth in our cool spring weather. Nature that can give you an indication of how far along the season is. You can start a journal on what plants are blooming in your garden and neighborhood as well as when you planted and the results. You can also track frosts by getting a min/max thermometer or finding a local weather station. Soil temperatures are also a good gauge for direct planting of seeds as well as seedlings. Tracking this kind of information can help you to get an early start in years to come. You can also get an early start by utilizing season extending devices like floating row covers or liquid filled hot caps (cloche).
- Plant perennials, flowering shrubs and vines now appearing in garden centers like Artemesia, Baby’s breath, Balloon flower, Bee Balm, columbines, coreopsis, daylilies, delphiniums, foxglove, lupines, bleeding hearts and roses just to name a few.
- There is still time to plant summer flowering bulbs like gladiolus, iris, and crocosmia as well.
- Transplant cool season annuals like snapdragons, pansies, English Daisies, calendula, sweet alyssum, stock, violas. Hold off on tender warm season annuals like marigolds and gazanias unless you provide protection.
- Start hardy warm season flowers from seed outdoors like nasturtiums, feverfew, baby blue eyes, Love-in-a-mist and flax.
- Trees shrubs and vines can be planted but avoid bareroot stock now. Stick with container grown plants at this late date.
- Weather is still ideal for laying sod, patching bare areas by overseeding or starting lawns from seed.
- Lawn mowing will begin as cool season grasses respond to ideal temperatures and spring rain. Most lawns will need to be mowed weekly. Keep lawns between 1-2 inches in the spring and don’t allow to get higher than 3 inches before you mow it again if possible.
- Test soil and fertilize lawn and adjust pH if necessary. Use a SOIL TEST KIT or the MINI 4-IN-1 GARDEN TESTER. Spring lawns are growing fast and will most likely need a fertilizer with a 3-1-2 (Nitrogen-Phosphours-Potash) ratio.
- There is still time to prune late flowering woody plants that bloom on this season’s growth like trumpet vine (Capmsis), Cross Vine (Bignonia), Glossy Abelia, Butterfly Bush, Bluebeard, Wild Lilac (Ceanothus), Hardy Fuchsias and Hydrangeas.
- Transplanting and hardening off plants. In all areas of the garden you may be transplanting plants both large and small. If plants have been grown in a sheltered area either indoors at your home or somewhere else in a greenhouse it behooves you to adjust the plants slowly to the outdoors. The plants will fare much better and grow faster if they have been allowed time to adjust to the increased light levels, wind as well as cooler temperatures. Ask you garden center if they know the history of the plant you are buying. If it has been grown outdoors,already outdoors for over 2 weeks at the center, or is a dormant/bareroot plant then you can forgo hardening them off. Otherwise before transplanting bring them into full outdoor exposure slowly. Bring them outside for about 4 hours during the warmest part of the day (noon to 4) during the first week and increase up incrementally to 8 hours and then in the second week leave it outside in a sheltered spot and then finally into a fully exposed spot similar to where you will be planting it.
- Increase fertilization and water of indoor plants. This increase in water and fertilizer is to coincide with the increased growth of house plants from the increased light levels as the sun moves southward and more directly into windows. You can check fertility and light levels with the MINI 4-IN-1 GARDEN TESTER
- Repot root bound plants. If plant lacks vigor, roots are coming out of drainage holes or if water drains through the plant before it can absorb the water it is more than likely time to transplant. Move up in put size by about 2 inches.
- Prepare plants for their trip outdoors. If you bring any of any indoor plants outdoors for the summer begin to harden them off as mentioned in the last bullet of Landscape Tasks. Do not leave them outside overnight until two weeks after the last frost date.
- Keep an eye out for the arrival of aphids. Ants usually bring aphids out early from their nests where they overwinter them. They feed off the aphids honeydew excrement and farm them like cows. Usually a strong blast of water will handle light infestations or for larger infestations use a neem soap spray.
- Slugs continue to increase in size and numbers this month. Monitor the organic slug bait levels and spread more in the garden if it runs low.
- Apples are blossoming so if you have had problems with Codling Moth larvae in your apples now is the time to set out the codling moth traps.
- PeachTree Borers – found attacking peach as well as plums, cherries apricots and nectarines (Prunus species) skewer into the entry holes with a thin wire to lance the larvae.
Vegetables, Herbs & Fruit
- Last call to start warm weather vegetables and herbs indoors during the first week of April. Start tomatoes, peppers, basil, cucumbers, cantaloupe, watermelon, squash (including zucchini), eggplants and potatoes from true seed.
- Transplant perennial and biennial herbs like parsley, chives, lovage but wait until after the last frost for tender herbs like basil and marjoram.
- You can still plant herbaceous (e.g. strawberry) and woody fruits (eg. Grapes, raspberries) out but avoid bareroot stock. Buy container grown plants this late in the season.
- Transplant cools season vegetables like broccoli, cabbage, cauliflower, leeks, onions (sets and transplants).
- Directly sow into the ground beets, Swiss chard, carrots, dill, endive, Jerusalem artichokes (tuber), radishes, parsnips, turnips, peas, bunching onions, leeks and potato tubers. If you are growing potatoes from “true seed” treat them like their warm weather relatives the tomato.