1. is it ok to cover the garlic with straw as a mulch which has previously treated with herbicide? The garlic will be grown on a wooden bed of 3ft x 7ft.
2. Are there any issues with mold formation or grubs, snails if this mulch is used
3. Will this still be considered as naturally grown with the treated straw is mulch?
4. How much of horse manure is required as fertilizer for garlic growing?
5. In spring once the snow is melted, how often should the garlic bed is to be watered.
1) Mulch: An initial consideration is whether you want to use straw (to cover the soil) or hay (which enriches it). See a previous posting on the Ask a Master Gardener. Hay versus straw for mulch.
It important to know the name of the herbicide was used on the straw. Once you know the name, search for the length of time it takes to break down after application and don’t use the straw until well after this time. If you can’t find out which herbicide was used, I suggest that you don’t use the straw. Garlic is a food crop and by adding herbicide-contaminated straw to the soil, you will add the herbicide to your garden too, in an unknown concentration.
2) Mold or pests if mulch used: If you use a straw mulch, there is no need to worry about mold, as this is common, since the straw often gets wet. The mold will not transmit disease to the garlic. Straw mulch acts as a barrier between pests and plants, but also may make an attractive hiding place for pests like grubs (which are insects in larval form) or snails (which may want to lay eggs under the mulch). Do not use too thick a layer of straw as compost, as one way to control grubs in particular is to expose them to air, so that predators like birds can find them. Remember that snails like a wet environment, so by watering the garden in the morning, not at night when moisture will remain on the mulch for longer, this may make the mulched area less attractive to snails. Make sure, though, that the plants are getting enough water. You could try using the mulch, and remove it if you find that the slugs are winning the battle!
3) Naturally grown: I think you want to know whether use of herbicide-contaminated straw mulch would be considered organic gardening. Organic gardening is done without pesticides or herbicides.
4) Manure: Horse manure is a good source of nitrogen for the garlic plants, but ensure that you know which drugs the horses have been given, as these can end up in the soil. Horse manure may also contain a lot of weed seeds and fresh manure can burn plant roots, so use well-aged composted manure. Spread it in a thin layer, up to 1.3 cm (1/2 inch) thick and no more than 8-10 cm (3-4 inches) over the course of the season in the same area, and work it into the soil. For more information, see
- Gardening know how. Making and using horse manure compost.
- University of Massachusetts Amherst. Composting horse manure.
5) Watering garlic bed: There is no way to predict how often the bed should be watered, as this depends on whether the growing season is rainy or dry. Generally, garlic needs about 2.5 cm (1 inch) of water per week when the weather is dry. Don’t water too much, as garlic does not like “wet feet” – this could rot the plants. Stop watering and fertilizing the garlic by around mid-July, once the plants stop producing leaves and start concentrating their energy in forming buds. Let the soil dry out, to avoid exposing the bulbs to disease.
For good general information about caring for garlic in the home garden, see:
- Toronto Master Gardeners. Growing garlic from cloves: A Toronto Master Gardeners Guide.
- Rutgers. Growing Garlic in the Home Garden
All the best with your garlic crop!